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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S I N F O --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2016, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package defines the structure of the abstract syntax tree. The Tree
-- package provides a basic tree structure. Sinfo describes how this structure
-- is used to represent the syntax of an Ada program.
-- The grammar in the RM is followed very closely in the tree design, and is
-- repeated as part of this source file.
-- The tree contains not only the full syntactic representation of the
-- program, but also the results of semantic analysis. In particular, the
-- nodes for defining identifiers, defining character literals and defining
-- operator symbols, collectively referred to as entities, represent what
-- would normally be regarded as the symbol table information. In addition a
-- number of the tree nodes contain semantic information.
-- WARNING: Several files are automatically generated from this package.
-- See below for details.
with Namet; use Namet;
with Types; use Types;
with Uintp; use Uintp;
with Urealp; use Urealp;
package Sinfo is
---------------------------------
-- Making Changes to This File --
---------------------------------
-- If changes are made to this file, a number of related steps must be
-- carried out to ensure consistency. First, if a field access function is
-- added, it appears in these places:
-- In sinfo.ads:
-- The documentation associated with the field (if semantic)
-- The documentation associated with the node
-- The spec of the access function
-- The spec of the set procedure
-- The entries in Is_Syntactic_Field
-- The pragma Inline for the access function
-- The pragma Inline for the set procedure
-- In sinfo.adb:
-- The body of the access function
-- The body of the set procedure
-- The field chosen must be consistent in all places, and, for a node that
-- is a subexpression, must not overlap any of the standard expression
-- fields.
-- In addition, if any of the standard expression fields is changed, then
-- the utility program which creates the Treeprs spec (in file treeprs.ads)
-- must be updated appropriately, since it special cases expression fields.
-- If a new tree node is added, then the following changes are made:
-- Add it to the documentation in the appropriate place
-- Add its fields to this documentation section
-- Define it in the appropriate classification in Node_Kind
-- Add an entry in Is_Syntactic_Field
-- In the body (sinfo), add entries to the access functions for all
-- its fields (except standard expression fields) to include the new
-- node in the checks.
-- Add an appropriate section to the case statement in sprint.adb
-- Add an appropriate section to the case statement in sem.adb
-- Add an appropriate section to the case statement in exp_util.adb
-- (Insert_Actions procedure)
-- For a subexpression, add an appropriate section to the case
-- statement in sem_eval.adb
-- For a subexpression, add an appropriate section to the case
-- statement in sem_res.adb
-- All back ends must be made aware of the new node kind.
-- Finally, four utility programs must be run:
-- (Optional.) Run CSinfo to check that you have made the changes
-- consistently. It checks most of the rules given above. This utility
-- reads sinfo.ads and sinfo.adb and generates a report to standard
-- output. This step is optional because XSinfo runs CSinfo.
-- Run XSinfo to create sinfo.h, the corresponding C header. This
-- utility reads sinfo.ads and generates sinfo.h. Note that it does
-- not need to read sinfo.adb, since the contents of the body are
-- algorithmically determinable from the spec.
-- Run XTreeprs to create treeprs.ads, an updated version of the module
-- that is used to drive the tree print routine. This utility reads (but
-- does not modify) treeprs.adt, the template that provides the basic
-- structure of the file, and then fills in the data from the comments
-- in sinfo.ads.
-- Run XNmake to create nmake.ads and nmake.adb, the package body and
-- spec of the Nmake package which contains functions for constructing
-- nodes.
-- The above steps are done automatically by the build scripts when you do
-- a full bootstrap.
-- Note: sometime we could write a utility that actually generated the body
-- of sinfo from the spec instead of simply checking it, since, as noted
-- above, the contents of the body can be determined from the spec.
--------------------------------
-- Implicit Nodes in the Tree --
--------------------------------
-- Generally the structure of the tree very closely follows the grammar as
-- defined in the RM. However, certain nodes are omitted to save space and
-- simplify semantic processing. Two general classes of such omitted nodes
-- are as follows:
-- If the only possibilities for a non-terminal are one or more other
-- non-terminals (i.e. the rule is a "skinny" rule), then usually the
-- corresponding node is omitted from the tree, and the target construct
-- appears directly. For example, a real type definition is either
-- floating point definition or a fixed point definition. No explicit node
-- appears for real type definition. Instead either the floating point
-- definition or fixed point definition appears directly.
-- If a non-terminal corresponds to a list of some other non-terminal
-- (possibly with separating punctuation), then usually it is omitted from
-- the tree, and a list of components appears instead. For example,
-- sequence of statements does not appear explicitly in the tree. Instead
-- a list of statements appears directly.
-- Some additional cases of omitted nodes occur and are documented
-- individually. In particular, many nodes are omitted in the tree
-- generated for an expression.
-------------------------------------------
-- Handling of Defining Identifier Lists --
-------------------------------------------
-- In several declarative forms in the syntax, lists of defining
-- identifiers appear (object declarations, component declarations, number
-- declarations etc.)
-- The semantics of such statements are equivalent to a series of identical
-- declarations of single defining identifiers (except that conformance
-- checks require the same grouping of identifiers in the parameter case).
-- To simplify semantic processing, the parser breaks down such multiple
-- declaration cases into sequences of single declarations, duplicating
-- type and initialization information as required. The flags More_Ids and
-- Prev_Ids are used to record the original form of the source in the case
-- where the original source used a list of names, More_Ids being set on
-- all but the last name and Prev_Ids being set on all but the first name.
-- These flags are used to reconstruct the original source (e.g. in the
-- Sprint package), and also are included in the conformance checks, but
-- otherwise have no semantic significance.
-- Note: the reason that we use More_Ids and Prev_Ids rather than
-- First_Name and Last_Name flags is so that the flags are off in the
-- normal one identifier case, which minimizes tree print output.
-----------------------
-- Use of Node Lists --
-----------------------
-- With a few exceptions, if a construction of the form {non-terminal}
-- appears in the tree, lists are used in the corresponding tree node (see
-- package Nlists for handling of node lists). In this case a field of the
-- parent node points to a list of nodes for the non-terminal. The field
-- name for such fields has a plural name which always ends in "s". For
-- example, a case statement has a field Alternatives pointing to list of
-- case statement alternative nodes.
-- Only fields pointing to lists have names ending in "s", so generally the
-- structure is strongly typed, fields not ending in s point to single
-- nodes, and fields ending in s point to lists.
-- The following example shows how a traversal of a list is written. We
-- suppose here that Stmt points to a N_Case_Statement node which has a
-- list field called Alternatives:
-- Alt := First (Alternatives (Stmt));
-- while Present (Alt) loop
-- ..
-- -- processing for case statement alternative Alt
-- ..
-- Alt := Next (Alt);
-- end loop;
-- The Present function tests for Empty, which in this case signals the end
-- of the list. First returns Empty immediately if the list is empty.
-- Present is defined in Atree, First and Next are defined in Nlists.
-- The exceptions to this rule occur with {DEFINING_IDENTIFIERS} in all
-- contexts, which is handled as described in the previous section, and
-- with {,library_unit_NAME} in the N_With_Clause mode, which is handled
-- using the First_Name and Last_Name flags, as further detailed in the
-- description of the N_With_Clause node.
-------------
-- Pragmas --
-------------
-- Pragmas can appear in many different context, but are not included in
-- the grammar. Still they must appear in the tree, so they can be properly
-- processed.
-- Two approaches are used. In some cases, an extra field is defined in an
-- appropriate node that contains a list of pragmas appearing in the
-- expected context. For example pragmas can appear before an
-- Accept_Alternative in a Selective_Accept_Statement, and these pragmas
-- appear in the Pragmas_Before field of the N_Accept_Alternative node.
-- The other approach is to simply allow pragmas to appear in syntactic
-- lists where the grammar (of course) does not include the possibility.
-- For example, the Variants field of an N_Variant_Part node points to a
-- list that can contain both N_Pragma and N_Variant nodes.
-- To make processing easier in the latter case, the Nlists package
-- provides a set of routines (First_Non_Pragma, Last_Non_Pragma,
-- Next_Non_Pragma, Prev_Non_Pragma) that allow such lists to be handled
-- ignoring all pragmas.
-- In the case of the variants list, we can either write:
-- Variant := First (Variants (N));
-- while Present (Variant) loop
-- ...
-- Variant := Next (Variant);
-- end loop;
-- or
-- Variant := First_Non_Pragma (Variants (N));
-- while Present (Variant) loop
-- ...
-- Variant := Next_Non_Pragma (Variant);
-- end loop;
-- In the first form of the loop, Variant can either be an N_Pragma or an
-- N_Variant node. In the second form, Variant can only be N_Variant since
-- all pragmas are skipped.
---------------------
-- Optional Fields --
---------------------
-- Fields which correspond to a section of the syntax enclosed in square
-- brackets are generally omitted (and the corresponding field set to Empty
-- for a node, or No_List for a list). The documentation of such fields
-- notes these cases. One exception to this rule occurs in the case of
-- possibly empty statement sequences (such as the sequence of statements
-- in an entry call alternative). Such cases appear in the syntax rules as
-- [SEQUENCE_OF_STATEMENTS] and the fields corresponding to such optional
-- statement sequences always contain an empty list (not No_List) if no
-- statements are present.
-- Note: the utility program that constructs the body and spec of the Nmake
-- package relies on the format of the comments to determine if a field
-- should have a default value in the corresponding make routine. The rule
-- is that if the first line of the description of the field contains the
-- string "(set to xxx if", then a default value of xxx is provided for
-- this field in the corresponding Make_yyy routine.
-----------------------------------
-- Note on Body/Spec Terminology --
-----------------------------------
-- In informal discussions about Ada, it is customary to refer to package
-- and subprogram specs and bodies. However, this is not technically
-- correct, what is normally referred to as a spec or specification is in
-- fact a package declaration or subprogram declaration. We are careful in
-- GNAT to use the correct terminology and in particular, the full word
-- specification is never used as an incorrect substitute for declaration.
-- The structure and terminology used in the tree also reflects the grammar
-- and thus uses declaration and specification in the technically correct
-- manner.
-- However, there are contexts in which the informal terminology is useful.
-- We have the word "body" to refer to the Interp_Etype declared by the
-- declaration of a unit body, and in some contexts we need similar term to
-- refer to the entity declared by the package or subprogram declaration,
-- and simply using declaration can be confusing since the body also has a
-- declaration.
-- An example of such a context is the link between the package body and
-- its declaration. With_Declaration is confusing, since the package body
-- itself is a declaration.
-- To deal with this problem, we reserve the informal term Spec, i.e. the
-- popular abbreviation used in this context, to refer to the entity
-- declared by the package or subprogram declaration. So in the above
-- example case, the field in the body is called With_Spec.
-- Another important context for the use of the word Spec is in error
-- messages, where a hyper-correct use of declaration would be confusing to
-- a typical Ada programmer, and even for an expert programmer can cause
-- confusion since the body has a declaration as well.
-- So, to summarize:
-- Declaration always refers to the syntactic entity that is called
-- a declaration. In particular, subprogram declaration
-- and package declaration are used to describe the
-- syntactic entity that includes the semicolon.
-- Specification always refers to the syntactic entity that is called
-- a specification. In particular, the terms procedure
-- specification, function specification, package
-- specification, subprogram specification always refer
-- to the syntactic entity that has no semicolon.
-- Spec is an informal term, used to refer to the entity
-- that is declared by a task declaration, protected
-- declaration, generic declaration, subprogram
-- declaration or package declaration.
-- This convention is followed throughout the GNAT documentation
-- both internal and external, and in all error message text.
------------------------
-- Internal Use Nodes --
------------------------
-- These are Node_Kind settings used in the internal implementation which
-- are not logically part of the specification.
-- N_Unused_At_Start
-- Completely unused entry at the start of the enumeration type. This
-- is inserted so that no legitimate value is zero, which helps to get
-- better debugging behavior, since zero is a likely uninitialized value).
-- N_Unused_At_End
-- Completely unused entry at the end of the enumeration type. This is
-- handy so that arrays with Node_Kind as the index type have an extra
-- entry at the end (see for example the use of the Pchar_Pos_Array in
-- Treepr, where the extra entry provides the limit value when dealing with
-- the last used entry in the array).
-----------------------------------------
-- Note on the settings of Sloc fields --
-----------------------------------------
-- The Sloc field of nodes that come from the source is set by the parser.
-- For internal nodes, and nodes generated during expansion the Sloc is
-- usually set in the call to the constructor for the node. In general the
-- Sloc value chosen for an internal node is the Sloc of the source node
-- whose processing is responsible for the expansion. For example, the Sloc
-- of an inherited primitive operation is the Sloc of the corresponding
-- derived type declaration.
-- For the nodes of a generic instantiation, the Sloc value is encoded to
-- represent both the original Sloc in the generic unit, and the Sloc of
-- the instantiation itself. See Sinput.ads for details.
-- Subprogram instances create two callable entities: one is the visible
-- subprogram instance, and the other is an anonymous subprogram nested
-- within a wrapper package that contains the renamings for the actuals.
-- Both of these entities have the Sloc of the defining entity in the
-- instantiation node. This simplifies some ASIS queries.
-----------------------
-- Field Definitions --
-----------------------
-- In the following node definitions, all fields, both syntactic and
-- semantic, are documented. The one exception is in the case of entities
-- (defining identifiers, character literals and operator symbols), where
-- the usage of the fields depends on the entity kind. Entity fields are
-- fully documented in the separate package Einfo.
-- In the node definitions, three common sets of fields are abbreviated to
-- save both space in the documentation, and also space in the string
-- (defined in Tree_Print_Strings) used to print trees. The following
-- abbreviations are used:
-- Note: the utility program that creates the Treeprs spec (in the file
-- xtreeprs.adb) knows about the special fields here, so it must be
-- modified if any change is made to these fields.
-- "plus fields for binary operator"
-- Chars (Name1) Name_Id for the operator
-- Left_Opnd (Node2) left operand expression
-- Right_Opnd (Node3) right operand expression
-- Entity (Node4-Sem) defining entity for operator
-- Associated_Node (Node4-Sem) for generic processing
-- Do_Overflow_Check (Flag17-Sem) set if overflow check needed
-- Has_Private_View (Flag11-Sem) set in generic units.
-- "plus fields for unary operator"
-- Chars (Name1) Name_Id for the operator
-- Right_Opnd (Node3) right operand expression
-- Entity (Node4-Sem) defining entity for operator
-- Associated_Node (Node4-Sem) for generic processing
-- Do_Overflow_Check (Flag17-Sem) set if overflow check needed
-- Has_Private_View (Flag11-Sem) set in generic units.
-- "plus fields for expression"
-- Paren_Count number of parentheses levels
-- Etype (Node5-Sem) type of the expression
-- Is_Overloaded (Flag5-Sem) >1 type interpretation exists
-- Is_Static_Expression (Flag6-Sem) set for static expression
-- Raises_Constraint_Error (Flag7-Sem) evaluation raises CE
-- Must_Not_Freeze (Flag8-Sem) set if must not freeze
-- Do_Range_Check (Flag9-Sem) set if a range check needed
-- Has_Dynamic_Length_Check (Flag10-Sem) set if length check inserted
-- Has_Dynamic_Range_Check (Flag12-Sem) set if range check inserted
-- Assignment_OK (Flag15-Sem) set if modification is OK
-- Is_Controlling_Actual (Flag16-Sem) set for controlling argument
-- Note: see under (EXPRESSION) for further details on the use of
-- the Paren_Count field to record the number of parentheses levels.
-- Node_Kind is the type used in the Nkind field to indicate the node kind.
-- The actual definition of this type is given later (the reason for this
-- is that we want the descriptions ordered by logical chapter in the RM,
-- but the type definition is reordered to facilitate the definition of
-- some subtype ranges. The individual descriptions of the nodes show how
-- the various fields are used in each node kind, as well as providing
-- logical names for the fields. Functions and procedures are provided for
-- accessing and setting these fields using these logical names.
-----------------------
-- Gigi Restrictions --
-----------------------
-- The tree passed to Gigi is more restricted than the general tree form.
-- For example, as a result of expansion, most of the tasking nodes can
-- never appear. For each node to which either a complete or partial
-- restriction applies, a note entitled "Gigi restriction" appears which
-- documents the restriction.
-- Note that most of these restrictions apply only to trees generated when
-- code is being generated, since they involved expander actions that
-- destroy the tree.
---------------
-- ASIS Mode --
---------------
-- When a file is compiled in ASIS mode (-gnatct), expansion is skipped,
-- and the analysis must generate a tree in a form that meets all ASIS
-- requirements.
-- ASIS must be able to recover the original tree that corresponds to the
-- source. It relies heavily on Original_Node for this purpose, which as
-- described in Atree, records the history when a node is rewritten. ASIS
-- uses Original_Node to recover the original node before the Rewrite.
-- At least in ASIS mode (not really important in non-ASIS mode), when
-- N1 is rewritten as N2:
-- The subtree rooted by the original node N1 should be fully decorated,
-- i.e. all semantic fields noted in sinfo.ads should be set properly
-- and any referenced entities should be complete (with exceptions for
-- representation information, noted below).
-- For all the direct descendants of N1 (original node) their Parent
-- links should point not to N1, but to N2 (rewriting node).
-- The Parent links of rewritten nodes (N1 in this example) are set in
-- some cases (to point to the rewritten parent), but in other cases
-- they are set to Empty. This needs sorting out ??? It would be much
-- cleaner if they could always be set in the original node ???
-- There are a few cases when ASIS has to use not the original, but the
-- rewritten tree structures. This happens when because of some important
-- technical reasons it is impossible or very hard to have the original
-- structure properly decorated by semantic information, and the rewritten
-- structure fully reproduces the original source. Below is the (incomplete
-- for the moment???) list of such exceptions:
--
-- Generic specifications and generic bodies
-- Function calls that use prefixed notation (Operand.Operation [(...)])
-- Representation Information
-- For the purposes of the data description annex, the representation
-- information for source declared entities must be complete in the
-- ASIS tree.
-- This requires that the front end call the back end (gigi/gcc) in
-- a special "back annotate only" mode to obtain information on layout
-- from the back end.
-- For the purposes of this special "back annotate only" mode, the
-- requirements that would normally need to be met to generate code
-- are relaxed as follows:
-- Anonymous types need not have full representation information (e.g.
-- sizes need not be set for types where the front end would normally
-- set the sizes), since anonymous types can be ignored in this mode.
-- In this mode, gigi will see at least fragments of a fully annotated
-- unexpanded tree. This means that it will encounter nodes it does
-- not normally handle (such as stubs, task bodies etc). It should
-- simply ignore these nodes, since they are not relevant to the task
-- of back annotating representation information.
-- Some other ASIS-specific issues are covered in specific comments in
-- sections for particular nodes or flags.
----------------
-- Ghost Mode --
----------------
-- The SPARK RM 6.9 defines two classes of constructs - Ghost entities and
-- Ghost statements. The intent of the feature is to treat Ghost constructs
-- as non-existent when Ghost assertion policy Ignore is in effect.
-- The corresponding nodes which map to Ghost constructs are:
-- Ghost entities
-- Declaration nodes
-- N_Package_Body
-- N_Subprogram_Body
-- Ghost statements
-- N_Assignment_Statement
-- N_Procedure_Call_Statement
-- N_Pragma
-- In addition, the compiler treats instantiations as Ghost entities
-- To achieve the removal of ignored Ghost constructs, the compiler relies
-- on global variable Ghost_Mode and a mechanism called "Ghost regions".
-- The values of the global variable are as follows:
-- 1. Check - All static semantics as defined in SPARK RM 6.9 are in
-- effect. The Ghost region has mode Check.
-- 2. Ignore - Same as Check, ignored Ghost code is not present in ALI
-- files, object files, and the final executable. The Ghost region
-- has mode Ignore.
-- 3. None - No Ghost region is in effect
-- A Ghost region is a compiler operating mode, similar to Check_Syntax,
-- however a region is much more finely grained and depends on the policy
-- in effect. The region starts prior to the analysis of a Ghost construct
-- and ends immediately after its expansion. The region is established as
-- follows:
-- 1. Declarations - Prior to analysis, if the declaration is subject to
-- pragma Ghost.
-- 2. Renaming declarations - Same as 1) or when the renamed entity is
-- Ghost.
-- 3. Completing declarations - Same as 1) or when the declaration is
-- partially analyzed and the declaration completes a Ghost entity.
-- 4. N_Package_Body, N_Subprogram_Body - Same as 1) or when the body is
-- partially analyzed and completes a Ghost entity.
-- 5. N_Assignment_Statement - After the left hand side is analyzed and
-- references a Ghost entity.
-- 6. N_Procedure_Call_Statement - After the name is analyzed and denotes
-- a Ghost procedure.
-- 7. N_Pragma - During analysis, when the related entity is Ghost or the
-- pragma encloses a Ghost entity.
-- 8. Instantiations - Save as 1) or when the instantiation is partially
-- analyzed and the generic template is Ghost.
-- Routines Mark_And_Set_Ghost_xxx install a new Ghost region and routine
-- Restore_Ghost_Mode ends a Ghost region. A region may be reinstalled
-- similar to scopes for decoupled expansion such as the generation of
-- dispatch tables or the creation of a predicate function.
-- If the mode of a Ghost region is Ignore, any newly created nodes as well
-- as source entities are marked as ignored Ghost. In additon, the marking
-- process signals all enclosing scopes that an ignored Ghost node resides
-- within. The compilation unit where the node resides is also added to an
-- auxiliary table for post processing.
-- After the analysis and expansion of all compilation units takes place
-- as well as the instantiation of all inlined [generic] bodies, the GNAT
-- driver initiates a separate pass which removes all ignored Ghost nodes
-- from all units stored in the auxiliary table.
--------------------
-- GNATprove Mode --
--------------------
-- When a file is compiled in GNATprove mode (-gnatd.F), a very light
-- expansion is performed and the analysis must generate a tree in a
-- form that meets additional requirements.
-- This light expansion does two transformations of the tree that cannot
-- be postponed till after semantic analysis:
-- 1. Replace object renamings by renamed object. This requires the
-- introduction of temporaries at the point of the renaming, which
-- must be properly analyzed.
-- 2. Fully qualify entity names. This is needed to generate suitable
-- local effects and call-graphs in ALI files, with the completely
-- qualified names (in particular the suffix to distinguish homonyms).
-- The tree after this light expansion should be fully analyzed
-- semantically, which sometimes requires the insertion of semantic
-- pre-analysis, for example for subprogram contracts and pragma
-- check/assert. In particular, all expression must have their proper type,
-- and semantic links should be set between tree nodes (partial to full
-- view, etc.) Some kinds of nodes should be either absent, or can be
-- ignored by the formal verification backend:
-- N_Object_Renaming_Declaration: can be ignored safely
-- N_Expression_Function: absent (rewritten)
-- N_Expression_With_Actions: absent (not generated)
-- SPARK cross-references are generated from the regular cross-references
-- (used for browsing and code understanding) and additional references
-- collected during semantic analysis, in particular on all dereferences.
-- These SPARK cross-references are output in a separate section of ALI
-- files, as described in spark_xrefs.adb. They are the basis for the
-- computation of data dependences in GNATprove. This implies that all
-- cross-references should be generated in this mode, even those that would
-- not make sense from a user point-of-view, and that cross-references that
-- do not lead to data dependences for subprograms can be safely ignored.
-- GNATprove relies on the following front end behaviors:
-- 1. The first declarations in the list of visible declarations of
-- a package declaration for a generic instance, up to the first
-- declaration which comes from source, should correspond to
-- the "mappings nodes" between formal and actual generic parameters.
-- 2. In addition pragma Debug statements are removed from the tree
-- (rewritten to NULL stmt), since they should be ignored in formal
-- verification.
-- 3. An error is also issued for missing subunits, similar to the
-- warning issued when generating code, to avoid formal verification
-- of a partial unit.
-- 4. Unconstrained types are not replaced by constrained types whose
-- bounds are generated from an expression: Expand_Subtype_From_Expr
-- should be a no-op.
-- 5. Errors (instead of warnings) are issued on compile-time-known
-- constraint errors even though such cases do not correspond to
-- illegalities in the Ada RM (this is simply another case where
-- GNATprove implements a subset of the full language).
--
-- However, there are a few exceptions to this rule for cases where
-- we want to allow the GNATprove analysis to proceed (e.g. range
-- checks on empty ranges, which typically appear in deactivated
-- code in a particular configuration).
-- 6. Subtypes should match in the AST, even after a generic is
-- instantiated. In particular, GNATprove relies on the fact that,
-- on a selected component, the type of the selected component is
-- the type of the corresponding component in the prefix of the
-- selected component.
--
-- Note that, in some cases, we know that this rule is broken by the
-- frontend. In particular, if the selected component is a packed
-- array depending on a discriminant of a unconstrained formal object
-- parameter of a generic.
-----------------------
-- Check Flag Fields --
-----------------------
-- The following flag fields appear in expression nodes:
-- Do_Division_Check
-- Do_Overflow_Check
-- Do_Range_Check
-- These three flags are always set by the front end during semantic
-- analysis, on expression nodes that may trigger the corresponding
-- check. The front end then inserts or not the check during expansion. In
-- particular, these flags should also be correctly set in ASIS mode and
-- GNATprove mode. As a special case, the front end does not insert a
-- Do_Division_Check flag on float exponentiation expressions, for the case
-- where the value is 0.0 and the exponent is negative, although this case
-- does lead to a division check failure.
-- Note: the expander always takes care of the Do_Range check case,
-- so this flag will never be set in the expanded tree passed to the
-- back end code generator.
-- Note that this accounts for all nodes that trigger the corresponding
-- checks, except for range checks on subtype_indications, which may be
-- required to check that a range_constraint is compatible with the given
-- subtype (RM 3.2.2(11)).
-- The following flag fields appear in various nodes:
-- Do_Accessibility_Check
-- Do_Discriminant_Check
-- Do_Length_Check
-- Do_Storage_Check
-- Do_Tag_Check
-- These flags are used in some specific cases by the front end, either
-- during semantic analysis or during expansion, and cannot be expected
-- to be set on all nodes that trigger the corresponding check.
------------------------
-- Common Flag Fields --
------------------------
-- The following flag fields appear in all nodes:
-- Analyzed
-- This flag is used to indicate that a node (and all its children have
-- been analyzed. It is used to avoid reanalysis of a node that has
-- already been analyzed, both for efficiency and functional correctness
-- reasons.
-- Comes_From_Source
-- This flag is set if the node comes directly from an explicit construct
-- in the source. It is normally on for any nodes built by the scanner or
-- parser from the source program, with the exception that in a few cases
-- the parser adds nodes to normalize the representation (in particular
-- a null statement is added to a package body if there is no begin/end
-- initialization section.
--
-- Most nodes inserted by the analyzer or expander are not considered
-- as coming from source, so the flag is off for such nodes. In a few
-- cases, the expander constructs nodes closely equivalent to nodes
-- from the source program (e.g. the allocator built for build-in-place
-- case), and the Comes_From_Source flag is deliberately set.
-- Error_Posted
-- This flag is used to avoid multiple error messages being posted on or
-- referring to the same node. This flag is set if an error message
-- refers to a node or is posted on its source location, and has the
-- effect of inhibiting further messages involving this same node.
-----------------------
-- Modify_Tree_For_C --
-----------------------
-- If the flag Opt.Modify_Tree_For_C is set True, then the tree is modified
-- in ways that help match the semantics better with C, easing the task of
-- interfacing to C code generators (other than GCC, where the work is done
-- in gigi, and there is no point in changing that), and also making life
-- easier for Cprint in generating C source code.
-- The current modifications implemented are as follows:
-- N_Op_Rotate_Left, N_Op_Rotate_Right, N_Shift_Right_Arithmetic nodes
-- are eliminated from the tree (since these operations do not exist in
-- C), and the operations are rewritten in terms of logical shifts and
-- other logical operations that do exist in C. See Exp_Ch4 expansion
-- routines for these operators for details of the transformations made.
-- The right operand of N_Op_Shift_Right and N_Op_Shift_Left is always
-- less than the word size (since other values are not well-defined in
-- C). This is done using an explicit test if necessary.
-- Min and Max attributes are expanded into equivalent if expressions,
-- dealing properly with side effect issues.
-- Mod for signed integer types is expanded into equivalent expressions
-- using Rem (which is % in C) and other C-available operators.
-- Functions returning bounded arrays are transformed into procedures
-- with an extra out parameter, and the calls updated accordingly.
-- Aggregates are only kept unexpanded for object declarations, otherwise
-- they are systematically expanded into loops (for arrays) and
-- individual assignments (for records).
-- Unconstrained array types are handled by means of fat pointers.
-- Postconditions are inlined by the frontend since their body may have
-- references to itypes defined in the enclosing subprogram.
------------------------------------
-- Description of Semantic Fields --
------------------------------------
-- The meaning of the syntactic fields is generally clear from their names
-- without any further description, since the names are chosen to
-- correspond very closely to the syntax in the reference manual. This
-- section describes the usage of the semantic fields, which are used to
-- contain additional information determined during semantic analysis.
-- ABE_Is_Certain (Flag18-Sem)
-- This flag is set in an instantiation node or a call node is determined
-- to be sure to raise an ABE. This is used to trigger special handling
-- of such cases, particularly in the instantiation case where we avoid
-- instantiating the body if this flag is set. This flag is also present
-- in an N_Formal_Package_Declaration node since formal package
-- declarations are treated like instantiations, but it is always set to
-- False in this context.
-- Accept_Handler_Records (List5-Sem)
-- This field is present only in an N_Accept_Alternative node. It is used
-- to temporarily hold the exception handler records from an accept
-- statement in a selective accept. These exception handlers will
-- eventually be placed in the Handler_Records list of the procedure
-- built for this accept (see Expand_N_Selective_Accept procedure in
-- Exp_Ch9 for further details).
-- Access_Types_To_Process (Elist2-Sem)
-- Present in N_Freeze_Entity nodes for Incomplete or private types.
-- Contains the list of access types which may require specific treatment
-- when the nature of the type completion is completely known. An example
-- of such treatment is the generation of the associated_final_chain.
-- Actions (List1-Sem)
-- This field contains a sequence of actions that are associated with the
-- node holding the field. See the individual node types for details of
-- how this field is used, as well as the description of the specific use
-- for a particular node type.
-- Activation_Chain_Entity (Node3-Sem)
-- This is used in tree nodes representing task activators (blocks,
-- subprogram bodies, package declarations, and task bodies). It is
-- initially Empty, and then gets set to point to the entity for the
-- declared Activation_Chain variable when the first task is declared.
-- When tasks are declared in the corresponding declarative region this
-- entity is located by name (its name is always _Chain) and the declared
-- tasks are added to the chain. Note that N_Extended_Return_Statement
-- does not have this attribute, although it does have an activation
-- chain. This chain is used to store the tasks temporarily, and is not
-- used for activating them. On successful completion of the return
-- statement, the tasks are moved to the caller's chain, and the caller
-- activates them.
-- Acts_As_Spec (Flag4-Sem)
-- A flag set in the N_Subprogram_Body node for a subprogram body which
-- is acting as its own spec. In the case of a library-level subprogram
-- the flag is set as well on the parent compilation unit node.
-- Actual_Designated_Subtype (Node4-Sem)
-- Present in N_Free_Statement and N_Explicit_Dereference nodes. If gigi
-- needs to known the dynamic constrained subtype of the designated
-- object, this attribute is set to that type. This is done for
-- N_Free_Statements for access-to-classwide types and access to
-- unconstrained packed array types, and for N_Explicit_Dereference when
-- the designated type is an unconstrained packed array and the
-- dereference is the prefix of a 'Size attribute reference.
-- Address_Warning_Posted (Flag18-Sem)
-- Present in N_Attribute_Definition nodes. Set to indicate that we have
-- posted a warning for the address clause regarding size or alignment
-- issues. Used to inhibit multiple redundant messages.
-- Aggregate_Bounds (Node3-Sem)
-- Present in array N_Aggregate nodes. If the bounds of the aggregate are
-- known at compile time, this field points to an N_Range node with those
-- bounds. Otherwise Empty.
-- All_Others (Flag11-Sem)
-- Present in an N_Others_Choice node. This flag is set for an others
-- exception where all exceptions are to be caught, even those that are
-- not normally handled (in particular the tasking abort signal). This
-- is used for translation of the at end handler into a normal exception
-- handler.
-- Aspect_Rep_Item (Node2-Sem)
-- Present in N_Aspect_Specification nodes. Points to the corresponding
-- pragma/attribute definition node used to process the aspect.
-- Assignment_OK (Flag15-Sem)
-- This flag is set in a subexpression node for an object, indicating
-- that the associated object can be modified, even if this would not
-- normally be permissible (either by direct assignment, or by being
-- passed as an out or in-out parameter). This is used by the expander
-- for a number of purposes, including initialization of constants and
-- limited type objects (such as tasks), setting discriminant fields,
-- setting tag values, etc. N_Object_Declaration nodes also have this
-- flag defined. Here it is used to indicate that an initialization
-- expression is valid, even where it would normally not be allowed
-- (e.g. where the type involved is limited). It is also used to stop
-- a Force_Evaluation call for an unchecked conversion, but this usage
-- is unclear and not documented ???
-- Associated_Node (Node4-Sem)
-- Present in nodes that can denote an entity: identifiers, character
-- literals, operator symbols, expanded names, operator nodes, and
-- attribute reference nodes (all these nodes have an Entity field).
-- This field is also present in N_Aggregate, N_Selected_Component, and
-- N_Extension_Aggregate nodes. This field is used in generic processing
-- to create links between the generic template and the generic copy.
-- See Sem_Ch12.Get_Associated_Node for full details. Note that this
-- field overlaps Entity, which is fine, since, as explained in Sem_Ch12,
-- the normal function of Entity is not required at the point where the
-- Associated_Node is set. Note also, that in generic templates, this
-- means that the Entity field does not necessarily point to an Entity.
-- Since the back end is expected to ignore generic templates, this is
-- harmless.
-- Atomic_Sync_Required (Flag14-Sem)
-- This flag is set on a node for which atomic synchronization is
-- required for the corresponding reference or modification.
-- At_End_Proc (Node1)
-- This field is present in an N_Handled_Sequence_Of_Statements node.
-- It contains an identifier reference for the cleanup procedure to be
-- called. See description of this node for further details.
-- Backwards_OK (Flag6-Sem)
-- A flag present in the N_Assignment_Statement node. It is used only
-- if the type being assigned is an array type, and is set if analysis
-- determines that it is definitely safe to do the copy backwards, i.e.
-- starting at the highest addressed element. This is the case if either
-- the operands do not overlap, or they may overlap, but if they do,
-- then the left operand is at a higher address than the right operand.
--
-- Note: If neither of the flags Forwards_OK or Backwards_OK is set, it
-- means that the front end could not determine that either direction is
-- definitely safe, and a runtime check may be required if the backend
-- cannot figure it out. If both flags Forwards_OK and Backwards_OK are
-- set, it means that the front end can assure no overlap of operands.
-- Body_To_Inline (Node3-Sem)
-- Present in subprogram declarations. Denotes analyzed but unexpanded
-- body of subprogram, to be used when inlining calls. Present when the
-- subprogram has an Inline pragma and inlining is enabled. If the
-- declaration is completed by a renaming_as_body, and the renamed entity
-- is a subprogram, the Body_To_Inline is the name of that entity, which
-- is used directly in later calls to the original subprogram.
-- Body_Required (Flag13-Sem)
-- A flag that appears in the N_Compilation_Unit node indicating that
-- the corresponding unit requires a body. For the package case, this
-- indicates that a completion is required. In Ada 95, if the flag is not
-- set for the package case, then a body may not be present. In Ada 83,
-- if the flag is not set for the package case, then body is optional.
-- For a subprogram declaration, the flag is set except in the case where
-- a pragma Import or Interface applies, in which case no body is
-- permitted (in Ada 83 or Ada 95).
-- By_Ref (Flag5-Sem)
-- Present in N_Simple_Return_Statement and N_Extended_Return_Statement,
-- this flag is set when the returned expression is already allocated on
-- the secondary stack and thus the result is passed by reference rather
-- than copied another time.
-- Cleanup_Actions (List5-Sem)
-- Present in block statements created for transient blocks, contains
-- additional cleanup actions carried over from the transient scope.
-- Check_Address_Alignment (Flag11-Sem)
-- A flag present in N_Attribute_Definition clause for a 'Address
-- attribute definition. This flag is set if a dynamic check should be
-- generated at the freeze point for the entity to which this address
-- clause applies. The reason that we need this flag is that we want to
-- check for range checks being suppressed at the point where the
-- attribute definition clause is given, rather than testing this at the
-- freeze point.
-- Comes_From_Extended_Return_Statement (Flag18-Sem)
-- Present in N_Simple_Return_Statement nodes. True if this node was
-- constructed as part of the N_Extended_Return_Statement expansion.
-- Compile_Time_Known_Aggregate (Flag18-Sem)
-- Present in N_Aggregate nodes. Set for aggregates which can be fully
-- evaluated at compile time without raising constraint error. Such
-- aggregates can be passed as is the back end without any expansion.
-- See Exp_Aggr for specific conditions under which this flag gets set.
-- Componentwise_Assignment (Flag14-Sem)
-- Present in N_Assignment_Statement nodes. Set for a record assignment
-- where all that needs doing is to expand it into component-by-component
-- assignments. This is used internally for the case of tagged types with
-- rep clauses, where we need to avoid recursion (we don't want to try to
-- generate a call to the primitive operation, because this is the case
-- where we are compiling the primitive operation). Note that when we are
-- expanding component assignments in this case, we never assign the _tag
-- field, but we recursively assign components of the parent type.
-- Condition_Actions (List3-Sem)
-- This field appears in else-if nodes and in the iteration scheme node
-- for while loops. This field is only used during semantic processing to
-- temporarily hold actions inserted into the tree. In the tree passed
-- to gigi, the condition actions field is always set to No_List. For
-- details on how this field is used, see the routine Insert_Actions in
-- package Exp_Util, and also the expansion routines for the relevant
-- nodes.
-- Context_Pending (Flag16-Sem)
-- This field appears in Compilation_Unit nodes, to indicate that the
-- context of the unit is being compiled. Used to detect circularities
-- that are not otherwise detected by the loading mechanism. Such
-- circularities can occur in the presence of limited and non-limited
-- with_clauses that mention the same units.
-- Controlling_Argument (Node1-Sem)
-- This field is set in procedure and function call nodes if the call
-- is a dispatching call (it is Empty for a non-dispatching call). It
-- indicates the source of the call's controlling tag. For procedure
-- calls, the Controlling_Argument is one of the actuals. For function
-- that has a dispatching result, it is an entity in the context of the
-- call that can provide a tag, or else it is the tag of the root type
-- of the class. It can also specify a tag directly rather than being a
-- tagged object. The latter is needed by the implementations of AI-239
-- and AI-260.
-- Conversion_OK (Flag14-Sem)
-- A flag set on type conversion nodes to indicate that the conversion
-- is to be considered as being valid, even though it is the case that
-- the conversion is not valid Ada. This is used for attributes Enum_Rep,
-- Fixed_Value and Integer_Value, for internal conversions done for
-- fixed-point operations, and for certain conversions for calls to
-- initialization procedures. If Conversion_OK is set, then Etype must be
-- set (the analyzer assumes that Etype has been set). For the case of
-- fixed-point operands, it also indicates that the conversion is to be
-- direct conversion of the underlying integer result, with no regard to
-- the small operand.
-- Convert_To_Return_False (Flag13-Sem)
-- Present in N_Raise_Expression nodes that appear in the body of the
-- special predicateM function used to test a predicate in the context
-- of a membership test, where raise expression results in returning a
-- value of False rather than raising an exception.
-- Corresponding_Aspect (Node3-Sem)
-- Present in N_Pragma node. Used to point back to the source aspect from
-- the corresponding pragma. This field is Empty for source pragmas.
-- Corresponding_Body (Node5-Sem)
-- This field is set in subprogram declarations, package declarations,
-- entry declarations of protected types, and in generic units. It points
-- to the defining entity for the corresponding body (NOT the node for
-- the body itself).
-- Corresponding_Formal_Spec (Node3-Sem)
-- This field is set in subprogram renaming declarations, where it points
-- to the defining entity for a formal subprogram in the case where the
-- renaming corresponds to a generic formal subprogram association in an
-- instantiation. The field is Empty if the renaming does not correspond
-- to such a formal association.
-- Corresponding_Generic_Association (Node5-Sem)
-- This field is defined for object declarations and object renaming
-- declarations. It is set for the declarations within an instance that
-- map generic formals to their actuals. If set, the field points to
-- a generic_association which is the original parent of the expression
-- or name appearing in the declaration. This simplifies ASIS queries.
-- Corresponding_Integer_Value (Uint4-Sem)
-- This field is set in real literals of fixed-point types (it is not
-- used for floating-point types). It contains the integer value used
-- to represent the fixed-point value. It is also set on the universal
-- real literals used to represent bounds of fixed-point base types
-- and their first named subtypes.
-- Corresponding_Spec (Node5-Sem)
-- This field is set in subprogram, package, task, and protected body
-- nodes, where it points to the defining entity in the corresponding
-- spec. The attribute is also set in N_With_Clause nodes where it points
-- to the defining entity for the with'ed spec, and in a subprogram
-- renaming declaration when it is a Renaming_As_Body. The field is Empty
-- if there is no corresponding spec, as in the case of a subprogram body
-- that serves as its own spec.
--
-- In Ada 2012, Corresponding_Spec is set on expression functions that
-- complete a subprogram declaration.
-- Corresponding_Spec_Of_Stub (Node2-Sem)
-- This field is present in subprogram, package, task and protected body
-- stubs where it points to the corresponding spec of the stub. Due to
-- clashes in the structure of nodes, we cannot use Corresponding_Spec.
-- Corresponding_Stub (Node3-Sem)
-- This field is present in an N_Subunit node. It holds the node in
-- the parent unit that is the stub declaration for the subunit. It is
-- set when analysis of the stub forces loading of the proper body. If
-- expansion of the proper body creates new declarative nodes, they are
-- inserted at the point of the corresponding_stub.
-- Dcheck_Function (Node5-Sem)
-- This field is present in an N_Variant node, It references the entity
-- for the discriminant checking function for the variant.
-- Default_Expression (Node5-Sem)
-- This field is Empty if there is no default expression. If there is a
-- simple default expression (one with no side effects), then this field
-- simply contains a copy of the Expression field (both point to the tree
-- for the default expression). Default_Expression is used for
-- conformance checking.
-- Default_Storage_Pool (Node3-Sem)
-- This field is present in N_Compilation_Unit_Aux nodes. It is set to a
-- copy of Opt.Default_Pool at the end of the compilation unit. See
-- package Opt for details. This is used for inheriting the
-- Default_Storage_Pool in child units.
-- Discr_Check_Funcs_Built (Flag11-Sem)
-- This flag is present in N_Full_Type_Declaration nodes. It is set when
-- discriminant checking functions are constructed. The purpose is to
-- avoid attempting to set these functions more than once.
-- Do_Accessibility_Check (Flag13-Sem)
-- This flag is set on N_Parameter_Specification nodes to indicate
-- that an accessibility check is required for the parameter. It is
-- not yet decided who takes care of this check (TBD ???).
-- Do_Discriminant_Check (Flag1-Sem)
-- This flag is set on N_Selected_Component nodes to indicate that a
-- discriminant check is required using the discriminant check routine
-- associated with the selector. The actual check is generated by the
-- expander when processing selected components. In the case of
-- Unchecked_Union, the flag is also set, but no discriminant check
-- routine is associated with the selector, and the expander does not
-- generate a check. This flag is also present in assignment statements
-- (and set if the assignment requires a discriminant check), and in type
-- conversion nodes (and set if the conversion requires a check).
-- Do_Division_Check (Flag13-Sem)
-- This flag is set on a division operator (/ mod rem) to indicate
-- that a zero divide check is required. The actual check is dealt
-- with by the backend (all the front end does is to set the flag).
-- Do_Length_Check (Flag4-Sem)
-- This flag is set in an N_Assignment_Statement, N_Op_And, N_Op_Or,
-- N_Op_Xor, or N_Type_Conversion node to indicate that a length check
-- is required. It is not determined who deals with this flag (???).
-- Do_Overflow_Check (Flag17-Sem)
-- This flag is set on an operator where an overflow check is required on
-- the operation. The actual check is dealt with by the backend (all the
-- front end does is to set the flag). The other cases where this flag is
-- used is on a Type_Conversion node and for attribute reference nodes.
-- For a type conversion, it means that the conversion is from one base
-- type to another, and the value may not fit in the target base type.
-- See also the description of Do_Range_Check for this case. The only
-- attribute references which use this flag are Pred and Succ, where it
-- means that the result should be checked for going outside the base
-- range. Note that this flag is not set for modular types. This flag is
-- also set on if and case expression nodes if we are operating in either
-- MINIMIZED or ELIMINATED overflow checking mode (to make sure that we
-- properly process overflow checking for dependent expressions).
-- Do_Range_Check (Flag9-Sem)
-- This flag is set on an expression which appears in a context where a
-- range check is required. The target type is clear from the context.
-- The contexts in which this flag can appear are the following:
-- Right side of an assignment. In this case the target type is
-- taken from the left side of the assignment, which is referenced
-- by the Name of the N_Assignment_Statement node.
-- Subscript expressions in an indexed component. In this case the
-- target type is determined from the type of the array, which is
-- referenced by the Prefix of the N_Indexed_Component node.
-- Argument expression for a parameter, appearing either directly in
-- the Parameter_Associations list of a call or as the Expression of an
-- N_Parameter_Association node that appears in this list. In either
-- case, the check is against the type of the formal. Note that the
-- flag is relevant only in IN and IN OUT parameters, and will be
-- ignored for OUT parameters, where no check is required in the call,
-- and if a check is required on the return, it is generated explicitly
-- with a type conversion.
-- Initialization expression for the initial value in an object
-- declaration. In this case the Do_Range_Check flag is set on
-- the initialization expression, and the check is against the
-- range of the type of the object being declared. This includes the
-- cases of expressions providing default discriminant values, and
-- expressions used to initialize record components.
-- The expression of a type conversion. In this case the range check is
-- against the target type of the conversion. See also the use of
-- Do_Overflow_Check on a type conversion. The distinction is that the
-- overflow check protects against a value that is outside the range of
-- the target base type, whereas a range check checks that the
-- resulting value (which is a value of the base type of the target
-- type), satisfies the range constraint of the target type.
-- Note: when a range check is required in contexts other than those
-- listed above (e.g. in a return statement), an additional type
-- conversion node is introduced to represent the required check.
-- A special case arises for the arguments of the Pred/Succ attributes.
-- Here the range check needed is against First + 1 .. Last (Pred) or
-- First .. Last - 1 (Succ) of the corresponding base type. Essentially
-- these checks are what would be performed within the implicit body of
-- the functions that correspond to these attributes. In these cases,
-- the Do_Range check flag is set on the argument to the attribute
-- function, and the back end must special case the appropriate range
-- to check against.
-- Do_Storage_Check (Flag17-Sem)
-- This flag is set in an N_Allocator node to indicate that a storage
-- check is required for the allocation, or in an N_Subprogram_Body node
-- to indicate that a stack check is required in the subprogram prologue.
-- The N_Allocator case is handled by the routine that expands the call
-- to the runtime routine. The N_Subprogram_Body case is handled by the
-- backend, and all the semantics does is set the flag.
-- Do_Tag_Check (Flag13-Sem)
-- This flag is set on an N_Assignment_Statement, N_Function_Call,
-- N_Procedure_Call_Statement, N_Type_Conversion,
-- N_Simple_Return_Statement, or N_Extended_Return_Statement
-- node to indicate that the tag check can be suppressed. It is not
-- yet decided how this flag is used (TBD ???).
-- Elaborate_Present (Flag4-Sem)
-- This flag is set in the N_With_Clause node to indicate that pragma
-- Elaborate pragma appears for the with'ed units.
-- Elaborate_All_Desirable (Flag9-Sem)
-- This flag is set in the N_With_Clause mode to indicate that the static
-- elaboration processing has determined that an Elaborate_All pragma is
-- desirable for correct elaboration for this unit.
-- Elaborate_All_Present (Flag14-Sem)
-- This flag is set in the N_With_Clause node to indicate that a
-- pragma Elaborate_All pragma appears for the with'ed units.
-- Elaborate_Desirable (Flag11-Sem)
-- This flag is set in the N_With_Clause mode to indicate that the static
-- elaboration processing has determined that an Elaborate pragma is
-- desirable for correct elaboration for this unit.
-- Else_Actions (List3-Sem)
-- This field is present in if expression nodes. During code
-- expansion we use the Insert_Actions procedure (in Exp_Util) to insert
-- actions at an appropriate place in the tree to get elaborated at the
-- right time. For if expressions, we have to be sure that the actions
-- for the Else branch are only elaborated if the condition is False.
-- The Else_Actions field is used as a temporary parking place for
-- these actions. The final tree is always rewritten to eliminate the
-- need for this field, so in the tree passed to Gigi, this field is
-- always set to No_List.
-- Enclosing_Variant (Node2-Sem)
-- This field is present in the N_Variant node and identifies the Node_Id
-- corresponding to the immediately enclosing variant when the variant is
-- nested, and N_Empty otherwise. Set during semantic processing of the
-- variant part of a record type.
-- Entity (Node4-Sem)
-- Appears in all direct names (identifiers, character literals, and
-- operator symbols), as well as expanded names, and attributes that
-- denote entities, such as 'Class. Points to entity for corresponding
-- defining occurrence. Set after name resolution. For identifiers in a
-- WITH list, the corresponding defining occurrence is in a separately
-- compiled file, and Entity must be set by the library Load procedure.
--
-- Note: During name resolution, the value in Entity may be temporarily
-- incorrect (e.g. during overload resolution, Entity is initially set to
-- the first possible correct interpretation, and then later modified if
-- necessary to contain the correct value after resolution).
--
-- Note: This field overlaps Associated_Node, which is used during
-- generic processing (see Sem_Ch12 for details). Note also that in
-- generic templates, this means that the Entity field does not always
-- point to an Entity. Since the back end is expected to ignore generic
-- templates, this is harmless.
--
-- Note: This field also appears in N_Attribute_Definition_Clause nodes.
-- It is used only for stream attributes definition clauses. In this
-- case, it denotes a (possibly dummy) subprogram entity that is declared
-- conceptually at the point of the clause. Thus the visibility of the
-- attribute definition clause (in the sense of 8.3(23) as amended by
-- AI-195) can be checked by testing the visibility of that subprogram.
--
-- Note: Normally the Entity field of an identifier points to the entity
-- for the corresponding defining identifier, and hence the Chars field
-- of an identifier will match the Chars field of the entity. However,
-- there is no requirement that these match, and there are obscure cases
-- of generated code where they do not match.
-- Note: Ada 2012 aspect specifications require additional links between
-- identifiers and various attributes. These attributes can be of
-- arbitrary types, and the entity field of identifiers that denote
-- aspects must be used to store arbitrary expressions for later semantic
-- checks. See section on aspect specifications for details.
-- Entity_Or_Associated_Node (Node4-Sem)
-- A synonym for both Entity and Associated_Node. Used by convention in
-- the code when referencing this field in cases where it is not known
-- whether the field contains an Entity or an Associated_Node.
-- Etype (Node5-Sem)
-- Appears in all expression nodes, all direct names, and all entities.
-- Points to the entity for the related type. Set after type resolution.
-- Normally this is the actual subtype of the expression. However, in
-- certain contexts such as the right side of an assignment, subscripts,
-- arguments to calls, returned value in a function, initial value etc.
-- it is the desired target type. In the event that this is different
-- from the actual type, the Do_Range_Check flag will be set if a range
-- check is required. Note: if the Is_Overloaded flag is set, then Etype
-- points to an essentially arbitrary choice from the possible set of
-- types.
-- Exception_Junk (Flag8-Sem)
-- This flag is set in a various nodes appearing in a statement sequence
-- to indicate that the corresponding node is an artifact of the
-- generated code for exception handling, and should be ignored when
-- analyzing the control flow of the relevant sequence of statements
-- (e.g. to check that it does not end with a bad return statement).
-- Exception_Label (Node5-Sem)
-- Appears in N_Push_xxx_Label nodes. Points to the entity of the label
-- to be used for transforming the corresponding exception into a goto,
-- or contains Empty, if this exception is not to be transformed. Also
-- appears in N_Exception_Handler nodes, where, if set, it indicates
-- that there may be a local raise for the handler, so that expansion
-- to allow a goto is required (and this field contains the label for
-- this goto). See Exp_Ch11.Expand_Local_Exception_Handlers for details.
-- Expansion_Delayed (Flag11-Sem)
-- Set on aggregates and extension aggregates that need a top-down rather
-- than bottom-up expansion. Typically aggregate expansion happens bottom
-- up. For nested aggregates the expansion is delayed until the enclosing
-- aggregate itself is expanded, e.g. in the context of a declaration. To
-- delay it we set this flag. This is done to avoid creating a temporary
-- for each level of a nested aggregates, and also to prevent the
-- premature generation of constraint checks. This is also a requirement
-- if we want to generate the proper attachment to the internal
-- finalization lists (for record with controlled components). Top down
-- expansion of aggregates is also used for in-place array aggregate
-- assignment or initialization. When the full context is known, the
-- target of the assignment or initialization is used to generate the
-- left-hand side of individual assignment to each sub-component.
-- Expression_Copy (Node2-Sem)
-- Present in N_Pragma_Argument_Association nodes. Contains a copy of the
-- original expression. This field is best used to store pragma-dependent
-- modifications performed on the original expression such as replacement
-- of the current type instance or substitutions of primitives.
-- First_Inlined_Subprogram (Node3-Sem)
-- Present in the N_Compilation_Unit node for the main program. Points
-- to a chain of entities for subprograms that are to be inlined. The
-- Next_Inlined_Subprogram field of these entities is used as a link
-- pointer with Empty marking the end of the list. This field is Empty
-- if there are no inlined subprograms or inlining is not active.
-- First_Named_Actual (Node4-Sem)
-- Present in procedure call statement and function call nodes, and also
-- in Intrinsic nodes. Set during semantic analysis to point to the first
-- named parameter where parameters are ordered by declaration order (as
-- opposed to the actual order in the call which may be different due to
-- named associations). Note: this field points to the explicit actual
-- parameter itself, not the N_Parameter_Association node (its parent).
-- First_Real_Statement (Node2-Sem)
-- Present in N_Handled_Sequence_Of_Statements node. Normally set to
-- Empty. Used only when declarations are moved into the statement part
-- of a construct as a result of wrapping an AT END handler that is
-- required to cover the declarations. In this case, this field is used
-- to remember the location in the statements list of the first real
-- statement, i.e. the statement that used to be first in the statement
-- list before the declarations were prepended.
-- First_Subtype_Link (Node5-Sem)
-- Present in N_Freeze_Entity node for an anonymous base type that is
-- implicitly created by the declaration of a first subtype. It points
-- to the entity for the first subtype.
-- Float_Truncate (Flag11-Sem)
-- A flag present in type conversion nodes. This is used for float to
-- integer conversions where truncation is required rather than rounding.
-- Forwards_OK (Flag5-Sem)
-- A flag present in the N_Assignment_Statement node. It is used only
-- if the type being assigned is an array type, and is set if analysis
-- determines that it is definitely safe to do the copy forwards, i.e.
-- starting at the lowest addressed element. This is the case if either
-- the operands do not overlap, or they may overlap, but if they do,
-- then the left operand is at a lower address than the right operand.
--
-- Note: If neither of the flags Forwards_OK or Backwards_OK is set, it
-- means that the front end could not determine that either direction is
-- definitely safe, and a runtime check may be required if the backend
-- cannot figure it out. If both flags Forwards_OK and Backwards_OK are
-- set, it means that the front end can assure no overlap of operands.
-- From_Aspect_Specification (Flag13-Sem)
-- Processing of aspect specifications typically results in insertion in
-- the tree of corresponding pragma or attribute definition clause nodes.
-- These generated nodes have the From_Aspect_Specification flag set to
-- indicate that they came from aspect specifications originally.
-- From_At_End (Flag4-Sem)
-- This flag is set on an N_Raise_Statement node if it corresponds to
-- the reraise statement generated as the last statement of an AT END
-- handler when SJLJ exception handling is active. It is used to stop
-- a bogus violation of restriction (No_Exception_Propagation), bogus
-- because if the restriction is set, the reraise is not generated.
-- From_At_Mod (Flag4-Sem)
-- This flag is set on the attribute definition clause node that is
-- generated by a transformation of an at mod phrase in a record
-- representation clause. This is used to give slightly different (Ada 83
-- compatible) semantics to such a clause, namely it is used to specify a
-- minimum acceptable alignment for the base type and all subtypes. In
-- Ada 95 terms, the actual alignment of the base type and all subtypes
-- must be a multiple of the given value, and the representation clause
-- is considered to be type specific instead of subtype specific.
-- From_Conditional_Expression (Flag1-Sem)
-- This flag is set on if and case statements generated by the expansion
-- of if and case expressions respectively. The flag is used to suppress
-- any finalization of controlled objects found within these statements.
-- From_Default (Flag6-Sem)
-- This flag is set on the subprogram renaming declaration created in an
-- instance for a formal subprogram, when the formal is declared with a
-- box, and there is no explicit actual. If the flag is present, the
-- declaration is treated as an implicit reference to the formal in the
-- ali file.
-- Generalized_Indexing (Node4-Sem)
-- Present in N_Indexed_Component nodes. Set for Indexed_Component nodes
-- that are Ada 2012 container indexing operations. The value of the
-- attribute is a function call (possibly dereferenced) that corresponds
-- to the proper expansion of the source indexing operation. Before
-- expansion, the source node is rewritten as the resolved generalized
-- indexing. In ASIS mode, the expansion does not take place, so that
-- the source is preserved and properly annotated with types.
-- Generic_Parent (Node5-Sem)
-- Generic_Parent is defined on declaration nodes that are instances. The
-- value of Generic_Parent is the generic entity from which the instance
-- is obtained. Generic_Parent is also defined for the renaming
-- declarations and object declarations created for the actuals in an
-- instantiation. The generic parent of such a declaration is the
-- corresponding generic association in the Instantiation node.
-- Generic_Parent_Type (Node4-Sem)
-- Generic_Parent_Type is defined on Subtype_Declaration nodes for the
-- actuals of formal private and derived types. Within the instance, the
-- operations on the actual are those inherited from the parent. For a
-- formal private type, the parent type is the generic type itself. The
-- Generic_Parent_Type is also used in an instance to determine whether a
-- private operation overrides an inherited one.
-- Handler_List_Entry (Node2-Sem)
-- This field is present in N_Object_Declaration nodes. It is set only
-- for the Handler_Record entry generated for an exception in zero cost
-- exception handling mode. It references the corresponding item in the
-- handler list, and is used to delete this entry if the corresponding
-- handler is deleted during optimization. For further details on why
-- this is required, see Exp_Ch11.Remove_Handler_Entries.
-- Has_Dereference_Action (Flag13-Sem)
-- This flag is present in N_Explicit_Dereference nodes. It is set to
-- indicate that the expansion has aready produced a call to primitive
-- Dereference of a System.Checked_Pools.Checked_Pool implementation.
-- Such dereference actions are produced for debugging purposes.
-- Has_Dynamic_Length_Check (Flag10-Sem)
-- This flag is present in all expression nodes. It is set to indicate
-- that one of the routines in unit Checks has generated a length check
-- action which has been inserted at the flagged node. This is used to
-- avoid the generation of duplicate checks.
-- Has_Dynamic_Range_Check (Flag12-Sem)
-- This flag is present in N_Subtype_Declaration nodes and on all
-- expression nodes. It is set to indicate that one of the routines in
-- unit Checks has generated a range check action which has been inserted
-- at the flagged node. This is used to avoid the generation of duplicate
-- checks. Why does this occur on N_Subtype_Declaration nodes, what does
-- it mean in that context???
-- Has_Local_Raise (Flag8-Sem)
-- Present in exception handler nodes. Set if the handler can be entered
-- via a local raise that gets transformed to a goto statement. This will
-- always be set if Local_Raise_Statements is non-empty, but can also be
-- set as a result of generation of N_Raise_xxx nodes, or flags set in
-- nodes requiring generation of back end checks.
-- Has_No_Elaboration_Code (Flag17-Sem)
-- A flag that appears in the N_Compilation_Unit node to indicate whether
-- or not elaboration code is present for this unit. It is initially set
-- true for subprogram specs and bodies and for all generic units and
-- false for non-generic package specs and bodies. Gigi may set the flag
-- in the non-generic package case if it determines that no elaboration
-- code is generated. Note that this flag is not related to the
-- Is_Preelaborated status, there can be preelaborated packages that
-- generate elaboration code, and non-preelaborated packages which do
-- not generate elaboration code.
-- Has_Pragma_Suppress_All (Flag14-Sem)
-- This flag is set in an N_Compilation_Unit node if the Suppress_All
-- pragma appears anywhere in the unit. This accommodates the rather
-- strange placement rules of other compilers (DEC permits it at the
-- end of a unit, and Rational allows it as a program unit pragma). We
-- allow it anywhere at all, and consider it equivalent to a pragma
-- Suppress (All_Checks) appearing at the start of the configuration
-- pragmas for the unit.
-- Has_Private_View (Flag11-Sem)
-- A flag present in generic nodes that have an entity, to indicate that
-- the node has a private type. Used to exchange private and full
-- declarations if the visibility at instantiation is different from the
-- visibility at generic definition.
-- Has_Relative_Deadline_Pragma (Flag9-Sem)
-- A flag present in N_Subprogram_Body and N_Task_Definition nodes to
-- flag the presence of a pragma Relative_Deadline.
-- Has_Self_Reference (Flag13-Sem)
-- Present in N_Aggregate and N_Extension_Aggregate. Indicates that one
-- of the expressions contains an access attribute reference to the
-- enclosing type. Such a self-reference can only appear in default-
-- initialized aggregate for a record type.
-- Has_SP_Choice (Flag15-Sem)
-- Present in all nodes containing a Discrete_Choices field (N_Variant,
-- N_Case_Expression_Alternative, N_Case_Statement_Alternative). Set to
-- True if the Discrete_Choices list has at least one occurrence of a
-- statically predicated subtype.
-- Has_Storage_Size_Pragma (Flag5-Sem)
-- A flag present in an N_Task_Definition node to flag the presence of a
-- Storage_Size pragma.
-- Has_Target_Names (Flag8-Sem)
-- Present in assignment statements. Indicates that the RHS contains
-- target names (see AI12-0125-3) and must be expanded accordingly.
-- Has_Wide_Character (Flag11-Sem)
-- Present in string literals, set if any wide character (i.e. character
-- code outside the Character range but within Wide_Character range)
-- appears in the string. Used to implement pragma preference rules.
-- Has_Wide_Wide_Character (Flag13-Sem)
-- Present in string literals, set if any wide character (i.e. character
-- code outside the Wide_Character range) appears in the string. Used to
-- implement pragma preference rules.
-- Header_Size_Added (Flag11-Sem)
-- Present in N_Attribute_Reference nodes, set only for attribute
-- Max_Size_In_Storage_Elements. The flag indicates that the size of the
-- hidden list header used by the runtime finalization support has been
-- added to the size of the prefix. The flag also prevents the infinite
-- expansion of the same attribute in the said context.
-- Hidden_By_Use_Clause (Elist4-Sem)
-- An entity list present in use clauses that appear within
-- instantiations. For the resolution of local entities, entities
-- introduced by these use clauses have priority over global ones, and
-- outer entities must be explicitly hidden/restored on exit.
-- Implicit_With (Flag16-Sem)
-- This flag is set in the N_With_Clause node that is implicitly
-- generated for runtime units that are loaded by the expander or in
-- GNATprove mode, and also for package System, if it is loaded
-- implicitly by a use of the 'Address or 'Tag attribute.
-- ??? There are other implicit with clauses as well.
-- Implicit_With_From_Instantiation (Flag12-Sem)
-- Set in N_With_Clause nodes from generic instantiations.
-- Import_Interface_Present (Flag16-Sem)
-- This flag is set in an Interface or Import pragma if a matching
-- pragma of the other kind is also present. This is used to avoid
-- generating some unwanted error messages.
-- Includes_Infinities (Flag11-Sem)
-- This flag is present in N_Range nodes. It is set for the range of
-- unconstrained float types defined in Standard, which include not only
-- the given range of values, but also legitimately can include infinite
-- values. This flag is false for any float type for which an explicit
-- range is given by the programmer, even if that range is identical to
-- the range for Float.
-- Incomplete_View (Node2-Sem)
-- Present in full type declarations that are completions of incomplete
-- type declarations. Denotes the corresponding incomplete type
-- declaration. Used to simplify the retrieval of primitive operations
-- that may be declared between the partial and the full view of an
-- untagged type.
-- Inherited_Discriminant (Flag13-Sem)
-- This flag is present in N_Component_Association nodes. It indicates
-- that a given component association in an extension aggregate is the
-- value obtained from a constraint on an ancestor. Used to prevent
-- double expansion when the aggregate has expansion delayed.
-- Instance_Spec (Node5-Sem)
-- This field is present in generic instantiation nodes, and also in
-- formal package declaration nodes (formal package declarations are
-- treated in a manner very similar to package instantiations). It points
-- to the node for the spec of the instance, inserted as part of the
-- semantic processing for instantiations in Sem_Ch12.
-- Is_Abort_Block (Flag4-Sem)
-- Present in N_Block_Statement nodes. True if the block protects a list
-- of statements with an Abort_Defer / Abort_Undefer_Direct pair.
-- Is_Accessibility_Actual (Flag13-Sem)
-- Present in N_Parameter_Association nodes. True if the parameter is
-- an extra actual that carries the accessibility level of the actual
-- for an access parameter, in a function that dispatches on result and
-- is called in a dispatching context. Used to prevent a formal/actual
-- mismatch when the call is rewritten as a dispatching call.
-- Is_Analyzed_Pragma (Flag5-Sem)
-- Present in N_Pragma nodes. Set for delayed pragmas that require a two
-- step analysis. The initial step is peformed by routine Analyze_Pragma
-- and verifies the overall legality of the pragma. The second step takes
-- place in the various Analyze_xxx_In_Decl_Part routines which perform
-- full analysis. The flag prevents the reanalysis of a delayed pragma.
-- Is_Expanded_Contract (Flag1-Sem)
-- Present in N_Contract nodes. Set if the contract has already undergone
-- expansion activities.
-- Is_Asynchronous_Call_Block (Flag7-Sem)
-- A flag set in a Block_Statement node to indicate that it is the
-- expansion of an asynchronous entry call. Such a block needs cleanup
-- handler to assure that the call is cancelled.
-- Is_Boolean_Aspect (Flag16-Sem)
-- Present in N_Aspect_Specification node. Set if the aspect is for a
-- boolean aspect (i.e. Aspect_Id is in Boolean_Aspect subtype).
-- Is_Checked (Flag11-Sem)
-- Present in N_Aspect_Specification and N_Pragma nodes. Set for an
-- assertion aspect or pragma, or check pragma for an assertion, that
-- is to be checked at run time. If either Is_Checked or Is_Ignored
-- is set (they cannot both be set), then this means that the status of
-- the pragma has been checked at the appropriate point and should not
-- be further modified (in some cases these flags are copied when a
-- pragma is rewritten).
-- Is_Checked_Ghost_Pragma (Flag3-Sem)
-- This flag is present in N_Pragma nodes. It is set when the pragma is
-- related to a checked Ghost entity or encloses a checked Ghost entity.
-- This flag has no relation to Is_Checked.
-- Is_Component_Left_Opnd (Flag13-Sem)
-- Is_Component_Right_Opnd (Flag14-Sem)
-- Present in concatenation nodes, to indicate that the corresponding
-- operand is of the component type of the result. Used in resolving
-- concatenation nodes in instances.
-- Is_Controlling_Actual (Flag16-Sem)
-- This flag is set on an expression that is a controlling argument in
-- a dispatching call. It is off in all other cases. See Sem_Disp for
-- details of its use.
-- Is_Delayed_Aspect (Flag14-Sem)
-- Present in N_Pragma and N_Attribute_Definition_Clause nodes which
-- come from aspect specifications, where the evaluation of the aspect
-- must be delayed to the freeze point. This flag is also set True in
-- the corresponding N_Aspect_Specification node.
-- Is_Disabled (Flag15-Sem)
-- A flag set in an N_Aspect_Specification or N_Pragma node if there was
-- a Check_Policy or Assertion_Policy (or in the case of a Debug_Pragma)
-- a Debug_Policy pragma that resulted in totally disabling the flagged
-- aspect or policy as a result of using the GNAT-defined policy DISABLE.
-- If this flag is set, the aspect or policy is not analyzed for semantic
-- correctness, so any expressions etc will not be marked as analyzed.
-- Is_Dynamic_Coextension (Flag18-Sem)
-- Present in allocator nodes, to indicate that this is an allocator
-- for an access discriminant of a dynamically allocated object. The
-- coextension must be deallocated and finalized at the same time as
-- the enclosing object.
-- Is_Entry_Barrier_Function (Flag8-Sem)
-- This flag is set on N_Subprogram_Declaration and N_Subprogram_Body
-- nodes which emulate the barrier function of a protected entry body.
-- The flag is used when checking for incorrect use of Current_Task.
-- Is_Expanded_Build_In_Place_Call (Flag11-Sem)
-- This flag is set in an N_Function_Call node to indicate that the extra
-- actuals to support a build-in-place style of call have been added to
-- the call.
-- Is_Finalization_Wrapper (Flag9-Sem)
-- This flag is present in N_Block_Statement nodes. It is set when the
-- block acts as a wrapper of a handled construct which has controlled
-- objects. The wrapper prevents interference between exception handlers
-- and At_End handlers.
-- Is_Generic_Contract_Pragma (Flag2-Sem)
-- This flag is present in N_Pragma nodes. It is set when the pragma is
-- a source construct, applies to a generic unit or its body and denotes
-- one of the following contract-related annotations:
-- Abstract_State
-- Contract_Cases
-- Depends
-- Extensions_Visible
-- Global
-- Initial_Condition
-- Initializes
-- Post
-- Post_Class
-- Postcondition
-- Pre
-- Pre_Class
-- Precondition
-- Refined_Depends
-- Refined_Global
-- Refined_Post
-- Refined_State
-- Test_Case
-- Is_Ignored (Flag9-Sem)
-- A flag set in an N_Aspect_Specification or N_Pragma node if there was
-- a Check_Policy or Assertion_Policy (or in the case of a Debug_Pragma)
-- a Debug_Policy pragma that specified a policy of IGNORE, DISABLE, or
-- OFF, for the pragma/aspect. If there was a Policy pragma specifying
-- a Policy of ON or CHECK, then this flag is reset. If no Policy pragma
-- gives a policy for the aspect or pragma, then there are two cases. For
-- an assertion aspect or pragma (one of the assertion kinds allowed in
-- an Assertion_Policy pragma), then Is_Ignored is set if assertions are
-- ignored because of the absence of a -gnata switch. For any other
-- aspects or pragmas, the flag is off. If this flag is set, the
-- aspect/pragma is fully analyzed and checked for other syntactic
-- and semantic errors, but it does not have any semantic effect.
-- Is_Ignored_Ghost_Pragma (Flag8-Sem)
-- This flag is present in N_Pragma nodes. It is set when the pragma is
-- related to an ignored Ghost entity or encloses ignored Ghost entity.
-- This flag has no relation to Is_Ignored.
-- Is_In_Discriminant_Check (Flag11-Sem)
-- This flag is present in a selected component, and is used to indicate
-- that the reference occurs within a discriminant check. The
-- significance is that optimizations based on assuming that the
-- discriminant check has a correct value cannot be performed in this
-- case (or the discriminant check may be optimized away).
-- Is_Inherited_Pragma (Flag4-Sem)
-- This flag is set in an N_Pragma node that appears in a N_Contract node
-- to indicate that the pragma has been inherited from a parent context.
-- Is_Machine_Number (Flag11-Sem)
-- This flag is set in an N_Real_Literal node to indicate that the value
-- is a machine number. This avoids some unnecessary cases of converting
-- real literals to machine numbers.
-- Is_Null_Loop (Flag16-Sem)
-- This flag is set in an N_Loop_Statement node if the corresponding loop
-- can be determined to be null at compile time. This is used to remove
-- the loop entirely at expansion time.
-- Is_Overloaded (Flag5-Sem)
-- A flag present in all expression nodes. Used temporarily during
-- overloading determination. The setting of this flag is not relevant
-- once overloading analysis is complete.
-- Is_Power_Of_2_For_Shift (Flag13-Sem)
-- A flag present only in N_Op_Expon nodes. It is set when the
-- exponentiation is of the form 2 ** N, where the type of N is an
-- unsigned integral subtype whose size does not exceed the size of
-- Standard_Integer (i.e. a type that can be safely converted to
-- Natural), and the exponentiation appears as the right operand of an
-- integer multiplication or an integer division where the dividend is
-- unsigned. It is also required that overflow checking is off for both
-- the exponentiation and the multiply/divide node. If this set of
-- conditions holds, and the flag is set, then the division or
-- multiplication can be (and is) converted to a shift.
-- Is_Prefixed_Call (Flag17-Sem)
-- This flag is set in a selected component within a generic unit, if
-- it resolves to a prefixed call to a primitive operation. The flag
-- is used to prevent accidental overloadings in an instance, when a
-- primitive operation and a private record component may be homographs.
-- Is_Protected_Subprogram_Body (Flag7-Sem)
-- A flag set in a Subprogram_Body block to indicate that it is the
-- implementation of a protected subprogram. Such a body needs cleanup
-- handler to make sure that the associated protected object is unlocked
-- when the subprogram completes.
-- Is_Qualified_Universal_Literal (Flag4-Sem)
-- Present in N_Qualified_Expression nodes. Set when the qualification is
-- converting a universal literal to a specific type. Such qualifiers aid
-- the resolution of accidental overloading of binary or unary operators
-- which may occur in instances.
-- Is_Static_Coextension (Flag14-Sem)
-- Present in N_Allocator nodes. Set if the allocator is a coextension
-- of an object allocated on the stack rather than the heap.
-- Is_Static_Expression (Flag6-Sem)
-- Indicates that an expression is a static expression according to the
-- rules in (RM 4.9). Note that it is possible for this flag to be set
-- when Raises_Constraint_Error is also set. In practice almost all cases
-- where a static expression is required do not allow an expression which
-- raises Constraint_Error, so almost always, callers should call the
-- Is_Ok_Static_Expression routine instead of testing this flag. See
-- spec of package Sem_Eval for full details on the use of this flag.
-- Is_Subprogram_Descriptor (Flag16-Sem)
-- Present in N_Object_Declaration, and set only for the object
-- declaration generated for a subprogram descriptor in fast exception
-- mode. See Exp_Ch11 for details of use.
-- Is_Task_Allocation_Block (Flag6-Sem)
-- A flag set in a Block_Statement node to indicate that it is the
-- expansion of a task allocator, or the allocator of an object
-- containing tasks. Such a block requires a cleanup handler to call
-- Expunge_Unactivated_Tasks to complete any tasks that have been
-- allocated but not activated when the allocator completes abnormally.
-- Is_Task_Body_Procedure (Flag1-Sem)
-- This flag is set on N_Subprogram_Declaration and N_Subprogram_Body
-- nodes which emulate the body of a task unit.
-- Is_Task_Master (Flag5-Sem)
-- A flag set in a Subprogram_Body, Block_Statement or Task_Body node to
-- indicate that the construct is a task master (i.e. has declared tasks
-- or declares an access to a task type).
-- Itype (Node1-Sem)
-- Used in N_Itype_Reference node to reference an itype for which it is
-- important to ensure that it is defined. See description of this node
-- for further details.
-- Kill_Range_Check (Flag11-Sem)
-- Used in an N_Unchecked_Type_Conversion node to indicate that the
-- result should not be subjected to range checks. This is used for the
-- implementation of Normalize_Scalars.
-- Label_Construct (Node2-Sem)
-- Used in an N_Implicit_Label_Declaration node. Refers to an N_Label,
-- N_Block_Statement or N_Loop_Statement node to which the label
-- declaration applies. This attribute is used both in the compiler and
-- in the implementation of ASIS queries. The field is left empty for the
-- special labels generated as part of expanding raise statements with a
-- local exception handler.
-- Library_Unit (Node4-Sem)
-- In a stub node, Library_Unit points to the compilation unit node of
-- the corresponding subunit.
--
-- In a with clause node, Library_Unit points to the spec of the with'ed
-- unit.
--
-- In a compilation unit node, the usage depends on the unit type:
--
-- For a library unit body, Library_Unit points to the compilation unit
-- node of the corresponding spec, unless it's a subprogram body with
-- Acts_As_Spec set, in which case it points to itself.
--
-- For a spec, Library_Unit points to the compilation unit node of the
-- corresponding body, if present. The body will be present if the spec
-- is or contains generics that we needed to instantiate. Similarly, the
-- body will be present if we needed it for inlining purposes. Thus, if
-- we have a spec/body pair, both of which are present, they point to
-- each other via Library_Unit.
--
-- For a subunit, Library_Unit points to the compilation unit node of
-- the parent body.
-- ??? not (always) true, in (at least some, maybe all?) cases it points
-- to the corresponding spec for the parent body.
--
-- Note that this field is not used to hold the parent pointer for child
-- unit (which might in any case need to use it for some other purpose as
-- described above). Instead for a child unit, implicit with's are
-- generated for all parents.
-- Local_Raise_Statements (Elist1)
-- This field is present in exception handler nodes. It is set to
-- No_Elist in the normal case. If there is at least one raise statement
-- which can potentially be handled as a local raise, then this field
-- points to a list of raise nodes, which are calls to a routine to raise
-- an exception. These are raise nodes which can be optimized into gotos
-- if the handler turns out to meet the conditions which permit this
-- transformation. Note that this does NOT include instances of the
-- N_Raise_xxx_Error nodes since the transformation of these nodes is
-- handled by the back end (using the N_Push/N_Pop mechanism).
-- Loop_Actions (List2-Sem)
-- A list present in Component_Association nodes in array aggregates.
-- Used to collect actions that must be executed within the loop because
-- they may need to be evaluated anew each time through.
-- Limited_View_Installed (Flag18-Sem)
-- Present in With_Clauses and in package specifications. If set on
-- with_clause, it indicates that this clause has created the current
-- limited view of the designated package. On a package specification, it
-- indicates that the limited view has already been created because the
-- package is mentioned in a limited_with_clause in the closure of the
-- unit being compiled.
-- Local_Raise_Not_OK (Flag7-Sem)
-- Present in N_Exception_Handler nodes. Set if the handler contains
-- a construct (reraise statement, or call to subprogram in package
-- GNAT.Current_Exception) that makes the handler unsuitable as a target
-- for a local raise (one that could otherwise be converted to a goto).
-- Must_Be_Byte_Aligned (Flag14-Sem)
-- This flag is present in N_Attribute_Reference nodes. It can be set
-- only for the Address and Unrestricted_Access attributes. If set it
-- means that the object for which the address/access is given must be on
-- a byte (more accurately a storage unit) boundary. If necessary, a copy
-- of the object is to be made before taking the address (this copy is in
-- the current scope on the stack frame). This is used for certain cases
-- of code generated by the expander that passes parameters by address.
--
-- The reason the copy is not made by the front end is that the back end
-- has more information about type layout and may be able to (but is not
-- guaranteed to) prevent making unnecessary copies.
-- Must_Not_Freeze (Flag8-Sem)
-- A flag present in all expression nodes. Normally expressions cause
-- freezing as described in the RM. If this flag is set, then this is
-- inhibited. This is used by the analyzer and expander to label nodes
-- that are created by semantic analysis or expansion and which must not
-- cause freezing even though they normally would. This flag is also
-- present in an N_Subtype_Indication node, since we also use these in
-- calls to Freeze_Expression.
-- Next_Entity (Node2-Sem)
-- Present in defining identifiers, defining character literals and
-- defining operator symbols (i.e. in all entities). The entities of a
-- scope are chained, and this field is used as the forward pointer for
-- this list. See Einfo for further details.
-- Next_Exit_Statement (Node3-Sem)
-- Present in N_Exit_Statement nodes. The exit statements for a loop are
-- chained (in reverse order of appearance) from the First_Exit_Statement
-- field of the E_Loop entity for the loop. Next_Exit_Statement points to
-- the next entry on this chain (Empty = end of list).
-- Next_Implicit_With (Node3-Sem)
-- Present in N_With_Clause. Part of a chain of with_clauses generated
-- in rtsfind to indicate implicit dependencies on predefined units. Used
-- to prevent multiple with_clauses for the same unit in a given context.
-- A postorder traversal of the tree whose nodes are units and whose
-- links are with_clauses defines the order in which CodePeer must
-- examine a compiled unit and its full context. This ordering ensures
-- that any subprogram call is examined after the subprogram declaration
-- has been seen.
-- Next_Named_Actual (Node4-Sem)
-- Present in parameter association nodes. Set during semantic analysis
-- to point to the next named parameter, where parameters are ordered by
-- declaration order (as opposed to the actual order in the call, which
-- may be different due to named associations). Not that this field
-- points to the explicit actual parameter itself, not to the
-- N_Parameter_Association node (its parent).
-- Next_Pragma (Node1-Sem)
-- Present in N_Pragma nodes. Used to create a linked list of pragma
-- nodes. Currently used for two purposes:
--
-- Create a list of linked Check_Policy pragmas. The head of this list
-- is stored in Opt.Check_Policy_List (which has further details).
--
-- Used by processing for Pre/Postcondition pragmas to store a list of
-- pragmas associated with the spec of a subprogram (see Sem_Prag for
-- details).
--
-- Used by processing for pragma SPARK_Mode to store multiple pragmas
-- the apply to the same construct. These are visible/private mode for
-- a package spec and declarative/statement mode for package body.
-- Next_Rep_Item (Node5-Sem)
-- Present in pragma nodes, attribute definition nodes, enumeration rep
-- clauses, record rep clauses, aspect specification nodes. Used to link
-- representation items that apply to an entity. See full description of
-- First_Rep_Item field in Einfo for further details.
-- Next_Use_Clause (Node3-Sem)
-- While use clauses are active during semantic processing, they are
-- chained from the scope stack entry, using Next_Use_Clause as a link
-- pointer, with Empty marking the end of the list. The head pointer is
-- in the scope stack entry (First_Use_Clause). At the end of semantic
-- processing (i.e. when Gigi sees the tree, the contents of this field
-- is undefined and should not be read).
-- No_Ctrl_Actions (Flag7-Sem)
-- Present in N_Assignment_Statement to indicate that no Finalize nor
-- Adjust should take place on this assignment even though the RHS is
-- controlled. Also indicates that the primitive _assign should not be
-- used for a tagged assignment. This is used in init procs and aggregate
-- expansions where the generated assignments are initializations, not
-- real assignments.
-- No_Elaboration_Check (Flag14-Sem)
-- Present in N_Function_Call and N_Procedure_Call_Statement. Indicates
-- that no elaboration check is needed on the call, because it appears in
-- the context of a local Suppress pragma. This is used on calls within
-- task bodies, where the actual elaboration checks are applied after
-- analysis, when the local scope stack is not present.
-- No_Entities_Ref_In_Spec (Flag8-Sem)
-- Present in N_With_Clause nodes. Set if the with clause is on the
-- package or subprogram spec where the main unit is the corresponding
-- body, and no entities of the with'ed unit are referenced by the spec
-- (an entity may still be referenced in the body, so this flag is used
-- to generate the proper message (see Sem_Util.Check_Unused_Withs for
-- full details).
-- No_Initialization (Flag13-Sem)
-- Present in N_Object_Declaration and N_Allocator to indicate that the
-- object must not be initialized (by Initialize or call to an init
-- proc). This is needed for controlled aggregates. When the Object
-- declaration has an expression, this flag means that this expression
-- should not be taken into account (needed for in place initialization
-- with aggregates, and for object with an address clause, which are
-- initialized with an assignment at freeze time).
-- No_Minimize_Eliminate (Flag17-Sem)
-- This flag is present in membership operator nodes (N_In/N_Not_In).
-- It is used to indicate that processing for extended overflow checking
-- modes is not required (this is used to prevent infinite recursion).
-- No_Side_Effect_Removal (Flag1-Sem)
-- Present in N_Function_Call nodes. Set when a function call does not
-- require side effect removal. This attribute suppresses the generation
-- of a temporary to capture the result of the function which eventually
-- replaces the function call.
-- No_Truncation (Flag17-Sem)
-- Present in N_Unchecked_Type_Conversion node. This flag has an effect
-- only if the RM_Size of the source is greater than the RM_Size of the
-- target for scalar operands. Normally in such a case we truncate some
-- higher order bits of the source, and then sign/zero extend the result
-- to form the output value. But if this flag is set, then we do not do
-- any truncation, so for example, if an 8 bit input is converted to 5
-- bit result which is in fact stored in 8 bits, then the high order
-- three bits of the target result will be copied from the source. This
-- is used for properly setting out of range values for use by pragmas
-- Initialize_Scalars and Normalize_Scalars.
-- Non_Aliased_Prefix (Flag18-Sem)
-- Present in N_Attribute_Reference nodes. Set only for the case of an
-- Unrestricted_Access reference whose prefix is non-aliased, which is
-- the case that is permitted for Unrestricted_Access except when the
-- expected type is a thin pointer to unconstrained array. This flag is
-- to assist in detecting this illegal use of Unrestricted_Access.
-- Null_Excluding_Subtype (Flag16)
-- Present in N_Access_To_Object_Definition. Indicates that the subtype
-- indication carries a null-exclusion indicator, which is distinct from
-- the null-exclusion indicator that may precede the access keyword.
-- Original_Discriminant (Node2-Sem)
-- Present in identifiers. Used in references to discriminants that
-- appear in generic units. Because the names of the discriminants may be
-- different in an instance, we use this field to recover the position of
-- the discriminant in the original type, and replace it with the
-- discriminant at the same position in the instantiated type.
-- Original_Entity (Node2-Sem)
-- Present in numeric literals. Used to denote the named number that has
-- been constant-folded into the given literal. If literal is from
-- source, or the result of some other constant-folding operation, then
-- Original_Entity is empty. This field is needed to handle properly
-- named numbers in generic units, where the Associated_Node field
-- interferes with the Entity field, making it impossible to preserve the
-- original entity at the point of instantiation (ASIS problem).
-- Others_Discrete_Choices (List1-Sem)
-- When a case statement or variant is analyzed, the semantic checks
-- determine the actual list of choices that correspond to an others
-- choice. This list is materialized for later use by the expander and
-- the Others_Discrete_Choices field of an N_Others_Choice node points to
-- this materialized list of choices, which is in standard format for a
-- list of discrete choices, except that of course it cannot contain an
-- N_Others_Choice entry.
-- Parent_Spec (Node4-Sem)
-- For a library unit that is a child unit spec (package or subprogram
-- declaration, generic declaration or instantiation, or library level
-- rename) this field points to the compilation unit node for the parent
-- package specification. This field is Empty for library bodies (the
-- parent spec in this case can be found from the corresponding spec).
-- Premature_Use (Node5-Sem)
-- Present in N_Incomplete_Type_Declaration node. Used for improved
-- error diagnostics: if there is a premature usage of an incomplete
-- type, a subsequently generated error message indicates the position
-- of its full declaration.
-- Present_Expr (Uint3-Sem)
-- Present in an N_Variant node. This has a meaningful value only after
-- Gigi has back annotated the tree with representation information. At
-- this point, it contains a reference to a gcc expression that depends
-- on the values of one or more discriminants. Give a set of discriminant
-- values, this expression evaluates to False (zero) if variant is not
-- present, and True (non-zero) if it is present. See unit Repinfo for
-- further details on gigi back annotation. This field is used during
-- ASIS processing (data decomposition annex) to determine if a field is
-- present or not.
-- Print_In_Hex (Flag13-Sem)
-- Set on an N_Integer_Literal node to indicate that the value should be
-- printed in hexadecimal in the sprint listing. Has no effect on
-- legality or semantics of program, only on the displayed output. This
-- is used to clarify output from the packed array cases.
-- Procedure_To_Call (Node2-Sem)
-- Present in N_Allocator, N_Free_Statement, N_Simple_Return_Statement,
-- and N_Extended_Return_Statement nodes. References the entity for the
-- declaration of the procedure to be called to accomplish the required
-- operation (i.e. for the Allocate procedure in the case of N_Allocator
-- and N_Simple_Return_Statement and N_Extended_Return_Statement (for
-- allocating the return value), and for the Deallocate procedure in the
-- case of N_Free_Statement.
-- Raises_Constraint_Error (Flag7-Sem)
-- Set on an expression whose evaluation will definitely fail constraint
-- error check. In the case of static expressions, this flag must be set
-- accurately (and if it is set, the expression is typically illegal
-- unless it appears as a non-elaborated branch of a short-circuit form).
-- For a non-static expression, this flag may be set whenever an
-- expression (e.g. an aggregate) is known to raise constraint error. If
-- set, the expression definitely will raise CE if elaborated at runtime.
-- If not set, the expression may or may not raise CE. In other words, on
-- static expressions, the flag is set accurately, on non-static
-- expressions it is set conservatively.
-- Redundant_Use (Flag13-Sem)
-- Present in nodes that can appear as an operand in a use clause or use
-- type clause (identifiers, expanded names, attribute references). Set
-- to indicate that a use is redundant (and therefore need not be undone
-- on scope exit).
-- Renaming_Exception (Node2-Sem)
-- Present in N_Exception_Declaration node. Used to point back to the
-- exception renaming for an exception declared within a subprogram.
-- What happens is that an exception declared in a subprogram is moved
-- to the library level with a unique name, and the original exception
-- becomes a renaming. This link from the library level exception to the
-- renaming declaration allows registering of the proper exception name.
-- Return_Statement_Entity (Node5-Sem)
-- Present in N_Simple_Return_Statement and N_Extended_Return_Statement.
-- Points to an E_Return_Statement representing the return statement.
-- Return_Object_Declarations (List3)
-- Present in N_Extended_Return_Statement. Points to a list initially
-- containing a single N_Object_Declaration representing the return
-- object. We use a list (instead of just a pointer to the object decl)
-- because Analyze wants to insert extra actions on this list.
-- Rounded_Result (Flag18-Sem)
-- Present in N_Type_Conversion, N_Op_Divide and N_Op_Multiply nodes.
-- Used in the fixed-point cases to indicate that the result must be
-- rounded as a result of the use of the 'Round attribute. Also used for
-- integer N_Op_Divide nodes to indicate that the result should be
-- rounded to the nearest integer (breaking ties away from zero), rather
-- than truncated towards zero as usual. These rounded integer operations
-- are the result of expansion of rounded fixed-point divide, conversion
-- and multiplication operations.
-- SCIL_Entity (Node4-Sem)
-- Present in SCIL nodes. References the specific tagged type associated
-- with the SCIL node (for an N_SCIL_Dispatching_Call node, this is
-- the controlling type of the call; for an N_SCIL_Membership_Test node
-- generated as part of testing membership in T'Class, this is T; for an
-- N_SCIL_Dispatch_Table_Tag_Init node, this is the type being declared).
-- SCIL_Controlling_Tag (Node5-Sem)
-- Present in N_SCIL_Dispatching_Call nodes. References the controlling
-- tag of a dispatching call. This is usually an N_Selected_Component
-- node (for a _tag component), but may be an N_Object_Declaration or
-- N_Parameter_Specification node in some cases (e.g., for a call to
-- a classwide streaming operation or a call to an instance of
-- Ada.Tags.Generic_Dispatching_Constructor).
-- SCIL_Tag_Value (Node5-Sem)
-- Present in N_SCIL_Membership_Test nodes. Used to reference the tag
-- of the value that is being tested.
-- SCIL_Target_Prim (Node2-Sem)
-- Present in N_SCIL_Dispatching_Call nodes. References the primitive
-- operation named (statically) in a dispatching call.
-- Scope (Node3-Sem)
-- Present in defining identifiers, defining character literals and
-- defining operator symbols (i.e. in all entities). The entities of a
-- scope all use this field to reference the corresponding scope entity.
-- See Einfo for further details.
-- Shift_Count_OK (Flag4-Sem)
-- A flag present in shift nodes to indicate that the shift count is
-- known to be in range, i.e. is in the range from zero to word length
-- minus one. If this flag is not set, then the shift count may be
-- outside this range, i.e. larger than the word length, and the code
-- must ensure that such shift counts give the appropriate result.
-- Source_Type (Node1-Sem)
-- Used in an N_Validate_Unchecked_Conversion node to point to the
-- source type entity for the unchecked conversion instantiation
-- which gigi must do size validation for.
-- Split_PPC (Flag17)
-- When a Pre or Post aspect specification is processed, it is broken
-- into AND THEN sections. The left most section has Split_PPC set to
-- False, indicating that it is the original specification (e.g. for
-- posting errors). For other sections, Split_PPC is set to True.
-- This flag is set in both the N_Aspect_Specification node itself,
-- and in the pragma which is generated from this node.
-- Storage_Pool (Node1-Sem)
-- Present in N_Allocator, N_Free_Statement, N_Simple_Return_Statement,
-- and N_Extended_Return_Statement nodes. References the entity for the
-- storage pool to be used for the allocate or free call or for the
-- allocation of the returned value from function. Empty indicates that
-- the global default pool is to be used. Note that in the case
-- of a return statement, this field is set only if the function returns
-- value of a type whose size is not known at compile time on the
-- secondary stack.
-- Suppress_Assignment_Checks (Flag18-Sem)
-- Used in generated N_Assignment_Statement nodes to suppress predicate
-- and range checks in cases where the generated code knows that the
-- value being assigned is in range and satisfies any predicate. Also
-- can be set in N_Object_Declaration nodes, to similarly suppress any
-- checks on the initializing value. In assignment statements it also
-- suppresses access checks in the generated code for out- and in-out
-- parameters in entry calls.
-- Suppress_Loop_Warnings (Flag17-Sem)
-- Used in N_Loop_Statement node to indicate that warnings within the
-- body of the loop should be suppressed. This is set when the range
-- of a FOR loop is known to be null, or is probably null (loop would
-- only execute if invalid values are present).
-- Target_Type (Node2-Sem)
-- Used in an N_Validate_Unchecked_Conversion node to point to the target
-- type entity for the unchecked conversion instantiation which gigi must
-- do size validation for.
-- Then_Actions (List3-Sem)
-- This field is present in if expression nodes. During code expansion
-- we use the Insert_Actions procedure (in Exp_Util) to insert actions
-- at an appropriate place in the tree to get elaborated at the right
-- time. For if expressions, we have to be sure that the actions for
-- for the Then branch are only elaborated if the condition is True.
-- The Then_Actions field is used as a temporary parking place for
-- these actions. The final tree is always rewritten to eliminate the
-- need for this field, so in the tree passed to Gigi, this field is
-- always set to No_List.
-- Treat_Fixed_As_Integer (Flag14-Sem)
-- This flag appears in operator nodes for divide, multiply, mod and rem
-- on fixed-point operands. It indicates that the operands are to be
-- treated as integer values, ignoring small values. This flag is only
-- set as a result of expansion of fixed-point operations. Typically a
-- fixed-point multiplication in the source generates subsidiary
-- multiplication and division operations that work with the underlying
-- integer values and have this flag set. Note that this flag is not
-- needed on other arithmetic operations (add, neg, subtract etc.) since
-- in these cases it is always the case that fixed is treated as integer.
-- The Etype field MUST be set if this flag is set. The analyzer knows to
-- leave such nodes alone, and whoever makes them must set the correct
-- Etype value.
-- TSS_Elist (Elist3-Sem)
-- Present in N_Freeze_Entity nodes. Holds an element list containing
-- entries for each TSS (type support subprogram) associated with the
-- frozen type. The elements of the list are the entities for the
-- subprograms (see package Exp_TSS for further details). Set to No_Elist
-- if there are no type support subprograms for the type or if the freeze
-- node is not for a type.
-- Uneval_Old_Accept (Flag7-Sem)
-- Present in N_Pragma nodes. Set True if Opt.Uneval_Old is set to 'A'
-- (accept) at the point where the pragma is encountered (including the
-- case of a pragma generated from an aspect specification). It is this
-- setting that is relevant, rather than the setting at the point where
-- a contract is finally analyzed after the delay till the freeze point.
-- Uneval_Old_Warn (Flag18-Sem)
-- Present in N_Pragma nodes. Set True if Opt.Uneval_Old is set to 'W'
-- (warn) at the point where the pragma is encountered (including the
-- case of a pragma generated from an aspect specification). It is this
-- setting that is relevant, rather than the setting at the point where
-- a contract is finally analyzed after the delay till the freeze point.
-- Unreferenced_In_Spec (Flag7-Sem)
-- Present in N_With_Clause nodes. Set if the with clause is on the
-- package or subprogram spec where the main unit is the corresponding
-- body, and is not referenced by the spec (it may still be referenced by
-- the body, so this flag is used to generate the proper message (see
-- Sem_Util.Check_Unused_Withs for details)
-- Uninitialized_Variable (Node3-Sem)
-- Present in N_Formal_Private_Type_Definition and in N_Private_
-- Extension_Declarations. Indicates that a variable in a generic unit
-- whose type is a formal private or derived type is read without being
-- initialized. Used to warn if the corresponding actual type is not
-- a fully initialized type.
-- Used_Operations (Elist5-Sem)
-- Present in N_Use_Type_Clause nodes. Holds the list of operations that
-- are made potentially use-visible by the clause. Simplifies processing
-- on exit from the scope of the use_type_clause, in particular in the
-- case of Use_All_Type, when those operations several scopes.
-- Was_Expression_Function (Flag18-Sem)
-- Present in N_Subprogram_Body. True if the original source had an
-- N_Expression_Function, which was converted to the N_Subprogram_Body
-- by Analyze_Expression_Function. This is needed by ASIS to correctly
-- recreate the expression function (for the instance body) when the
-- completion of a generic function declaration is an expression
-- function.
-- Was_Originally_Stub (Flag13-Sem)
-- This flag is set in the node for a proper body that replaces stub.
-- During the analysis procedure, stubs in some situations get rewritten
-- by the corresponding bodies, and we set this flag to remember that
-- this happened. Note that it is not good enough to rely on the use of
-- Original_Node here because of the case of nested instantiations where
-- the substituted node can be copied.
-- Withed_Body (Node1-Sem)
-- Present in N_With_Clause nodes. Set if the unit in whose context
-- the with_clause appears instantiates a generic contained in the
-- library unit of the with_clause and as a result loads its body.
-- Used for a more precise unit traversal for CodePeer.
--------------------------------------------------
-- Note on Use of End_Label and End_Span Fields --
--------------------------------------------------
-- Several constructs have end lines:
-- Loop Statement end loop [loop_IDENTIFIER];
-- Package Specification end [[PARENT_UNIT_NAME .] IDENTIFIER]
-- Task Definition end [task_IDENTIFIER]
-- Protected Definition end [protected_IDENTIFIER]
-- Protected Body end [protected_IDENTIFIER]
-- Block Statement end [block_IDENTIFIER];
-- Subprogram Body end [DESIGNATOR];
-- Package Body end [[PARENT_UNIT_NAME .] IDENTIFIER];
-- Task Body end [task_IDENTIFIER];
-- Accept Statement end [entry_IDENTIFIER]];
-- Entry Body end [entry_IDENTIFIER];
-- If Statement end if;
-- Case Statement end case;
-- Record Definition end record;
-- Enumeration Definition );
-- The End_Label and End_Span fields are used to mark the locations of
-- these lines, and also keep track of the label in the case where a label
-- is present.
-- For the first group above, the End_Label field of the corresponding node
-- is used to point to the label identifier. In the case where there is no
-- label in the source, the parser supplies a dummy identifier (with
-- Comes_From_Source set to False), and the Sloc of this dummy identifier
-- marks the location of the token following the END token.
-- For the second group, the use of End_Label is similar, but the End_Label
-- is found in the N_Handled_Sequence_Of_Statements node. This is done
-- simply because in some cases there is no room in the parent node.
-- For the third group, there is never any label, and instead of using
-- End_Label, we use the End_Span field which gives the location of the
-- token following END, relative to the starting Sloc of the construct,
-- i.e. add Sloc (Node) + End_Span (Node) to get the Sloc of the IF or CASE
-- following the End_Label.
-- The record definition case is handled specially, we treat it as though
-- it required an optional label which is never present, and so the parser
-- always builds a dummy identifier with Comes From Source set False. The
-- reason we do this, rather than using End_Span in this case, is that we
-- want to generate a cross-ref entry for the end of a record, since it
-- represents a scope for name declaration purposes.
-- The enumeration definition case is handled in an exactly similar manner,
-- building a dummy identifier to get a cross-reference.
-- Note: the reason we store the difference as a Uint, instead of storing
-- the Source_Ptr value directly, is that Source_Ptr values cannot be
-- distinguished from other types of values, and we count on all general
-- use fields being self describing. To make things easier for clients,
-- note that we provide function End_Location, and procedure
-- Set_End_Location to allow access to the logical value (which is the
-- Source_Ptr value for the end token).
---------------------
-- Syntactic Nodes --
---------------------
---------------------
-- 2.3 Identifier --
---------------------
-- IDENTIFIER ::= IDENTIFIER_LETTER {[UNDERLINE] LETTER_OR_DIGIT}
-- LETTER_OR_DIGIT ::= IDENTIFIER_LETTER | DIGIT
-- An IDENTIFIER shall not be a reserved word
-- In the Ada grammar identifiers are the bottom level tokens which have
-- very few semantics. Actual program identifiers are direct names. If
-- we were being 100% honest with the grammar, then we would have a node
-- called N_Direct_Name which would point to an identifier. However,
-- that's too many extra nodes, so we just use the N_Identifier node
-- directly as a direct name, and it contains the expression fields and
-- Entity field that correspond to its use as a direct name. In those
-- few cases where identifiers appear in contexts where they are not
-- direct names (pragmas, pragma argument associations, attribute
-- references and attribute definition clauses), the Chars field of the
-- node contains the Name_Id for the identifier name.
-- Note: in GNAT, a reserved word can be treated as an identifier in two
-- cases. First, an incorrect use of a reserved word as an identifier is
-- diagnosed and then treated as a normal identifier. Second, an
-- attribute designator of the form of a reserved word (access, delta,
-- digits, range) is treated as an identifier.
-- Note: The set of letters that is permitted in an identifier depends
-- on the character set in use. See package Csets for full details.
-- N_Identifier
-- Sloc points to identifier
-- Chars (Name1) contains the Name_Id for the identifier
-- Entity (Node4-Sem)
-- Associated_Node (Node4-Sem)
-- Original_Discriminant (Node2-Sem)
-- Redundant_Use (Flag13-Sem)
-- Atomic_Sync_Required (Flag14-Sem)
-- Has_Private_View (Flag11-Sem) (set in generic units)
-- plus fields for expression
--------------------------
-- 2.4 Numeric Literal --
--------------------------
-- NUMERIC_LITERAL ::= DECIMAL_LITERAL | BASED_LITERAL
----------------------------
-- 2.4.1 Decimal Literal --
----------------------------
-- DECIMAL_LITERAL ::= NUMERAL [.NUMERAL] [EXPONENT]
-- NUMERAL ::= DIGIT {[UNDERLINE] DIGIT}
-- EXPONENT ::= E [+] NUMERAL | E - NUMERAL
-- Decimal literals appear in the tree as either integer literal nodes
-- or real literal nodes, depending on whether a period is present.
-- Note: literal nodes appear as a result of direct use of literals
-- in the source program, and also as the result of evaluating
-- expressions at compile time. In the latter case, it is possible
-- to construct real literals that have no syntactic representation
-- using the standard literal format. Such literals are listed by
-- Sprint using the notation [numerator / denominator].
-- Note: the value of an integer literal node created by the front end
-- is never outside the range of values of the base type. However, it
-- can be the case that the created value is outside the range of the
-- particular subtype. This happens in the case of integer overflows
-- with checks suppressed.
-- N_Integer_Literal
-- Sloc points to literal
-- Original_Entity (Node2-Sem) If not Empty, holds Named_Number that
-- has been constant-folded into its literal value.
-- Intval (Uint3) contains integer value of literal
-- Print_In_Hex (Flag13-Sem)
-- plus fields for expression
-- N_Real_Literal
-- Sloc points to literal
-- Original_Entity (Node2-Sem) If not Empty, holds Named_Number that
-- has been constant-folded into its literal value.
-- Realval (Ureal3) contains real value of literal
-- Corresponding_Integer_Value (Uint4-Sem)
-- Is_Machine_Number (Flag11-Sem)
-- plus fields for expression
--------------------------
-- 2.4.2 Based Literal --
--------------------------
-- BASED_LITERAL ::=
-- BASE # BASED_NUMERAL [.BASED_NUMERAL] # [EXPONENT]
-- BASE ::= NUMERAL
-- BASED_NUMERAL ::=
-- EXTENDED_DIGIT {[UNDERLINE] EXTENDED_DIGIT}
-- EXTENDED_DIGIT ::= DIGIT | A | B | C | D | E | F
-- Based literals appear in the tree as either integer literal nodes
-- or real literal nodes, depending on whether a period is present.
----------------------------
-- 2.5 Character Literal --
----------------------------
-- CHARACTER_LITERAL ::= ' GRAPHIC_CHARACTER '
-- N_Character_Literal
-- Sloc points to literal
-- Chars (Name1) contains the Name_Id for the identifier
-- Char_Literal_Value (Uint2) contains the literal value
-- Entity (Node4-Sem)
-- Associated_Node (Node4-Sem)
-- Has_Private_View (Flag11-Sem) set in generic units.
-- plus fields for expression
-- Note: the Entity field will be missing (set to Empty) for character
-- literals whose type is Standard.Wide_Character or Standard.Character
-- or a type derived from one of these two. In this case the character
-- literal stands for its own coding. The reason we take this irregular
-- short cut is to avoid the need to build lots of junk defining
-- character literal nodes.
-------------------------
-- 2.6 String Literal --
-------------------------
-- STRING LITERAL ::= "{STRING_ELEMENT}"
-- A STRING_ELEMENT is either a pair of quotation marks ("), or a
-- single GRAPHIC_CHARACTER other than a quotation mark.
--
-- Is_Folded_In_Parser is True if the parser created this literal by
-- folding a sequence of "&" operators. For example, if the source code
-- says "aaa" & "bbb" & "ccc", and this produces "aaabbbccc", the flag
-- is set. This flag is needed because the parser doesn't know about
-- visibility, so the folded result might be wrong, and semantic
-- analysis needs to check for that.
-- N_String_Literal
-- Sloc points to literal
-- Strval (Str3) contains Id of string value
-- Has_Wide_Character (Flag11-Sem)
-- Has_Wide_Wide_Character (Flag13-Sem)
-- Is_Folded_In_Parser (Flag4)
-- plus fields for expression
------------------
-- 2.7 Comment --
------------------
-- A COMMENT starts with two adjacent hyphens and extends up to the
-- end of the line. A COMMENT may appear on any line of a program.
-- Comments are skipped by the scanner and do not appear in the tree.
-- It is possible to reconstruct the position of comments with respect
-- to the elements of the tree by using the source position (Sloc)
-- pointers that appear in every tree node.
-----------------
-- 2.8 Pragma --
-----------------
-- PRAGMA ::= pragma IDENTIFIER
-- [(PRAGMA_ARGUMENT_ASSOCIATION {, PRAGMA_ARGUMENT_ASSOCIATION})];
-- Note that a pragma may appear in the tree anywhere a declaration
-- or a statement may appear, as well as in some other situations
-- which are explicitly documented.
-- N_Pragma
-- Sloc points to PRAGMA
-- Next_Pragma (Node1-Sem)
-- Pragma_Argument_Associations (List2) (set to No_List if none)
-- Corresponding_Aspect (Node3-Sem) (set to Empty if not present)
-- Pragma_Identifier (Node4)
-- Next_Rep_Item (Node5-Sem)
-- Class_Present (Flag6) set if from Aspect with 'Class
-- From_Aspect_Specification (Flag13-Sem)
-- Import_Interface_Present (Flag16-Sem)
-- Is_Analyzed_Pragma (Flag5-Sem)
-- Is_Checked (Flag11-Sem)
-- Is_Checked_Ghost_Pragma (Flag3-Sem)
-- Is_Delayed_Aspect (Flag14-Sem)
-- Is_Disabled (Flag15-Sem)
-- Is_Generic_Contract_Pragma (Flag2-Sem)
-- Is_Ignored (Flag9-Sem)
-- Is_Ignored_Ghost_Pragma (Flag8-Sem)
-- Is_Inherited_Pragma (Flag4-Sem)
-- Split_PPC (Flag17) set if corresponding aspect had Split_PPC set
-- Uneval_Old_Accept (Flag7-Sem)
-- Uneval_Old_Warn (Flag18-Sem)
-- Note: we should have a section on what pragmas are passed on to
-- the back end to be processed. This section should note that pragma
-- Psect_Object is always converted to Common_Object, but there are
-- undoubtedly many other similar notes required ???
-- Note: utility functions Pragma_Name_Unmapped and Pragma_Name may be
-- applied to pragma nodes to obtain the Chars or its mapped version.
-- Note: if From_Aspect_Specification is set, then Sloc points to the
-- aspect name, as does the Pragma_Identifier. In this case if the
-- pragma has a local name argument (such as pragma Inline), it is
-- resolved to point to the specific entity affected by the pragma.
--------------------------------------
-- 2.8 Pragma Argument Association --
--------------------------------------
-- PRAGMA_ARGUMENT_ASSOCIATION ::=
-- [pragma_argument_IDENTIFIER =>] NAME
-- | [pragma_argument_IDENTIFIER =>] EXPRESSION
-- In Ada 2012, there are two more possibilities:
-- PRAGMA_ARGUMENT_ASSOCIATION ::=
-- [pragma_argument_ASPECT_MARK =>] NAME
-- | [pragma_argument_ASPECT_MARK =>] EXPRESSION
-- where the interesting allowed cases (which do not fit the syntax of
-- the first alternative above) are
-- ASPECT_MARK => Pre'Class |
-- Post'Class |
-- Type_Invariant'Class |
-- Invariant'Class
-- We allow this special usage in all Ada modes, but it would be a
-- pain to allow these aspects to pervade the pragma syntax, and the
-- representation of pragma nodes internally. So what we do is to
-- replace these ASPECT_MARK forms with identifiers whose name is one
-- of the special internal names _Pre, _Post or _Type_Invariant.
-- We do a similar replacement of these Aspect_Mark forms in the
-- Expression of a pragma argument association for the cases of
-- the first arguments of any Check pragmas and Check_Policy pragmas
-- N_Pragma_Argument_Association
-- Sloc points to first token in association
-- Chars (Name1) (set to No_Name if no pragma argument identifier)
-- Expression_Copy (Node2-Sem)
-- Expression (Node3)
------------------------
-- 2.9 Reserved Word --
------------------------
-- Reserved words are parsed by the scanner, and returned as the
-- corresponding token types (e.g. PACKAGE is returned as Tok_Package)
----------------------------
-- 3.1 Basic Declaration --
----------------------------
-- BASIC_DECLARATION ::=
-- TYPE_DECLARATION | SUBTYPE_DECLARATION
-- | OBJECT_DECLARATION | NUMBER_DECLARATION
-- | SUBPROGRAM_DECLARATION | ABSTRACT_SUBPROGRAM_DECLARATION
-- | PACKAGE_DECLARATION | RENAMING_DECLARATION
-- | EXCEPTION_DECLARATION | GENERIC_DECLARATION
-- | GENERIC_INSTANTIATION
-- Basic declaration also includes IMPLICIT_LABEL_DECLARATION
-- see further description in section on semantic nodes.
-- Also, in the tree that is constructed, a pragma may appear
-- anywhere that a declaration may appear.
------------------------------
-- 3.1 Defining Identifier --
------------------------------
-- DEFINING_IDENTIFIER ::= IDENTIFIER
-- A defining identifier is an entity, which has additional fields
-- depending on the setting of the Ekind field. These additional
-- fields are defined (and access subprograms declared) in package
-- Einfo.
-- Note: N_Defining_Identifier is an extended node whose fields are
-- deliberate layed out to match the layout of fields in an ordinary
-- N_Identifier node allowing for easy alteration of an identifier
-- node into a defining identifier node. For details, see procedure
-- Sinfo.CN.Change_Identifier_To_Defining_Identifier.
-- N_Defining_Identifier
-- Sloc points to identifier
-- Chars (Name1) contains the Name_Id for the identifier
-- Next_Entity (Node2-Sem)
-- Scope (Node3-Sem)
-- Etype (Node5-Sem)
-----------------------------
-- 3.2.1 Type Declaration --
-----------------------------
-- TYPE_DECLARATION ::=
-- FULL_TYPE_DECLARATION
-- | INCOMPLETE_TYPE_DECLARATION
-- | PRIVATE_TYPE_DECLARATION
-- | PRIVATE_EXTENSION_DECLARATION
----------------------------------
-- 3.2.1 Full Type Declaration --
----------------------------------
-- FULL_TYPE_DECLARATION ::=
-- type DEFINING_IDENTIFIER [KNOWN_DISCRIMINANT_PART]
-- is TYPE_DEFINITION
-- [ASPECT_SPECIFICATIONS];
-- | TASK_TYPE_DECLARATION
-- | PROTECTED_TYPE_DECLARATION
-- The full type declaration node is used only for the first case. The
-- second case (concurrent type declaration), is represented directly
-- by a task type declaration or a protected type declaration.
-- N_Full_Type_Declaration
-- Sloc points to TYPE
-- Defining_Identifier (Node1)
-- Incomplete_View (Node2-Sem)
-- Discriminant_Specifications (List4) (set to No_List if none)
-- Type_Definition (Node3)
-- Discr_Check_Funcs_Built (Flag11-Sem)
----------------------------
-- 3.2.1 Type Definition --
----------------------------
-- TYPE_DEFINITION ::=
-- ENUMERATION_TYPE_DEFINITION | INTEGER_TYPE_DEFINITION
-- | REAL_TYPE_DEFINITION | ARRAY_TYPE_DEFINITION
-- | RECORD_TYPE_DEFINITION | ACCESS_TYPE_DEFINITION
-- | DERIVED_TYPE_DEFINITION | INTERFACE_TYPE_DEFINITION
--------------------------------
-- 3.2.2 Subtype Declaration --
--------------------------------
-- SUBTYPE_DECLARATION ::=
-- subtype DEFINING_IDENTIFIER is [NULL_EXCLUSION] SUBTYPE_INDICATION
-- [ASPECT_SPECIFICATIONS];
-- The subtype indication field is set to Empty for subtypes
-- declared in package Standard (Positive, Natural).
-- N_Subtype_Declaration
-- Sloc points to SUBTYPE
-- Defining_Identifier (Node1)
-- Null_Exclusion_Present (Flag11)
-- Subtype_Indication (Node5)
-- Generic_Parent_Type (Node4-Sem) (set for an actual derived type).
-- Exception_Junk (Flag8-Sem)
-- Has_Dynamic_Range_Check (Flag12-Sem)
-------------------------------
-- 3.2.2 Subtype Indication --
-------------------------------
-- SUBTYPE_INDICATION ::= SUBTYPE_MARK [CONSTRAINT]
-- Note: if no constraint is present, the subtype indication appears
-- directly in the tree as a subtype mark. The N_Subtype_Indication
-- node is used only if a constraint is present.
-- Note: [For Ada 2005 (AI-231)]: Because Ada 2005 extends this rule
-- with the null-exclusion part (see AI-231), we had to introduce a new
-- attribute in all the parents of subtype_indication nodes to indicate
-- if the null-exclusion is present.
-- Note: the reason that this node has expression fields is that a
-- subtype indication can appear as an operand of a membership test.
-- N_Subtype_Indication
-- Sloc points to first token of subtype mark
-- Subtype_Mark (Node4)
-- Constraint (Node3)
-- Etype (Node5-Sem)
-- Must_Not_Freeze (Flag8-Sem)
-- Note: Depending on context, the Etype is either the entity of the
-- Subtype_Mark field, or it is an itype constructed to reify the
-- subtype indication. In particular, such itypes are created for a
-- subtype indication that appears in an array type declaration. This
-- simplifies constraint checking in indexed components.
-- For subtype indications that appear in scalar type and subtype
-- declarations, the Etype is the entity of the subtype mark.
-------------------------
-- 3.2.2 Subtype Mark --
-------------------------
-- SUBTYPE_MARK ::= subtype_NAME
-----------------------
-- 3.2.2 Constraint --
-----------------------
-- CONSTRAINT ::= SCALAR_CONSTRAINT | COMPOSITE_CONSTRAINT
------------------------------
-- 3.2.2 Scalar Constraint --
------------------------------
-- SCALAR_CONSTRAINT ::=
-- RANGE_CONSTRAINT | DIGITS_CONSTRAINT | DELTA_CONSTRAINT
---------------------------------
-- 3.2.2 Composite Constraint --
---------------------------------
-- COMPOSITE_CONSTRAINT ::=
-- INDEX_CONSTRAINT | DISCRIMINANT_CONSTRAINT
-------------------------------
-- 3.3.1 Object Declaration --
-------------------------------
-- OBJECT_DECLARATION ::=
-- DEFINING_IDENTIFIER_LIST : [aliased] [constant]
-- [NULL_EXCLUSION] SUBTYPE_INDICATION [:= EXPRESSION]
-- [ASPECT_SPECIFICATIONS];
-- | DEFINING_IDENTIFIER_LIST : [aliased] [constant]
-- ACCESS_DEFINITION [:= EXPRESSION]
-- [ASPECT_SPECIFICATIONS];
-- | DEFINING_IDENTIFIER_LIST : [aliased] [constant]
-- ARRAY_TYPE_DEFINITION [:= EXPRESSION]
-- [ASPECT_SPECIFICATIONS];
-- | SINGLE_TASK_DECLARATION
-- | SINGLE_PROTECTED_DECLARATION
-- Note: aliased is not permitted in Ada 83 mode
-- The N_Object_Declaration node is only for the first three cases.
-- Single task declaration is handled by P_Task (9.1)
-- Single protected declaration is handled by P_protected (9.5)
-- Although the syntax allows multiple identifiers in the list, the
-- semantics is as though successive declarations were given with
-- identical type definition and expression components. To simplify
-- semantic processing, the parser represents a multiple declaration
-- case as a sequence of single declarations, using the More_Ids and
-- Prev_Ids flags to preserve the original source form as described
-- in the section on "Handling of Defining Identifier Lists".
-- The flag Has_Init_Expression is set if an initializing expression
-- is present. Normally it is set if and only if Expression contains
-- a non-empty value, but there is an exception to this. When the
-- initializing expression is an aggregate which requires explicit
-- assignments, the Expression field gets set to Empty, but this flag
-- is still set, so we don't forget we had an initializing expression.
-- Note: if a range check is required for the initialization
-- expression then the Do_Range_Check flag is set in the Expression,
-- with the check being done against the type given by the object
-- definition, which is also the Etype of the defining identifier.
-- Note: the contents of the Expression field must be ignored (i.e.
-- treated as though it were Empty) if No_Initialization is set True.
-- Note: the back end places some restrictions on the form of the
-- Expression field. If the object being declared is Atomic, then
-- the Expression may not have the form of an aggregate (since this
-- might cause the back end to generate separate assignments). In this
-- case the front end must generate an extra temporary and initialize
-- this temporary as required (the temporary itself is not atomic).
-- Note: there is not node kind for object definition. Instead, the
-- corresponding field holds a subtype indication, an array type
-- definition, or (Ada 2005, AI-406) an access definition.
-- N_Object_Declaration
-- Sloc points to first identifier
-- Defining_Identifier (Node1)
-- Aliased_Present (Flag4)
-- Constant_Present (Flag17) set if CONSTANT appears
-- Null_Exclusion_Present (Flag11)
-- Object_Definition (Node4) subtype indic./array type def./access def.
-- Expression (Node3) (set to Empty if not present)
-- Handler_List_Entry (Node2-Sem)
-- Corresponding_Generic_Association (Node5-Sem)
-- More_Ids (Flag5) (set to False if no more identifiers in list)
-- Prev_Ids (Flag6) (set to False if no previous identifiers in list)
-- No_Initialization (Flag13-Sem)
-- Assignment_OK (Flag15-Sem)
-- Exception_Junk (Flag8-Sem)
-- Is_Subprogram_Descriptor (Flag16-Sem)
-- Has_Init_Expression (Flag14)
-- Suppress_Assignment_Checks (Flag18-Sem)
-------------------------------------
-- 3.3.1 Defining Identifier List --
-------------------------------------
-- DEFINING_IDENTIFIER_LIST ::=
-- DEFINING_IDENTIFIER {, DEFINING_IDENTIFIER}
-------------------------------
-- 3.3.2 Number Declaration --
-------------------------------
-- NUMBER_DECLARATION ::=
-- DEFINING_IDENTIFIER_LIST : constant := static_EXPRESSION;
-- Although the syntax allows multiple identifiers in the list, the
-- semantics is as though successive declarations were given with
-- identical expressions. To simplify semantic processing, the parser
-- represents a multiple declaration case as a sequence of single
-- declarations, using the More_Ids and Prev_Ids flags to preserve
-- the original source form as described in the section on "Handling
-- of Defining Identifier Lists".
-- N_Number_Declaration
-- Sloc points to first identifier
-- Defining_Identifier (Node1)
-- Expression (Node3)
-- More_Ids (Flag5) (set to False if no more identifiers in list)
-- Prev_Ids (Flag6) (set to False if no previous identifiers in list)
----------------------------------
-- 3.4 Derived Type Definition --
----------------------------------
-- DERIVED_TYPE_DEFINITION ::=
-- [abstract] [limited] new [NULL_EXCLUSION] parent_SUBTYPE_INDICATION
-- [[and INTERFACE_LIST] RECORD_EXTENSION_PART]
-- Note: ABSTRACT, LIMITED and record extension part are not permitted
-- in Ada 83 mode
-- Note: a record extension part is required if ABSTRACT is present
-- N_Derived_Type_Definition
-- Sloc points to NEW
-- Abstract_Present (Flag4)
-- Null_Exclusion_Present (Flag11) (set to False if not present)
-- Subtype_Indication (Node5)
-- Record_Extension_Part (Node3) (set to Empty if not present)
-- Limited_Present (Flag17)
-- Task_Present (Flag5) set in task interfaces
-- Protected_Present (Flag6) set in protected interfaces
-- Synchronized_Present (Flag7) set in interfaces
-- Interface_List (List2) (set to No_List if none)
-- Interface_Present (Flag16) set in abstract interfaces
-- Note: Task_Present, Protected_Present, Synchronized_Present,
-- Interface_List, and Interface_Present are used for abstract
-- interfaces (see comments for INTERFACE_TYPE_DEFINITION).
---------------------------
-- 3.5 Range Constraint --
---------------------------
-- RANGE_CONSTRAINT ::= range RANGE
-- N_Range_Constraint
-- Sloc points to RANGE
-- Range_Expression (Node4)
----------------
-- 3.5 Range --
----------------
-- RANGE ::=
-- RANGE_ATTRIBUTE_REFERENCE
-- | SIMPLE_EXPRESSION .. SIMPLE_EXPRESSION
-- Note: the case of a range given as a range attribute reference
-- appears directly in the tree as an attribute reference.
-- Note: the field name for a reference to a range is Range_Expression
-- rather than Range, because range is a reserved keyword in Ada.
-- Note: the reason that this node has expression fields is that a
-- range can appear as an operand of a membership test. The Etype
-- field is the type of the range (we do NOT construct an implicit
-- subtype to represent the range exactly).
-- N_Range
-- Sloc points to ..
-- Low_Bound (Node1)
-- High_Bound (Node2)
-- Includes_Infinities (Flag11)
-- plus fields for expression
-- Note: if the range appears in a context, such as a subtype
-- declaration, where range checks are required on one or both of
-- the expression fields, then type conversion nodes are inserted
-- to represent the required checks.
----------------------------------------
-- 3.5.1 Enumeration Type Definition --
----------------------------------------
-- ENUMERATION_TYPE_DEFINITION ::=
-- (ENUMERATION_LITERAL_SPECIFICATION
-- {, ENUMERATION_LITERAL_SPECIFICATION})
-- Note: the Literals field in the node described below is null for
-- the case of the standard types CHARACTER and WIDE_CHARACTER, for
-- which special processing handles these types as special cases.
-- N_Enumeration_Type_Definition
-- Sloc points to left parenthesis
-- Literals (List1) (Empty for CHARACTER or WIDE_CHARACTER)
-- End_Label (Node4) (set to Empty if internally generated record)
----------------------------------------------
-- 3.5.1 Enumeration Literal Specification --
----------------------------------------------
-- ENUMERATION_LITERAL_SPECIFICATION ::=
-- DEFINING_IDENTIFIER | DEFINING_CHARACTER_LITERAL
---------------------------------------
-- 3.5.1 Defining Character Literal --
---------------------------------------
-- DEFINING_CHARACTER_LITERAL ::= CHARACTER_LITERAL
-- A defining character literal is an entity, which has additional
-- fields depending on the setting of the Ekind field. These
-- additional fields are defined (and access subprograms declared)
-- in package Einfo.
-- Note: N_Defining_Character_Literal is an extended node whose fields
-- are deliberate layed out to match the layout of fields in an ordinary
-- N_Character_Literal node allowing for easy alteration of a character
-- literal node into a defining character literal node. For details, see
-- Sinfo.CN.Change_Character_Literal_To_Defining_Character_Literal.
-- N_Defining_Character_Literal
-- Sloc points to literal
-- Chars (Name1) contains the Name_Id for the identifier
-- Next_Entity (Node2-Sem)
-- Scope (Node3-Sem)
-- Etype (Node5-Sem)
------------------------------------
-- 3.5.4 Integer Type Definition --
------------------------------------
-- Note: there is an error in this rule in the latest version of the
-- grammar, so we have retained the old rule pending clarification.
-- INTEGER_TYPE_DEFINITION ::=
-- SIGNED_INTEGER_TYPE_DEFINITION
-- | MODULAR_TYPE_DEFINITION
-------------------------------------------
-- 3.5.4 Signed Integer Type Definition --
-------------------------------------------
-- SIGNED_INTEGER_TYPE_DEFINITION ::=
-- range static_SIMPLE_EXPRESSION .. static_SIMPLE_EXPRESSION
-- Note: the Low_Bound and High_Bound fields are set to Empty
-- for integer types defined in package Standard.
-- N_Signed_Integer_Type_Definition
-- Sloc points to RANGE
-- Low_Bound (Node1)
-- High_Bound (Node2)
------------------------------------
-- 3.5.4 Modular Type Definition --
------------------------------------
-- MODULAR_TYPE_DEFINITION ::= mod static_EXPRESSION
-- N_Modular_Type_Definition
-- Sloc points to MOD
-- Expression (Node3)
---------------------------------
-- 3.5.6 Real Type Definition --
---------------------------------
-- REAL_TYPE_DEFINITION ::=
-- FLOATING_POINT_DEFINITION | FIXED_POINT_DEFINITION
--------------------------------------
-- 3.5.7 Floating Point Definition --
--------------------------------------
-- FLOATING_POINT_DEFINITION ::=
-- digits static_SIMPLE_EXPRESSION [REAL_RANGE_SPECIFICATION]
-- Note: The Digits_Expression and Real_Range_Specifications fields
-- are set to Empty for floating-point types declared in Standard.
-- N_Floating_Point_Definition
-- Sloc points to DIGITS
-- Digits_Expression (Node2)
-- Real_Range_Specification (Node4) (set to Empty if not present)
-------------------------------------
-- 3.5.7 Real Range Specification --
-------------------------------------
-- REAL_RANGE_SPECIFICATION ::=
-- range static_SIMPLE_EXPRESSION .. static_SIMPLE_EXPRESSION
-- N_Real_Range_Specification
-- Sloc points to RANGE
-- Low_Bound (Node1)
-- High_Bound (Node2)
-----------------------------------
-- 3.5.9 Fixed Point Definition --
-----------------------------------
-- FIXED_POINT_DEFINITION ::=
-- ORDINARY_FIXED_POINT_DEFINITION | DECIMAL_FIXED_POINT_DEFINITION
--------------------------------------------
-- 3.5.9 Ordinary Fixed Point Definition --
--------------------------------------------
-- ORDINARY_FIXED_POINT_DEFINITION ::=
-- delta static_EXPRESSION REAL_RANGE_SPECIFICATION
-- Note: In Ada 83, the EXPRESSION must be a SIMPLE_EXPRESSION
-- N_Ordinary_Fixed_Point_Definition
-- Sloc points to DELTA
-- Delta_Expression (Node3)
-- Real_Range_Specification (Node4)
-------------------------------------------
-- 3.5.9 Decimal Fixed Point Definition --
-------------------------------------------
-- DECIMAL_FIXED_POINT_DEFINITION ::=
-- delta static_EXPRESSION
-- digits static_EXPRESSION [REAL_RANGE_SPECIFICATION]
-- Note: decimal types are not permitted in Ada 83 mode
-- N_Decimal_Fixed_Point_Definition
-- Sloc points to DELTA
-- Delta_Expression (Node3)
-- Digits_Expression (Node2)
-- Real_Range_Specification (Node4) (set to Empty if not present)
------------------------------
-- 3.5.9 Digits Constraint --
------------------------------
-- DIGITS_CONSTRAINT ::=
-- digits static_EXPRESSION [RANGE_CONSTRAINT]
-- Note: in Ada 83, the EXPRESSION must be a SIMPLE_EXPRESSION
-- Note: in Ada 95, reduced accuracy subtypes are obsolescent
-- N_Digits_Constraint
-- Sloc points to DIGITS
-- Digits_Expression (Node2)
-- Range_Constraint (Node4) (set to Empty if not present)
--------------------------------
-- 3.6 Array Type Definition --
--------------------------------
-- ARRAY_TYPE_DEFINITION ::=
-- UNCONSTRAINED_ARRAY_DEFINITION | CONSTRAINED_ARRAY_DEFINITION
-----------------------------------------
-- 3.6 Unconstrained Array Definition --
-----------------------------------------
-- UNCONSTRAINED_ARRAY_DEFINITION ::=
-- array (INDEX_SUBTYPE_DEFINITION {, INDEX_SUBTYPE_DEFINITION}) of
-- COMPONENT_DEFINITION
-- Note: dimensionality of array is indicated by number of entries in
-- the Subtype_Marks list, which has one entry for each dimension.
-- N_Unconstrained_Array_Definition
-- Sloc points to ARRAY
-- Subtype_Marks (List2)
-- Component_Definition (Node4)
-----------------------------------
-- 3.6 Index Subtype Definition --
-----------------------------------
-- INDEX_SUBTYPE_DEFINITION ::= SUBTYPE_MARK range <>
-- There is no explicit node in the tree for an index subtype
-- definition since the N_Unconstrained_Array_Definition node
-- incorporates the type marks which appear in this context.
---------------------------------------
-- 3.6 Constrained Array Definition --
---------------------------------------
-- CONSTRAINED_ARRAY_DEFINITION ::=
-- array (DISCRETE_SUBTYPE_DEFINITION
-- {, DISCRETE_SUBTYPE_DEFINITION})
-- of COMPONENT_DEFINITION
-- Note: dimensionality of array is indicated by number of entries
-- in the Discrete_Subtype_Definitions list, which has one entry
-- for each dimension.
-- N_Constrained_Array_Definition
-- Sloc points to ARRAY
-- Discrete_Subtype_Definitions (List2)
-- Component_Definition (Node4)
-- Note: although the language allows the full syntax for discrete
-- subtype definitions (i.e. a discrete subtype indication or a range),
-- in the generated tree, we always rewrite these as N_Range nodes.
--------------------------------------
-- 3.6 Discrete Subtype Definition --
--------------------------------------
-- DISCRETE_SUBTYPE_DEFINITION ::=
-- discrete_SUBTYPE_INDICATION | RANGE
-------------------------------
-- 3.6 Component Definition --
-------------------------------
-- COMPONENT_DEFINITION ::=
-- [aliased] [NULL_EXCLUSION] SUBTYPE_INDICATION | ACCESS_DEFINITION
-- Note: although the syntax does not permit a component definition to
-- be an anonymous array (and the parser will diagnose such an attempt
-- with an appropriate message), it is possible for anonymous arrays
-- to appear as component definitions. The semantics and back end handle
-- this case properly, and the expander in fact generates such cases.
-- Access_Definition is an optional field that gives support to
-- Ada 2005 (AI-230). The parser generates nodes that have either the
-- Subtype_Indication field or else the Access_Definition field.
-- N_Component_Definition
-- Sloc points to ALIASED, ACCESS or to first token of subtype mark
-- Aliased_Present (Flag4)
-- Null_Exclusion_Present (Flag11)
-- Subtype_Indication (Node5) (set to Empty if not present)
-- Access_Definition (Node3) (set to Empty if not present)
-----------------------------
-- 3.6.1 Index Constraint --
-----------------------------
-- INDEX_CONSTRAINT ::= (DISCRETE_RANGE {, DISCRETE_RANGE})
-- It is not in general possible to distinguish between discriminant
-- constraints and index constraints at parse time, since a simple
-- name could be either the subtype mark of a discrete range, or an
-- expression in a discriminant association with no name. Either
-- entry appears simply as the name, and the semantic parse must
-- distinguish between the two cases. Thus we use a common tree
-- node format for both of these constraint types.
-- See Discriminant_Constraint for format of node
---------------------------
-- 3.6.1 Discrete Range --
---------------------------
-- DISCRETE_RANGE ::= discrete_SUBTYPE_INDICATION | RANGE
----------------------------
-- 3.7 Discriminant Part --
----------------------------
-- DISCRIMINANT_PART ::=
-- UNKNOWN_DISCRIMINANT_PART | KNOWN_DISCRIMINANT_PART
------------------------------------
-- 3.7 Unknown Discriminant Part --
------------------------------------
-- UNKNOWN_DISCRIMINANT_PART ::= (<>)
-- Note: unknown discriminant parts are not permitted in Ada 83 mode
-- There is no explicit node in the tree for an unknown discriminant
-- part. Instead the Unknown_Discriminants_Present flag is set in the
-- parent node.
----------------------------------
-- 3.7 Known Discriminant Part --
----------------------------------
-- KNOWN_DISCRIMINANT_PART ::=
-- (DISCRIMINANT_SPECIFICATION {; DISCRIMINANT_SPECIFICATION})
-------------------------------------
-- 3.7 Discriminant Specification --
-------------------------------------
-- DISCRIMINANT_SPECIFICATION ::=
-- DEFINING_IDENTIFIER_LIST : [NULL_EXCLUSION] SUBTYPE_MARK
-- [:= DEFAULT_EXPRESSION]
-- | DEFINING_IDENTIFIER_LIST : ACCESS_DEFINITION
-- [:= DEFAULT_EXPRESSION]
-- Although the syntax allows multiple identifiers in the list, the
-- semantics is as though successive specifications were given with
-- identical type definition and expression components. To simplify
-- semantic processing, the parser represents a multiple declaration
-- case as a sequence of single specifications, using the More_Ids and
-- Prev_Ids flags to preserve the original source form as described
-- in the section on "Handling of Defining Identifier Lists".
-- N_Discriminant_Specification
-- Sloc points to first identifier
-- Defining_Identifier (Node1)
-- Null_Exclusion_Present (Flag11)
-- Discriminant_Type (Node5) subtype mark or access parameter definition
-- Expression (Node3) (set to Empty if no default expression)
-- More_Ids (Flag5) (set to False if no more identifiers in list)
-- Prev_Ids (Flag6) (set to False if no previous identifiers in list)
-----------------------------
-- 3.7 Default Expression --
-----------------------------
-- DEFAULT_EXPRESSION ::= EXPRESSION
------------------------------------
-- 3.7.1 Discriminant Constraint --
------------------------------------
-- DISCRIMINANT_CONSTRAINT ::=
-- (DISCRIMINANT_ASSOCIATION {, DISCRIMINANT_ASSOCIATION})
-- It is not in general possible to distinguish between discriminant
-- constraints and index constraints at parse time, since a simple
-- name could be either the subtype mark of a discrete range, or an
-- expression in a discriminant association with no name. Either
-- entry appears simply as the name, and the semantic parse must
-- distinguish between the two cases. Thus we use a common tree
-- node format for both of these constraint types.
-- N_Index_Or_Discriminant_Constraint
-- Sloc points to left paren
-- Constraints (List1) points to list of discrete ranges or
-- discriminant associations
-------------------------------------
-- 3.7.1 Discriminant Association --
-------------------------------------
-- DISCRIMINANT_ASSOCIATION ::=
-- [discriminant_SELECTOR_NAME
-- {| discriminant_SELECTOR_NAME} =>] EXPRESSION
-- Note: a discriminant association that has no selector name list
-- appears directly as an expression in the tree.
-- N_Discriminant_Association
-- Sloc points to first token of discriminant association
-- Selector_Names (List1) (always non-empty, since if no selector
-- names are present, this node is not used, see comment above)
-- Expression (Node3)
---------------------------------
-- 3.8 Record Type Definition --
---------------------------------
-- RECORD_TYPE_DEFINITION ::=
-- [[abstract] tagged] [limited] RECORD_DEFINITION
-- Note: ABSTRACT, TAGGED, LIMITED are not permitted in Ada 83 mode
-- There is no explicit node in the tree for a record type definition.
-- Instead the flags for Tagged_Present and Limited_Present appear in
-- the N_Record_Definition node for a record definition appearing in
-- the context of a record type definition.
----------------------------
-- 3.8 Record Definition --
----------------------------
-- RECORD_DEFINITION ::=
-- record
-- COMPONENT_LIST
-- end record
-- | null record
-- Note: the Abstract_Present, Tagged_Present and Limited_Present
-- flags appear only for a record definition appearing in a record
-- type definition.
-- Note: the NULL RECORD case is not permitted in Ada 83
-- N_Record_Definition
-- Sloc points to RECORD or NULL
-- End_Label (Node4) (set to Empty if internally generated record)
-- Abstract_Present (Flag4)
-- Tagged_Present (Flag15)
-- Limited_Present (Flag17)
-- Component_List (Node1) empty in null record case
-- Null_Present (Flag13) set in null record case
-- Task_Present (Flag5) set in task interfaces
-- Protected_Present (Flag6) set in protected interfaces
-- Synchronized_Present (Flag7) set in interfaces
-- Interface_Present (Flag16) set in abstract interfaces
-- Interface_List (List2) (set to No_List if none)
-- Note: Task_Present, Protected_Present, Synchronized _Present,
-- Interface_List and Interface_Present are used for abstract
-- interfaces (see comments for INTERFACE_TYPE_DEFINITION).
-------------------------
-- 3.8 Component List --
-------------------------
-- COMPONENT_LIST ::=
-- COMPONENT_ITEM {COMPONENT_ITEM}
-- | {COMPONENT_ITEM} VARIANT_PART
-- | null;
-- N_Component_List
-- Sloc points to first token of component list
-- Component_Items (List3)
-- Variant_Part (Node4) (set to Empty if no variant part)
-- Null_Present (Flag13)
-------------------------
-- 3.8 Component Item --
-------------------------
-- COMPONENT_ITEM ::= COMPONENT_DECLARATION | REPRESENTATION_CLAUSE
-- Note: A component item can also be a pragma, and in the tree
-- that is obtained after semantic processing, a component item
-- can be an N_Null node resulting from a non-recognized pragma.
--------------------------------
-- 3.8 Component Declaration --
--------------------------------
-- COMPONENT_DECLARATION ::=
-- DEFINING_IDENTIFIER_LIST : COMPONENT_DEFINITION
-- [:= DEFAULT_EXPRESSION]
-- [ASPECT_SPECIFICATIONS];
-- Note: although the syntax does not permit a component definition to
-- be an anonymous array (and the parser will diagnose such an attempt
-- with an appropriate message), it is possible for anonymous arrays
-- to appear as component definitions. The semantics and back end handle
-- this case properly, and the expander in fact generates such cases.
-- Although the syntax allows multiple identifiers in the list, the
-- semantics is as though successive declarations were given with the
-- same component definition and expression components. To simplify
-- semantic processing, the parser represents a multiple declaration
-- case as a sequence of single declarations, using the More_Ids and
-- Prev_Ids flags to preserve the original source form as described
-- in the section on "Handling of Defining Identifier Lists".
-- N_Component_Declaration
-- Sloc points to first identifier
-- Defining_Identifier (Node1)
-- Component_Definition (Node4)
-- Expression (Node3) (set to Empty if no default expression)
-- More_Ids (Flag5) (set to False if no more identifiers in list)
-- Prev_Ids (Flag6) (set to False if no previous identifiers in list)
-------------------------
-- 3.8.1 Variant Part --
-------------------------
-- VARIANT_PART ::=
-- case discriminant_DIRECT_NAME is
-- VARIANT {VARIANT}
-- end case;
-- Note: the variants list can contain pragmas as well as variants.
-- In a properly formed program there is at least one variant.
-- N_Variant_Part
-- Sloc points to CASE
-- Name (Node2)
-- Variants (List1)
--------------------
-- 3.8.1 Variant --
--------------------
-- VARIANT ::=
-- when DISCRETE_CHOICE_LIST =>
-- COMPONENT_LIST
-- N_Variant
-- Sloc points to WHEN
-- Discrete_Choices (List4)
-- Component_List (Node1)
-- Enclosing_Variant (Node2-Sem)
-- Present_Expr (Uint3-Sem)
-- Dcheck_Function (Node5-Sem)
-- Has_SP_Choice (Flag15-Sem)
-- Note: in the list of Discrete_Choices, the tree passed to the back
-- end does not have choice entries corresponding to names of statically
-- predicated subtypes. Such entries are always expanded out to the list
-- of equivalent values or ranges. The ASIS tree generated in -gnatct
-- mode also has this expansion, but done with a proper Rewrite call on
-- the N_Variant node so that ASIS can properly retrieve the original.
---------------------------------
-- 3.8.1 Discrete Choice List --
---------------------------------
-- DISCRETE_CHOICE_LIST ::= DISCRETE_CHOICE {| DISCRETE_CHOICE}
----------------------------
-- 3.8.1 Discrete Choice --
----------------------------
-- DISCRETE_CHOICE ::= EXPRESSION | DISCRETE_RANGE | others
-- Note: in Ada 83 mode, the expression must be a simple expression
-- The only choice that appears explicitly is the OTHERS choice, as
-- defined here. Other cases of discrete choice (expression and
-- discrete range) appear directly. This production is also used
-- for the OTHERS possibility of an exception choice.
-- Note: in accordance with the syntax, the parser does not check that
-- OTHERS appears at the end on its own in a choice list context. This
-- is a semantic check.
-- N_Others_Choice
-- Sloc points to OTHERS
-- Others_Discrete_Choices (List1-Sem)
-- All_Others (Flag11-Sem)
----------------------------------
-- 3.9.1 Record Extension Part --
----------------------------------
-- RECORD_EXTENSION_PART ::= with RECORD_DEFINITION
-- Note: record extension parts are not permitted in Ada 83 mode
--------------------------------------
-- 3.9.4 Interface Type Definition --
--------------------------------------
-- INTERFACE_TYPE_DEFINITION ::=
-- [limited | task | protected | synchronized]
-- interface [interface_list]
-- Note: Interfaces are implemented with N_Record_Definition and
-- N_Derived_Type_Definition nodes because most of the support
-- for the analysis of abstract types has been reused to
-- analyze abstract interfaces.
----------------------------------
-- 3.10 Access Type Definition --
----------------------------------
-- ACCESS_TYPE_DEFINITION ::=
-- ACCESS_TO_OBJECT_DEFINITION
-- | ACCESS_TO_SUBPROGRAM_DEFINITION
--------------------------
-- 3.10 Null Exclusion --
--------------------------
-- NULL_EXCLUSION ::= not null
---------------------------------------
-- 3.10 Access To Object Definition --
---------------------------------------
-- ACCESS_TO_OBJECT_DEFINITION ::=
-- [NULL_EXCLUSION] access [GENERAL_ACCESS_MODIFIER]
-- SUBTYPE_INDICATION
-- N_Access_To_Object_Definition
-- Sloc points to ACCESS
-- All_Present (Flag15)
-- Null_Exclusion_Present (Flag11)
-- Null_Excluding_Subtype (Flag16)
-- Subtype_Indication (Node5)
-- Constant_Present (Flag17)
-----------------------------------
-- 3.10 General Access Modifier --
-----------------------------------
-- GENERAL_ACCESS_MODIFIER ::= all | constant
-- Note: general access modifiers are not permitted in Ada 83 mode
-- There is no explicit node in the tree for general access modifier.
-- Instead the All_Present or Constant_Present flags are set in the
-- parent node.
-------------------------------------------
-- 3.10 Access To Subprogram Definition --
-------------------------------------------
-- ACCESS_TO_SUBPROGRAM_DEFINITION
-- [NULL_EXCLUSION] access [protected] procedure PARAMETER_PROFILE
-- | [NULL_EXCLUSION] access [protected] function
-- PARAMETER_AND_RESULT_PROFILE
-- Note: access to subprograms are not permitted in Ada 83 mode
-- N_Access_Function_Definition
-- Sloc points to ACCESS
-- Null_Exclusion_Present (Flag11)
-- Null_Exclusion_In_Return_Present (Flag14)
-- Protected_Present (Flag6)
-- Parameter_Specifications (List3) (set to No_List if no formal part)
-- Result_Definition (Node4) result subtype (subtype mark or access def)
-- N_Access_Procedure_Definition
-- Sloc points to ACCESS
-- Null_Exclusion_Present (Flag11)
-- Protected_Present (Flag6)
-- Parameter_Specifications (List3) (set to No_List if no formal part)
-----------------------------
-- 3.10 Access Definition --
-----------------------------
-- ACCESS_DEFINITION ::=
-- [NULL_EXCLUSION] access [GENERAL_ACCESS_MODIFIER] SUBTYPE_MARK
-- | ACCESS_TO_SUBPROGRAM_DEFINITION
-- Note: access to subprograms are an Ada 2005 (AI-254) extension
-- N_Access_Definition
-- Sloc points to ACCESS
-- Null_Exclusion_Present (Flag11)
-- All_Present (Flag15)
-- Constant_Present (Flag17)
-- Subtype_Mark (Node4)
-- Access_To_Subprogram_Definition (Node3) (set to Empty if not present)
-----------------------------------------
-- 3.10.1 Incomplete Type Declaration --
-----------------------------------------
-- INCOMPLETE_TYPE_DECLARATION ::=
-- type DEFINING_IDENTIFIER [DISCRIMINANT_PART] [IS TAGGED];
-- N_Incomplete_Type_Declaration
-- Sloc points to TYPE
-- Defining_Identifier (Node1)
-- Discriminant_Specifications (List4) (set to No_List if no
-- discriminant part, or if the discriminant part is an
-- unknown discriminant part)
-- Premature_Use (Node5-Sem) used for improved diagnostics.
-- Unknown_Discriminants_Present (Flag13) set if (<>) discriminant
-- Tagged_Present (Flag15)
----------------------------
-- 3.11 Declarative Part --
----------------------------
-- DECLARATIVE_PART ::= {DECLARATIVE_ITEM}
-- Note: although the parser enforces the syntactic requirement that
-- a declarative part can contain only declarations, the semantic
-- processing may add statements to the list of actions in a
-- declarative part, so the code generator should be prepared
-- to accept a statement in this position.
----------------------------
-- 3.11 Declarative Item --
----------------------------
-- DECLARATIVE_ITEM ::= BASIC_DECLARATIVE_ITEM | BODY
----------------------------------
-- 3.11 Basic Declarative Item --
----------------------------------
-- BASIC_DECLARATIVE_ITEM ::=
-- BASIC_DECLARATION | REPRESENTATION_CLAUSE | USE_CLAUSE
----------------
-- 3.11 Body --
----------------
-- BODY ::= PROPER_BODY | BODY_STUB
-----------------------
-- 3.11 Proper Body --
-----------------------
-- PROPER_BODY ::=
-- SUBPROGRAM_BODY | PACKAGE_BODY | TASK_BODY | PROTECTED_BODY
---------------
-- 4.1 Name --
---------------
-- NAME ::=
-- DIRECT_NAME | EXPLICIT_DEREFERENCE
-- | INDEXED_COMPONENT | SLICE
-- | SELECTED_COMPONENT | ATTRIBUTE_REFERENCE
-- | TYPE_CONVERSION | FUNCTION_CALL
-- | CHARACTER_LITERAL
----------------------
-- 4.1 Direct Name --
----------------------
-- DIRECT_NAME ::= IDENTIFIER | OPERATOR_SYMBOL
-----------------
-- 4.1 Prefix --
-----------------
-- PREFIX ::= NAME | IMPLICIT_DEREFERENCE
-------------------------------
-- 4.1 Explicit Dereference --
-------------------------------
-- EXPLICIT_DEREFERENCE ::= NAME . all
-- N_Explicit_Dereference
-- Sloc points to ALL
-- Prefix (Node3)
-- Actual_Designated_Subtype (Node4-Sem)
-- Atomic_Sync_Required (Flag14-Sem)
-- Has_Dereference_Action (Flag13-Sem)
-- plus fields for expression
-------------------------------
-- 4.1 Implicit Dereference --
-------------------------------
-- IMPLICIT_DEREFERENCE ::= NAME
------------------------------
-- 4.1.1 Indexed Component --
------------------------------
-- INDEXED_COMPONENT ::= PREFIX (EXPRESSION {, EXPRESSION})
-- Note: the parser may generate this node in some situations where it
-- should be a function call. The semantic pass must correct this
-- misidentification (which is inevitable at the parser level).
-- N_Indexed_Component
-- Sloc contains a copy of the Sloc value of the Prefix
-- Prefix (Node3)
-- Expressions (List1)
-- Generalized_Indexing (Node4-Sem)
-- Atomic_Sync_Required (Flag14-Sem)
-- plus fields for expression
-- Note: if any of the subscripts requires a range check, then the
-- Do_Range_Check flag is set on the corresponding expression, with
-- the index type being determined from the type of the Prefix, which
-- references the array being indexed.
-- Note: in a fully analyzed and expanded indexed component node, and
-- hence in any such node that gigi sees, if the prefix is an access
-- type, then an explicit dereference operation has been inserted.
------------------
-- 4.1.2 Slice --
------------------
-- SLICE ::= PREFIX (DISCRETE_RANGE)
-- Note: an implicit subtype is created to describe the resulting
-- type, so that the bounds of this type are the bounds of the slice.
-- N_Slice
-- Sloc points to first token of prefix
-- Prefix (Node3)
-- Discrete_Range (Node4)
-- plus fields for expression
-------------------------------
-- 4.1.3 Selected Component --
-------------------------------
-- SELECTED_COMPONENT ::= PREFIX . SELECTOR_NAME
-- Note: selected components that are semantically expanded names get
-- changed during semantic processing into the separate N_Expanded_Name
-- node. See description of this node in the section on semantic nodes.
-- N_Selected_Component
-- Sloc points to the period
-- Prefix (Node3)
-- Selector_Name (Node2)
-- Associated_Node (Node4-Sem)
-- Do_Discriminant_Check (Flag1-Sem)
-- Is_In_Discriminant_Check (Flag11-Sem)
-- Is_Prefixed_Call (Flag17-Sem)
-- Atomic_Sync_Required (Flag14-Sem)
-- plus fields for expression
--------------------------
-- 4.1.3 Selector Name --
--------------------------
-- SELECTOR_NAME ::= IDENTIFIER | CHARACTER_LITERAL | OPERATOR_SYMBOL
--------------------------------
-- 4.1.4 Attribute Reference --
--------------------------------
-- ATTRIBUTE_REFERENCE ::= PREFIX ' ATTRIBUTE_DESIGNATOR
-- Note: the syntax is quite ambiguous at this point. Consider:
-- A'Length (X) X is part of the attribute designator
-- A'Pos (X) X is an explicit actual parameter of function A'Pos
-- A'Class (X) X is the expression of a type conversion
-- It would be possible for the parser to distinguish these cases
-- by looking at the attribute identifier. However, that would mean
-- more work in introducing new implementation defined attributes,
-- and also it would mean that special processing for attributes
-- would be scattered around, instead of being centralized in the
-- semantic routine that handles an N_Attribute_Reference node.
-- Consequently, the parser in all the above cases stores the
-- expression (X in these examples) as a single element list in
-- in the Expressions field of the N_Attribute_Reference node.
-- Similarly, for attributes like Max which take two arguments,
-- we store the two arguments as a two element list in the
-- Expressions field. Of course it is clear at parse time that
-- this case is really a function call with an attribute as the
-- prefix, but it turns out to be convenient to handle the two
-- argument case in a similar manner to the one argument case,
-- and indeed in general the parser will accept any number of
-- expressions in this position and store them as a list in the
-- attribute reference node. This allows for future addition of
-- attributes that take more than two arguments.
-- Note: named associates are not permitted in function calls where
-- the function is an attribute (see RM 6.4(3)) so it is legitimate
-- to skip the normal subprogram argument processing.
-- Note: for the attributes whose designators are technically keywords,
-- i.e. digits, access, delta, range, the Attribute_Name field contains
-- the corresponding name, even though no identifier is involved.
-- Note: the generated code may contain stream attributes applied to
-- limited types for which no stream routines exist officially. In such
-- case, the result is to use the stream attribute for the underlying
-- full type, or in the case of a protected type, the components
-- (including any discriminants) are merely streamed in order.
-- See Exp_Attr for a complete description of which attributes are
-- passed onto Gigi, and which are handled entirely by the front end.
-- Gigi restriction: For the Pos attribute, the prefix cannot be
-- a non-standard enumeration type or a nonzero/zero semantics
-- boolean type, so the value is simply the stored representation.
-- Gigi requirement: For the Mechanism_Code attribute, if the prefix
-- references a subprogram that is a renaming, then the front end must
-- rewrite the attribute to refer directly to the renamed entity.
-- Note: syntactically the prefix of an attribute reference must be a
-- name, and this (somewhat artificial) requirement is enforced by the
-- parser. However, for many attributes, such as 'Valid, it is quite
-- reasonable to apply the attribute to any value, and hence to any
-- expression. Internally in the tree, the prefix is an expression which
-- does not have to be a name, and this is handled fine by the semantic
-- analysis and expansion, and back ends. This arises for the case of
-- attribute references built by the expander (e.g. 'Valid for the case
-- of an implicit validity check).
-- Note: In generated code, the Address and Unrestricted_Access
-- attributes can be applied to any expression, and the meaning is
-- to create an object containing the value (the object is in the
-- current stack frame), and pass the address of this value. If the
-- Must_Be_Byte_Aligned flag is set, then the object whose address
-- is taken must be on a byte (storage unit) boundary, and if it is
-- not (or may not be), then the generated code must create a copy
-- that is byte aligned, and pass the address of this copy.
-- N_Attribute_Reference
-- Sloc points to apostrophe
-- Prefix (Node3) (general expression, see note above)
-- Attribute_Name (Name2) identifier name from attribute designator
-- Expressions (List1) (set to No_List if no associated expressions)
-- Entity (Node4-Sem) used if the attribute yields a type
-- Associated_Node (Node4-Sem)
-- Do_Overflow_Check (Flag17-Sem)
-- Header_Size_Added (Flag11-Sem)
-- Must_Be_Byte_Aligned (Flag14-Sem)
-- Non_Aliased_Prefix (Flag18-Sem)
-- Redundant_Use (Flag13-Sem)
-- plus fields for expression
-- Note: in Modify_Tree_For_C mode, Max and Min attributes are expanded
-- into equivalent if expressions, properly taking care of side effects.
---------------------------------
-- 4.1.4 Attribute Designator --
---------------------------------
-- ATTRIBUTE_DESIGNATOR ::=
-- IDENTIFIER [(static_EXPRESSION)]
-- | access | delta | digits
-- There is no explicit node in the tree for an attribute designator.
-- Instead the Attribute_Name and Expressions fields of the parent
-- node (N_Attribute_Reference node) hold the information.
-- Note: if ACCESS, DELTA or DIGITS appears in an attribute
-- designator, then they are treated as identifiers internally
-- rather than the keywords of the same name.
--------------------------------------
-- 4.1.4 Range Attribute Reference --
--------------------------------------
-- RANGE_ATTRIBUTE_REFERENCE ::= PREFIX ' RANGE_ATTRIBUTE_DESIGNATOR
-- A range attribute reference is represented in the tree using the
-- normal N_Attribute_Reference node.
---------------------------------------
-- 4.1.4 Range Attribute Designator --
---------------------------------------
-- RANGE_ATTRIBUTE_DESIGNATOR ::= Range [(static_EXPRESSION)]
-- A range attribute designator is represented in the tree using the
-- normal N_Attribute_Reference node.
--------------------
-- 4.3 Aggregate --
--------------------
-- AGGREGATE ::=
-- RECORD_AGGREGATE | EXTENSION_AGGREGATE | ARRAY_AGGREGATE
-----------------------------
-- 4.3.1 Record Aggregate --
-----------------------------
-- RECORD_AGGREGATE ::= (RECORD_COMPONENT_ASSOCIATION_LIST)
-- N_Aggregate
-- Sloc points to left parenthesis
-- Expressions (List1) (set to No_List if none or null record case)
-- Component_Associations (List2) (set to No_List if none)
-- Null_Record_Present (Flag17)
-- Aggregate_Bounds (Node3-Sem)
-- Associated_Node (Node4-Sem)
-- Compile_Time_Known_Aggregate (Flag18-Sem)
-- Expansion_Delayed (Flag11-Sem)
-- Has_Self_Reference (Flag13-Sem)
-- plus fields for expression
-- Note: this structure is used for both record and array aggregates
-- since the two cases are not separable by the parser. The parser
-- makes no attempt to enforce consistency here, so it is up to the
-- semantic phase to make sure that the aggregate is consistent (i.e.
-- that it is not a "half-and-half" case that mixes record and array
-- syntax. In particular, for a record aggregate, the expressions
-- field will be set if there are positional associations.
-- Note: N_Aggregate is not used for all aggregates; in particular,
-- there is a separate node kind for extension aggregates.
-- Note: gigi/gcc can handle array aggregates correctly providing that
-- they are entirely positional, and the array subtype involved has a
-- known at compile time length and is not bit packed, or a convention
-- Fortran array with more than one dimension. If these conditions
-- are not met, then the front end must translate the aggregate into
-- an appropriate set of assignments into a temporary.
-- Note: for the record aggregate case, gigi/gcc can handle most cases
-- of record aggregates, including those for packed, and rep-claused
-- records, and also variant records, providing that there are no
-- variable length fields whose size is not known at compile time,
-- and providing that the aggregate is presented in fully named form.
-- The other situation in which array aggregates and record aggregates
-- cannot be passed to the back end is if assignment to one or more
-- components itself needs expansion, e.g. in the case of an assignment
-- of an object of a controlled type. In such cases, the front end
-- must expand the aggregate to a series of assignments, and apply
-- the required expansion to the individual assignment statements.
----------------------------------------------
-- 4.3.1 Record Component Association List --
----------------------------------------------
-- RECORD_COMPONENT_ASSOCIATION_LIST ::=
-- RECORD_COMPONENT_ASSOCIATION {, RECORD_COMPONENT_ASSOCIATION}
-- | null record
-- There is no explicit node in the tree for a record component
-- association list. Instead the Null_Record_Present flag is set in
-- the parent node for the NULL RECORD case.
------------------------------------------------------
-- 4.3.1 Record Component Association (also 4.3.3) --
------------------------------------------------------
-- RECORD_COMPONENT_ASSOCIATION ::=
-- [COMPONENT_CHOICE_LIST =>] EXPRESSION
-- N_Component_Association
-- Sloc points to first selector name
-- Choices (List1)
-- Loop_Actions (List2-Sem)
-- Expression (Node3) (empty if Box_Present)
-- Box_Present (Flag15)
-- Inherited_Discriminant (Flag13)
-- Note: this structure is used for both record component associations
-- and array component associations, since the two cases aren't always
-- separable by the parser. The choices list may represent either a
-- list of selector names in the record aggregate case, or a list of
-- discrete choices in the array aggregate case or an N_Others_Choice
-- node (which appears as a singleton list). Box_Present gives support
-- to Ada 2005 (AI-287).
----------------------------------
-- 4.3.1 Component Choice List --
----------------------------------
-- COMPONENT_CHOICE_LIST ::=
-- component_SELECTOR_NAME {| component_SELECTOR_NAME}
-- | others
-- The entries of a component choice list appear in the Choices list of
-- the associated N_Component_Association, as either selector names, or
-- as an N_Others_Choice node.
--------------------------------
-- 4.3.2 Extension Aggregate --
--------------------------------
-- EXTENSION_AGGREGATE ::=
-- (ANCESTOR_PART with RECORD_COMPONENT_ASSOCIATION_LIST)
-- Note: extension aggregates are not permitted in Ada 83 mode
-- N_Extension_Aggregate
-- Sloc points to left parenthesis
-- Ancestor_Part (Node3)
-- Associated_Node (Node4-Sem)
-- Expressions (List1) (set to No_List if none or null record case)
-- Component_Associations (List2) (set to No_List if none)
-- Null_Record_Present (Flag17)
-- Expansion_Delayed (Flag11-Sem)
-- Has_Self_Reference (Flag13-Sem)
-- plus fields for expression
--------------------------
-- 4.3.2 Ancestor Part --