| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- I T Y P E S -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1992-2022, 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. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNAT; see file COPYING3. If not, go to -- |
| -- http://www.gnu.org/licenses for a complete copy of the license. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This package contains declarations for handling of implicit types |
| |
| with Einfo; use Einfo; |
| with Einfo.Entities; use Einfo.Entities; |
| with Sem_Util; use Sem_Util; |
| with Types; use Types; |
| |
| package Itypes is |
| |
| -------------------- |
| -- Implicit Types -- |
| -------------------- |
| |
| -- Implicit types (Itypes) are types and subtypes created by the semantic |
| -- phase or the expander to reflect the underlying semantics. These could |
| -- be generated by building trees for corresponding declarations and then |
| -- analyzing these trees, but there are three reasons for not doing this |
| -- in some cases: |
| |
| -- 1. The declarations would require more tree nodes |
| |
| -- 2. In some cases, the elaboration of these types is associated |
| -- with internal nodes in the tree. |
| |
| -- 3. For some types, notably class wide types, there is no Ada |
| -- declaration that would correspond to the desired entity. |
| |
| -- So instead, implicit types are constructed by simply creating an |
| -- appropriate entity with the help of routines in this package. These |
| -- entities are fully decorated, as described in Einfo (just as though |
| -- they had been created by the normal analysis procedure). |
| |
| -- The type declaration declaring an Itype must be analyzed with checks |
| -- off because this declaration has not been inserted in the tree (if it |
| -- has been then it is not an Itype), and hence checks that would be |
| -- generated during the analysis cannot be inserted in the tree. At any |
| -- rate, Itype analysis should always be done with checks off, otherwise |
| -- duplicate checks will most likely be emitted. |
| |
| -- Unlike types declared explicitly, implicit types are defined on first |
| -- use, which means that Gigi detects the use of such types, and defines |
| -- them at the point of the first use automatically. |
| |
| -- Although Itypes are not explicitly declared, they are associated with |
| -- a specific node in the tree (roughly the node that caused them to be |
| -- created), via the Associated_Node_For_Itype field. This association is |
| -- used particularly by New_Copy_Tree, which uses it to determine whether |
| -- or not to copy a referenced Itype. If the associated node is part of |
| -- the tree to be copied by New_Copy_Tree, then (since the idea of the |
| -- call to New_Copy_Tree is to create a complete duplicate of a tree, |
| -- as though it had appeared separately in the source), the Itype in |
| -- question is duplicated as part of the New_Copy_Tree processing. |
| |
| -- As a consequence of this copying mechanism, the association between |
| -- Itypes and associated nodes must be one-to-one: several Itypes must |
| -- not share an associated node. For example, the semantic decoration |
| -- of an array aggregate generates several Itypes: for each index subtype |
| -- and for the array subtype. The associated node of each index subtype |
| -- is the corresponding range expression. |
| |
| -- Notes on the use of the Parent field of an Itype |
| |
| -- In some cases, we do create a declaration node for an itype, and in |
| -- such cases, the Parent field of the Itype points to this declaration |
| -- in the normal manner. This case can be detected by checking for a |
| -- non-empty Parent field referencing a declaration whose Defining_Entity |
| -- is the Itype in question. |
| |
| -- In some other cases, where we don't generate such a declaration, as |
| -- described above, the Itype is attached to the tree implicitly by being |
| -- referenced elsewhere, e.g. as the Etype of some object. In this case |
| -- the Parent field may be Empty. |
| |
| -- In other cases where we don't generate a declaration for the Itype, |
| -- the Itype may be attached to an arbitrary node in the tree, using |
| -- the Parent field. This Parent field may even reference a declaration |
| -- for a related different entity (hence the description of the tests |
| -- needed for the case where a declaration for the Itype is created). |
| |
| ------------------ |
| -- Create_Itype -- |
| ------------------ |
| |
| function Create_Itype |
| (Ekind : Entity_Kind; |
| Related_Nod : Node_Id; |
| Related_Id : Entity_Id := Empty; |
| Suffix : Character := ' '; |
| Suffix_Index : Int := 0; |
| Scope_Id : Entity_Id := Current_Scope) return Entity_Id; |
| -- Used to create a new Itype |
| -- |
| -- Related_Nod is the node for which this Itype was created. It is |
| -- set as the Associated_Node_For_Itype of the new Itype. The Sloc of |
| -- the new Itype is that of this node. |
| -- |
| -- Related_Id is present only if the implicit type name may be referenced |
| -- as a public symbol, and thus needs a unique external name. The name |
| -- is created by a call to: |
| -- |
| -- New_External_Name (Chars (Related_Id), Suffix, Suffix_Index, 'T') |
| -- |
| -- If the implicit type does not need an external name, then the |
| -- Related_Id parameter is omitted (and hence Empty). In this case |
| -- Suffix and Suffix_Index are ignored and the implicit type name is |
| -- created by a call to Make_Temporary. |
| -- |
| -- Note that in all cases, the name starts with "T". This is used |
| -- to identify implicit types in the error message handling circuits. |
| -- |
| -- The Scope_Id parameter specifies the scope of the created type, and |
| -- is normally the Current_Scope as shown, but can be set otherwise. |
| -- |
| -- The size/align fields are initialized to unknown (Uint_0). |
| -- |
| -- If Ekind is in Access_Subprogram_Kind, Can_Use_Internal_Rep is set True, |
| -- unless Always_Compatible_Rep_On_Target is True. |
| |
| --------------------------------- |
| -- Create_Null_Excluding_Itype -- |
| --------------------------------- |
| |
| function Create_Null_Excluding_Itype |
| (T : Entity_Id; |
| Related_Nod : Node_Id; |
| Scope_Id : Entity_Id := Current_Scope) return Entity_Id; |
| -- Ada 2005 (AI-231): T is an access type and this subprogram creates and |
| -- returns an internal access-subtype declaration of T that has the null |
| -- exclusion attribute set to True. |
| -- |
| -- Usage of null-excluding Itypes |
| -- ------------------------------ |
| -- |
| -- type T1 is access ... |
| -- type T2 is not null T1; |
| -- |
| -- type Rec is record |
| -- Comp : not null T1; |
| -- end record; |
| -- |
| -- type Arr is array (...) of not null T1; |
| -- |
| -- Instead of associating the not-null attribute with the defining ids of |
| -- these declarations, we generate an internal subtype declaration of T1 |
| -- that has the null exclusion attribute set to true. |
| |
| end Itypes; |
