| // Copyright 2013 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // This file implements type-checking of identifiers and type expressions. |
| |
| package types |
| |
| import ( |
| "fmt" |
| "go/ast" |
| "go/constant" |
| "go/internal/typeparams" |
| "strings" |
| ) |
| |
| // ident type-checks identifier e and initializes x with the value or type of e. |
| // If an error occurred, x.mode is set to invalid. |
| // For the meaning of def, see Checker.definedType, below. |
| // If wantType is set, the identifier e is expected to denote a type. |
| // |
| func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, wantType bool) { |
| x.mode = invalid |
| x.expr = e |
| |
| // Note that we cannot use check.lookup here because the returned scope |
| // may be different from obj.Parent(). See also Scope.LookupParent doc. |
| scope, obj := check.scope.LookupParent(e.Name, check.pos) |
| switch obj { |
| case nil: |
| if e.Name == "_" { |
| // Blank identifiers are never declared, but the current identifier may |
| // be a placeholder for a receiver type parameter. In this case we can |
| // resolve its type and object from Checker.recvTParamMap. |
| if tpar := check.recvTParamMap[e]; tpar != nil { |
| x.mode = typexpr |
| x.typ = tpar |
| } else { |
| check.error(e, _InvalidBlank, "cannot use _ as value or type") |
| } |
| } else { |
| check.errorf(e, _UndeclaredName, "undeclared name: %s", e.Name) |
| } |
| return |
| case universeAny, universeComparable: |
| if !check.allowVersion(check.pkg, 1, 18) { |
| check.errorf(e, _UndeclaredName, "undeclared name: %s (requires version go1.18 or later)", e.Name) |
| return // avoid follow-on errors |
| } |
| } |
| check.recordUse(e, obj) |
| |
| // Type-check the object. |
| // Only call Checker.objDecl if the object doesn't have a type yet |
| // (in which case we must actually determine it) or the object is a |
| // TypeName and we also want a type (in which case we might detect |
| // a cycle which needs to be reported). Otherwise we can skip the |
| // call and avoid a possible cycle error in favor of the more |
| // informative "not a type/value" error that this function's caller |
| // will issue (see issue #25790). |
| typ := obj.Type() |
| if _, gotType := obj.(*TypeName); typ == nil || gotType && wantType { |
| check.objDecl(obj, def) |
| typ = obj.Type() // type must have been assigned by Checker.objDecl |
| } |
| assert(typ != nil) |
| |
| // The object may have been dot-imported. |
| // If so, mark the respective package as used. |
| // (This code is only needed for dot-imports. Without them, |
| // we only have to mark variables, see *Var case below). |
| if pkgName := check.dotImportMap[dotImportKey{scope, obj.Name()}]; pkgName != nil { |
| pkgName.used = true |
| } |
| |
| switch obj := obj.(type) { |
| case *PkgName: |
| check.errorf(e, _InvalidPkgUse, "use of package %s not in selector", obj.name) |
| return |
| |
| case *Const: |
| check.addDeclDep(obj) |
| if typ == Typ[Invalid] { |
| return |
| } |
| if obj == universeIota { |
| if check.iota == nil { |
| check.errorf(e, _InvalidIota, "cannot use iota outside constant declaration") |
| return |
| } |
| x.val = check.iota |
| } else { |
| x.val = obj.val |
| } |
| assert(x.val != nil) |
| x.mode = constant_ |
| |
| case *TypeName: |
| if check.isBrokenAlias(obj) { |
| check.errorf(e, _InvalidDeclCycle, "invalid use of type alias %s in recursive type (see issue #50729)", obj.name) |
| return |
| } |
| x.mode = typexpr |
| |
| case *Var: |
| // It's ok to mark non-local variables, but ignore variables |
| // from other packages to avoid potential race conditions with |
| // dot-imported variables. |
| if obj.pkg == check.pkg { |
| obj.used = true |
| } |
| check.addDeclDep(obj) |
| if typ == Typ[Invalid] { |
| return |
| } |
| x.mode = variable |
| |
| case *Func: |
| check.addDeclDep(obj) |
| x.mode = value |
| |
| case *Builtin: |
| x.id = obj.id |
| x.mode = builtin |
| |
| case *Nil: |
| x.mode = value |
| |
| default: |
| unreachable() |
| } |
| |
| x.typ = typ |
| } |
| |
| // typ type-checks the type expression e and returns its type, or Typ[Invalid]. |
| // The type must not be an (uninstantiated) generic type. |
| func (check *Checker) typ(e ast.Expr) Type { |
| return check.definedType(e, nil) |
| } |
| |
| // varType type-checks the type expression e and returns its type, or Typ[Invalid]. |
| // The type must not be an (uninstantiated) generic type and it must not be a |
| // constraint interface. |
| func (check *Checker) varType(e ast.Expr) Type { |
| typ := check.definedType(e, nil) |
| check.validVarType(e, typ) |
| return typ |
| } |
| |
| // validVarType reports an error if typ is a constraint interface. |
| // The expression e is used for error reporting, if any. |
| func (check *Checker) validVarType(e ast.Expr, typ Type) { |
| // If we have a type parameter there's nothing to do. |
| if isTypeParam(typ) { |
| return |
| } |
| |
| // We don't want to call under() or complete interfaces while we are in |
| // the middle of type-checking parameter declarations that might belong |
| // to interface methods. Delay this check to the end of type-checking. |
| check.later(func() { |
| if t, _ := under(typ).(*Interface); t != nil { |
| tset := computeInterfaceTypeSet(check, e.Pos(), t) // TODO(gri) is this the correct position? |
| if !tset.IsMethodSet() { |
| if tset.comparable { |
| check.softErrorf(e, _MisplacedConstraintIface, "interface is (or embeds) comparable") |
| } else { |
| check.softErrorf(e, _MisplacedConstraintIface, "interface contains type constraints") |
| } |
| } |
| } |
| }) |
| } |
| |
| // definedType is like typ but also accepts a type name def. |
| // If def != nil, e is the type specification for the defined type def, declared |
| // in a type declaration, and def.underlying will be set to the type of e before |
| // any components of e are type-checked. |
| // |
| func (check *Checker) definedType(e ast.Expr, def *Named) Type { |
| typ := check.typInternal(e, def) |
| assert(isTyped(typ)) |
| if isGeneric(typ) { |
| check.errorf(e, _WrongTypeArgCount, "cannot use generic type %s without instantiation", typ) |
| typ = Typ[Invalid] |
| } |
| check.recordTypeAndValue(e, typexpr, typ, nil) |
| return typ |
| } |
| |
| // genericType is like typ but the type must be an (uninstantiated) generic |
| // type. If reason is non-nil and the type expression was a valid type but not |
| // generic, reason will be populated with a message describing the error. |
| func (check *Checker) genericType(e ast.Expr, reason *string) Type { |
| typ := check.typInternal(e, nil) |
| assert(isTyped(typ)) |
| if typ != Typ[Invalid] && !isGeneric(typ) { |
| if reason != nil { |
| *reason = check.sprintf("%s is not a generic type", typ) |
| } |
| typ = Typ[Invalid] |
| } |
| // TODO(gri) what is the correct call below? |
| check.recordTypeAndValue(e, typexpr, typ, nil) |
| return typ |
| } |
| |
| // goTypeName returns the Go type name for typ and |
| // removes any occurrences of "types." from that name. |
| func goTypeName(typ Type) string { |
| return strings.ReplaceAll(fmt.Sprintf("%T", typ), "types.", "") |
| } |
| |
| // typInternal drives type checking of types. |
| // Must only be called by definedType or genericType. |
| // |
| func (check *Checker) typInternal(e0 ast.Expr, def *Named) (T Type) { |
| if trace { |
| check.trace(e0.Pos(), "-- type %s", e0) |
| check.indent++ |
| defer func() { |
| check.indent-- |
| var under Type |
| if T != nil { |
| // Calling under() here may lead to endless instantiations. |
| // Test case: type T[P any] *T[P] |
| under = safeUnderlying(T) |
| } |
| if T == under { |
| check.trace(e0.Pos(), "=> %s // %s", T, goTypeName(T)) |
| } else { |
| check.trace(e0.Pos(), "=> %s (under = %s) // %s", T, under, goTypeName(T)) |
| } |
| }() |
| } |
| |
| switch e := e0.(type) { |
| case *ast.BadExpr: |
| // ignore - error reported before |
| |
| case *ast.Ident: |
| var x operand |
| check.ident(&x, e, def, true) |
| |
| switch x.mode { |
| case typexpr: |
| typ := x.typ |
| def.setUnderlying(typ) |
| return typ |
| case invalid: |
| // ignore - error reported before |
| case novalue: |
| check.errorf(&x, _NotAType, "%s used as type", &x) |
| default: |
| check.errorf(&x, _NotAType, "%s is not a type", &x) |
| } |
| |
| case *ast.SelectorExpr: |
| var x operand |
| check.selector(&x, e, def) |
| |
| switch x.mode { |
| case typexpr: |
| typ := x.typ |
| def.setUnderlying(typ) |
| return typ |
| case invalid: |
| // ignore - error reported before |
| case novalue: |
| check.errorf(&x, _NotAType, "%s used as type", &x) |
| default: |
| check.errorf(&x, _NotAType, "%s is not a type", &x) |
| } |
| |
| case *ast.IndexExpr, *ast.IndexListExpr: |
| ix := typeparams.UnpackIndexExpr(e) |
| if !check.allowVersion(check.pkg, 1, 18) { |
| check.softErrorf(inNode(e, ix.Lbrack), _UnsupportedFeature, "type instantiation requires go1.18 or later") |
| } |
| return check.instantiatedType(ix, def) |
| |
| case *ast.ParenExpr: |
| // Generic types must be instantiated before they can be used in any form. |
| // Consequently, generic types cannot be parenthesized. |
| return check.definedType(e.X, def) |
| |
| case *ast.ArrayType: |
| if e.Len == nil { |
| typ := new(Slice) |
| def.setUnderlying(typ) |
| typ.elem = check.varType(e.Elt) |
| return typ |
| } |
| |
| typ := new(Array) |
| def.setUnderlying(typ) |
| typ.len = check.arrayLength(e.Len) |
| typ.elem = check.varType(e.Elt) |
| if typ.len >= 0 { |
| return typ |
| } |
| |
| case *ast.Ellipsis: |
| // dots are handled explicitly where they are legal |
| // (array composite literals and parameter lists) |
| check.error(e, _InvalidDotDotDot, "invalid use of '...'") |
| check.use(e.Elt) |
| |
| case *ast.StructType: |
| typ := new(Struct) |
| def.setUnderlying(typ) |
| check.structType(typ, e) |
| return typ |
| |
| case *ast.StarExpr: |
| typ := new(Pointer) |
| typ.base = Typ[Invalid] // avoid nil base in invalid recursive type declaration |
| def.setUnderlying(typ) |
| typ.base = check.varType(e.X) |
| return typ |
| |
| case *ast.FuncType: |
| typ := new(Signature) |
| def.setUnderlying(typ) |
| check.funcType(typ, nil, e) |
| return typ |
| |
| case *ast.InterfaceType: |
| typ := check.newInterface() |
| def.setUnderlying(typ) |
| if def != nil { |
| typ.obj = def.obj |
| } |
| check.interfaceType(typ, e, def) |
| return typ |
| |
| case *ast.MapType: |
| typ := new(Map) |
| def.setUnderlying(typ) |
| |
| typ.key = check.varType(e.Key) |
| typ.elem = check.varType(e.Value) |
| |
| // spec: "The comparison operators == and != must be fully defined |
| // for operands of the key type; thus the key type must not be a |
| // function, map, or slice." |
| // |
| // Delay this check because it requires fully setup types; |
| // it is safe to continue in any case (was issue 6667). |
| check.later(func() { |
| if !Comparable(typ.key) { |
| var why string |
| if isTypeParam(typ.key) { |
| why = " (missing comparable constraint)" |
| } |
| check.errorf(e.Key, _IncomparableMapKey, "incomparable map key type %s%s", typ.key, why) |
| } |
| }) |
| |
| return typ |
| |
| case *ast.ChanType: |
| typ := new(Chan) |
| def.setUnderlying(typ) |
| |
| dir := SendRecv |
| switch e.Dir { |
| case ast.SEND | ast.RECV: |
| // nothing to do |
| case ast.SEND: |
| dir = SendOnly |
| case ast.RECV: |
| dir = RecvOnly |
| default: |
| check.invalidAST(e, "unknown channel direction %d", e.Dir) |
| // ok to continue |
| } |
| |
| typ.dir = dir |
| typ.elem = check.varType(e.Value) |
| return typ |
| |
| default: |
| check.errorf(e0, _NotAType, "%s is not a type", e0) |
| } |
| |
| typ := Typ[Invalid] |
| def.setUnderlying(typ) |
| return typ |
| } |
| |
| func (check *Checker) instantiatedType(ix *typeparams.IndexExpr, def *Named) (res Type) { |
| pos := ix.X.Pos() |
| if trace { |
| check.trace(pos, "-- instantiating %s with %s", ix.X, ix.Indices) |
| check.indent++ |
| defer func() { |
| check.indent-- |
| // Don't format the underlying here. It will always be nil. |
| check.trace(pos, "=> %s", res) |
| }() |
| } |
| |
| var reason string |
| gtyp := check.genericType(ix.X, &reason) |
| if reason != "" { |
| check.invalidOp(ix.Orig, _NotAGenericType, "%s (%s)", ix.Orig, reason) |
| } |
| if gtyp == Typ[Invalid] { |
| return gtyp // error already reported |
| } |
| |
| orig, _ := gtyp.(*Named) |
| if orig == nil { |
| panic(fmt.Sprintf("%v: cannot instantiate %v", ix.Pos(), gtyp)) |
| } |
| |
| // evaluate arguments |
| targs := check.typeList(ix.Indices) |
| if targs == nil { |
| def.setUnderlying(Typ[Invalid]) // avoid errors later due to lazy instantiation |
| return Typ[Invalid] |
| } |
| |
| // enableTypeTypeInference controls whether to infer missing type arguments |
| // using constraint type inference. See issue #51527. |
| const enableTypeTypeInference = false |
| |
| // create the instance |
| ctxt := check.bestContext(nil) |
| h := ctxt.instanceHash(orig, targs) |
| // targs may be incomplete, and require inference. In any case we should de-duplicate. |
| inst, _ := ctxt.lookup(h, orig, targs).(*Named) |
| // If inst is non-nil, we can't just return here. Inst may have been |
| // constructed via recursive substitution, in which case we wouldn't do the |
| // validation below. Ensure that the validation (and resulting errors) runs |
| // for each instantiated type in the source. |
| if inst == nil { |
| // x may be a selector for an imported type; use its start pos rather than x.Pos(). |
| tname := NewTypeName(ix.Pos(), orig.obj.pkg, orig.obj.name, nil) |
| inst = check.newNamed(tname, orig, nil, nil, nil) // underlying, methods and tparams are set when named is resolved |
| inst.targs = newTypeList(targs) |
| inst = ctxt.update(h, orig, targs, inst).(*Named) |
| } |
| def.setUnderlying(inst) |
| |
| inst.resolver = func(ctxt *Context, n *Named) (*TypeParamList, Type, *methodList) { |
| tparams := n.orig.TypeParams().list() |
| |
| targs := n.targs.list() |
| if enableTypeTypeInference && len(targs) < len(tparams) { |
| // If inference fails, len(inferred) will be 0, and inst.underlying will |
| // be set to Typ[Invalid] in expandNamed. |
| inferred := check.infer(ix.Orig, tparams, targs, nil, nil) |
| if len(inferred) > len(targs) { |
| n.targs = newTypeList(inferred) |
| } |
| } |
| |
| return expandNamed(ctxt, n, pos) |
| } |
| |
| // orig.tparams may not be set up, so we need to do expansion later. |
| check.later(func() { |
| // This is an instance from the source, not from recursive substitution, |
| // and so it must be resolved during type-checking so that we can report |
| // errors. |
| inst.resolve(ctxt) |
| // Since check is non-nil, we can still mutate inst. Unpinning the resolver |
| // frees some memory. |
| inst.resolver = nil |
| check.recordInstance(ix.Orig, inst.TypeArgs().list(), inst) |
| |
| if check.validateTArgLen(pos, inst.tparams.Len(), inst.targs.Len()) { |
| if i, err := check.verify(pos, inst.tparams.list(), inst.targs.list()); err != nil { |
| // best position for error reporting |
| pos := ix.Pos() |
| if i < len(ix.Indices) { |
| pos = ix.Indices[i].Pos() |
| } |
| check.softErrorf(atPos(pos), _InvalidTypeArg, err.Error()) |
| } else { |
| check.mono.recordInstance(check.pkg, pos, inst.tparams.list(), inst.targs.list(), ix.Indices) |
| } |
| } |
| |
| check.validType(inst) |
| }) |
| |
| return inst |
| } |
| |
| // arrayLength type-checks the array length expression e |
| // and returns the constant length >= 0, or a value < 0 |
| // to indicate an error (and thus an unknown length). |
| func (check *Checker) arrayLength(e ast.Expr) int64 { |
| // If e is an identifier, the array declaration might be an |
| // attempt at a parameterized type declaration with missing |
| // constraint. Provide an error message that mentions array |
| // length. |
| if name, _ := e.(*ast.Ident); name != nil { |
| obj := check.lookup(name.Name) |
| if obj == nil { |
| check.errorf(name, _InvalidArrayLen, "undeclared name %s for array length", name.Name) |
| return -1 |
| } |
| if _, ok := obj.(*Const); !ok { |
| check.errorf(name, _InvalidArrayLen, "invalid array length %s", name.Name) |
| return -1 |
| } |
| } |
| |
| var x operand |
| check.expr(&x, e) |
| if x.mode != constant_ { |
| if x.mode != invalid { |
| check.errorf(&x, _InvalidArrayLen, "array length %s must be constant", &x) |
| } |
| return -1 |
| } |
| |
| if isUntyped(x.typ) || isInteger(x.typ) { |
| if val := constant.ToInt(x.val); val.Kind() == constant.Int { |
| if representableConst(val, check, Typ[Int], nil) { |
| if n, ok := constant.Int64Val(val); ok && n >= 0 { |
| return n |
| } |
| check.errorf(&x, _InvalidArrayLen, "invalid array length %s", &x) |
| return -1 |
| } |
| } |
| } |
| |
| check.errorf(&x, _InvalidArrayLen, "array length %s must be integer", &x) |
| return -1 |
| } |
| |
| // typeList provides the list of types corresponding to the incoming expression list. |
| // If an error occurred, the result is nil, but all list elements were type-checked. |
| func (check *Checker) typeList(list []ast.Expr) []Type { |
| res := make([]Type, len(list)) // res != nil even if len(list) == 0 |
| for i, x := range list { |
| t := check.varType(x) |
| if t == Typ[Invalid] { |
| res = nil |
| } |
| if res != nil { |
| res[i] = t |
| } |
| } |
| return res |
| } |
