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[dev.typeparams] go/types: delay interface check for type bounds
This is a port of CL 331690 to go/types. It diverges from that CL due to the different representation of Fields in the AST. Change-Id: I3ae9ac3a0172dc58ac748f28772d87b00db0732a Reviewed-on: https://go-review.googlesource.com/c/go/+/335034 Trust: Robert Findley <rfindley@google.com> Run-TryBot: Robert Findley <rfindley@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
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@ -724,13 +724,8 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *Named) {
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}
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func (check *Checker) collectTypeParams(list *ast.FieldList) (tparams []*TypeName) {
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// Type parameter lists should not be empty. The parser will
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// complain but we still may get an incorrect AST: ignore it.
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if list.NumFields() == 0 {
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return
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}
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func (check *Checker) collectTypeParams(list *ast.FieldList) []*TypeName {
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var tparams []*TypeName
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// Declare type parameters up-front, with empty interface as type bound.
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// The scope of type parameters starts at the beginning of the type parameter
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// list (so we can have mutually recursive parameterized interfaces).
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@ -738,46 +733,22 @@ func (check *Checker) collectTypeParams(list *ast.FieldList) (tparams []*TypeNam
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tparams = check.declareTypeParams(tparams, f.Names)
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}
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setBoundAt := func(at int, bound Type) {
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assert(IsInterface(bound))
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tparams[at].typ.(*TypeParam).bound = bound
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}
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index := 0
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var bound Type
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for _, f := range list.List {
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if f.Type == nil {
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goto next
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}
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// The predeclared identifier "any" is visible only as a constraint
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// in a type parameter list. Look for it before general constraint
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// resolution.
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if tident, _ := unparen(f.Type).(*ast.Ident); tident != nil && tident.Name == "any" && check.lookup("any") == nil {
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bound = universeAny
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} else {
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bound = check.typ(f.Type)
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}
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// type bound must be an interface
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// TODO(gri) We should delay the interface check because
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// we may not have a complete interface yet:
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// type C(type T C) interface {}
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// (issue #39724).
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if _, ok := under(bound).(*Interface); ok {
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// Otherwise, set the bound for each type parameter.
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for i := range f.Names {
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setBoundAt(index+i, bound)
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}
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} else if bound != Typ[Invalid] {
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check.errorf(f.Type, _Todo, "%s is not an interface", bound)
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bound = check.boundType(f.Type)
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for i := range f.Names {
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tparams[index+i].typ.(*TypeParam).bound = bound
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}
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next:
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index += len(f.Names)
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}
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return
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return tparams
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}
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func (check *Checker) declareTypeParams(tparams []*TypeName, names []*ast.Ident) []*TypeName {
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@ -795,6 +766,23 @@ func (check *Checker) declareTypeParams(tparams []*TypeName, names []*ast.Ident)
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return tparams
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}
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// boundType type-checks the type expression e and returns its type, or Typ[Invalid].
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// The type must be an interface, including the predeclared type "any".
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func (check *Checker) boundType(e ast.Expr) Type {
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// The predeclared identifier "any" is visible only as a type bound in a type parameter list.
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if name, _ := unparen(e).(*ast.Ident); name != nil && name.Name == "any" && check.lookup("any") == nil {
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return universeAny
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}
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bound := check.typ(e)
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check.later(func() {
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if _, ok := under(bound).(*Interface); !ok && bound != Typ[Invalid] {
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check.errorf(e, _Todo, "%s is not an interface", bound)
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}
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})
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return bound
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}
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func (check *Checker) collectMethods(obj *TypeName) {
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// get associated methods
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// (Checker.collectObjects only collects methods with non-blank names;
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37
src/go/types/testdata/fixedbugs/issue40789.go2
vendored
Normal file
37
src/go/types/testdata/fixedbugs/issue40789.go2
vendored
Normal file
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@ -0,0 +1,37 @@
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import "fmt"
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func main() {
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m := map[string]int{
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"a": 6,
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"b": 7,
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}
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fmt.Println(copyMap[map[string]int, string, int](m))
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}
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type Map[K comparable, V any] interface {
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map[K] V
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}
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func copyMap[M Map[K, V], K comparable, V any](m M) M {
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m1 := make(M)
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for k, v := range m {
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m1[k] = v
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}
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return m1
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}
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// simpler test case from the same issue
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type A[X comparable] interface {
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[]X
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}
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func f[B A[X], X comparable]() B {
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return nil
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}
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@ -623,7 +623,11 @@ func (check *Checker) newTypeParam(obj *TypeName, index int, bound Type) *TypePa
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}
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func (t *TypeParam) Bound() *Interface {
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iface := asInterface(t.bound)
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// we may not have an interface (error reported elsewhere)
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iface, _ := under(t.bound).(*Interface)
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if iface == nil {
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return &emptyInterface
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}
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// use the type bound position if we have one
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pos := token.NoPos
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if n, _ := t.bound.(*Named); n != nil {
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