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cmd/compile: add missing shape check in (*Tsubster).tinter
Add a missing shape check in (*Tsubster).tinter when substituting on a generic type which is an empty interface, analogous to same check in (*Tsubster).tstruct. Empty structs/interfaces that have rparams (i.e. are a generic type or a shape type) need to get a new type of their rparams - they will be different even though they don't have any fields/methods. Without this shape check, we were not correctly completing the Token[int] type during substitution in the example in the issue. This issue only happens for a generic type which is an empty interface (i.e. doesn't actually use the type param, hence quite unusual). Added the test case already created by Keith. Fixes #50841 Change-Id: Ia985b9f52c0e87ed0647b46373e44c51cb748ba4 Reviewed-on: https://go-review.googlesource.com/c/go/+/381175 Trust: Dan Scales <danscales@google.com> Run-TryBot: Dan Scales <danscales@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
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@ -1326,9 +1326,9 @@ func (ts *Tsubster) typ1(t *types.Type) *types.Type {
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func (ts *Tsubster) tstruct(t *types.Type, force bool) *types.Type {
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if t.NumFields() == 0 {
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if t.HasTParam() || t.HasShape() {
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// For an empty struct, we need to return a new type,
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// since it may now be fully instantiated (HasTParam
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// becomes false).
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// For an empty struct, we need to return a new type, if
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// substituting from a generic type or shape type, since it
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// will change HasTParam/HasShape flags.
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return types.NewStruct(t.Pkg(), nil)
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}
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return t
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@ -1387,10 +1387,10 @@ func (ts *Tsubster) tstruct(t *types.Type, force bool) *types.Type {
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// tinter substitutes type params in types of the methods of an interface type.
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func (ts *Tsubster) tinter(t *types.Type, force bool) *types.Type {
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if t.Methods().Len() == 0 {
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if t.HasTParam() {
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// For an empty interface, we need to return a new type,
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// since it may now be fully instantiated (HasTParam
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// becomes false).
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if t.HasTParam() || t.HasShape() {
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// For an empty interface, we need to return a new type, if
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// substituting from a generic type or shape type, since
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// since it will change HasTParam/HasShape flags.
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return types.NewInterface(t.Pkg(), nil, false)
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}
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return t
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22
test/typeparam/issue50841.dir/a.go
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22
test/typeparam/issue50841.dir/a.go
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@ -0,0 +1,22 @@
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// Copyright 2022 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 a
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func Marshal[foobar any]() {
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_ = NewEncoder[foobar]()
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}
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func NewEncoder[foobar any]() *Encoder[foobar] {
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return nil
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}
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type Encoder[foobar any] struct {
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}
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func (e *Encoder[foobar]) EncodeToken(t Token[foobar]) {
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}
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type Token[foobar any] any
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11
test/typeparam/issue50841.dir/b.go
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11
test/typeparam/issue50841.dir/b.go
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@ -0,0 +1,11 @@
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// Copyright 2022 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 b
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import "a"
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func F() {
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a.Marshal[int]()
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}
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7
test/typeparam/issue50841.go
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7
test/typeparam/issue50841.go
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@ -0,0 +1,7 @@
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// compiledir -G=3
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// Copyright 2022 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 ignored
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