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[dev.typeparams] go/types: use correct type parameter list in missingMethod

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This is a port of CL 321232 to go/types, adjusted to add a missing
comment and to remove optional support for method type params.

Fixes #46275

Change-Id: I63fcbb669e7607876a888fca89b9064568805448
Reviewed-on: https://go-review.googlesource.com/c/go/+/324751
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>
This commit is contained in:
Rob Findley 2021-06-03 10:57:09 -04:00 committed by Robert Findley
parent 62c40878e4
commit 090a17c998
2 changed files with 35 additions and 1 deletions
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9
src/go/types/lookup.go
View file

@ -327,11 +327,15 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method,
return m, f
}
// both methods must have the same number of type parameters
ftyp := f.typ.(*Signature)
mtyp := m.typ.(*Signature)
if len(ftyp.tparams) != len(mtyp.tparams) {
return m, f
}
if len(ftyp.tparams) > 0 {
panic("internal error: method with type parameters")
}
// If the methods have type parameters we don't care whether they
// are the same or not, as long as they match up. Use unification
@ -385,6 +389,9 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method,
if len(ftyp.tparams) != len(mtyp.tparams) {
return m, f
}
if len(ftyp.tparams) > 0 {
panic("internal error: method with type parameters")
}
// If V is a (instantiated) generic type, its methods are still
// parameterized using the original (declaration) receiver type
@ -412,7 +419,7 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method,
// TODO(gri) is this always correct? what about type bounds?
// (Alternative is to rename/subst type parameters and compare.)
u := newUnifier(check, true)
u.x.init(ftyp.tparams)
u.x.init(ftyp.rparams)
if !u.unify(ftyp, mtyp) {
return m, f
}

27
src/go/types/testdata/fixedbugs/issue46275.go2 vendored Normal file
View file

@ -0,0 +1,27 @@
// Copyright 2021 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.
package issue46275
type N[T any] struct {
*N[T]
t T
}
func (n *N[T]) Elem() T {
return n.t
}
type I interface {
Elem() string
}
func _() {
var n1 *N[string]
var _ I = n1
type NS N[string]
var n2 *NS
var _ I = n2
}