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go/types: do not declare new methods on instantiated types

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This is a port of CL 345472 to go/types.

Change-Id: I0e2a88909ecebe9dea3325244153f5c74e4c3ce7
Reviewed-on: https://go-review.googlesource.com/c/go/+/346553
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Robert Findley 2021-08-31 17:09:47 -04:00
parent 5e9ba0b1bd
commit b2f09cd717
2 changed files with 28 additions and 1 deletions
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8
src/go/types/signature.go
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@ -127,7 +127,7 @@ func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast
// Also: Don't report an error via genericType since it will be reported
// again when we type-check the signature.
// TODO(gri) maybe the receiver should be marked as invalid instead?
if recv := asNamed(check.genericType(rname, false)); recv != nil {
if recv, _ := check.genericType(rname, false).(*Named); recv != nil {
recvTParams = recv.TParams().list()
}
}
@ -201,6 +201,12 @@ func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast
switch T := rtyp.(type) {
case *Named:
T.expand(nil)
// The receiver type may be an instantiated type referred to
// by an alias (which cannot have receiver parameters for now).
if T.TArgs() != nil && sig.RParams() == nil {
check.errorf(atPos(recv.pos), _Todo, "cannot define methods on instantiated type %s", recv.typ)
break
}
// spec: "The type denoted by T is called the receiver base type; it must not
// be a pointer or interface type and it must be declared in the same package
// as the method."

21
src/go/types/testdata/fixedbugs/issue47968.go2 vendored Normal file
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@ -0,0 +1,21 @@
// 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 p
type T[P any] struct{}
func (T[P]) m1()
type A1 = T
func (A1[P]) m2() {}
type A2 = T[int]
func (A2 /* ERROR cannot define methods on instantiated type T\[int\] */) m3() {}
func (_ /* ERROR cannot define methods on instantiated type T\[int\] */ A2) m4() {}
func (T[int]) m5() {} // int is the type parameter name, not an instantiation
func (T[* /* ERROR must be an identifier */ int]) m6() {} // syntax error