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go/types: produce empty type set for invalid ~T

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This is a clean port of CL 366278 from types2 to go/types.

For #49739.

Change-Id: I2e2cb739c02fcc07e012499c7b65b13b057875ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/367197
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer 2021-11-26 12:43:06 -08:00
parent 2f6d382050
commit 1ab677a797
2 changed files with 33 additions and 6 deletions
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23
src/go/types/testdata/fixedbugs/issue49739.go2 vendored Normal file
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@ -0,0 +1,23 @@
// 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.
// Verify that we get an empty type set (not just an error)
// when using an invalid ~A.
package p
type A int
type C interface {
~ /* ERROR invalid use of ~ */ A
}
func f[_ C]() {}
func g[_ interface{ C }]() {}
func h[_ C | int]() {}
func _() {
_ = f[int /* ERROR cannot implement C \(empty type set\) */]
_ = g[int /* ERROR cannot implement interface{C} \(empty type set\) */]
_ = h[int]
}

14
src/go/types/typeset.go
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@ -365,14 +365,18 @@ func computeUnionTypeSet(check *Checker, pos token.Pos, utyp *Union) *_TypeSet {
var allTerms termlist
for _, t := range utyp.terms {
var terms termlist
switch u := under(t.typ).(type) {
case *Interface:
u := under(t.typ)
if ui, _ := u.(*Interface); ui != nil {
// For now we don't permit type parameters as constraints.
assert(!isTypeParam(t.typ))
terms = computeInterfaceTypeSet(check, pos, u).terms
default:
if t.typ == Typ[Invalid] {
terms = computeInterfaceTypeSet(check, pos, ui).terms
} else if t.typ == Typ[Invalid] {
continue
} else {
if t.tilde && !Identical(t.typ, u) {
// There is no underlying type which is t.typ.
// The corresponding type set is empty.
t = nil // ∅ term
}
terms = termlist{(*term)(t)}
}