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[dev.typeparams] cmd/compile/internal/types2: embedding stand-alone type parameters is not permitted

For #47127.

Change-Id: Ie979ff56ae7c2dd0e5ce0ff39588f98ae68b5ee9
Reviewed-on: https://go-review.googlesource.com/c/go/+/334151
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 2021-07-12 22:39:39 -07:00
parent 3a047326e8
commit 4ff0e04c2e
9 changed files with 87 additions and 40 deletions

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@ -232,7 +232,7 @@ func _[T interface{ ~func() }](f T) {
type sliceOf[E any] interface{ ~[]E }
func append[T interface{}, S sliceOf[T], T2 interface{ T }](s S, t ...T2) S
func append[T interface{}, S sliceOf[T], T2 interface{}](s S, t ...T2) S
var f func()
var cancelSlice []context.CancelFunc

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@ -8,19 +8,20 @@ import "strconv"
type any interface{}
func f0[A any, B interface{~C}, C interface{~D}, D interface{~A}](A, B, C, D)
func _() {
f := f0[string]
f("a", "b", "c", "d")
f0("a", "b", "c", "d")
}
func f1[A any, B interface{~A}](A, B)
func _() {
f := f1[int]
f(int(0), int(0))
f1(int(0), int(0))
}
// Embedding stand-alone type parameters is not permitted for now. Disabled.
// func f0[A any, B interface{~C}, C interface{~D}, D interface{~A}](A, B, C, D)
// func _() {
// f := f0[string]
// f("a", "b", "c", "d")
// f0("a", "b", "c", "d")
// }
//
// func f1[A any, B interface{~A}](A, B)
// func _() {
// f := f1[int]
// f(int(0), int(0))
// f1(int(0), int(0))
// }
func f2[A any, B interface{~[]A}](A, B)
func _() {
@ -29,13 +30,14 @@ func _() {
f2(byte(0), []byte{})
}
func f3[A any, B interface{~C}, C interface{~*A}](A, B, C)
func _() {
f := f3[int]
var x int
f(x, &x, &x)
f3(x, &x, &x)
}
// Embedding stand-alone type parameters is not permitted for now. Disabled.
// func f3[A any, B interface{~C}, C interface{~*A}](A, B, C)
// func _() {
// f := f3[int]
// var x int
// f(x, &x, &x)
// f3(x, &x, &x)
// }
func f4[A any, B interface{~[]C}, C interface{~*A}](A, B, C)
func _() {

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@ -31,9 +31,10 @@ type x7[A any] struct{ foo7 }
func main7() { var _ foo7 = x7[int]{} }
// crash 8
type foo8[A any] interface { ~A }
func bar8[A foo8[A]](a A) {}
func main8() {}
// Embedding stand-alone type parameters is not permitted for now. Disabled.
// type foo8[A any] interface { ~A }
// func bar8[A foo8[A]](a A) {}
// func main8() {}
// crash 9
type foo9[A any] interface { foo9 /* ERROR illegal cycle */ [A] }

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@ -4,6 +4,9 @@
package p
// Embedding stand-alone type parameters is not permitted for now. Disabled.
/*
import "fmt"
// Minimal test case.
@ -25,3 +28,4 @@ func Print[T constr[T]](s []T) {
func f() {
Print([]string{"Hello, ", "playground\n"})
}
*/

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@ -2,14 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// TODO(gri) Eventually, once we disallow type lists, we need to
// adjust this code: for 1.17 we don't accept type parameters,
// and for 1.18 this code is valid.
// Leaving for now so we can see that existing errors
// are being reported.
package go1_17 // don't permit non-interface elements in interfaces
package p
type T[P any] interface{
P // ERROR P is a type parameter, not an interface
P // ERROR cannot embed a type parameter
}

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@ -0,0 +1,37 @@
// 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.
// Embedding of stand-alone type parameters is not permitted.
package p
type (
_[P any] interface{ *P | []P | chan P | map[string]P }
_[P any] interface{ P /* ERROR "cannot embed a type parameter" */ }
_[P any] interface{ ~P /* ERROR "cannot embed a type parameter" */ }
_[P any] interface{ int | P /* ERROR "cannot embed a type parameter" */ }
_[P any] interface{ int | ~P /* ERROR "cannot embed a type parameter" */ }
)
func _[P any]() {
type (
_[P any] interface{ *P | []P | chan P | map[string]P }
_[P any] interface{ P /* ERROR "cannot embed a type parameter" */ }
_[P any] interface{ ~P /* ERROR "cannot embed a type parameter" */ }
_[P any] interface{ int | P /* ERROR "cannot embed a type parameter" */ }
_[P any] interface{ int | ~P /* ERROR "cannot embed a type parameter" */ }
_ interface{ *P | []P | chan P | map[string]P }
_ interface{ P /* ERROR "cannot embed a type parameter" */ }
_ interface{ ~P /* ERROR "cannot embed a type parameter" */ }
_ interface{ int | P /* ERROR "cannot embed a type parameter" */ }
_ interface{ int | ~P /* ERROR "cannot embed a type parameter" */ }
)
}
func _[P any, Q interface{ *P | []P | chan P | map[string]P }]()
func _[P any, Q interface{ P /* ERROR "cannot embed a type parameter" */ }]()
func _[P any, Q interface{ ~P /* ERROR "cannot embed a type parameter" */ }]()
func _[P any, Q interface{ int | P /* ERROR "cannot embed a type parameter" */ }]()
func _[P any, Q interface{ int | ~P /* ERROR "cannot embed a type parameter" */ }]()

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@ -216,11 +216,9 @@ func computeTypeSet(check *Checker, pos syntax.Pos, ityp *Interface) *TypeSet {
// interface before go1.18.
types = typ
case *TypeParam:
if check != nil && !check.allowVersion(check.pkg, 1, 18) {
check.errorf(pos, "%s is a type parameter, not an interface", typ)
continue
}
types = typ
// Embedding stand-alone type parameters is not permitted for now.
// This case is handled during union parsing.
unreachable()
default:
if typ == Typ[Invalid] {
continue

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@ -128,13 +128,18 @@ func parseUnion(check *Checker, tlist []syntax.Expr) Type {
return newUnion(types, tilde)
}
func parseTilde(check *Checker, x syntax.Expr) (Type, bool) {
tilde := false
func parseTilde(check *Checker, x syntax.Expr) (typ Type, tilde bool) {
if op, _ := x.(*syntax.Operation); op != nil && op.Op == syntax.Tilde {
x = op.X
tilde = true
}
return check.anyType(x), tilde
typ = check.anyType(x)
// embedding stand-alone type parameters is not permitted (issue #47127).
if _, ok := under(typ).(*TypeParam); ok {
check.error(x, "cannot embed a type parameter")
typ = Typ[Invalid]
}
return
}
// intersect computes the intersection of the types x and y,

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@ -67,6 +67,8 @@ func _[V any, T interface { type map[string]V }](p T) V {
// Testing partial and full type inference, including the case where the types can
// be inferred without needing the types of the function arguments.
// Cannot embed stand-alone type parameters. Disabled for now.
/*
func f0[A any, B interface{type C}, C interface{type D}, D interface{type A}](A, B, C, D)
func _() {
f := f0[string]
@ -82,6 +84,7 @@ func _() {
f(0, 0)
f1(0, 0)
}
*/
func f2[A any, B interface{type []A}](_ A, _ B)
func _() {
@ -92,6 +95,8 @@ func _() {
// f2(0, []byte{}) - this one doesn't work
}
// Cannot embed stand-alone type parameters. Disabled for now.
/*
func f3[A any, B interface{type C}, C interface{type *A}](a A, _ B, c C)
func _() {
f := f3[int]
@ -99,6 +104,7 @@ func _() {
f(x, &x, &x)
f3(x, &x, &x)
}
*/
func f4[A any, B interface{type []C}, C interface{type *A}](_ A, _ B, c C)
func _() {