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[dev.typeparams] go/types: implement <-ch where ch is of type parameter type
This is a port of CL 333709 to go/types, adjusted for the different error API. Fixes #43671 Change-Id: Ifd340149bfbcabe401cec74398cb83f2ae812e51 Reviewed-on: https://go-review.googlesource.com/c/go/+/335075 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>
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@ -144,6 +144,14 @@ var op2str2 = [...]string{
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token.SHL: "shift",
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}
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func underIs(typ Type, f func(Type) bool) bool {
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u := under(typ)
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if tpar, _ := u.(*TypeParam); tpar != nil {
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return tpar.underIs(f)
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}
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return f(u)
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}
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// The unary expression e may be nil. It's passed in for better error messages only.
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func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
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check.expr(x, e.X)
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@ -164,19 +172,29 @@ func (check *Checker) unary(x *operand, e *ast.UnaryExpr) {
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return
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case token.ARROW:
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typ := asChan(x.typ)
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if typ == nil {
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var elem Type
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if !underIs(x.typ, func(u Type) bool {
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ch, _ := u.(*Chan)
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if ch == nil {
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check.invalidOp(x, _InvalidReceive, "cannot receive from non-channel %s", x)
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x.mode = invalid
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return
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return false
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}
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if typ.dir == SendOnly {
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if ch.dir == SendOnly {
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check.invalidOp(x, _InvalidReceive, "cannot receive from send-only channel %s", x)
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return false
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}
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if elem != nil && !Identical(ch.elem, elem) {
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check.invalidOp(x, _Todo, "channels of %s must have the same element type", x)
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return false
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}
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elem = ch.elem
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return true
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}) {
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x.mode = invalid
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return
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}
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x.mode = commaok
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x.typ = typ.elem
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x.typ = elem
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check.hasCallOrRecv = true
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return
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}
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58
src/go/types/testdata/fixedbugs/issue43671.go2
vendored
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58
src/go/types/testdata/fixedbugs/issue43671.go2
vendored
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@ -0,0 +1,58 @@
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// Copyright 2021 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 p
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type C0 interface{ int }
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type C1 interface{ chan int }
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type C2 interface{ chan int | <-chan int }
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type C3 interface{ chan int | chan float32 }
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type C4 interface{ chan int | chan<- int }
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type C5[T any] interface{ ~chan T | <-chan T }
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func _[T any](ch T) {
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<-ch // ERROR cannot receive from non-channel
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}
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func _[T C0](ch T) {
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<-ch // ERROR cannot receive from non-channel
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}
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func _[T C1](ch T) {
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<-ch
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}
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func _[T C2](ch T) {
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<-ch
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}
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func _[T C3](ch T) {
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<-ch // ERROR channels of ch .* must have the same element type
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}
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func _[T C4](ch T) {
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<-ch // ERROR cannot receive from send-only channel
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}
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func _[T C5[X], X any](ch T, x X) {
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x = <-ch
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}
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// test case from issue, slightly modified
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type RecvChan[T any] interface {
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~chan T | ~<-chan T
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}
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func _[T any, C RecvChan[T]](ch C) T {
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return <-ch
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}
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func f[T any, C interface{ chan T }](ch C) T {
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return <-ch
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}
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func _(ch chan int) {
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var x int = f(ch) // test constraint type inference for this case
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_ = x
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}
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