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The new comparison rule was added to the spec by changeset: 5605:33abb649cb63 user: Robert Griesemer <gri@golang.org> date: Thu Jun 03 16:55:50 2010 -0700 files: doc/go_spec.html description: go spec: Base comparison compatibility on assignment compatibility. Specifically: - Simplified definition of comparison compatibility and folded into section on comparison operators since it's only used there. This is a small language change/cleanup. As a consequence: - An interface value may now be compared against a non-interface value. - Channels with opposite directions cannot be compared directly anymore (per discussion with rsc). R=rsc, r, iant, ken2 CC=golang-dev https://golang.org/cl/1462041 but never implemented. Fixes #1070. R=ken2 CC=golang-dev https://golang.org/cl/2116047
43 lines
913 B
Go
43 lines
913 B
Go
// errchk $G -e $D/$F.go
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// Copyright 2010 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 main
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func use(bool) {}
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type T1 *int
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type T2 *int
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func main() {
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// Arguments to comparison must be
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// assignable one to the other (or vice versa)
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// so chan int can be compared against
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// directional channels but channel of different
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// direction cannot be compared against each other.
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var c1 chan <-int
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var c2 <-chan int
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var c3 chan int
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use(c1 == c2) // ERROR "invalid operation"
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use(c2 == c1) // ERROR "invalid operation"
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use(c1 == c3)
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use(c2 == c2)
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use(c3 == c1)
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use(c3 == c2)
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// Same applies to named types.
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var p1 T1
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var p2 T2
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var p3 *int
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use(p1 == p2) // ERROR "invalid operation"
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use(p2 == p1) // ERROR "invalid operation"
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use(p1 == p3)
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use(p2 == p2)
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use(p3 == p1)
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use(p3 == p2)
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}
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