mirror of
https://github.com/golang/go
synced 2024-11-21 15:34:45 -07:00
23bd214aee
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
131 lines
2.4 KiB
Go
131 lines
2.4 KiB
Go
// $G $D/$F.go && $L $F.$A && ./$A.out
|
|
|
|
// Copyright 2009 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 main
|
|
|
|
import "unsafe"
|
|
|
|
func use(bool) {}
|
|
|
|
func stringptr(s string) uintptr { return *(*uintptr)(unsafe.Pointer(&s)) }
|
|
|
|
func isfalse(b bool) {
|
|
if b {
|
|
// stack will explain where
|
|
panic("wanted false, got true")
|
|
}
|
|
}
|
|
|
|
func istrue(b bool) {
|
|
if !b {
|
|
// stack will explain where
|
|
panic("wanted true, got false")
|
|
}
|
|
}
|
|
|
|
type T *int
|
|
|
|
func main() {
|
|
var a []int
|
|
var b map[string]int
|
|
|
|
var c string = "hello"
|
|
var d string = "hel" // try to get different pointer
|
|
d = d + "lo"
|
|
if stringptr(c) == stringptr(d) {
|
|
panic("compiler too smart -- got same string")
|
|
}
|
|
|
|
var e = make(chan int)
|
|
|
|
var ia interface{} = a
|
|
var ib interface{} = b
|
|
var ic interface{} = c
|
|
var id interface{} = d
|
|
var ie interface{} = e
|
|
|
|
// these comparisons are okay because
|
|
// string compare is okay and the others
|
|
// are comparisons where the types differ.
|
|
isfalse(ia == ib)
|
|
isfalse(ia == ic)
|
|
isfalse(ia == id)
|
|
isfalse(ib == ic)
|
|
isfalse(ib == id)
|
|
istrue(ic == id)
|
|
istrue(ie == ie)
|
|
|
|
// these are okay because one side of the
|
|
// comparison need only be assignable to the other.
|
|
isfalse(a == ib)
|
|
isfalse(a == ic)
|
|
isfalse(a == id)
|
|
isfalse(b == ic)
|
|
isfalse(b == id)
|
|
istrue(c == id)
|
|
istrue(e == ie)
|
|
|
|
isfalse(ia == b)
|
|
isfalse(ia == c)
|
|
isfalse(ia == d)
|
|
isfalse(ib == c)
|
|
isfalse(ib == d)
|
|
istrue(ic == d)
|
|
istrue(ie == e)
|
|
|
|
// 6g used to let this go through as true.
|
|
var g uint64 = 123
|
|
var h int64 = 123
|
|
var ig interface{} = g
|
|
var ih interface{} = h
|
|
isfalse(ig == ih)
|
|
|
|
// map of interface should use == on interface values,
|
|
// not memory.
|
|
// TODO: should m[c], m[d] be valid here?
|
|
var m = make(map[interface{}]int)
|
|
m[ic] = 1
|
|
m[id] = 2
|
|
if m[ic] != 2 {
|
|
println("m[ic] = ", m[ic])
|
|
panic("bad m[ic]")
|
|
}
|
|
|
|
// non-interface comparisons
|
|
{
|
|
c := make(chan int)
|
|
c1 := (<-chan int)(c)
|
|
c2 := (chan<- int)(c)
|
|
istrue(c == c1)
|
|
istrue(c == c2)
|
|
istrue(c1 == c)
|
|
istrue(c2 == c)
|
|
|
|
d := make(chan int)
|
|
isfalse(c == d)
|
|
isfalse(d == c)
|
|
isfalse(d == c1)
|
|
isfalse(d == c2)
|
|
isfalse(c1 == d)
|
|
isfalse(c2 == d)
|
|
}
|
|
|
|
// named types vs not
|
|
{
|
|
var x = new(int)
|
|
var y T
|
|
var z T = x
|
|
|
|
isfalse(x == y)
|
|
istrue(x == z)
|
|
isfalse(y == z)
|
|
|
|
isfalse(y == x)
|
|
istrue(z == x)
|
|
isfalse(z == y)
|
|
}
|
|
}
|