mirror of
https://github.com/golang/go
synced 2024-09-24 15:30:13 -06:00
196b663075
To allow these types as map keys, we must fill in equal and hash functions in their algorithm tables. Structs or arrays that are "just memory", like [2]int, can and do continue to use the AMEM algorithm. Structs or arrays that contain special values like strings or interface values use generated functions for both equal and hash. The runtime helper func runtime.equal(t, x, y) bool handles the general equality case for x == y and calls out to the equal implementation in the algorithm table. For short values (<= 4 struct fields or array elements), the sequence of elementwise comparisons is inlined instead of calling runtime.equal. R=ken, mpimenov CC=golang-dev https://golang.org/cl/5451105
68 lines
1.7 KiB
Go
68 lines
1.7 KiB
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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type T3 struct{ z []int }
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var t3 T3
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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|incompatible"
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use(c2 == c1) // ERROR "invalid operation|incompatible"
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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|incompatible"
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use(p2 == p1) // ERROR "invalid operation|incompatible"
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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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// Comparison of structs should have a good message
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use(t3 == t3) // ERROR "struct|expected"
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// Slices, functions, and maps too.
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var x []int
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var f func()
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var m map[int]int
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use(x == x) // ERROR "slice can only be compared to nil"
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use(f == f) // ERROR "func can only be compared to nil"
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use(m == m) // ERROR "map can only be compared to nil"
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// Comparison with interface that cannot return true
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// (would panic).
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var i interface{}
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use(i == x) // ERROR "invalid operation"
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use(x == i) // ERROR "invalid operation"
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use(i == f) // ERROR "invalid operation"
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use(f == i) // ERROR "invalid operation"
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use(i == m) // ERROR "invalid operation"
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use(m == i) // ERROR "invalid operation"
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}
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