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502958ffa6
Array values are comparable if values of the array element type are comparable. Fixes #6526. LGTM=khr R=rsc, bradfitz, khr CC=golang-codereviews https://golang.org/cl/58580043
86 lines
2.1 KiB
Go
86 lines
2.1 KiB
Go
// errorcheck
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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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// Verify that incorrect comparisons are detected.
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// Does not compile.
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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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type T4 struct {
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_ []int
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a float64
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}
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var t4 T4
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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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// Arrays are comparable if and only if their element type is comparable.
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var a1 [1]int
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var a2 [1]func()
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var a3 [0]func()
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use(a1 == a1)
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use(a2 == a2) // ERROR "invalid operation|invalid comparison"
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use(a3 == a3) // ERROR "invalid operation|invalid comparison"
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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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use(t4 == t4) // ERROR "cannot be compared|non-comparable"
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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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