gcc/testsuite/go.test/test/cmp6.go

   1 // errorcheck
   2
   3 // Copyright 2010 The Go Authors. All rights reserved.
   4 // Use of this source code is governed by a BSD-style
   5 // license that can be found in the LICENSE file.
   6
   7 // Verify that incorrect comparisons are detected.
   8 // Does not compile.
   9
  10 package main
  11
  12 func use(bool) {}
  13
  14 type T1 *int
  15 type T2 *int
  16
  17 type T3 struct{ z []int }
  18
  19 var t3 T3
  20
  21 type T4 struct {
  22         _ []int
  23         a float64
  24 }
  25
  26 var t4 T4
  27
  28 func main() {
  29         // Arguments to comparison must be
  30         // assignable one to the other (or vice versa)
  31         // so chan int can be compared against
  32         // directional channels but channel of different
  33         // direction cannot be compared against each other.
  34         var c1 chan<- int
  35         var c2 <-chan int
  36         var c3 chan int
  37
  38         use(c1 == c2) // ERROR "invalid operation|incompatible"
  39         use(c2 == c1) // ERROR "invalid operation|incompatible"
  40         use(c1 == c3)
  41         use(c2 == c2)
  42         use(c3 == c1)
  43         use(c3 == c2)
  44
  45         // Same applies to named types.
  46         var p1 T1
  47         var p2 T2
  48         var p3 *int
  49
  50         use(p1 == p2) // ERROR "invalid operation|incompatible"
  51         use(p2 == p1) // ERROR "invalid operation|incompatible"
  52         use(p1 == p3)
  53         use(p2 == p2)
  54         use(p3 == p1)
  55         use(p3 == p2)
  56
  57         // Arrays are comparable if and only if their element type is comparable.
  58         var a1 [1]int
  59         var a2 [1]func()
  60         var a3 [0]func()
  61         use(a1 == a1)
  62         use(a2 == a2) // ERROR "invalid operation|invalid comparison"
  63         use(a3 == a3) // ERROR "invalid operation|invalid comparison"
  64
  65         // Comparison of structs should have a good message
  66         use(t3 == t3) // ERROR "struct|expected"
  67         use(t4 == t4) // ERROR "cannot be compared|non-comparable"
  68
  69         // Slices, functions, and maps too.
  70         var x []int
  71         var f func()
  72         var m map[int]int
  73         use(x == x) // ERROR "slice can only be compared to nil"
  74         use(f == f) // ERROR "func can only be compared to nil"
  75         use(m == m) // ERROR "map can only be compared to nil"
  76
  77         // Comparison with interface that cannot return true
  78         // (would panic).
  79         var i interface{}
  80         use(i == x) // ERROR "invalid operation"
  81         use(x == i) // ERROR "invalid operation"
  82         use(i == f) // ERROR "invalid operation"
  83         use(f == i) // ERROR "invalid operation"
  84         use(i == m) // ERROR "invalid operation"
  85         use(m == i) // ERROR "invalid operation"
  86 }