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      1 // errorcheck
      2 
      3 // Copyright 2016 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 switch statements with duplicate cases are detected by the compiler.
      8 // Does not compile.
      9 
     10 package main
     11 
     12 import "fmt"
     13 
     14 func f0(x int) {
     15 	switch x {
     16 	case 0:
     17 	case 0: // ERROR "duplicate case 0 in switch"
     18 	}
     19 
     20 	switch x {
     21 	case 0:
     22 	case int(0): // ERROR "duplicate case 0 in switch"
     23 	}
     24 }
     25 
     26 func f1(x float32) {
     27 	switch x {
     28 	case 5:
     29 	case 5: // ERROR "duplicate case 5 in switch"
     30 	case 5.0: // ERROR "duplicate case 5 in switch"
     31 	}
     32 }
     33 
     34 func f2(s string) {
     35 	switch s {
     36 	case "":
     37 	case "": // ERROR "duplicate case .. in switch"
     38 	case "abc":
     39 	case "abc": // ERROR "duplicate case .abc. in switch"
     40 	}
     41 }
     42 
     43 func f3(e interface{}) {
     44 	switch e {
     45 	case 0:
     46 	case 0: // ERROR "duplicate case 0 in switch"
     47 	case int64(0):
     48 	case float32(10):
     49 	case float32(10): // ERROR "duplicate case float32\(10\) in switch"
     50 	case float64(10):
     51 	case float64(10): // ERROR "duplicate case float64\(10\) in switch"
     52 	}
     53 }
     54 
     55 func f4(e interface{}) {
     56 	switch e.(type) {
     57 	case int:
     58 	case int: // ERROR "duplicate case int in type switch"
     59 	case int64:
     60 	case error:
     61 	case error: // ERROR "duplicate case error in type switch"
     62 	case fmt.Stringer:
     63 	case fmt.Stringer: // ERROR "duplicate case fmt.Stringer in type switch"
     64 	case struct {
     65 		i int "tag1"
     66 	}:
     67 	case struct {
     68 		i int "tag2"
     69 	}:
     70 	case struct {
     71 		i int "tag1"
     72 	}: // ERROR "duplicate case struct { i int .tag1. } in type switch"
     73 	}
     74 }
     75 
     76 func f5(a [1]int) {
     77 	switch a {
     78 	case [1]int{0}:
     79 	case [1]int{0}: // OK -- see issue 15896
     80 	}
     81 }
     82 
     83 // Ensure duplicate const bool clauses are accepted.
     84 func f6() int {
     85 	switch {
     86 	case 0 == 0:
     87 		return 0
     88 	case 1 == 1: // Intentionally OK, even though a duplicate of the above const true
     89 		return 1
     90 	}
     91 	return 2
     92 }
     93 
     94 // Ensure duplicates in ranges are detected (issue #17517).
     95 func f7(a int) {
     96 	switch a {
     97 	case 0:
     98 	case 0, 1: // ERROR "duplicate case 0"
     99 	case 1, 2, 3, 4: // ERROR "duplicate case 1"
    100 	}
    101 }
    102