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Source file test/switch5.go

Documentation: test

  // errorcheck
  
  // Copyright 2016 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.
  
  // Verify that switch statements with duplicate cases are detected by the compiler.
  // Does not compile.
  
  package main
  
  func f0(x int) {
  	switch x {
  	case 0:
  	case 0: // ERROR "duplicate case 0 in switch"
  	}
  
  	switch x {
  	case 0:
  	case int(0): // ERROR "duplicate case int.0. .value 0. in switch"
  	}
  }
  
  func f1(x float32) {
  	switch x {
  	case 5:
  	case 5: // ERROR "duplicate case 5 in switch"
  	case 5.0: // ERROR "duplicate case 5 in switch"
  	}
  }
  
  func f2(s string) {
  	switch s {
  	case "":
  	case "": // ERROR "duplicate case .. in switch"
  	case "abc":
  	case "abc": // ERROR "duplicate case .abc. in switch"
  	}
  }
  
  func f3(e interface{}) {
  	switch e {
  	case 0:
  	case 0: // ERROR "duplicate case 0 in switch"
  	case int64(0):
  	case float32(10):
  	case float32(10): // ERROR "duplicate case float32\(10\) .value 10. in switch"
  	case float64(10):
  	case float64(10): // ERROR "duplicate case float64\(10\) .value 10. in switch"
  	}
  }
  
  func f5(a [1]int) {
  	switch a {
  	case [1]int{0}:
  	case [1]int{0}: // OK -- see issue 15896
  	}
  }
  
  // Ensure duplicate const bool clauses are accepted.
  func f6() int {
  	switch {
  	case 0 == 0:
  		return 0
  	case 1 == 1: // Intentionally OK, even though a duplicate of the above const true
  		return 1
  	}
  	return 2
  }
  
  // Ensure duplicates in ranges are detected (issue #17517).
  func f7(a int) {
  	switch a {
  	case 0:
  	case 0, 1: // ERROR "duplicate case 0"
  	case 1, 2, 3, 4: // ERROR "duplicate case 1"
  	}
  }
  
  // Ensure duplicates with simple literals are printed as they were
  // written, not just their values. Particularly useful for runes.
  func f8(r rune) {
  	const x = 10
  	switch r {
  	case 33, 33: // ERROR "duplicate case 33 in switch"
  	case 34, '"': // ERROR "duplicate case '"' .value 34. in switch"
  	case 35, rune('#'): // ERROR "duplicate case rune.'#'. .value 35. in switch"
  	case 36, rune(36): // ERROR "duplicate case rune.36. .value 36. in switch"
  	case 37, '$'+1: // ERROR "duplicate case '\$' \+ 1 .value 37. in switch"
  	case 'b':
  	case 'a', 'b', 'c', 'd': // ERROR "duplicate case 'b' .value 98."
  	case x, x: // ERROR "duplicate case x .value 10."
  	}
  }
  

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