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Source file test/typeswitch2.go

Documentation: test

  // errorcheck
  
  // Copyright 2009 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 various erroneous type switches are caught be the compiler.
  // Does not compile.
  
  package main
  
  import "io"
  
  func whatis(x interface{}) string {
  	switch x.(type) {
  	case int:
  		return "int"
  	case int: // ERROR "duplicate"
  		return "int8"
  	case io.Reader:
  		return "Reader1"
  	case io.Reader: // ERROR "duplicate"
  		return "Reader2"
  	case interface {
  		r()
  		w()
  	}:
  		return "rw"
  	case interface {	// ERROR "duplicate"
  		w()
  		r()
  	}:
  		return "wr"
  
  	}
  	return ""
  }
  
  func notused(x interface{}) {
  	// The first t is in a different scope than the 2nd t; it cannot
  	// be accessed (=> declared and not used error); but it is legal
  	// to declare it.
  	switch t := 0; t := x.(type) { // ERROR "declared and not used"
  	case int:
  		_ = t // this is using the t of "t := x.(type)"
  	}
  }
  

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