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Source file src/cmd/vet/testdata/shadow.go

Documentation: cmd/vet/testdata

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // This file contains tests for the shadowed variable checker.
     6  // Some of these errors are caught by the compiler (shadowed return parameters for example)
     7  // but are nonetheless useful tests.
     8  
     9  package testdata
    10  
    11  import "os"
    12  
    13  func ShadowRead(f *os.File, buf []byte) (err error) {
    14  	var x int
    15  	if f != nil {
    16  		err := 3 // OK - different type.
    17  		_ = err
    18  	}
    19  	if f != nil {
    20  		_, err := f.Read(buf) // ERROR "declaration of .err. shadows declaration at testdata/shadow.go:13"
    21  		if err != nil {
    22  			return err
    23  		}
    24  		i := 3 // OK
    25  		_ = i
    26  	}
    27  	if f != nil {
    28  		x := one()               // ERROR "declaration of .x. shadows declaration at testdata/shadow.go:14"
    29  		var _, err = f.Read(buf) // ERROR "declaration of .err. shadows declaration at testdata/shadow.go:13"
    30  		if x == 1 && err != nil {
    31  			return err
    32  		}
    33  	}
    34  	for i := 0; i < 10; i++ {
    35  		i := i // OK: obviously intentional idiomatic redeclaration
    36  		go func() {
    37  			println(i)
    38  		}()
    39  	}
    40  	var shadowTemp interface{}
    41  	switch shadowTemp := shadowTemp.(type) { // OK: obviously intentional idiomatic redeclaration
    42  	case int:
    43  		println("OK")
    44  		_ = shadowTemp
    45  	}
    46  	if shadowTemp := shadowTemp; true { // OK: obviously intentional idiomatic redeclaration
    47  		var f *os.File // OK because f is not mentioned later in the function.
    48  		// The declaration of x is a shadow because x is mentioned below.
    49  		var x int // ERROR "declaration of .x. shadows declaration at testdata/shadow.go:14"
    50  		_, _, _ = x, f, shadowTemp
    51  	}
    52  	// Use a couple of variables to trigger shadowing errors.
    53  	_, _ = err, x
    54  	return
    55  }
    56  
    57  func one() int {
    58  	return 1
    59  }
    60  

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