github.com/peggyl/go@v0.0.0-20151008231540-ae315999c2d5/src/cmd/vet/testdata/shadow.go (about)

     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  		var _, err = f.Read(buf) // ERROR "declaration of err shadows declaration at testdata/shadow.go:13"
    29  		if err != nil {
    30  			return err
    31  		}
    32  	}
    33  	for i := 0; i < 10; i++ {
    34  		i := i // OK: obviously intentional idiomatic redeclaration
    35  		go func() {
    36  			println(i)
    37  		}()
    38  	}
    39  	var shadowTemp interface{}
    40  	switch shadowTemp := shadowTemp.(type) { // OK: obviously intentional idiomatic redeclaration
    41  	case int:
    42  		println("OK")
    43  		_ = shadowTemp
    44  	}
    45  	if shadowTemp := shadowTemp; true { // OK: obviously intentional idiomatic redeclaration
    46  		var f *os.File // OK because f is not mentioned later in the function.
    47  		// The declaration of x is a shadow because x is mentioned below.
    48  		var x int // ERROR "declaration of x shadows declaration at testdata/shadow.go:14"
    49  		_, _, _ = x, f, shadowTemp
    50  	}
    51  	// Use a couple of variables to trigger shadowing errors.
    52  	_, _ = err, x
    53  	return
    54  }