github.com/zach-klippenstein/go@v0.0.0-20150108044943-fcfbeb3adf58/test/convlit.go (about)

     1  // errorcheck
     2  
     3  // Copyright 2009 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 illegal assignments with both explicit and implicit conversions of literals are detected.
     8  // Does not compile.
     9  
    10  package main
    11  
    12  // explicit conversion of constants
    13  var x1 = string(1)
    14  var x2 string = string(1)
    15  var x3 = int(1.5)     // ERROR "convert|truncate"
    16  var x4 int = int(1.5) // ERROR "convert|truncate"
    17  var x5 = "a" + string(1)
    18  var x6 = int(1e100)      // ERROR "overflow"
    19  var x7 = float32(1e1000) // ERROR "overflow"
    20  
    21  // implicit conversions merit scrutiny
    22  var s string
    23  var bad1 string = 1  // ERROR "conver|incompatible|invalid|cannot"
    24  var bad2 = s + 1     // ERROR "conver|incompatible|invalid"
    25  var bad3 = s + 'a'   // ERROR "conver|incompatible|invalid"
    26  var bad4 = "a" + 1   // ERROR "literals|incompatible|convert|invalid"
    27  var bad5 = "a" + 'a' // ERROR "literals|incompatible|convert|invalid"
    28  
    29  var bad6 int = 1.5       // ERROR "convert|truncate"
    30  var bad7 int = 1e100     // ERROR "overflow"
    31  var bad8 float32 = 1e200 // ERROR "overflow"
    32  
    33  // but these implicit conversions are okay
    34  var good1 string = "a"
    35  var good2 int = 1.0
    36  var good3 int = 1e9
    37  var good4 float64 = 1e20
    38  
    39  // explicit conversion of string is okay
    40  var _ = []rune("abc")
    41  var _ = []byte("abc")
    42  
    43  // implicit is not
    44  var _ []int = "abc"  // ERROR "cannot use|incompatible|invalid"
    45  var _ []byte = "abc" // ERROR "cannot use|incompatible|invalid"
    46  
    47  // named string is okay
    48  type Tstring string
    49  
    50  var ss Tstring = "abc"
    51  var _ = []rune(ss)
    52  var _ = []byte(ss)
    53  
    54  // implicit is still not
    55  var _ []rune = ss // ERROR "cannot use|incompatible|invalid"
    56  var _ []byte = ss // ERROR "cannot use|incompatible|invalid"
    57  
    58  // named slice is now ok
    59  type Trune []rune
    60  type Tbyte []byte
    61  
    62  var _ = Trune("abc") // ok
    63  var _ = Tbyte("abc") // ok
    64  
    65  // implicit is still not
    66  var _ Trune = "abc" // ERROR "cannot use|incompatible|invalid"
    67  var _ Tbyte = "abc" // ERROR "cannot use|incompatible|invalid"