modernc.org/gc@v1.0.1-0.20240304020402-f0dba7c97c2b/testdata/errchk/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  import "unsafe"
    13  
    14  // explicit conversion of constants
    15  var x1 = string(1)
    16  var x2 string = string(1)
    17  var x3 = int(1.5)     // ERROR "convert|truncate"
    18  var x4 int = int(1.5) // ERROR "convert|truncate"
    19  var x5 = "a" + string(1)
    20  var x6 = int(1e100)      // ERROR "overflow"
    21  var x7 = float32(1e1000) // ERROR "overflow"
    22  
    23  // unsafe.Pointer can only convert to/from uintptr
    24  var _ = string(unsafe.Pointer(uintptr(65)))  // ERROR "convert"
    25  var _ = float64(unsafe.Pointer(uintptr(65))) // ERROR "convert"
    26  var _ = int(unsafe.Pointer(uintptr(65)))     // ERROR "convert"
    27  
    28  // implicit conversions merit scrutiny
    29  var s string
    30  var bad1 string = 1  // ERROR "conver|incompatible|invalid|cannot"
    31  var bad2 = s + 1     // ERROR "conver|incompatible|invalid"
    32  var bad3 = s + 'a'   // ERROR "conver|incompatible|invalid"
    33  var bad4 = "a" + 1   // ERROR "literals|incompatible|convert|invalid"
    34  var bad5 = "a" + 'a' // ERROR "literals|incompatible|convert|invalid"
    35  
    36  var bad6 int = 1.5       // ERROR "convert|truncate"
    37  var bad7 int = 1e100     // ERROR "overflow"
    38  var bad8 float32 = 1e200 // ERROR "overflow"
    39  
    40  // but these implicit conversions are okay
    41  var good1 string = "a"
    42  var good2 int = 1.0
    43  var good3 int = 1e9
    44  var good4 float64 = 1e20
    45  
    46  // explicit conversion of string is okay
    47  var _ = []rune("abc")
    48  var _ = []byte("abc")
    49  
    50  // implicit is not
    51  var _ []int = "abc"  // ERROR "cannot use|incompatible|invalid"
    52  var _ []byte = "abc" // ERROR "cannot use|incompatible|invalid"
    53  
    54  // named string is okay
    55  type Tstring string
    56  
    57  var ss Tstring = "abc"
    58  var _ = []rune(ss)
    59  var _ = []byte(ss)
    60  
    61  // implicit is still not
    62  var _ []rune = ss // ERROR "cannot use|incompatible|invalid"
    63  var _ []byte = ss // ERROR "cannot use|incompatible|invalid"
    64  
    65  // named slice is now ok
    66  type Trune []rune
    67  type Tbyte []byte
    68  
    69  var _ = Trune("abc") // ok
    70  var _ = Tbyte("abc") // ok
    71  
    72  // implicit is still not
    73  var _ Trune = "abc" // ERROR "cannot use|incompatible|invalid"
    74  var _ Tbyte = "abc" // ERROR "cannot use|incompatible|invalid"