| 1 | // Copyright 2020 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 | // Package stringintconv defines an Analyzer that flags type conversions |
| 6 | // from integers to strings. |
| 7 | package stringintconv |
| 8 | |
| 9 | import ( |
| 10 | "fmt" |
| 11 | "go/ast" |
| 12 | "go/types" |
| 13 | "strings" |
| 14 | |
| 15 | "golang.org/x/tools/go/analysis" |
| 16 | "golang.org/x/tools/go/analysis/passes/inspect" |
| 17 | "golang.org/x/tools/go/ast/inspector" |
| 18 | "golang.org/x/tools/internal/typeparams" |
| 19 | ) |
| 20 | |
| 21 | const Doc = `check for string(int) conversions |
| 22 | |
| 23 | This checker flags conversions of the form string(x) where x is an integer |
| 24 | (but not byte or rune) type. Such conversions are discouraged because they |
| 25 | return the UTF-8 representation of the Unicode code point x, and not a decimal |
| 26 | string representation of x as one might expect. Furthermore, if x denotes an |
| 27 | invalid code point, the conversion cannot be statically rejected. |
| 28 | |
| 29 | For conversions that intend on using the code point, consider replacing them |
| 30 | with string(rune(x)). Otherwise, strconv.Itoa and its equivalents return the |
| 31 | string representation of the value in the desired base. |
| 32 | ` |
| 33 | |
| 34 | var Analyzer = &analysis.Analyzer{ |
| 35 | Name: "stringintconv", |
| 36 | Doc: Doc, |
| 37 | Requires: []*analysis.Analyzer{inspect.Analyzer}, |
| 38 | Run: run, |
| 39 | } |
| 40 | |
| 41 | // describe returns a string describing the type typ contained within the type |
| 42 | // set of inType. If non-empty, inName is used as the name of inType (this is |
| 43 | // necessary so that we can use alias type names that may not be reachable from |
| 44 | // inType itself). |
| 45 | func describe(typ, inType types.Type, inName string) string { |
| 46 | name := inName |
| 47 | if typ != inType { |
| 48 | name = typeName(typ) |
| 49 | } |
| 50 | if name == "" { |
| 51 | return "" |
| 52 | } |
| 53 | |
| 54 | var parentheticals []string |
| 55 | if underName := typeName(typ.Underlying()); underName != "" && underName != name { |
| 56 | parentheticals = append(parentheticals, underName) |
| 57 | } |
| 58 | |
| 59 | if typ != inType && inName != "" && inName != name { |
| 60 | parentheticals = append(parentheticals, "in "+inName) |
| 61 | } |
| 62 | |
| 63 | if len(parentheticals) > 0 { |
| 64 | name += " (" + strings.Join(parentheticals, ", ") + ")" |
| 65 | } |
| 66 | |
| 67 | return name |
| 68 | } |
| 69 | |
| 70 | func typeName(typ types.Type) string { |
| 71 | if v, _ := typ.(interface{ Name() string }); v != nil { |
| 72 | return v.Name() |
| 73 | } |
| 74 | if v, _ := typ.(interface{ Obj() *types.TypeName }); v != nil { |
| 75 | return v.Obj().Name() |
| 76 | } |
| 77 | return "" |
| 78 | } |
| 79 | |
| 80 | func run(pass *analysis.Pass) (interface{}, error) { |
| 81 | inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector) |
| 82 | nodeFilter := []ast.Node{ |
| 83 | (*ast.CallExpr)(nil), |
| 84 | } |
| 85 | inspect.Preorder(nodeFilter, func(n ast.Node) { |
| 86 | call := n.(*ast.CallExpr) |
| 87 | |
| 88 | if len(call.Args) != 1 { |
| 89 | return |
| 90 | } |
| 91 | arg := call.Args[0] |
| 92 | |
| 93 | // Retrieve target type name. |
| 94 | var tname *types.TypeName |
| 95 | switch fun := call.Fun.(type) { |
| 96 | case *ast.Ident: |
| 97 | tname, _ = pass.TypesInfo.Uses[fun].(*types.TypeName) |
| 98 | case *ast.SelectorExpr: |
| 99 | tname, _ = pass.TypesInfo.Uses[fun.Sel].(*types.TypeName) |
| 100 | } |
| 101 | if tname == nil { |
| 102 | return |
| 103 | } |
| 104 | |
| 105 | // In the conversion T(v) of a value v of type V to a target type T, we |
| 106 | // look for types T0 in the type set of T and V0 in the type set of V, such |
| 107 | // that V0->T0 is a problematic conversion. If T and V are not type |
| 108 | // parameters, this amounts to just checking if V->T is a problematic |
| 109 | // conversion. |
| 110 | |
| 111 | // First, find a type T0 in T that has an underlying type of string. |
| 112 | T := tname.Type() |
| 113 | ttypes, err := structuralTypes(T) |
| 114 | if err != nil { |
| 115 | return // invalid type |
| 116 | } |
| 117 | |
| 118 | var T0 types.Type // string type in the type set of T |
| 119 | |
| 120 | for _, tt := range ttypes { |
| 121 | u, _ := tt.Underlying().(*types.Basic) |
| 122 | if u != nil && u.Kind() == types.String { |
| 123 | T0 = tt |
| 124 | break |
| 125 | } |
| 126 | } |
| 127 | |
| 128 | if T0 == nil { |
| 129 | // No target types have an underlying type of string. |
| 130 | return |
| 131 | } |
| 132 | |
| 133 | // Next, find a type V0 in V that has an underlying integral type that is |
| 134 | // not byte or rune. |
| 135 | V := pass.TypesInfo.TypeOf(arg) |
| 136 | vtypes, err := structuralTypes(V) |
| 137 | if err != nil { |
| 138 | return // invalid type |
| 139 | } |
| 140 | |
| 141 | var V0 types.Type // integral type in the type set of V |
| 142 | |
| 143 | for _, vt := range vtypes { |
| 144 | u, _ := vt.Underlying().(*types.Basic) |
| 145 | if u != nil && u.Info()&types.IsInteger != 0 { |
| 146 | switch u.Kind() { |
| 147 | case types.Byte, types.Rune, types.UntypedRune: |
| 148 | continue |
| 149 | } |
| 150 | V0 = vt |
| 151 | break |
| 152 | } |
| 153 | } |
| 154 | |
| 155 | if V0 == nil { |
| 156 | // No source types are non-byte or rune integer types. |
| 157 | return |
| 158 | } |
| 159 | |
| 160 | convertibleToRune := true // if true, we can suggest a fix |
| 161 | for _, t := range vtypes { |
| 162 | if !types.ConvertibleTo(t, types.Typ[types.Rune]) { |
| 163 | convertibleToRune = false |
| 164 | break |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | target := describe(T0, T, tname.Name()) |
| 169 | source := describe(V0, V, typeName(V)) |
| 170 | |
| 171 | if target == "" || source == "" { |
| 172 | return // something went wrong |
| 173 | } |
| 174 | |
| 175 | diag := analysis.Diagnostic{ |
| 176 | Pos: n.Pos(), |
| 177 | Message: fmt.Sprintf("conversion from %s to %s yields a string of one rune, not a string of digits (did you mean fmt.Sprint(x)?)", source, target), |
| 178 | } |
| 179 | |
| 180 | if convertibleToRune { |
| 181 | diag.SuggestedFixes = []analysis.SuggestedFix{ |
| 182 | { |
| 183 | Message: "Did you mean to convert a rune to a string?", |
| 184 | TextEdits: []analysis.TextEdit{ |
| 185 | { |
| 186 | Pos: arg.Pos(), |
| 187 | End: arg.Pos(), |
| 188 | NewText: []byte("rune("), |
| 189 | }, |
| 190 | { |
| 191 | Pos: arg.End(), |
| 192 | End: arg.End(), |
| 193 | NewText: []byte(")"), |
| 194 | }, |
| 195 | }, |
| 196 | }, |
| 197 | } |
| 198 | } |
| 199 | pass.Report(diag) |
| 200 | }) |
| 201 | return nil, nil |
| 202 | } |
| 203 | |
| 204 | func structuralTypes(t types.Type) ([]types.Type, error) { |
| 205 | var structuralTypes []types.Type |
| 206 | switch t := t.(type) { |
| 207 | case *typeparams.TypeParam: |
| 208 | terms, err := typeparams.StructuralTerms(t) |
| 209 | if err != nil { |
| 210 | return nil, err |
| 211 | } |
| 212 | for _, term := range terms { |
| 213 | structuralTypes = append(structuralTypes, term.Type()) |
| 214 | } |
| 215 | default: |
| 216 | structuralTypes = append(structuralTypes, t) |
| 217 | } |
| 218 | return structuralTypes, nil |
| 219 | } |
| 220 |
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