| // Copyright 2020 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package stringintconv defines an Analyzer that flags type conversions |
| // from integers to strings. |
| package stringintconv |
| |
| import ( |
| "fmt" |
| "go/ast" |
| "go/types" |
| "strings" |
| |
| "golang.org/x/tools/go/analysis" |
| "golang.org/x/tools/go/analysis/passes/inspect" |
| "golang.org/x/tools/go/ast/inspector" |
| "golang.org/x/tools/internal/typeparams" |
| ) |
| |
| const Doc = `check for string(int) conversions |
| |
| This checker flags conversions of the form string(x) where x is an integer |
| (but not byte or rune) type. Such conversions are discouraged because they |
| return the UTF-8 representation of the Unicode code point x, and not a decimal |
| string representation of x as one might expect. Furthermore, if x denotes an |
| invalid code point, the conversion cannot be statically rejected. |
| |
| For conversions that intend on using the code point, consider replacing them |
| with string(rune(x)). Otherwise, strconv.Itoa and its equivalents return the |
| string representation of the value in the desired base. |
| ` |
| |
| var Analyzer = &analysis.Analyzer{ |
| Name: "stringintconv", |
| Doc: Doc, |
| Requires: []*analysis.Analyzer{inspect.Analyzer}, |
| Run: run, |
| } |
| |
| // describe returns a string describing the type typ contained within the type |
| // set of inType. If non-empty, inName is used as the name of inType (this is |
| // necessary so that we can use alias type names that may not be reachable from |
| // inType itself). |
| func describe(typ, inType types.Type, inName string) string { |
| name := inName |
| if typ != inType { |
| name = typeName(typ) |
| } |
| if name == "" { |
| return "" |
| } |
| |
| var parentheticals []string |
| if underName := typeName(typ.Underlying()); underName != "" && underName != name { |
| parentheticals = append(parentheticals, underName) |
| } |
| |
| if typ != inType && inName != "" && inName != name { |
| parentheticals = append(parentheticals, "in "+inName) |
| } |
| |
| if len(parentheticals) > 0 { |
| name += " (" + strings.Join(parentheticals, ", ") + ")" |
| } |
| |
| return name |
| } |
| |
| func typeName(typ types.Type) string { |
| if v, _ := typ.(interface{ Name() string }); v != nil { |
| return v.Name() |
| } |
| if v, _ := typ.(interface{ Obj() *types.TypeName }); v != nil { |
| return v.Obj().Name() |
| } |
| return "" |
| } |
| |
| func run(pass *analysis.Pass) (interface{}, error) { |
| inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector) |
| nodeFilter := []ast.Node{ |
| (*ast.CallExpr)(nil), |
| } |
| inspect.Preorder(nodeFilter, func(n ast.Node) { |
| call := n.(*ast.CallExpr) |
| |
| if len(call.Args) != 1 { |
| return |
| } |
| arg := call.Args[0] |
| |
| // Retrieve target type name. |
| var tname *types.TypeName |
| switch fun := call.Fun.(type) { |
| case *ast.Ident: |
| tname, _ = pass.TypesInfo.Uses[fun].(*types.TypeName) |
| case *ast.SelectorExpr: |
| tname, _ = pass.TypesInfo.Uses[fun.Sel].(*types.TypeName) |
| } |
| if tname == nil { |
| return |
| } |
| |
| // In the conversion T(v) of a value v of type V to a target type T, we |
| // look for types T0 in the type set of T and V0 in the type set of V, such |
| // that V0->T0 is a problematic conversion. If T and V are not type |
| // parameters, this amounts to just checking if V->T is a problematic |
| // conversion. |
| |
| // First, find a type T0 in T that has an underlying type of string. |
| T := tname.Type() |
| ttypes, err := structuralTypes(T) |
| if err != nil { |
| return // invalid type |
| } |
| |
| var T0 types.Type // string type in the type set of T |
| |
| for _, tt := range ttypes { |
| u, _ := tt.Underlying().(*types.Basic) |
| if u != nil && u.Kind() == types.String { |
| T0 = tt |
| break |
| } |
| } |
| |
| if T0 == nil { |
| // No target types have an underlying type of string. |
| return |
| } |
| |
| // Next, find a type V0 in V that has an underlying integral type that is |
| // not byte or rune. |
| V := pass.TypesInfo.TypeOf(arg) |
| vtypes, err := structuralTypes(V) |
| if err != nil { |
| return // invalid type |
| } |
| |
| var V0 types.Type // integral type in the type set of V |
| |
| for _, vt := range vtypes { |
| u, _ := vt.Underlying().(*types.Basic) |
| if u != nil && u.Info()&types.IsInteger != 0 { |
| switch u.Kind() { |
| case types.Byte, types.Rune, types.UntypedRune: |
| continue |
| } |
| V0 = vt |
| break |
| } |
| } |
| |
| if V0 == nil { |
| // No source types are non-byte or rune integer types. |
| return |
| } |
| |
| convertibleToRune := true // if true, we can suggest a fix |
| for _, t := range vtypes { |
| if !types.ConvertibleTo(t, types.Typ[types.Rune]) { |
| convertibleToRune = false |
| break |
| } |
| } |
| |
| target := describe(T0, T, tname.Name()) |
| source := describe(V0, V, typeName(V)) |
| |
| if target == "" || source == "" { |
| return // something went wrong |
| } |
| |
| diag := analysis.Diagnostic{ |
| Pos: n.Pos(), |
| 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), |
| } |
| |
| if convertibleToRune { |
| diag.SuggestedFixes = []analysis.SuggestedFix{ |
| { |
| Message: "Did you mean to convert a rune to a string?", |
| TextEdits: []analysis.TextEdit{ |
| { |
| Pos: arg.Pos(), |
| End: arg.Pos(), |
| NewText: []byte("rune("), |
| }, |
| { |
| Pos: arg.End(), |
| End: arg.End(), |
| NewText: []byte(")"), |
| }, |
| }, |
| }, |
| } |
| } |
| pass.Report(diag) |
| }) |
| return nil, nil |
| } |
| |
| func structuralTypes(t types.Type) ([]types.Type, error) { |
| var structuralTypes []types.Type |
| switch t := t.(type) { |
| case *typeparams.TypeParam: |
| terms, err := typeparams.StructuralTerms(t) |
| if err != nil { |
| return nil, err |
| } |
| for _, term := range terms { |
| structuralTypes = append(structuralTypes, term.Type()) |
| } |
| default: |
| structuralTypes = append(structuralTypes, t) |
| } |
| return structuralTypes, nil |
| } |