1 // Copyright 2018 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.
16 "golang.org/x/tools/internal/event"
17 "golang.org/x/tools/internal/lsp/protocol"
18 errors "golang.org/x/xerrors"
21 // IdentifierInfo holds information about an identifier in Go source.
22 type IdentifierInfo struct {
32 Declaration Declaration
36 // enclosing is an expression used to determine the link anchor for an
37 // identifier. If it's a named type, it should be exported.
44 type Declaration struct {
45 MappedRange []MappedRange
49 // typeSwitchImplicit indicates that the declaration is in an implicit
50 // type switch. Its type is the type of the variable on the right-hand
51 // side of the type switch.
52 typeSwitchImplicit types.Type
55 // Identifier returns identifier information for a position
56 // in a file, accounting for a potentially incomplete selector.
57 func Identifier(ctx context.Context, snapshot Snapshot, fh FileHandle, pos protocol.Position) (*IdentifierInfo, error) {
58 ctx, done := event.Start(ctx, "source.Identifier")
61 pkgs, err := snapshot.PackagesForFile(ctx, fh.URI(), TypecheckAll)
66 return nil, fmt.Errorf("no packages for file %v", fh.URI())
68 sort.Slice(pkgs, func(i, j int) bool {
69 return len(pkgs[i].CompiledGoFiles()) < len(pkgs[j].CompiledGoFiles())
72 for _, pkg := range pkgs {
73 pgf, err := pkg.File(fh.URI())
77 spn, err := pgf.Mapper.PointSpan(pos)
81 rng, err := spn.Range(pgf.Mapper.Converter)
85 var ident *IdentifierInfo
86 ident, findErr = findIdentifier(ctx, snapshot, pkg, pgf.File, rng.Start)
94 // ErrNoIdentFound is error returned when no identifer is found at a particular position
95 var ErrNoIdentFound = errors.New("no identifier found")
97 func findIdentifier(ctx context.Context, snapshot Snapshot, pkg Package, file *ast.File, pos token.Pos) (*IdentifierInfo, error) {
98 // Handle import specs separately, as there is no formal position for a
99 // package declaration.
100 if result, err := importSpec(snapshot, pkg, file, pos); result != nil || err != nil {
103 path := pathEnclosingObjNode(file, pos)
105 return nil, ErrNoIdentFound
108 qf := Qualifier(file, pkg.GetTypes(), pkg.GetTypesInfo())
110 ident, _ := path[0].(*ast.Ident)
112 return nil, ErrNoIdentFound
114 // Special case for package declarations, since they have no
115 // corresponding types.Object.
116 if ident == file.Name {
117 rng, err := posToMappedRange(snapshot, pkg, file.Name.Pos(), file.Name.End())
121 var declAST *ast.File
122 for _, pgf := range pkg.CompiledGoFiles() {
123 if pgf.File.Doc != nil {
127 // If there's no package documentation, just use current file.
131 declRng, err := posToMappedRange(snapshot, pkg, declAST.Name.Pos(), declAST.Name.End())
135 return &IdentifierInfo{
136 Name: file.Name.Name,
142 Declaration: Declaration{
144 MappedRange: []MappedRange{declRng},
149 result := &IdentifierInfo{
154 enclosing: searchForEnclosing(pkg.GetTypesInfo(), path),
157 result.Name = result.ident.Name
159 if result.MappedRange, err = posToMappedRange(snapshot, pkg, result.ident.Pos(), result.ident.End()); err != nil {
163 result.Declaration.obj = pkg.GetTypesInfo().ObjectOf(result.ident)
164 if result.Declaration.obj == nil {
165 // If there was no types.Object for the declaration, there might be an
166 // implicit local variable declaration in a type switch.
167 if objs, typ := typeSwitchImplicits(pkg, path); len(objs) > 0 {
168 // There is no types.Object for the declaration of an implicit local variable,
169 // but all of the types.Objects associated with the usages of this variable can be
170 // used to connect it back to the declaration.
171 // Preserve the first of these objects and treat it as if it were the declaring object.
172 result.Declaration.obj = objs[0]
173 result.Declaration.typeSwitchImplicit = typ
175 // Probably a type error.
176 return nil, errors.Errorf("%w for ident %v", errNoObjectFound, result.Name)
180 // Handle builtins separately.
181 if result.Declaration.obj.Parent() == types.Universe {
182 builtin, err := snapshot.BuiltinPackage(ctx)
186 builtinObj := builtin.Package.Scope.Lookup(result.Name)
187 if builtinObj == nil {
188 return nil, fmt.Errorf("no builtin object for %s", result.Name)
190 decl, ok := builtinObj.Decl.(ast.Node)
192 return nil, errors.Errorf("no declaration for %s", result.Name)
194 result.Declaration.node = decl
196 // The builtin package isn't in the dependency graph, so the usual
197 // utilities won't work here.
198 rng := NewMappedRange(snapshot.FileSet(), builtin.ParsedFile.Mapper, decl.Pos(), decl.Pos()+token.Pos(len(result.Name)))
199 result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
203 // (error).Error is a special case of builtin. Lots of checks to confirm
204 // that this is the builtin Error.
205 if obj := result.Declaration.obj; obj.Parent() == nil && obj.Pkg() == nil && obj.Name() == "Error" {
206 if _, ok := obj.Type().(*types.Signature); ok {
207 builtin, err := snapshot.BuiltinPackage(ctx)
211 // Look up "error" and then navigate to its only method.
212 // The Error method does not appear in the builtin package's scope.log.Pri
213 const errorName = "error"
214 builtinObj := builtin.Package.Scope.Lookup(errorName)
215 if builtinObj == nil {
216 return nil, fmt.Errorf("no builtin object for %s", errorName)
218 decl, ok := builtinObj.Decl.(ast.Node)
220 return nil, errors.Errorf("no declaration for %s", errorName)
222 spec, ok := decl.(*ast.TypeSpec)
224 return nil, fmt.Errorf("no type spec for %s", errorName)
226 iface, ok := spec.Type.(*ast.InterfaceType)
228 return nil, fmt.Errorf("%s is not an interface", errorName)
230 if iface.Methods.NumFields() != 1 {
231 return nil, fmt.Errorf("expected 1 method for %s, got %v", errorName, iface.Methods.NumFields())
233 method := iface.Methods.List[0]
234 if len(method.Names) != 1 {
235 return nil, fmt.Errorf("expected 1 name for %v, got %v", method, len(method.Names))
237 name := method.Names[0].Name
238 result.Declaration.node = method
239 rng := NewMappedRange(snapshot.FileSet(), builtin.ParsedFile.Mapper, method.Pos(), method.Pos()+token.Pos(len(name)))
240 result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
245 // If the original position was an embedded field, we want to jump
246 // to the field's type definition, not the field's definition.
247 if v, ok := result.Declaration.obj.(*types.Var); ok && v.Embedded() {
248 // types.Info.Uses contains the embedded field's *types.TypeName.
249 if typeName := pkg.GetTypesInfo().Uses[ident]; typeName != nil {
250 result.Declaration.obj = typeName
254 rng, err := objToMappedRange(snapshot, pkg, result.Declaration.obj)
258 result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
260 if result.Declaration.node, err = objToDecl(ctx, snapshot, pkg, result.Declaration.obj); err != nil {
263 typ := pkg.GetTypesInfo().TypeOf(result.ident)
268 result.Type.Object = typeToObject(typ)
269 if result.Type.Object != nil {
270 // Identifiers with the type "error" are a special case with no position.
271 if hasErrorType(result.Type.Object) {
274 if result.Type.MappedRange, err = objToMappedRange(snapshot, pkg, result.Type.Object); err != nil {
281 func searchForEnclosing(info *types.Info, path []ast.Node) types.Type {
282 for _, n := range path {
283 switch n := n.(type) {
284 case *ast.SelectorExpr:
285 if sel, ok := info.Selections[n]; ok {
286 recv := Deref(sel.Recv())
288 // Keep track of the last exported type seen.
289 var exported types.Type
290 if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
293 // We don't want the last element, as that's the field or
295 for _, index := range sel.Index()[:len(sel.Index())-1] {
296 if r, ok := recv.Underlying().(*types.Struct); ok {
297 recv = Deref(r.Field(index).Type())
298 if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
305 case *ast.CompositeLit:
306 if t, ok := info.Types[n]; ok {
310 if _, ok := n.Type.(*ast.StructType); ok {
311 if t, ok := info.Defs[n.Name]; ok {
320 func typeToObject(typ types.Type) types.Object {
321 switch typ := typ.(type) {
325 return typeToObject(typ.Elem())
331 func hasErrorType(obj types.Object) bool {
332 return types.IsInterface(obj.Type()) && obj.Pkg() == nil && obj.Name() == "error"
335 func objToDecl(ctx context.Context, snapshot Snapshot, srcPkg Package, obj types.Object) (ast.Decl, error) {
336 pgf, _, err := FindPosInPackage(snapshot, srcPkg, obj.Pos())
340 posToDecl, err := snapshot.PosToDecl(ctx, pgf)
344 return posToDecl[obj.Pos()], nil
347 // importSpec handles positions inside of an *ast.ImportSpec.
348 func importSpec(snapshot Snapshot, pkg Package, file *ast.File, pos token.Pos) (*IdentifierInfo, error) {
349 var imp *ast.ImportSpec
350 for _, spec := range file.Imports {
351 if spec.Path.Pos() <= pos && pos < spec.Path.End() {
358 importPath, err := strconv.Unquote(imp.Path.Value)
360 return nil, errors.Errorf("import path not quoted: %s (%v)", imp.Path.Value, err)
362 result := &IdentifierInfo{
367 if result.MappedRange, err = posToMappedRange(snapshot, pkg, imp.Path.Pos(), imp.Path.End()); err != nil {
370 // Consider the "declaration" of an import spec to be the imported package.
371 importedPkg, err := pkg.GetImport(importPath)
375 // Return all of the files in the package as the definition of the import spec.
376 for _, dst := range importedPkg.GetSyntax() {
377 rng, err := posToMappedRange(snapshot, pkg, dst.Pos(), dst.End())
381 result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
384 result.Declaration.node = imp
388 // typeSwitchImplicits returns all the implicit type switch objects that
389 // correspond to the leaf *ast.Ident. It also returns the original type
390 // associated with the identifier (outside of a case clause).
391 func typeSwitchImplicits(pkg Package, path []ast.Node) ([]types.Object, types.Type) {
392 ident, _ := path[0].(*ast.Ident)
398 ts *ast.TypeSwitchStmt
399 assign *ast.AssignStmt
401 obj = pkg.GetTypesInfo().ObjectOf(ident)
404 // Walk our ancestors to determine if our leaf ident refers to a
405 // type switch variable, e.g. the "a" from "switch a := b.(type)".
407 for i := 1; i < len(path); i++ {
408 switch n := path[i].(type) {
409 case *ast.AssignStmt:
410 // Check if ident is the "a" in "a := foo.(type)". The "a" in
411 // this case has no types.Object, so check for ident equality.
412 if len(n.Lhs) == 1 && n.Lhs[0] == ident {
415 case *ast.CaseClause:
416 // Check if ident is a use of "a" within a case clause. Each
417 // case clause implicitly maps "a" to a different types.Object,
418 // so check if ident's object is the case clause's implicit
420 if obj != nil && pkg.GetTypesInfo().Implicits[n] == obj {
423 case *ast.TypeSwitchStmt:
424 // Look for the type switch that owns our previously found
425 // *ast.AssignStmt or *ast.CaseClause.
426 if n.Assign == assign {
431 for _, stmt := range n.Body.List {
442 // Our leaf ident refers to a type switch variable. Fan out to the
443 // type switch's implicit case clause objects.
444 var objs []types.Object
445 for _, cc := range ts.Body.List {
446 if ccObj := pkg.GetTypesInfo().Implicits[cc]; ccObj != nil {
447 objs = append(objs, ccObj)
450 // The right-hand side of a type switch should only have one
451 // element, and we need to track its type in order to generate
452 // hover information for implicit type switch variables.
454 if assign, ok := ts.Assign.(*ast.AssignStmt); ok && len(assign.Rhs) == 1 {
455 if rhs := assign.Rhs[0].(*ast.TypeAssertExpr); ok {
456 typ = pkg.GetTypesInfo().TypeOf(rhs.X)