internal/lsp/source/identifier.go - tools - Git at Google

 // Copyright 2018 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 source

 import (
 	"context"
 	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
 	"sort"
 	"strconv"

 	"golang.org/x/tools/internal/event"
 	"golang.org/x/tools/internal/lsp/protocol"
 	errors "golang.org/x/xerrors"
 )

 // IdentifierInfo holds information about an identifier in Go source.
 type IdentifierInfo struct {
 	Name     string
 	Snapshot Snapshot
 	MappedRange

 	Type struct {
 		MappedRange
 		Object types.Object
 	}

 	Declaration Declaration

 	ident *ast.Ident

 	// enclosing is an expression used to determine the link anchor for an
 	// identifier. If it's a named type, it should be exported.
 	enclosing types.Type

 	pkg Package
 	qf  types.Qualifier
 }

 type Declaration struct {
 	MappedRange []MappedRange
 	node        ast.Node
 	obj         types.Object

 	// typeSwitchImplicit indicates that the declaration is in an implicit
 	// type switch. Its type is the type of the variable on the right-hand
 	// side of the type switch.
 	typeSwitchImplicit types.Type
 }

 // Identifier returns identifier information for a position
 // in a file, accounting for a potentially incomplete selector.
 func Identifier(ctx context.Context, snapshot Snapshot, fh FileHandle, pos protocol.Position) (*IdentifierInfo, error) {
 	ctx, done := event.Start(ctx, "source.Identifier")
 	defer done()

 	pkgs, err := snapshot.PackagesForFile(ctx, fh.URI(), TypecheckAll)
 	if err != nil {
 		return nil, err
 	}
 	if len(pkgs) == 0 {
 		return nil, fmt.Errorf("no packages for file %v", fh.URI())
 	}
 	sort.Slice(pkgs, func(i, j int) bool {
 		return len(pkgs[i].CompiledGoFiles()) < len(pkgs[j].CompiledGoFiles())
 	})
 	var findErr error
 	for _, pkg := range pkgs {
 		pgf, err := pkg.File(fh.URI())
 		if err != nil {
 			return nil, err
 		}
 		spn, err := pgf.Mapper.PointSpan(pos)
 		if err != nil {
 			return nil, err
 		}
 		rng, err := spn.Range(pgf.Mapper.Converter)
 		if err != nil {
 			return nil, err
 		}
 		var ident *IdentifierInfo
 		ident, findErr = findIdentifier(ctx, snapshot, pkg, pgf.File, rng.Start)
 		if findErr == nil {
 			return ident, nil
 		}
 	}
 	return nil, findErr
 }

 // ErrNoIdentFound is error returned when no identifer is found at a particular position
 var ErrNoIdentFound = errors.New("no identifier found")

 func findIdentifier(ctx context.Context, snapshot Snapshot, pkg Package, file *ast.File, pos token.Pos) (*IdentifierInfo, error) {
 	// Handle import specs separately, as there is no formal position for a
 	// package declaration.
 	if result, err := importSpec(snapshot, pkg, file, pos); result != nil || err != nil {
 		if snapshot.View().Options().ImportShortcut.ShowDefinition() {
 			return result, err
 		}
 		return nil, nil
 	}
 	path := pathEnclosingObjNode(file, pos)
 	if path == nil {
 		return nil, ErrNoIdentFound
 	}

 	qf := Qualifier(file, pkg.GetTypes(), pkg.GetTypesInfo())

 	ident, _ := path[0].(*ast.Ident)
 	if ident == nil {
 		return nil, ErrNoIdentFound
 	}
 	// Special case for package declarations, since they have no
 	// corresponding types.Object.
 	if ident == file.Name {
 		rng, err := posToMappedRange(snapshot, pkg, file.Name.Pos(), file.Name.End())
 		if err != nil {
 			return nil, err
 		}
 		var declAST *ast.File
 		for _, pgf := range pkg.CompiledGoFiles() {
 			if pgf.File.Doc != nil {
 				declAST = pgf.File
 			}
 		}
 		// If there's no package documentation, just use current file.
 		if declAST == nil {
 			declAST = file
 		}
 		declRng, err := posToMappedRange(snapshot, pkg, declAST.Name.Pos(), declAST.Name.End())
 		if err != nil {
 			return nil, err
 		}
 		return &IdentifierInfo{
 			Name:        file.Name.Name,
 			ident:       file.Name,
 			MappedRange: rng,
 			pkg:         pkg,
 			qf:          qf,
 			Snapshot:    snapshot,
 			Declaration: Declaration{
 				node:        declAST.Name,
 				MappedRange: []MappedRange{declRng},
 			},
 		}, nil
 	}

 	result := &IdentifierInfo{
 		Snapshot:  snapshot,
 		qf:        qf,
 		pkg:       pkg,
 		ident:     ident,
 		enclosing: searchForEnclosing(pkg.GetTypesInfo(), path),
 	}

 	result.Name = result.ident.Name
 	var err error
 	if result.MappedRange, err = posToMappedRange(snapshot, pkg, result.ident.Pos(), result.ident.End()); err != nil {
 		return nil, err
 	}

 	result.Declaration.obj = pkg.GetTypesInfo().ObjectOf(result.ident)
 	if result.Declaration.obj == nil {
 		// If there was no types.Object for the declaration, there might be an
 		// implicit local variable declaration in a type switch.
 		if objs, typ := typeSwitchImplicits(pkg, path); len(objs) > 0 {
 			// There is no types.Object for the declaration of an implicit local variable,
 			// but all of the types.Objects associated with the usages of this variable can be
 			// used to connect it back to the declaration.
 			// Preserve the first of these objects and treat it as if it were the declaring object.
 			result.Declaration.obj = objs[0]
 			result.Declaration.typeSwitchImplicit = typ
 		} else {
 			// Probably a type error.
 			return nil, errors.Errorf("%w for ident %v", errNoObjectFound, result.Name)
 		}
 	}

 	// Handle builtins separately.
 	if result.Declaration.obj.Parent() == types.Universe {
 		builtin, err := snapshot.BuiltinPackage(ctx)
 		if err != nil {
 			return nil, err
 		}
 		builtinObj := builtin.Package.Scope.Lookup(result.Name)
 		if builtinObj == nil {
 			return nil, fmt.Errorf("no builtin object for %s", result.Name)
 		}
 		decl, ok := builtinObj.Decl.(ast.Node)
 		if !ok {
 			return nil, errors.Errorf("no declaration for %s", result.Name)
 		}
 		result.Declaration.node = decl

 		// The builtin package isn't in the dependency graph, so the usual
 		// utilities won't work here.
 		rng := NewMappedRange(snapshot.FileSet(), builtin.ParsedFile.Mapper, decl.Pos(), decl.Pos()+token.Pos(len(result.Name)))
 		result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
 		return result, nil
 	}

 	// (error).Error is a special case of builtin. Lots of checks to confirm
 	// that this is the builtin Error.
 	if obj := result.Declaration.obj; obj.Parent() == nil && obj.Pkg() == nil && obj.Name() == "Error" {
 		if _, ok := obj.Type().(*types.Signature); ok {
 			builtin, err := snapshot.BuiltinPackage(ctx)
 			if err != nil {
 				return nil, err
 			}
 			// Look up "error" and then navigate to its only method.
 			// The Error method does not appear in the builtin package's scope.log.Pri
 			const errorName = "error"
 			builtinObj := builtin.Package.Scope.Lookup(errorName)
 			if builtinObj == nil {
 				return nil, fmt.Errorf("no builtin object for %s", errorName)
 			}
 			decl, ok := builtinObj.Decl.(ast.Node)
 			if !ok {
 				return nil, errors.Errorf("no declaration for %s", errorName)
 			}
 			spec, ok := decl.(*ast.TypeSpec)
 			if !ok {
 				return nil, fmt.Errorf("no type spec for %s", errorName)
 			}
 			iface, ok := spec.Type.(*ast.InterfaceType)
 			if !ok {
 				return nil, fmt.Errorf("%s is not an interface", errorName)
 			}
 			if iface.Methods.NumFields() != 1 {
 				return nil, fmt.Errorf("expected 1 method for %s, got %v", errorName, iface.Methods.NumFields())
 			}
 			method := iface.Methods.List[0]
 			if len(method.Names) != 1 {
 				return nil, fmt.Errorf("expected 1 name for %v, got %v", method, len(method.Names))
 			}
 			name := method.Names[0].Name
 			result.Declaration.node = method
 			rng := NewMappedRange(snapshot.FileSet(), builtin.ParsedFile.Mapper, method.Pos(), method.Pos()+token.Pos(len(name)))
 			result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
 			return result, nil
 		}
 	}

 	// If the original position was an embedded field, we want to jump
 	// to the field's type definition, not the field's definition.
 	if v, ok := result.Declaration.obj.(*types.Var); ok && v.Embedded() {
 		// types.Info.Uses contains the embedded field's *types.TypeName.
 		if typeName := pkg.GetTypesInfo().Uses[ident]; typeName != nil {
 			result.Declaration.obj = typeName
 		}
 	}

 	rng, err := objToMappedRange(snapshot, pkg, result.Declaration.obj)
 	if err != nil {
 		return nil, err
 	}
 	result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)

 	if result.Declaration.node, err = objToDecl(ctx, snapshot, pkg, result.Declaration.obj); err != nil {
 		return nil, err
 	}
 	typ := pkg.GetTypesInfo().TypeOf(result.ident)
 	if typ == nil {
 		return result, nil
 	}

 	result.Type.Object = typeToObject(typ)
 	if result.Type.Object != nil {
 		// Identifiers with the type "error" are a special case with no position.
 		if hasErrorType(result.Type.Object) {
 			return result, nil
 		}
 		if result.Type.MappedRange, err = objToMappedRange(snapshot, pkg, result.Type.Object); err != nil {
 			return nil, err
 		}
 	}
 	return result, nil
 }

 func searchForEnclosing(info *types.Info, path []ast.Node) types.Type {
 	for _, n := range path {
 		switch n := n.(type) {
 		case *ast.SelectorExpr:
 			if sel, ok := info.Selections[n]; ok {
 				recv := Deref(sel.Recv())

 				// Keep track of the last exported type seen.
 				var exported types.Type
 				if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
 					exported = named
 				}
 				// We don't want the last element, as that's the field or
 				// method itself.
 				for _, index := range sel.Index()[:len(sel.Index())-1] {
 					if r, ok := recv.Underlying().(*types.Struct); ok {
 						recv = Deref(r.Field(index).Type())
 						if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
 							exported = named
 						}
 					}
 				}
 				return exported
 			}
 		case *ast.CompositeLit:
 			if t, ok := info.Types[n]; ok {
 				return t.Type
 			}
 		case *ast.TypeSpec:
 			if _, ok := n.Type.(*ast.StructType); ok {
 				if t, ok := info.Defs[n.Name]; ok {
 					return t.Type()
 				}
 			}
 		}
 	}
 	return nil
 }

 func typeToObject(typ types.Type) types.Object {
 	switch typ := typ.(type) {
 	case *types.Named:
 		return typ.Obj()
 	case *types.Pointer:
 		return typeToObject(typ.Elem())
 	default:
 		return nil
 	}
 }

 func hasErrorType(obj types.Object) bool {
 	return types.IsInterface(obj.Type()) && obj.Pkg() == nil && obj.Name() == "error"
 }

 func objToDecl(ctx context.Context, snapshot Snapshot, srcPkg Package, obj types.Object) (ast.Decl, error) {
 	pgf, _, err := FindPosInPackage(snapshot, srcPkg, obj.Pos())
 	if err != nil {
 		return nil, err
 	}
 	posToDecl, err := snapshot.PosToDecl(ctx, pgf)
 	if err != nil {
 		return nil, err
 	}
 	return posToDecl[obj.Pos()], nil
 }

 // importSpec handles positions inside of an *ast.ImportSpec.
 func importSpec(snapshot Snapshot, pkg Package, file *ast.File, pos token.Pos) (*IdentifierInfo, error) {
 	var imp *ast.ImportSpec
 	for _, spec := range file.Imports {
 		if spec.Path.Pos() <= pos && pos < spec.Path.End() {
 			imp = spec
 		}
 	}
 	if imp == nil {
 		return nil, nil
 	}
 	importPath, err := strconv.Unquote(imp.Path.Value)
 	if err != nil {
 		return nil, errors.Errorf("import path not quoted: %s (%v)", imp.Path.Value, err)
 	}
 	result := &IdentifierInfo{
 		Snapshot: snapshot,
 		Name:     importPath,
 		pkg:      pkg,
 	}
 	if result.MappedRange, err = posToMappedRange(snapshot, pkg, imp.Path.Pos(), imp.Path.End()); err != nil {
 		return nil, err
 	}
 	// Consider the "declaration" of an import spec to be the imported package.
 	importedPkg, err := pkg.GetImport(importPath)
 	if err != nil {
 		return nil, err
 	}
 	// Return all of the files in the package as the definition of the import spec.
 	for _, dst := range importedPkg.GetSyntax() {
 		rng, err := posToMappedRange(snapshot, pkg, dst.Pos(), dst.End())
 		if err != nil {
 			return nil, err
 		}
 		result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
 	}

 	result.Declaration.node = imp
 	return result, nil
 }

 // typeSwitchImplicits returns all the implicit type switch objects that
 // correspond to the leaf *ast.Ident. It also returns the original type
 // associated with the identifier (outside of a case clause).
 func typeSwitchImplicits(pkg Package, path []ast.Node) ([]types.Object, types.Type) {
 	ident, _ := path[0].(*ast.Ident)
 	if ident == nil {
 		return nil, nil
 	}

 	var (
 		ts     *ast.TypeSwitchStmt
 		assign *ast.AssignStmt
 		cc     *ast.CaseClause
 		obj    = pkg.GetTypesInfo().ObjectOf(ident)
 	)

 	// Walk our ancestors to determine if our leaf ident refers to a
 	// type switch variable, e.g. the "a" from "switch a := b.(type)".
 Outer:
 	for i := 1; i < len(path); i++ {
 		switch n := path[i].(type) {
 		case *ast.AssignStmt:
 			// Check if ident is the "a" in "a := foo.(type)". The "a" in
 			// this case has no types.Object, so check for ident equality.
 			if len(n.Lhs) == 1 && n.Lhs[0] == ident {
 				assign = n
 			}
 		case *ast.CaseClause:
 			// Check if ident is a use of "a" within a case clause. Each
 			// case clause implicitly maps "a" to a different types.Object,
 			// so check if ident's object is the case clause's implicit
 			// object.
 			if obj != nil && pkg.GetTypesInfo().Implicits[n] == obj {
 				cc = n
 			}
 		case *ast.TypeSwitchStmt:
 			// Look for the type switch that owns our previously found
 			// *ast.AssignStmt or *ast.CaseClause.
 			if n.Assign == assign {
 				ts = n
 				break Outer
 			}

 			for _, stmt := range n.Body.List {
 				if stmt == cc {
 					ts = n
 					break Outer
 				}
 			}
 		}
 	}
 	if ts == nil {
 		return nil, nil
 	}
 	// Our leaf ident refers to a type switch variable. Fan out to the
 	// type switch's implicit case clause objects.
 	var objs []types.Object
 	for _, cc := range ts.Body.List {
 		if ccObj := pkg.GetTypesInfo().Implicits[cc]; ccObj != nil {
 			objs = append(objs, ccObj)
 		}
 	}
 	// The right-hand side of a type switch should only have one
 	// element, and we need to track its type in order to generate
 	// hover information for implicit type switch variables.
 	var typ types.Type
 	if assign, ok := ts.Assign.(*ast.AssignStmt); ok && len(assign.Rhs) == 1 {
 		if rhs := assign.Rhs[0].(*ast.TypeAssertExpr); ok {
 			typ = pkg.GetTypesInfo().TypeOf(rhs.X)
 		}
 	}
 	return objs, typ
 }
	// Copyright 2018 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 source

	import (
	"context"
	"fmt"
	"go/ast"
	"go/token"
	"go/types"
	"sort"
	"strconv"

	"golang.org/x/tools/internal/event"
	"golang.org/x/tools/internal/lsp/protocol"
	errors "golang.org/x/xerrors"
	)

	// IdentifierInfo holds information about an identifier in Go source.
	type IdentifierInfo struct {
	Name string
	Snapshot Snapshot
	MappedRange

	Type struct {
	MappedRange
	Object types.Object
	}

	Declaration Declaration

	ident *ast.Ident

	// enclosing is an expression used to determine the link anchor for an
	// identifier. If it's a named type, it should be exported.
	enclosing types.Type

	pkg Package
	qf types.Qualifier
	}

	type Declaration struct {
	MappedRange []MappedRange
	node ast.Node
	obj types.Object

	// typeSwitchImplicit indicates that the declaration is in an implicit
	// type switch. Its type is the type of the variable on the right-hand
	// side of the type switch.
	typeSwitchImplicit types.Type
	}

	// Identifier returns identifier information for a position
	// in a file, accounting for a potentially incomplete selector.
	func Identifier(ctx context.Context, snapshot Snapshot, fh FileHandle, pos protocol.Position) (*IdentifierInfo, error) {
	ctx, done := event.Start(ctx, "source.Identifier")
	defer done()

	pkgs, err := snapshot.PackagesForFile(ctx, fh.URI(), TypecheckAll)
	if err != nil {
	return nil, err
	}
	if len(pkgs) == 0 {
	return nil, fmt.Errorf("no packages for file %v", fh.URI())
	}
	sort.Slice(pkgs, func(i, j int) bool {
	return len(pkgs[i].CompiledGoFiles()) < len(pkgs[j].CompiledGoFiles())
	})
	var findErr error
	for _, pkg := range pkgs {
	pgf, err := pkg.File(fh.URI())
	if err != nil {
	return nil, err
	}
	spn, err := pgf.Mapper.PointSpan(pos)
	if err != nil {
	return nil, err
	}
	rng, err := spn.Range(pgf.Mapper.Converter)
	if err != nil {
	return nil, err
	}
	var ident *IdentifierInfo
	ident, findErr = findIdentifier(ctx, snapshot, pkg, pgf.File, rng.Start)
	if findErr == nil {
	return ident, nil
	}
	}
	return nil, findErr
	}

	// ErrNoIdentFound is error returned when no identifer is found at a particular position
	var ErrNoIdentFound = errors.New("no identifier found")

	func findIdentifier(ctx context.Context, snapshot Snapshot, pkg Package, file ast.File, pos token.Pos) (IdentifierInfo, error) {
	// Handle import specs separately, as there is no formal position for a
	// package declaration.
	if result, err := importSpec(snapshot, pkg, file, pos); result != nil \|\| err != nil {
	if snapshot.View().Options().ImportShortcut.ShowDefinition() {
	return result, err
	}
	return nil, nil
	}
	path := pathEnclosingObjNode(file, pos)
	if path == nil {
	return nil, ErrNoIdentFound
	}

	qf := Qualifier(file, pkg.GetTypes(), pkg.GetTypesInfo())

	ident, _ := path[0].(*ast.Ident)
	if ident == nil {
	return nil, ErrNoIdentFound
	}
	// Special case for package declarations, since they have no
	// corresponding types.Object.
	if ident == file.Name {
	rng, err := posToMappedRange(snapshot, pkg, file.Name.Pos(), file.Name.End())
	if err != nil {
	return nil, err
	}
	var declAST *ast.File
	for _, pgf := range pkg.CompiledGoFiles() {
	if pgf.File.Doc != nil {
	declAST = pgf.File
	}
	}
	// If there's no package documentation, just use current file.
	if declAST == nil {
	declAST = file
	}
	declRng, err := posToMappedRange(snapshot, pkg, declAST.Name.Pos(), declAST.Name.End())
	if err != nil {
	return nil, err
	}
	return &IdentifierInfo{
	Name: file.Name.Name,
	ident: file.Name,
	MappedRange: rng,
	pkg: pkg,
	qf: qf,
	Snapshot: snapshot,
	Declaration: Declaration{
	node: declAST.Name,
	MappedRange: []MappedRange{declRng},
	},
	}, nil
	}

	result := &IdentifierInfo{
	Snapshot: snapshot,
	qf: qf,
	pkg: pkg,
	ident: ident,
	enclosing: searchForEnclosing(pkg.GetTypesInfo(), path),
	}

	result.Name = result.ident.Name
	var err error
	if result.MappedRange, err = posToMappedRange(snapshot, pkg, result.ident.Pos(), result.ident.End()); err != nil {
	return nil, err
	}

	result.Declaration.obj = pkg.GetTypesInfo().ObjectOf(result.ident)
	if result.Declaration.obj == nil {
	// If there was no types.Object for the declaration, there might be an
	// implicit local variable declaration in a type switch.
	if objs, typ := typeSwitchImplicits(pkg, path); len(objs) > 0 {
	// There is no types.Object for the declaration of an implicit local variable,
	// but all of the types.Objects associated with the usages of this variable can be
	// used to connect it back to the declaration.
	// Preserve the first of these objects and treat it as if it were the declaring object.
	result.Declaration.obj = objs[0]
	result.Declaration.typeSwitchImplicit = typ
	} else {
	// Probably a type error.
	return nil, errors.Errorf("%w for ident %v", errNoObjectFound, result.Name)
	}
	}

	// Handle builtins separately.
	if result.Declaration.obj.Parent() == types.Universe {
	builtin, err := snapshot.BuiltinPackage(ctx)
	if err != nil {
	return nil, err
	}
	builtinObj := builtin.Package.Scope.Lookup(result.Name)
	if builtinObj == nil {
	return nil, fmt.Errorf("no builtin object for %s", result.Name)
	}
	decl, ok := builtinObj.Decl.(ast.Node)
	if !ok {
	return nil, errors.Errorf("no declaration for %s", result.Name)
	}
	result.Declaration.node = decl

	// The builtin package isn't in the dependency graph, so the usual
	// utilities won't work here.
	rng := NewMappedRange(snapshot.FileSet(), builtin.ParsedFile.Mapper, decl.Pos(), decl.Pos()+token.Pos(len(result.Name)))
	result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
	return result, nil
	}

	// (error).Error is a special case of builtin. Lots of checks to confirm
	// that this is the builtin Error.
	if obj := result.Declaration.obj; obj.Parent() == nil && obj.Pkg() == nil && obj.Name() == "Error" {
	if _, ok := obj.Type().(*types.Signature); ok {
	builtin, err := snapshot.BuiltinPackage(ctx)
	if err != nil {
	return nil, err
	}
	// Look up "error" and then navigate to its only method.
	// The Error method does not appear in the builtin package's scope.log.Pri
	const errorName = "error"
	builtinObj := builtin.Package.Scope.Lookup(errorName)
	if builtinObj == nil {
	return nil, fmt.Errorf("no builtin object for %s", errorName)
	}
	decl, ok := builtinObj.Decl.(ast.Node)
	if !ok {
	return nil, errors.Errorf("no declaration for %s", errorName)
	}
	spec, ok := decl.(*ast.TypeSpec)
	if !ok {
	return nil, fmt.Errorf("no type spec for %s", errorName)
	}
	iface, ok := spec.Type.(*ast.InterfaceType)
	if !ok {
	return nil, fmt.Errorf("%s is not an interface", errorName)
	}
	if iface.Methods.NumFields() != 1 {
	return nil, fmt.Errorf("expected 1 method for %s, got %v", errorName, iface.Methods.NumFields())
	}
	method := iface.Methods.List[0]
	if len(method.Names) != 1 {
	return nil, fmt.Errorf("expected 1 name for %v, got %v", method, len(method.Names))
	}
	name := method.Names[0].Name
	result.Declaration.node = method
	rng := NewMappedRange(snapshot.FileSet(), builtin.ParsedFile.Mapper, method.Pos(), method.Pos()+token.Pos(len(name)))
	result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
	return result, nil
	}
	}

	// If the original position was an embedded field, we want to jump
	// to the field's type definition, not the field's definition.
	if v, ok := result.Declaration.obj.(*types.Var); ok && v.Embedded() {
	// types.Info.Uses contains the embedded field's *types.TypeName.
	if typeName := pkg.GetTypesInfo().Uses[ident]; typeName != nil {
	result.Declaration.obj = typeName
	}
	}

	rng, err := objToMappedRange(snapshot, pkg, result.Declaration.obj)
	if err != nil {
	return nil, err
	}
	result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)

	if result.Declaration.node, err = objToDecl(ctx, snapshot, pkg, result.Declaration.obj); err != nil {
	return nil, err
	}
	typ := pkg.GetTypesInfo().TypeOf(result.ident)
	if typ == nil {
	return result, nil
	}

	result.Type.Object = typeToObject(typ)
	if result.Type.Object != nil {
	// Identifiers with the type "error" are a special case with no position.
	if hasErrorType(result.Type.Object) {
	return result, nil
	}
	if result.Type.MappedRange, err = objToMappedRange(snapshot, pkg, result.Type.Object); err != nil {
	return nil, err
	}
	}
	return result, nil
	}

	func searchForEnclosing(info *types.Info, path []ast.Node) types.Type {
	for _, n := range path {
	switch n := n.(type) {
	case *ast.SelectorExpr:
	if sel, ok := info.Selections[n]; ok {
	recv := Deref(sel.Recv())

	// Keep track of the last exported type seen.
	var exported types.Type
	if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
	exported = named
	}
	// We don't want the last element, as that's the field or
	// method itself.
	for _, index := range sel.Index()[:len(sel.Index())-1] {
	if r, ok := recv.Underlying().(*types.Struct); ok {
	recv = Deref(r.Field(index).Type())
	if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
	exported = named
	}
	}
	}
	return exported
	}
	case *ast.CompositeLit:
	if t, ok := info.Types[n]; ok {
	return t.Type
	}
	case *ast.TypeSpec:
	if _, ok := n.Type.(*ast.StructType); ok {
	if t, ok := info.Defs[n.Name]; ok {
	return t.Type()
	}
	}
	}
	}
	return nil
	}

	func typeToObject(typ types.Type) types.Object {
	switch typ := typ.(type) {
	case *types.Named:
	return typ.Obj()
	case *types.Pointer:
	return typeToObject(typ.Elem())
	default:
	return nil
	}
	}

	func hasErrorType(obj types.Object) bool {
	return types.IsInterface(obj.Type()) && obj.Pkg() == nil && obj.Name() == "error"
	}

	func objToDecl(ctx context.Context, snapshot Snapshot, srcPkg Package, obj types.Object) (ast.Decl, error) {
	pgf, _, err := FindPosInPackage(snapshot, srcPkg, obj.Pos())
	if err != nil {
	return nil, err
	}
	posToDecl, err := snapshot.PosToDecl(ctx, pgf)
	if err != nil {
	return nil, err
	}
	return posToDecl[obj.Pos()], nil
	}

	// importSpec handles positions inside of an *ast.ImportSpec.
	func importSpec(snapshot Snapshot, pkg Package, file ast.File, pos token.Pos) (IdentifierInfo, error) {
	var imp *ast.ImportSpec
	for _, spec := range file.Imports {
	if spec.Path.Pos() <= pos && pos < spec.Path.End() {
	imp = spec
	}
	}
	if imp == nil {
	return nil, nil
	}
	importPath, err := strconv.Unquote(imp.Path.Value)
	if err != nil {
	return nil, errors.Errorf("import path not quoted: %s (%v)", imp.Path.Value, err)
	}
	result := &IdentifierInfo{
	Snapshot: snapshot,
	Name: importPath,
	pkg: pkg,
	}
	if result.MappedRange, err = posToMappedRange(snapshot, pkg, imp.Path.Pos(), imp.Path.End()); err != nil {
	return nil, err
	}
	// Consider the "declaration" of an import spec to be the imported package.
	importedPkg, err := pkg.GetImport(importPath)
	if err != nil {
	return nil, err
	}
	// Return all of the files in the package as the definition of the import spec.
	for _, dst := range importedPkg.GetSyntax() {
	rng, err := posToMappedRange(snapshot, pkg, dst.Pos(), dst.End())
	if err != nil {
	return nil, err
	}
	result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
	}

	result.Declaration.node = imp
	return result, nil
	}

	// typeSwitchImplicits returns all the implicit type switch objects that
	// correspond to the leaf *ast.Ident. It also returns the original type
	// associated with the identifier (outside of a case clause).
	func typeSwitchImplicits(pkg Package, path []ast.Node) ([]types.Object, types.Type) {
	ident, _ := path[0].(*ast.Ident)
	if ident == nil {
	return nil, nil
	}

	var (
	ts *ast.TypeSwitchStmt
	assign *ast.AssignStmt
	cc *ast.CaseClause
	obj = pkg.GetTypesInfo().ObjectOf(ident)
	)

	// Walk our ancestors to determine if our leaf ident refers to a
	// type switch variable, e.g. the "a" from "switch a := b.(type)".
	Outer:
	for i := 1; i < len(path); i++ {
	switch n := path[i].(type) {
	case *ast.AssignStmt:
	// Check if ident is the "a" in "a := foo.(type)". The "a" in
	// this case has no types.Object, so check for ident equality.
	if len(n.Lhs) == 1 && n.Lhs[0] == ident {
	assign = n
	}
	case *ast.CaseClause:
	// Check if ident is a use of "a" within a case clause. Each
	// case clause implicitly maps "a" to a different types.Object,
	// so check if ident's object is the case clause's implicit
	// object.
	if obj != nil && pkg.GetTypesInfo().Implicits[n] == obj {
	cc = n
	}
	case *ast.TypeSwitchStmt:
	// Look for the type switch that owns our previously found
	// ast.AssignStmt or ast.CaseClause.
	if n.Assign == assign {
	ts = n
	break Outer
	}

	for _, stmt := range n.Body.List {
	if stmt == cc {
	ts = n
	break Outer
	}
	}
	}
	}
	if ts == nil {
	return nil, nil
	}
	// Our leaf ident refers to a type switch variable. Fan out to the
	// type switch's implicit case clause objects.
	var objs []types.Object
	for _, cc := range ts.Body.List {
	if ccObj := pkg.GetTypesInfo().Implicits[cc]; ccObj != nil {
	objs = append(objs, ccObj)
	}
	}
	// The right-hand side of a type switch should only have one
	// element, and we need to track its type in order to generate
	// hover information for implicit type switch variables.
	var typ types.Type
	if assign, ok := ts.Assign.(*ast.AssignStmt); ok && len(assign.Rhs) == 1 {
	if rhs := assign.Rhs[0].(*ast.TypeAssertExpr); ok {
	typ = pkg.GetTypesInfo().TypeOf(rhs.X)
	}
	}
	return objs, typ
	}