gopls/internal/lsp/source/highlight.go - tools - Git at Google

 // Copyright 2019 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"
 	"strings"

 	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/internal/event"
 )

 func Highlight(ctx context.Context, snapshot Snapshot, fh FileHandle, position protocol.Position) ([]protocol.Range, error) {
 	ctx, done := event.Start(ctx, "source.Highlight")
 	defer done()

 	// We always want fully parsed files for highlight, regardless
 	// of whether the file belongs to a workspace package.
 	pkg, pgf, err := PackageForFile(ctx, snapshot, fh.URI(), TypecheckFull, NarrowestPackage)
 	if err != nil {
 		return nil, fmt.Errorf("getting package for Highlight: %w", err)
 	}

 	pos, err := pgf.PositionPos(position)
 	if err != nil {
 		return nil, err
 	}
 	path, _ := astutil.PathEnclosingInterval(pgf.File, pos, pos)
 	if len(path) == 0 {
 		return nil, fmt.Errorf("no enclosing position found for %v:%v", position.Line, position.Character)
 	}
 	// If start == end for astutil.PathEnclosingInterval, the 1-char interval
 	// following start is used instead. As a result, we might not get an exact
 	// match so we should check the 1-char interval to the left of the passed
 	// in position to see if that is an exact match.
 	if _, ok := path[0].(*ast.Ident); !ok {
 		if p, _ := astutil.PathEnclosingInterval(pgf.File, pos-1, pos-1); p != nil {
 			switch p[0].(type) {
 			case *ast.Ident, *ast.SelectorExpr:
 				path = p // use preceding ident/selector
 			}
 		}
 	}
 	result, err := highlightPath(path, pgf.File, pkg.GetTypesInfo())
 	if err != nil {
 		return nil, err
 	}
 	var ranges []protocol.Range
 	for rng := range result {
 		rng, err := pgf.PosRange(rng.start, rng.end)
 		if err != nil {
 			return nil, err
 		}
 		ranges = append(ranges, rng)
 	}
 	return ranges, nil
 }

 func highlightPath(path []ast.Node, file *ast.File, info *types.Info) (map[posRange]struct{}, error) {
 	result := make(map[posRange]struct{})
 	switch node := path[0].(type) {
 	case *ast.BasicLit:
 		if len(path) > 1 {
 			if _, ok := path[1].(*ast.ImportSpec); ok {
 				err := highlightImportUses(path, info, result)
 				return result, err
 			}
 		}
 		highlightFuncControlFlow(path, result)
 	case *ast.ReturnStmt, *ast.FuncDecl, *ast.FuncType:
 		highlightFuncControlFlow(path, result)
 	case *ast.Ident:
 		// Check if ident is inside return or func decl.
 		highlightFuncControlFlow(path, result)
 		highlightIdentifier(node, file, info, result)
 	case *ast.ForStmt, *ast.RangeStmt:
 		highlightLoopControlFlow(path, result)
 	case *ast.SwitchStmt:
 		highlightSwitchFlow(path, result)
 	case *ast.BranchStmt:
 		// BREAK can exit a loop, switch or select, while CONTINUE exit a loop so
 		// these need to be handled separately. They can also be embedded in any
 		// other loop/switch/select if they have a label. TODO: add support for
 		// GOTO and FALLTHROUGH as well.
 		if node.Label != nil {
 			highlightLabeledFlow(node, result)
 		} else {
 			switch node.Tok {
 			case token.BREAK:
 				highlightUnlabeledBreakFlow(path, result)
 			case token.CONTINUE:
 				highlightLoopControlFlow(path, result)
 			}
 		}
 	default:
 		// If the cursor is in an unidentified area, return empty results.
 		return nil, nil
 	}
 	return result, nil
 }

 type posRange struct {
 	start, end token.Pos
 }

 func highlightFuncControlFlow(path []ast.Node, result map[posRange]struct{}) {
 	var enclosingFunc ast.Node
 	var returnStmt *ast.ReturnStmt
 	var resultsList *ast.FieldList
 	inReturnList := false

 Outer:
 	// Reverse walk the path till we get to the func block.
 	for i, n := range path {
 		switch node := n.(type) {
 		case *ast.KeyValueExpr:
 			// If cursor is in a key: value expr, we don't want control flow highlighting
 			return
 		case *ast.CallExpr:
 			// If cursor is an arg in a callExpr, we don't want control flow highlighting.
 			if i > 0 {
 				for _, arg := range node.Args {
 					if arg == path[i-1] {
 						return
 					}
 				}
 			}
 		case *ast.Field:
 			inReturnList = true
 		case *ast.FuncLit:
 			enclosingFunc = n
 			resultsList = node.Type.Results
 			break Outer
 		case *ast.FuncDecl:
 			enclosingFunc = n
 			resultsList = node.Type.Results
 			break Outer
 		case *ast.ReturnStmt:
 			returnStmt = node
 			// If the cursor is not directly in a *ast.ReturnStmt, then
 			// we need to know if it is within one of the values that is being returned.
 			inReturnList = inReturnList || path[0] != returnStmt
 		}
 	}
 	// Cursor is not in a function.
 	if enclosingFunc == nil {
 		return
 	}
 	// If the cursor is on a "return" or "func" keyword, we should highlight all of the exit
 	// points of the function, including the "return" and "func" keywords.
 	highlightAllReturnsAndFunc := path[0] == returnStmt || path[0] == enclosingFunc
 	switch path[0].(type) {
 	case *ast.Ident, *ast.BasicLit:
 		// Cursor is in an identifier and not in a return statement or in the results list.
 		if returnStmt == nil && !inReturnList {
 			return
 		}
 	case *ast.FuncType:
 		highlightAllReturnsAndFunc = true
 	}
 	// The user's cursor may be within the return statement of a function,
 	// or within the result section of a function's signature.
 	// index := -1
 	var nodes []ast.Node
 	if returnStmt != nil {
 		for _, n := range returnStmt.Results {
 			nodes = append(nodes, n)
 		}
 	} else if resultsList != nil {
 		for _, n := range resultsList.List {
 			nodes = append(nodes, n)
 		}
 	}
 	_, index := nodeAtPos(nodes, path[0].Pos())

 	// Highlight the correct argument in the function declaration return types.
 	if resultsList != nil && -1 < index && index < len(resultsList.List) {
 		rng := posRange{
 			start: resultsList.List[index].Pos(),
 			end:   resultsList.List[index].End(),
 		}
 		result[rng] = struct{}{}
 	}
 	// Add the "func" part of the func declaration.
 	if highlightAllReturnsAndFunc {
 		r := posRange{
 			start: enclosingFunc.Pos(),
 			end:   enclosingFunc.Pos() + token.Pos(len("func")),
 		}
 		result[r] = struct{}{}
 	}
 	ast.Inspect(enclosingFunc, func(n ast.Node) bool {
 		// Don't traverse any other functions.
 		switch n.(type) {
 		case *ast.FuncDecl, *ast.FuncLit:
 			return enclosingFunc == n
 		}
 		ret, ok := n.(*ast.ReturnStmt)
 		if !ok {
 			return true
 		}
 		var toAdd ast.Node
 		// Add the entire return statement, applies when highlight the word "return" or "func".
 		if highlightAllReturnsAndFunc {
 			toAdd = n
 		}
 		// Add the relevant field within the entire return statement.
 		if -1 < index && index < len(ret.Results) {
 			toAdd = ret.Results[index]
 		}
 		if toAdd != nil {
 			result[posRange{start: toAdd.Pos(), end: toAdd.End()}] = struct{}{}
 		}
 		return false
 	})
 }

 func highlightUnlabeledBreakFlow(path []ast.Node, result map[posRange]struct{}) {
 	// Reverse walk the path until we find closest loop, select, or switch.
 	for _, n := range path {
 		switch n.(type) {
 		case *ast.ForStmt, *ast.RangeStmt:
 			highlightLoopControlFlow(path, result)
 			return // only highlight the innermost statement
 		case *ast.SwitchStmt:
 			highlightSwitchFlow(path, result)
 			return
 		case *ast.SelectStmt:
 			// TODO: add highlight when breaking a select.
 			return
 		}
 	}
 }

 func highlightLabeledFlow(node *ast.BranchStmt, result map[posRange]struct{}) {
 	obj := node.Label.Obj
 	if obj == nil || obj.Decl == nil {
 		return
 	}
 	label, ok := obj.Decl.(*ast.LabeledStmt)
 	if !ok {
 		return
 	}
 	switch label.Stmt.(type) {
 	case *ast.ForStmt, *ast.RangeStmt:
 		highlightLoopControlFlow([]ast.Node{label.Stmt, label}, result)
 	case *ast.SwitchStmt:
 		highlightSwitchFlow([]ast.Node{label.Stmt, label}, result)
 	}
 }

 func labelFor(path []ast.Node) *ast.Ident {
 	if len(path) > 1 {
 		if n, ok := path[1].(*ast.LabeledStmt); ok {
 			return n.Label
 		}
 	}
 	return nil
 }

 func highlightLoopControlFlow(path []ast.Node, result map[posRange]struct{}) {
 	var loop ast.Node
 	var loopLabel *ast.Ident
 	stmtLabel := labelFor(path)
 Outer:
 	// Reverse walk the path till we get to the for loop.
 	for i := range path {
 		switch n := path[i].(type) {
 		case *ast.ForStmt, *ast.RangeStmt:
 			loopLabel = labelFor(path[i:])

 			if stmtLabel == nil || loopLabel == stmtLabel {
 				loop = n
 				break Outer
 			}
 		}
 	}
 	if loop == nil {
 		return
 	}

 	// Add the for statement.
 	rng := posRange{
 		start: loop.Pos(),
 		end:   loop.Pos() + token.Pos(len("for")),
 	}
 	result[rng] = struct{}{}

 	// Traverse AST to find branch statements within the same for-loop.
 	ast.Inspect(loop, func(n ast.Node) bool {
 		switch n.(type) {
 		case *ast.ForStmt, *ast.RangeStmt:
 			return loop == n
 		case *ast.SwitchStmt, *ast.SelectStmt:
 			return false
 		}
 		b, ok := n.(*ast.BranchStmt)
 		if !ok {
 			return true
 		}
 		if b.Label == nil || labelDecl(b.Label) == loopLabel {
 			result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
 		}
 		return true
 	})

 	// Find continue statements in the same loop or switches/selects.
 	ast.Inspect(loop, func(n ast.Node) bool {
 		switch n.(type) {
 		case *ast.ForStmt, *ast.RangeStmt:
 			return loop == n
 		}

 		if n, ok := n.(*ast.BranchStmt); ok && n.Tok == token.CONTINUE {
 			result[posRange{start: n.Pos(), end: n.End()}] = struct{}{}
 		}
 		return true
 	})

 	// We don't need to check other for loops if we aren't looking for labeled statements.
 	if loopLabel == nil {
 		return
 	}

 	// Find labeled branch statements in any loop.
 	ast.Inspect(loop, func(n ast.Node) bool {
 		b, ok := n.(*ast.BranchStmt)
 		if !ok {
 			return true
 		}
 		// statement with labels that matches the loop
 		if b.Label != nil && labelDecl(b.Label) == loopLabel {
 			result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
 		}
 		return true
 	})
 }

 func highlightSwitchFlow(path []ast.Node, result map[posRange]struct{}) {
 	var switchNode ast.Node
 	var switchNodeLabel *ast.Ident
 	stmtLabel := labelFor(path)
 Outer:
 	// Reverse walk the path till we get to the switch statement.
 	for i := range path {
 		switch n := path[i].(type) {
 		case *ast.SwitchStmt:
 			switchNodeLabel = labelFor(path[i:])
 			if stmtLabel == nil || switchNodeLabel == stmtLabel {
 				switchNode = n
 				break Outer
 			}
 		}
 	}
 	// Cursor is not in a switch statement
 	if switchNode == nil {
 		return
 	}

 	// Add the switch statement.
 	rng := posRange{
 		start: switchNode.Pos(),
 		end:   switchNode.Pos() + token.Pos(len("switch")),
 	}
 	result[rng] = struct{}{}

 	// Traverse AST to find break statements within the same switch.
 	ast.Inspect(switchNode, func(n ast.Node) bool {
 		switch n.(type) {
 		case *ast.SwitchStmt:
 			return switchNode == n
 		case *ast.ForStmt, *ast.RangeStmt, *ast.SelectStmt:
 			return false
 		}

 		b, ok := n.(*ast.BranchStmt)
 		if !ok || b.Tok != token.BREAK {
 			return true
 		}

 		if b.Label == nil || labelDecl(b.Label) == switchNodeLabel {
 			result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
 		}
 		return true
 	})

 	// We don't need to check other switches if we aren't looking for labeled statements.
 	if switchNodeLabel == nil {
 		return
 	}

 	// Find labeled break statements in any switch
 	ast.Inspect(switchNode, func(n ast.Node) bool {
 		b, ok := n.(*ast.BranchStmt)
 		if !ok || b.Tok != token.BREAK {
 			return true
 		}

 		if b.Label != nil && labelDecl(b.Label) == switchNodeLabel {
 			result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
 		}

 		return true
 	})
 }

 func labelDecl(n *ast.Ident) *ast.Ident {
 	if n == nil {
 		return nil
 	}
 	if n.Obj == nil {
 		return nil
 	}
 	if n.Obj.Decl == nil {
 		return nil
 	}
 	stmt, ok := n.Obj.Decl.(*ast.LabeledStmt)
 	if !ok {
 		return nil
 	}
 	return stmt.Label
 }

 func highlightImportUses(path []ast.Node, info *types.Info, result map[posRange]struct{}) error {
 	basicLit, ok := path[0].(*ast.BasicLit)
 	if !ok {
 		return fmt.Errorf("highlightImportUses called with an ast.Node of type %T", basicLit)
 	}
 	ast.Inspect(path[len(path)-1], func(node ast.Node) bool {
 		if imp, ok := node.(*ast.ImportSpec); ok && imp.Path == basicLit {
 			result[posRange{start: node.Pos(), end: node.End()}] = struct{}{}
 			return false
 		}
 		n, ok := node.(*ast.Ident)
 		if !ok {
 			return true
 		}
 		obj, ok := info.ObjectOf(n).(*types.PkgName)
 		if !ok {
 			return true
 		}
 		if !strings.Contains(basicLit.Value, obj.Name()) {
 			return true
 		}
 		result[posRange{start: n.Pos(), end: n.End()}] = struct{}{}
 		return false
 	})
 	return nil
 }

 func highlightIdentifier(id *ast.Ident, file *ast.File, info *types.Info, result map[posRange]struct{}) {
 	// TODO(rfindley): idObj may be nil. Note that returning early in this case
 	// causes tests to fail (because the nObj == idObj check below was succeeded
 	// for nil == nil!)
 	//
 	// Revisit this. If ObjectOf is nil, there are type errors, and it seems
 	// reasonable for identifier highlighting not to work.
 	idObj := info.ObjectOf(id)
 	pkgObj, isImported := idObj.(*types.PkgName)
 	ast.Inspect(file, func(node ast.Node) bool {
 		if imp, ok := node.(*ast.ImportSpec); ok && isImported {
 			highlightImport(pkgObj, imp, result)
 		}
 		n, ok := node.(*ast.Ident)
 		if !ok {
 			return true
 		}
 		if n.Name != id.Name {
 			return false
 		}
 		if nObj := info.ObjectOf(n); nObj == idObj {
 			result[posRange{start: n.Pos(), end: n.End()}] = struct{}{}
 		}
 		return false
 	})
 }

 func highlightImport(obj *types.PkgName, imp *ast.ImportSpec, result map[posRange]struct{}) {
 	if imp.Name != nil || imp.Path == nil {
 		return
 	}
 	if !strings.Contains(imp.Path.Value, obj.Name()) {
 		return
 	}
 	result[posRange{start: imp.Path.Pos(), end: imp.Path.End()}] = struct{}{}
 }
	// Copyright 2019 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"
	"strings"

	"golang.org/x/tools/go/ast/astutil"
	"golang.org/x/tools/gopls/internal/lsp/protocol"
	"golang.org/x/tools/internal/event"
	)

	func Highlight(ctx context.Context, snapshot Snapshot, fh FileHandle, position protocol.Position) ([]protocol.Range, error) {
	ctx, done := event.Start(ctx, "source.Highlight")
	defer done()

	// We always want fully parsed files for highlight, regardless
	// of whether the file belongs to a workspace package.
	pkg, pgf, err := PackageForFile(ctx, snapshot, fh.URI(), TypecheckFull, NarrowestPackage)
	if err != nil {
	return nil, fmt.Errorf("getting package for Highlight: %w", err)
	}

	pos, err := pgf.PositionPos(position)
	if err != nil {
	return nil, err
	}
	path, _ := astutil.PathEnclosingInterval(pgf.File, pos, pos)
	if len(path) == 0 {
	return nil, fmt.Errorf("no enclosing position found for %v:%v", position.Line, position.Character)
	}
	// If start == end for astutil.PathEnclosingInterval, the 1-char interval
	// following start is used instead. As a result, we might not get an exact
	// match so we should check the 1-char interval to the left of the passed
	// in position to see if that is an exact match.
	if _, ok := path[0].(*ast.Ident); !ok {
	if p, _ := astutil.PathEnclosingInterval(pgf.File, pos-1, pos-1); p != nil {
	switch p[0].(type) {
	case ast.Ident, ast.SelectorExpr:
	path = p // use preceding ident/selector
	}
	}
	}
	result, err := highlightPath(path, pgf.File, pkg.GetTypesInfo())
	if err != nil {
	return nil, err
	}
	var ranges []protocol.Range
	for rng := range result {
	rng, err := pgf.PosRange(rng.start, rng.end)
	if err != nil {
	return nil, err
	}
	ranges = append(ranges, rng)
	}
	return ranges, nil
	}

	func highlightPath(path []ast.Node, file ast.File, info types.Info) (map[posRange]struct{}, error) {
	result := make(map[posRange]struct{})
	switch node := path[0].(type) {
	case *ast.BasicLit:
	if len(path) > 1 {
	if _, ok := path[1].(*ast.ImportSpec); ok {
	err := highlightImportUses(path, info, result)
	return result, err
	}
	}
	highlightFuncControlFlow(path, result)
	case ast.ReturnStmt, ast.FuncDecl, *ast.FuncType:
	highlightFuncControlFlow(path, result)
	case *ast.Ident:
	// Check if ident is inside return or func decl.
	highlightFuncControlFlow(path, result)
	highlightIdentifier(node, file, info, result)
	case ast.ForStmt, ast.RangeStmt:
	highlightLoopControlFlow(path, result)
	case *ast.SwitchStmt:
	highlightSwitchFlow(path, result)
	case *ast.BranchStmt:
	// BREAK can exit a loop, switch or select, while CONTINUE exit a loop so
	// these need to be handled separately. They can also be embedded in any
	// other loop/switch/select if they have a label. TODO: add support for
	// GOTO and FALLTHROUGH as well.
	if node.Label != nil {
	highlightLabeledFlow(node, result)
	} else {
	switch node.Tok {
	case token.BREAK:
	highlightUnlabeledBreakFlow(path, result)
	case token.CONTINUE:
	highlightLoopControlFlow(path, result)
	}
	}
	default:
	// If the cursor is in an unidentified area, return empty results.
	return nil, nil
	}
	return result, nil
	}

	type posRange struct {
	start, end token.Pos
	}

	func highlightFuncControlFlow(path []ast.Node, result map[posRange]struct{}) {
	var enclosingFunc ast.Node
	var returnStmt *ast.ReturnStmt
	var resultsList *ast.FieldList
	inReturnList := false

	Outer:
	// Reverse walk the path till we get to the func block.
	for i, n := range path {
	switch node := n.(type) {
	case *ast.KeyValueExpr:
	// If cursor is in a key: value expr, we don't want control flow highlighting
	return
	case *ast.CallExpr:
	// If cursor is an arg in a callExpr, we don't want control flow highlighting.
	if i > 0 {
	for _, arg := range node.Args {
	if arg == path[i-1] {
	return
	}
	}
	}
	case *ast.Field:
	inReturnList = true
	case *ast.FuncLit:
	enclosingFunc = n
	resultsList = node.Type.Results
	break Outer
	case *ast.FuncDecl:
	enclosingFunc = n
	resultsList = node.Type.Results
	break Outer
	case *ast.ReturnStmt:
	returnStmt = node
	// If the cursor is not directly in a *ast.ReturnStmt, then
	// we need to know if it is within one of the values that is being returned.
	inReturnList = inReturnList \|\| path[0] != returnStmt
	}
	}
	// Cursor is not in a function.
	if enclosingFunc == nil {
	return
	}
	// If the cursor is on a "return" or "func" keyword, we should highlight all of the exit
	// points of the function, including the "return" and "func" keywords.
	highlightAllReturnsAndFunc := path[0] == returnStmt \|\| path[0] == enclosingFunc
	switch path[0].(type) {
	case ast.Ident, ast.BasicLit:
	// Cursor is in an identifier and not in a return statement or in the results list.
	if returnStmt == nil && !inReturnList {
	return
	}
	case *ast.FuncType:
	highlightAllReturnsAndFunc = true
	}
	// The user's cursor may be within the return statement of a function,
	// or within the result section of a function's signature.
	// index := -1
	var nodes []ast.Node
	if returnStmt != nil {
	for _, n := range returnStmt.Results {
	nodes = append(nodes, n)
	}
	} else if resultsList != nil {
	for _, n := range resultsList.List {
	nodes = append(nodes, n)
	}
	}
	_, index := nodeAtPos(nodes, path[0].Pos())

	// Highlight the correct argument in the function declaration return types.
	if resultsList != nil && -1 < index && index < len(resultsList.List) {
	rng := posRange{
	start: resultsList.List[index].Pos(),
	end: resultsList.List[index].End(),
	}
	result[rng] = struct{}{}
	}
	// Add the "func" part of the func declaration.
	if highlightAllReturnsAndFunc {
	r := posRange{
	start: enclosingFunc.Pos(),
	end: enclosingFunc.Pos() + token.Pos(len("func")),
	}
	result[r] = struct{}{}
	}
	ast.Inspect(enclosingFunc, func(n ast.Node) bool {
	// Don't traverse any other functions.
	switch n.(type) {
	case ast.FuncDecl, ast.FuncLit:
	return enclosingFunc == n
	}
	ret, ok := n.(*ast.ReturnStmt)
	if !ok {
	return true
	}
	var toAdd ast.Node
	// Add the entire return statement, applies when highlight the word "return" or "func".
	if highlightAllReturnsAndFunc {
	toAdd = n
	}
	// Add the relevant field within the entire return statement.
	if -1 < index && index < len(ret.Results) {
	toAdd = ret.Results[index]
	}
	if toAdd != nil {
	result[posRange{start: toAdd.Pos(), end: toAdd.End()}] = struct{}{}
	}
	return false
	})
	}

	func highlightUnlabeledBreakFlow(path []ast.Node, result map[posRange]struct{}) {
	// Reverse walk the path until we find closest loop, select, or switch.
	for _, n := range path {
	switch n.(type) {
	case ast.ForStmt, ast.RangeStmt:
	highlightLoopControlFlow(path, result)
	return // only highlight the innermost statement
	case *ast.SwitchStmt:
	highlightSwitchFlow(path, result)
	return
	case *ast.SelectStmt:
	// TODO: add highlight when breaking a select.
	return
	}
	}
	}

	func highlightLabeledFlow(node *ast.BranchStmt, result map[posRange]struct{}) {
	obj := node.Label.Obj
	if obj == nil \|\| obj.Decl == nil {
	return
	}
	label, ok := obj.Decl.(*ast.LabeledStmt)
	if !ok {
	return
	}
	switch label.Stmt.(type) {
	case ast.ForStmt, ast.RangeStmt:
	highlightLoopControlFlow([]ast.Node{label.Stmt, label}, result)
	case *ast.SwitchStmt:
	highlightSwitchFlow([]ast.Node{label.Stmt, label}, result)
	}
	}

	func labelFor(path []ast.Node) *ast.Ident {
	if len(path) > 1 {
	if n, ok := path[1].(*ast.LabeledStmt); ok {
	return n.Label
	}
	}
	return nil
	}

	func highlightLoopControlFlow(path []ast.Node, result map[posRange]struct{}) {
	var loop ast.Node
	var loopLabel *ast.Ident
	stmtLabel := labelFor(path)
	Outer:
	// Reverse walk the path till we get to the for loop.
	for i := range path {
	switch n := path[i].(type) {
	case ast.ForStmt, ast.RangeStmt:
	loopLabel = labelFor(path[i:])

	if stmtLabel == nil \|\| loopLabel == stmtLabel {
	loop = n
	break Outer
	}
	}
	}
	if loop == nil {
	return
	}

	// Add the for statement.
	rng := posRange{
	start: loop.Pos(),
	end: loop.Pos() + token.Pos(len("for")),
	}
	result[rng] = struct{}{}

	// Traverse AST to find branch statements within the same for-loop.
	ast.Inspect(loop, func(n ast.Node) bool {
	switch n.(type) {
	case ast.ForStmt, ast.RangeStmt:
	return loop == n
	case ast.SwitchStmt, ast.SelectStmt:
	return false
	}
	b, ok := n.(*ast.BranchStmt)
	if !ok {
	return true
	}
	if b.Label == nil \|\| labelDecl(b.Label) == loopLabel {
	result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
	}
	return true
	})

	// Find continue statements in the same loop or switches/selects.
	ast.Inspect(loop, func(n ast.Node) bool {
	switch n.(type) {
	case ast.ForStmt, ast.RangeStmt:
	return loop == n
	}

	if n, ok := n.(*ast.BranchStmt); ok && n.Tok == token.CONTINUE {
	result[posRange{start: n.Pos(), end: n.End()}] = struct{}{}
	}
	return true
	})

	// We don't need to check other for loops if we aren't looking for labeled statements.
	if loopLabel == nil {
	return
	}

	// Find labeled branch statements in any loop.
	ast.Inspect(loop, func(n ast.Node) bool {
	b, ok := n.(*ast.BranchStmt)
	if !ok {
	return true
	}
	// statement with labels that matches the loop
	if b.Label != nil && labelDecl(b.Label) == loopLabel {
	result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
	}
	return true
	})
	}

	func highlightSwitchFlow(path []ast.Node, result map[posRange]struct{}) {
	var switchNode ast.Node
	var switchNodeLabel *ast.Ident
	stmtLabel := labelFor(path)
	Outer:
	// Reverse walk the path till we get to the switch statement.
	for i := range path {
	switch n := path[i].(type) {
	case *ast.SwitchStmt:
	switchNodeLabel = labelFor(path[i:])
	if stmtLabel == nil \|\| switchNodeLabel == stmtLabel {
	switchNode = n
	break Outer
	}
	}
	}
	// Cursor is not in a switch statement
	if switchNode == nil {
	return
	}

	// Add the switch statement.
	rng := posRange{
	start: switchNode.Pos(),
	end: switchNode.Pos() + token.Pos(len("switch")),
	}
	result[rng] = struct{}{}

	// Traverse AST to find break statements within the same switch.
	ast.Inspect(switchNode, func(n ast.Node) bool {
	switch n.(type) {
	case *ast.SwitchStmt:
	return switchNode == n
	case ast.ForStmt, ast.RangeStmt, *ast.SelectStmt:
	return false
	}

	b, ok := n.(*ast.BranchStmt)
	if !ok \|\| b.Tok != token.BREAK {
	return true
	}

	if b.Label == nil \|\| labelDecl(b.Label) == switchNodeLabel {
	result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
	}
	return true
	})

	// We don't need to check other switches if we aren't looking for labeled statements.
	if switchNodeLabel == nil {
	return
	}

	// Find labeled break statements in any switch
	ast.Inspect(switchNode, func(n ast.Node) bool {
	b, ok := n.(*ast.BranchStmt)
	if !ok \|\| b.Tok != token.BREAK {
	return true
	}

	if b.Label != nil && labelDecl(b.Label) == switchNodeLabel {
	result[posRange{start: b.Pos(), end: b.End()}] = struct{}{}
	}

	return true
	})
	}

	func labelDecl(n ast.Ident) ast.Ident {
	if n == nil {
	return nil
	}
	if n.Obj == nil {
	return nil
	}
	if n.Obj.Decl == nil {
	return nil
	}
	stmt, ok := n.Obj.Decl.(*ast.LabeledStmt)
	if !ok {
	return nil
	}
	return stmt.Label
	}

	func highlightImportUses(path []ast.Node, info *types.Info, result map[posRange]struct{}) error {
	basicLit, ok := path[0].(*ast.BasicLit)
	if !ok {
	return fmt.Errorf("highlightImportUses called with an ast.Node of type %T", basicLit)
	}
	ast.Inspect(path[len(path)-1], func(node ast.Node) bool {
	if imp, ok := node.(*ast.ImportSpec); ok && imp.Path == basicLit {
	result[posRange{start: node.Pos(), end: node.End()}] = struct{}{}
	return false
	}
	n, ok := node.(*ast.Ident)
	if !ok {
	return true
	}
	obj, ok := info.ObjectOf(n).(*types.PkgName)
	if !ok {
	return true
	}
	if !strings.Contains(basicLit.Value, obj.Name()) {
	return true
	}
	result[posRange{start: n.Pos(), end: n.End()}] = struct{}{}
	return false
	})
	return nil
	}

	func highlightIdentifier(id ast.Ident, file ast.File, info *types.Info, result map[posRange]struct{}) {
	// TODO(rfindley): idObj may be nil. Note that returning early in this case
	// causes tests to fail (because the nObj == idObj check below was succeeded
	// for nil == nil!)
	//
	// Revisit this. If ObjectOf is nil, there are type errors, and it seems
	// reasonable for identifier highlighting not to work.
	idObj := info.ObjectOf(id)
	pkgObj, isImported := idObj.(*types.PkgName)
	ast.Inspect(file, func(node ast.Node) bool {
	if imp, ok := node.(*ast.ImportSpec); ok && isImported {
	highlightImport(pkgObj, imp, result)
	}
	n, ok := node.(*ast.Ident)
	if !ok {
	return true
	}
	if n.Name != id.Name {
	return false
	}
	if nObj := info.ObjectOf(n); nObj == idObj {
	result[posRange{start: n.Pos(), end: n.End()}] = struct{}{}
	}
	return false
	})
	}

	func highlightImport(obj types.PkgName, imp ast.ImportSpec, result map[posRange]struct{}) {
	if imp.Name != nil \|\| imp.Path == nil {
	return
	}
	if !strings.Contains(imp.Path.Value, obj.Name()) {
	return
	}
	result[posRange{start: imp.Path.Pos(), end: imp.Path.End()}] = struct{}{}
	}