diff --git a/src/pkg/go/printer/performance_test.go b/src/pkg/go/printer/performance_test.go
new file mode 100644
index 00000000000..31de0b7ad40
--- /dev/null
+++ b/src/pkg/go/printer/performance_test.go
@@ -0,0 +1,62 @@
+// Copyright 2009 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.
+
+// This file implements a simple printer performance benchmark:
+// gotest -bench=BenchmarkPrint 
+
+package printer
+
+import (
+	"bytes"
+	"go/ast"
+	"go/parser"
+	"io"
+	"io/ioutil"
+	"log"
+	"testing"
+)
+
+
+var testfile *ast.File
+
+
+func testprint(out io.Writer, file *ast.File) {
+	if _, err := (&Config{TabIndent | UseSpaces, 8}).Fprint(out, fset, file); err != nil {
+		log.Fatalf("print error: %s", err)
+	}
+}
+
+
+// cannot initialize in init because (printer) Fprint launches goroutines.
+func initialize() {
+	const filename = "testdata/parser.go"
+
+	src, err := ioutil.ReadFile(filename)
+	if err != nil {
+		log.Fatalf("%s", err)
+	}
+
+	file, err := parser.ParseFile(fset, filename, src, parser.ParseComments)
+	if err != nil {
+		log.Fatalf("%s", err)
+	}
+
+	var buf bytes.Buffer
+	testprint(&buf, file)
+	if !bytes.Equal(buf.Bytes(), src) {
+		log.Fatalf("print error: %s not idempotent", filename)
+	}
+
+	testfile = file
+}
+
+
+func BenchmarkPrint(b *testing.B) {
+	if testfile == nil {
+		initialize()
+	}
+	for i := 0; i < b.N; i++ {
+		testprint(ioutil.Discard, testfile)
+	}
+}
diff --git a/src/pkg/go/printer/testdata/parser.go b/src/pkg/go/printer/testdata/parser.go
new file mode 100644
index 00000000000..5c57e41d130
--- /dev/null
+++ b/src/pkg/go/printer/testdata/parser.go
@@ -0,0 +1,2252 @@
+// Copyright 2009 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 parser implements a parser for Go source files. Input may be
+// provided in a variety of forms (see the various Parse* functions); the
+// output is an abstract syntax tree (AST) representing the Go source. The
+// parser is invoked through one of the Parse* functions.
+//
+package parser
+
+import (
+	"fmt"
+	"go/ast"
+	"go/scanner"
+	"go/token"
+)
+
+
+// The mode parameter to the Parse* functions is a set of flags (or 0).
+// They control the amount of source code parsed and other optional
+// parser functionality.
+//
+const (
+	PackageClauseOnly uint = 1 << iota // parsing stops after package clause
+	ImportsOnly                        // parsing stops after import declarations
+	ParseComments                      // parse comments and add them to AST
+	Trace                              // print a trace of parsed productions
+	DeclarationErrors                  // report declaration errors
+)
+
+
+// The parser structure holds the parser's internal state.
+type parser struct {
+	file *token.File
+	scanner.ErrorVector
+	scanner scanner.Scanner
+
+	// Tracing/debugging
+	mode   uint // parsing mode
+	trace  bool // == (mode & Trace != 0)
+	indent uint // indentation used for tracing output
+
+	// Comments
+	comments    []*ast.CommentGroup
+	leadComment *ast.CommentGroup // last lead comment
+	lineComment *ast.CommentGroup // last line comment
+
+	// Next token
+	pos token.Pos   // token position
+	tok token.Token // one token look-ahead
+	lit string      // token literal
+
+	// Non-syntactic parser control
+	exprLev int // < 0: in control clause, >= 0: in expression
+
+	// Ordinary identifer scopes
+	pkgScope   *ast.Scope        // pkgScope.Outer == nil
+	topScope   *ast.Scope        // top-most scope; may be pkgScope
+	unresolved []*ast.Ident      // unresolved identifiers
+	imports    []*ast.ImportSpec // list of imports
+
+	// Label scope
+	// (maintained by open/close LabelScope)
+	labelScope  *ast.Scope     // label scope for current function
+	targetStack [][]*ast.Ident // stack of unresolved labels
+}
+
+
+// scannerMode returns the scanner mode bits given the parser's mode bits.
+func scannerMode(mode uint) uint {
+	var m uint = scanner.InsertSemis
+	if mode&ParseComments != 0 {
+		m |= scanner.ScanComments
+	}
+	return m
+}
+
+
+func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode uint) {
+	p.file = fset.AddFile(filename, fset.Base(), len(src))
+	p.scanner.Init(p.file, src, p, scannerMode(mode))
+
+	p.mode = mode
+	p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently)
+
+	p.next()
+
+	// set up the pkgScope here (as opposed to in parseFile) because
+	// there are other parser entry points (ParseExpr, etc.)
+	p.openScope()
+	p.pkgScope = p.topScope
+
+	// for the same reason, set up a label scope
+	p.openLabelScope()
+}
+
+
+// ----------------------------------------------------------------------------
+// Scoping support
+
+func (p *parser) openScope() {
+	p.topScope = ast.NewScope(p.topScope)
+}
+
+
+func (p *parser) closeScope() {
+	p.topScope = p.topScope.Outer
+}
+
+
+func (p *parser) openLabelScope() {
+	p.labelScope = ast.NewScope(p.labelScope)
+	p.targetStack = append(p.targetStack, nil)
+}
+
+
+func (p *parser) closeLabelScope() {
+	// resolve labels
+	n := len(p.targetStack) - 1
+	scope := p.labelScope
+	for _, ident := range p.targetStack[n] {
+		ident.Obj = scope.Lookup(ident.Name)
+		if ident.Obj == nil && p.mode&DeclarationErrors != 0 {
+			p.error(ident.Pos(), fmt.Sprintf("label %s undefined", ident.Name))
+		}
+	}
+	// pop label scope
+	p.targetStack = p.targetStack[0:n]
+	p.labelScope = p.labelScope.Outer
+}
+
+
+func (p *parser) declare(decl interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
+	for _, ident := range idents {
+		assert(ident.Obj == nil, "identifier already declared or resolved")
+		if ident.Name != "_" {
+			obj := ast.NewObj(kind, ident.Name)
+			// remember the corresponding declaration for redeclaration
+			// errors and global variable resolution/typechecking phase
+			obj.Decl = decl
+			if alt := scope.Insert(obj); alt != nil && p.mode&DeclarationErrors != 0 {
+				prevDecl := ""
+				if pos := alt.Pos(); pos.IsValid() {
+					prevDecl = fmt.Sprintf("\n\tprevious declaration at %s", p.file.Position(pos))
+				}
+				p.error(ident.Pos(), fmt.Sprintf("%s redeclared in this block%s", ident.Name, prevDecl))
+			}
+			ident.Obj = obj
+		}
+	}
+}
+
+
+func (p *parser) shortVarDecl(idents []*ast.Ident) {
+	// Go spec: A short variable declaration may redeclare variables
+	// provided they were originally declared in the same block with
+	// the same type, and at least one of the non-blank variables is new.
+	n := 0 // number of new variables
+	for _, ident := range idents {
+		assert(ident.Obj == nil, "identifier already declared or resolved")
+		if ident.Name != "_" {
+			obj := ast.NewObj(ast.Var, ident.Name)
+			// short var declarations cannot have redeclaration errors
+			// and are not global => no need to remember the respective
+			// declaration
+			alt := p.topScope.Insert(obj)
+			if alt == nil {
+				n++ // new declaration
+				alt = obj
+			}
+			ident.Obj = alt
+		}
+	}
+	if n == 0 && p.mode&DeclarationErrors != 0 {
+		p.error(idents[0].Pos(), "no new variables on left side of :=")
+	}
+}
+
+
+// The unresolved object is a sentinel to mark identifiers that have been added
+// to the list of unresolved identifiers. The sentinel is only used for verifying
+// internal consistency.
+var unresolved = new(ast.Object)
+
+
+func (p *parser) resolve(x ast.Expr) {
+	// nothing to do if x is not an identifier or the blank identifier
+	ident, _ := x.(*ast.Ident)
+	if ident == nil {
+		return
+	}
+	assert(ident.Obj == nil, "identifier already declared or resolved")
+	if ident.Name == "_" {
+		return
+	}
+	// try to resolve the identifier
+	for s := p.topScope; s != nil; s = s.Outer {
+		if obj := s.Lookup(ident.Name); obj != nil {
+			ident.Obj = obj
+			return
+		}
+	}
+	// all local scopes are known, so any unresolved identifier
+	// must be found either in the file scope, package scope
+	// (perhaps in another file), or universe scope --- collect
+	// them so that they can be resolved later
+	ident.Obj = unresolved
+	p.unresolved = append(p.unresolved, ident)
+}
+
+
+// ----------------------------------------------------------------------------
+// Parsing support
+
+func (p *parser) printTrace(a ...interface{}) {
+	const dots = ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " +
+		". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "
+	const n = uint(len(dots))
+	pos := p.file.Position(p.pos)
+	fmt.Printf("%5d:%3d: ", pos.Line, pos.Column)
+	i := 2 * p.indent
+	for ; i > n; i -= n {
+		fmt.Print(dots)
+	}
+	fmt.Print(dots[0:i])
+	fmt.Println(a...)
+}
+
+
+func trace(p *parser, msg string) *parser {
+	p.printTrace(msg, "(")
+	p.indent++
+	return p
+}
+
+
+// Usage pattern: defer un(trace(p, "..."));
+func un(p *parser) {
+	p.indent--
+	p.printTrace(")")
+}
+
+
+// Advance to the next token.
+func (p *parser) next0() {
+	// Because of one-token look-ahead, print the previous token
+	// when tracing as it provides a more readable output. The
+	// very first token (!p.pos.IsValid()) is not initialized
+	// (it is token.ILLEGAL), so don't print it .
+	if p.trace && p.pos.IsValid() {
+		s := p.tok.String()
+		switch {
+		case p.tok.IsLiteral():
+			p.printTrace(s, p.lit)
+		case p.tok.IsOperator(), p.tok.IsKeyword():
+			p.printTrace("\"" + s + "\"")
+		default:
+			p.printTrace(s)
+		}
+	}
+
+	p.pos, p.tok, p.lit = p.scanner.Scan()
+}
+
+// Consume a comment and return it and the line on which it ends.
+func (p *parser) consumeComment() (comment *ast.Comment, endline int) {
+	// /*-style comments may end on a different line than where they start.
+	// Scan the comment for '\n' chars and adjust endline accordingly.
+	endline = p.file.Line(p.pos)
+	if p.lit[1] == '*' {
+		// don't use range here - no need to decode Unicode code points
+		for i := 0; i < len(p.lit); i++ {
+			if p.lit[i] == '\n' {
+				endline++
+			}
+		}
+	}
+
+	comment = &ast.Comment{p.pos, p.lit}
+	p.next0()
+
+	return
+}
+
+
+// Consume a group of adjacent comments, add it to the parser's
+// comments list, and return it together with the line at which
+// the last comment in the group ends. An empty line or non-comment
+// token terminates a comment group.
+//
+func (p *parser) consumeCommentGroup() (comments *ast.CommentGroup, endline int) {
+	var list []*ast.Comment
+	endline = p.file.Line(p.pos)
+	for p.tok == token.COMMENT && endline+1 >= p.file.Line(p.pos) {
+		var comment *ast.Comment
+		comment, endline = p.consumeComment()
+		list = append(list, comment)
+	}
+
+	// add comment group to the comments list
+	comments = &ast.CommentGroup{list}
+	p.comments = append(p.comments, comments)
+
+	return
+}
+
+
+// Advance to the next non-comment token. In the process, collect
+// any comment groups encountered, and remember the last lead and
+// and line comments.
+//
+// A lead comment is a comment group that starts and ends in a
+// line without any other tokens and that is followed by a non-comment
+// token on the line immediately after the comment group.
+//
+// A line comment is a comment group that follows a non-comment
+// token on the same line, and that has no tokens after it on the line
+// where it ends.
+//
+// Lead and line comments may be considered documentation that is
+// stored in the AST.
+//
+func (p *parser) next() {
+	p.leadComment = nil
+	p.lineComment = nil
+	line := p.file.Line(p.pos) // current line
+	p.next0()
+
+	if p.tok == token.COMMENT {
+		var comment *ast.CommentGroup
+		var endline int
+
+		if p.file.Line(p.pos) == line {
+			// The comment is on same line as the previous token; it
+			// cannot be a lead comment but may be a line comment.
+			comment, endline = p.consumeCommentGroup()
+			if p.file.Line(p.pos) != endline {
+				// The next token is on a different line, thus
+				// the last comment group is a line comment.
+				p.lineComment = comment
+			}
+		}
+
+		// consume successor comments, if any
+		endline = -1
+		for p.tok == token.COMMENT {
+			comment, endline = p.consumeCommentGroup()
+		}
+
+		if endline+1 == p.file.Line(p.pos) {
+			// The next token is following on the line immediately after the
+			// comment group, thus the last comment group is a lead comment.
+			p.leadComment = comment
+		}
+	}
+}
+
+
+func (p *parser) error(pos token.Pos, msg string) {
+	p.Error(p.file.Position(pos), msg)
+}
+
+
+func (p *parser) errorExpected(pos token.Pos, msg string) {
+	msg = "expected " + msg
+	if pos == p.pos {
+		// the error happened at the current position;
+		// make the error message more specific
+		if p.tok == token.SEMICOLON && p.lit[0] == '\n' {
+			msg += ", found newline"
+		} else {
+			msg += ", found '" + p.tok.String() + "'"
+			if p.tok.IsLiteral() {
+				msg += " " + p.lit
+			}
+		}
+	}
+	p.error(pos, msg)
+}
+
+
+func (p *parser) expect(tok token.Token) token.Pos {
+	pos := p.pos
+	if p.tok != tok {
+		p.errorExpected(pos, "'"+tok.String()+"'")
+	}
+	p.next() // make progress
+	return pos
+}
+
+
+func (p *parser) expectSemi() {
+	if p.tok != token.RPAREN && p.tok != token.RBRACE {
+		p.expect(token.SEMICOLON)
+	}
+}
+
+
+func assert(cond bool, msg string) {
+	if !cond {
+		panic("go/parser internal error: " + msg)
+	}
+}
+
+
+// ----------------------------------------------------------------------------
+// Identifiers
+
+func (p *parser) parseIdent() *ast.Ident {
+	pos := p.pos
+	name := "_"
+	if p.tok == token.IDENT {
+		name = p.lit
+		p.next()
+	} else {
+		p.expect(token.IDENT) // use expect() error handling
+	}
+	return &ast.Ident{pos, name, nil}
+}
+
+
+func (p *parser) parseIdentList() (list []*ast.Ident) {
+	if p.trace {
+		defer un(trace(p, "IdentList"))
+	}
+
+	list = append(list, p.parseIdent())
+	for p.tok == token.COMMA {
+		p.next()
+		list = append(list, p.parseIdent())
+	}
+
+	return
+}
+
+
+// ----------------------------------------------------------------------------
+// Common productions
+
+// If lhs is set, result list elements which are identifiers are not resolved.
+func (p *parser) parseExprList(lhs bool) (list []ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "ExpressionList"))
+	}
+
+	list = append(list, p.parseExpr(lhs))
+	for p.tok == token.COMMA {
+		p.next()
+		list = append(list, p.parseExpr(lhs))
+	}
+
+	return
+}
+
+
+func (p *parser) parseLhsList() []ast.Expr {
+	list := p.parseExprList(true)
+	switch p.tok {
+	case token.DEFINE:
+		// lhs of a short variable declaration
+		p.shortVarDecl(p.makeIdentList(list))
+	case token.COLON:
+		// lhs of a label declaration or a communication clause of a select
+		// statement (parseLhsList is not called when parsing the case clause
+		// of a switch statement):
+		// - labels are declared by the caller of parseLhsList
+		// - for communication clauses, if there is a stand-alone identifier
+		//   followed by a colon, we have a syntax error; there is no need
+		//   to resolve the identifier in that case
+	default:
+		// identifiers must be declared elsewhere
+		for _, x := range list {
+			p.resolve(x)
+		}
+	}
+	return list
+}
+
+
+func (p *parser) parseRhsList() []ast.Expr {
+	return p.parseExprList(false)
+}
+
+
+// ----------------------------------------------------------------------------
+// Types
+
+func (p *parser) parseType() ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Type"))
+	}
+
+	typ := p.tryType()
+
+	if typ == nil {
+		pos := p.pos
+		p.errorExpected(pos, "type")
+		p.next() // make progress
+		return &ast.BadExpr{pos, p.pos}
+	}
+
+	return typ
+}
+
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) parseTypeName() ast.Expr {
+	if p.trace {
+		defer un(trace(p, "TypeName"))
+	}
+
+	ident := p.parseIdent()
+	// don't resolve ident yet - it may be a parameter or field name
+
+	if p.tok == token.PERIOD {
+		// ident is a package name
+		p.next()
+		p.resolve(ident)
+		sel := p.parseIdent()
+		return &ast.SelectorExpr{ident, sel}
+	}
+
+	return ident
+}
+
+
+func (p *parser) parseArrayType(ellipsisOk bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "ArrayType"))
+	}
+
+	lbrack := p.expect(token.LBRACK)
+	var len ast.Expr
+	if ellipsisOk && p.tok == token.ELLIPSIS {
+		len = &ast.Ellipsis{p.pos, nil}
+		p.next()
+	} else if p.tok != token.RBRACK {
+		len = p.parseRhs()
+	}
+	p.expect(token.RBRACK)
+	elt := p.parseType()
+
+	return &ast.ArrayType{lbrack, len, elt}
+}
+
+
+func (p *parser) makeIdentList(list []ast.Expr) []*ast.Ident {
+	idents := make([]*ast.Ident, len(list))
+	for i, x := range list {
+		ident, isIdent := x.(*ast.Ident)
+		if !isIdent {
+			pos := x.(ast.Expr).Pos()
+			p.errorExpected(pos, "identifier")
+			ident = &ast.Ident{pos, "_", nil}
+		}
+		idents[i] = ident
+	}
+	return idents
+}
+
+
+func (p *parser) parseFieldDecl(scope *ast.Scope) *ast.Field {
+	if p.trace {
+		defer un(trace(p, "FieldDecl"))
+	}
+
+	doc := p.leadComment
+
+	// fields
+	list, typ := p.parseVarList(false)
+
+	// optional tag
+	var tag *ast.BasicLit
+	if p.tok == token.STRING {
+		tag = &ast.BasicLit{p.pos, p.tok, p.lit}
+		p.next()
+	}
+
+	// analyze case
+	var idents []*ast.Ident
+	if typ != nil {
+		// IdentifierList Type
+		idents = p.makeIdentList(list)
+	} else {
+		// ["*"] TypeName (AnonymousField)
+		typ = list[0] // we always have at least one element
+		p.resolve(typ)
+		if n := len(list); n > 1 || !isTypeName(deref(typ)) {
+			pos := typ.Pos()
+			p.errorExpected(pos, "anonymous field")
+			typ = &ast.BadExpr{pos, list[n-1].End()}
+		}
+	}
+
+	p.expectSemi() // call before accessing p.linecomment
+
+	field := &ast.Field{doc, idents, typ, tag, p.lineComment}
+	p.declare(field, scope, ast.Var, idents...)
+
+	return field
+}
+
+
+func (p *parser) parseStructType() *ast.StructType {
+	if p.trace {
+		defer un(trace(p, "StructType"))
+	}
+
+	pos := p.expect(token.STRUCT)
+	lbrace := p.expect(token.LBRACE)
+	scope := ast.NewScope(nil) // struct scope
+	var list []*ast.Field
+	for p.tok == token.IDENT || p.tok == token.MUL || p.tok == token.LPAREN {
+		// a field declaration cannot start with a '(' but we accept
+		// it here for more robust parsing and better error messages
+		// (parseFieldDecl will check and complain if necessary)
+		list = append(list, p.parseFieldDecl(scope))
+	}
+	rbrace := p.expect(token.RBRACE)
+
+	// TODO(gri): store struct scope in AST
+	return &ast.StructType{pos, &ast.FieldList{lbrace, list, rbrace}, false}
+}
+
+
+func (p *parser) parsePointerType() *ast.StarExpr {
+	if p.trace {
+		defer un(trace(p, "PointerType"))
+	}
+
+	star := p.expect(token.MUL)
+	base := p.parseType()
+
+	return &ast.StarExpr{star, base}
+}
+
+
+func (p *parser) tryVarType(isParam bool) ast.Expr {
+	if isParam && p.tok == token.ELLIPSIS {
+		pos := p.pos
+		p.next()
+		typ := p.tryIdentOrType(isParam) // don't use parseType so we can provide better error message
+		if typ == nil {
+			p.error(pos, "'...' parameter is missing type")
+			typ = &ast.BadExpr{pos, p.pos}
+		}
+		if p.tok != token.RPAREN {
+			p.error(pos, "can use '...' with last parameter type only")
+		}
+		return &ast.Ellipsis{pos, typ}
+	}
+	return p.tryIdentOrType(false)
+}
+
+
+func (p *parser) parseVarType(isParam bool) ast.Expr {
+	typ := p.tryVarType(isParam)
+	if typ == nil {
+		pos := p.pos
+		p.errorExpected(pos, "type")
+		p.next() // make progress
+		typ = &ast.BadExpr{pos, p.pos}
+	}
+	return typ
+}
+
+
+func (p *parser) parseVarList(isParam bool) (list []ast.Expr, typ ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "VarList"))
+	}
+
+	// a list of identifiers looks like a list of type names
+	for {
+		// parseVarType accepts any type (including parenthesized ones)
+		// even though the syntax does not permit them here: we
+		// accept them all for more robust parsing and complain
+		// afterwards
+		list = append(list, p.parseVarType(isParam))
+		if p.tok != token.COMMA {
+			break
+		}
+		p.next()
+	}
+
+	// if we had a list of identifiers, it must be followed by a type
+	typ = p.tryVarType(isParam)
+	if typ != nil {
+		p.resolve(typ)
+	}
+
+	return
+}
+
+
+func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params []*ast.Field) {
+	if p.trace {
+		defer un(trace(p, "ParameterList"))
+	}
+
+	list, typ := p.parseVarList(ellipsisOk)
+	if typ != nil {
+		// IdentifierList Type
+		idents := p.makeIdentList(list)
+		field := &ast.Field{nil, idents, typ, nil, nil}
+		params = append(params, field)
+		// Go spec: The scope of an identifier denoting a function
+		// parameter or result variable is the function body.
+		p.declare(field, scope, ast.Var, idents...)
+		if p.tok == token.COMMA {
+			p.next()
+		}
+
+		for p.tok != token.RPAREN && p.tok != token.EOF {
+			idents := p.parseIdentList()
+			typ := p.parseVarType(ellipsisOk)
+			field := &ast.Field{nil, idents, typ, nil, nil}
+			params = append(params, field)
+			// Go spec: The scope of an identifier denoting a function
+			// parameter or result variable is the function body.
+			p.declare(field, scope, ast.Var, idents...)
+			if p.tok != token.COMMA {
+				break
+			}
+			p.next()
+		}
+
+	} else {
+		// Type { "," Type } (anonymous parameters)
+		params = make([]*ast.Field, len(list))
+		for i, x := range list {
+			p.resolve(x)
+			params[i] = &ast.Field{Type: x}
+		}
+	}
+
+	return
+}
+
+
+func (p *parser) parseParameters(scope *ast.Scope, ellipsisOk bool) *ast.FieldList {
+	if p.trace {
+		defer un(trace(p, "Parameters"))
+	}
+
+	var params []*ast.Field
+	lparen := p.expect(token.LPAREN)
+	if p.tok != token.RPAREN {
+		params = p.parseParameterList(scope, ellipsisOk)
+	}
+	rparen := p.expect(token.RPAREN)
+
+	return &ast.FieldList{lparen, params, rparen}
+}
+
+
+func (p *parser) parseResult(scope *ast.Scope) *ast.FieldList {
+	if p.trace {
+		defer un(trace(p, "Result"))
+	}
+
+	if p.tok == token.LPAREN {
+		return p.parseParameters(scope, false)
+	}
+
+	typ := p.tryType()
+	if typ != nil {
+		list := make([]*ast.Field, 1)
+		list[0] = &ast.Field{Type: typ}
+		return &ast.FieldList{List: list}
+	}
+
+	return nil
+}
+
+
+func (p *parser) parseSignature(scope *ast.Scope) (params, results *ast.FieldList) {
+	if p.trace {
+		defer un(trace(p, "Signature"))
+	}
+
+	params = p.parseParameters(scope, true)
+	results = p.parseResult(scope)
+
+	return
+}
+
+
+func (p *parser) parseFuncType() (*ast.FuncType, *ast.Scope) {
+	if p.trace {
+		defer un(trace(p, "FuncType"))
+	}
+
+	pos := p.expect(token.FUNC)
+	scope := ast.NewScope(p.topScope) // function scope
+	params, results := p.parseSignature(scope)
+
+	return &ast.FuncType{pos, params, results}, scope
+}
+
+
+func (p *parser) parseMethodSpec(scope *ast.Scope) *ast.Field {
+	if p.trace {
+		defer un(trace(p, "MethodSpec"))
+	}
+
+	doc := p.leadComment
+	var idents []*ast.Ident
+	var typ ast.Expr
+	x := p.parseTypeName()
+	if ident, isIdent := x.(*ast.Ident); isIdent && p.tok == token.LPAREN {
+		// method
+		idents = []*ast.Ident{ident}
+		scope := ast.NewScope(nil) // method scope
+		params, results := p.parseSignature(scope)
+		typ = &ast.FuncType{token.NoPos, params, results}
+	} else {
+		// embedded interface
+		typ = x
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	spec := &ast.Field{doc, idents, typ, nil, p.lineComment}
+	p.declare(spec, scope, ast.Fun, idents...)
+
+	return spec
+}
+
+
+func (p *parser) parseInterfaceType() *ast.InterfaceType {
+	if p.trace {
+		defer un(trace(p, "InterfaceType"))
+	}
+
+	pos := p.expect(token.INTERFACE)
+	lbrace := p.expect(token.LBRACE)
+	scope := ast.NewScope(nil) // interface scope
+	var list []*ast.Field
+	for p.tok == token.IDENT {
+		list = append(list, p.parseMethodSpec(scope))
+	}
+	rbrace := p.expect(token.RBRACE)
+
+	// TODO(gri): store interface scope in AST
+	return &ast.InterfaceType{pos, &ast.FieldList{lbrace, list, rbrace}, false}
+}
+
+
+func (p *parser) parseMapType() *ast.MapType {
+	if p.trace {
+		defer un(trace(p, "MapType"))
+	}
+
+	pos := p.expect(token.MAP)
+	p.expect(token.LBRACK)
+	key := p.parseType()
+	p.expect(token.RBRACK)
+	value := p.parseType()
+
+	return &ast.MapType{pos, key, value}
+}
+
+
+func (p *parser) parseChanType() *ast.ChanType {
+	if p.trace {
+		defer un(trace(p, "ChanType"))
+	}
+
+	pos := p.pos
+	dir := ast.SEND | ast.RECV
+	if p.tok == token.CHAN {
+		p.next()
+		if p.tok == token.ARROW {
+			p.next()
+			dir = ast.SEND
+		}
+	} else {
+		p.expect(token.ARROW)
+		p.expect(token.CHAN)
+		dir = ast.RECV
+	}
+	value := p.parseType()
+
+	return &ast.ChanType{pos, dir, value}
+}
+
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) tryIdentOrType(ellipsisOk bool) ast.Expr {
+	switch p.tok {
+	case token.IDENT:
+		return p.parseTypeName()
+	case token.LBRACK:
+		return p.parseArrayType(ellipsisOk)
+	case token.STRUCT:
+		return p.parseStructType()
+	case token.MUL:
+		return p.parsePointerType()
+	case token.FUNC:
+		typ, _ := p.parseFuncType()
+		return typ
+	case token.INTERFACE:
+		return p.parseInterfaceType()
+	case token.MAP:
+		return p.parseMapType()
+	case token.CHAN, token.ARROW:
+		return p.parseChanType()
+	case token.LPAREN:
+		lparen := p.pos
+		p.next()
+		typ := p.parseType()
+		rparen := p.expect(token.RPAREN)
+		return &ast.ParenExpr{lparen, typ, rparen}
+	}
+
+	// no type found
+	return nil
+}
+
+
+func (p *parser) tryType() ast.Expr {
+	typ := p.tryIdentOrType(false)
+	if typ != nil {
+		p.resolve(typ)
+	}
+	return typ
+}
+
+
+// ----------------------------------------------------------------------------
+// Blocks
+
+func (p *parser) parseStmtList() (list []ast.Stmt) {
+	if p.trace {
+		defer un(trace(p, "StatementList"))
+	}
+
+	for p.tok != token.CASE && p.tok != token.DEFAULT && p.tok != token.RBRACE && p.tok != token.EOF {
+		list = append(list, p.parseStmt())
+	}
+
+	return
+}
+
+
+func (p *parser) parseBody(scope *ast.Scope) *ast.BlockStmt {
+	if p.trace {
+		defer un(trace(p, "Body"))
+	}
+
+	lbrace := p.expect(token.LBRACE)
+	p.topScope = scope // open function scope
+	p.openLabelScope()
+	list := p.parseStmtList()
+	p.closeLabelScope()
+	p.closeScope()
+	rbrace := p.expect(token.RBRACE)
+
+	return &ast.BlockStmt{lbrace, list, rbrace}
+}
+
+
+func (p *parser) parseBlockStmt() *ast.BlockStmt {
+	if p.trace {
+		defer un(trace(p, "BlockStmt"))
+	}
+
+	lbrace := p.expect(token.LBRACE)
+	p.openScope()
+	list := p.parseStmtList()
+	p.closeScope()
+	rbrace := p.expect(token.RBRACE)
+
+	return &ast.BlockStmt{lbrace, list, rbrace}
+}
+
+
+// ----------------------------------------------------------------------------
+// Expressions
+
+func (p *parser) parseFuncTypeOrLit() ast.Expr {
+	if p.trace {
+		defer un(trace(p, "FuncTypeOrLit"))
+	}
+
+	typ, scope := p.parseFuncType()
+	if p.tok != token.LBRACE {
+		// function type only
+		return typ
+	}
+
+	p.exprLev++
+	body := p.parseBody(scope)
+	p.exprLev--
+
+	return &ast.FuncLit{typ, body}
+}
+
+
+// parseOperand may return an expression or a raw type (incl. array
+// types of the form [...]T. Callers must verify the result.
+// If lhs is set and the result is an identifier, it is not resolved.
+//
+func (p *parser) parseOperand(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Operand"))
+	}
+
+	switch p.tok {
+	case token.IDENT:
+		x := p.parseIdent()
+		if !lhs {
+			p.resolve(x)
+		}
+		return x
+
+	case token.INT, token.FLOAT, token.IMAG, token.CHAR, token.STRING:
+		x := &ast.BasicLit{p.pos, p.tok, p.lit}
+		p.next()
+		return x
+
+	case token.LPAREN:
+		lparen := p.pos
+		p.next()
+		p.exprLev++
+		x := p.parseRhs()
+		p.exprLev--
+		rparen := p.expect(token.RPAREN)
+		return &ast.ParenExpr{lparen, x, rparen}
+
+	case token.FUNC:
+		return p.parseFuncTypeOrLit()
+
+	default:
+		if typ := p.tryIdentOrType(true); typ != nil {
+			// could be type for composite literal or conversion
+			_, isIdent := typ.(*ast.Ident)
+			assert(!isIdent, "type cannot be identifier")
+			return typ
+		}
+	}
+
+	pos := p.pos
+	p.errorExpected(pos, "operand")
+	p.next() // make progress
+	return &ast.BadExpr{pos, p.pos}
+}
+
+
+func (p *parser) parseSelector(x ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Selector"))
+	}
+
+	sel := p.parseIdent()
+
+	return &ast.SelectorExpr{x, sel}
+}
+
+
+func (p *parser) parseTypeAssertion(x ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "TypeAssertion"))
+	}
+
+	p.expect(token.LPAREN)
+	var typ ast.Expr
+	if p.tok == token.TYPE {
+		// type switch: typ == nil
+		p.next()
+	} else {
+		typ = p.parseType()
+	}
+	p.expect(token.RPAREN)
+
+	return &ast.TypeAssertExpr{x, typ}
+}
+
+
+func (p *parser) parseIndexOrSlice(x ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "IndexOrSlice"))
+	}
+
+	lbrack := p.expect(token.LBRACK)
+	p.exprLev++
+	var low, high ast.Expr
+	isSlice := false
+	if p.tok != token.COLON {
+		low = p.parseRhs()
+	}
+	if p.tok == token.COLON {
+		isSlice = true
+		p.next()
+		if p.tok != token.RBRACK {
+			high = p.parseRhs()
+		}
+	}
+	p.exprLev--
+	rbrack := p.expect(token.RBRACK)
+
+	if isSlice {
+		return &ast.SliceExpr{x, lbrack, low, high, rbrack}
+	}
+	return &ast.IndexExpr{x, lbrack, low, rbrack}
+}
+
+
+func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
+	if p.trace {
+		defer un(trace(p, "CallOrConversion"))
+	}
+
+	lparen := p.expect(token.LPAREN)
+	p.exprLev++
+	var list []ast.Expr
+	var ellipsis token.Pos
+	for p.tok != token.RPAREN && p.tok != token.EOF && !ellipsis.IsValid() {
+		list = append(list, p.parseRhs())
+		if p.tok == token.ELLIPSIS {
+			ellipsis = p.pos
+			p.next()
+		}
+		if p.tok != token.COMMA {
+			break
+		}
+		p.next()
+	}
+	p.exprLev--
+	rparen := p.expect(token.RPAREN)
+
+	return &ast.CallExpr{fun, lparen, list, ellipsis, rparen}
+}
+
+
+func (p *parser) parseElement(keyOk bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Element"))
+	}
+
+	if p.tok == token.LBRACE {
+		return p.parseLiteralValue(nil)
+	}
+
+	x := p.parseExpr(keyOk) // don't resolve if map key
+	if keyOk {
+		if p.tok == token.COLON {
+			colon := p.pos
+			p.next()
+			return &ast.KeyValueExpr{x, colon, p.parseElement(false)}
+		}
+		p.resolve(x) // not a map key
+	}
+
+	return x
+}
+
+
+func (p *parser) parseElementList() (list []ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "ElementList"))
+	}
+
+	for p.tok != token.RBRACE && p.tok != token.EOF {
+		list = append(list, p.parseElement(true))
+		if p.tok != token.COMMA {
+			break
+		}
+		p.next()
+	}
+
+	return
+}
+
+
+func (p *parser) parseLiteralValue(typ ast.Expr) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "LiteralValue"))
+	}
+
+	lbrace := p.expect(token.LBRACE)
+	var elts []ast.Expr
+	p.exprLev++
+	if p.tok != token.RBRACE {
+		elts = p.parseElementList()
+	}
+	p.exprLev--
+	rbrace := p.expect(token.RBRACE)
+	return &ast.CompositeLit{typ, lbrace, elts, rbrace}
+}
+
+
+// checkExpr checks that x is an expression (and not a type).
+func (p *parser) checkExpr(x ast.Expr) ast.Expr {
+	switch t := unparen(x).(type) {
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.BasicLit:
+	case *ast.FuncLit:
+	case *ast.CompositeLit:
+	case *ast.ParenExpr:
+		panic("unreachable")
+	case *ast.SelectorExpr:
+	case *ast.IndexExpr:
+	case *ast.SliceExpr:
+	case *ast.TypeAssertExpr:
+		if t.Type == nil {
+			// the form X.(type) is only allowed in type switch expressions
+			p.errorExpected(x.Pos(), "expression")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	case *ast.CallExpr:
+	case *ast.StarExpr:
+	case *ast.UnaryExpr:
+		if t.Op == token.RANGE {
+			// the range operator is only allowed at the top of a for statement
+			p.errorExpected(x.Pos(), "expression")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	case *ast.BinaryExpr:
+	default:
+		// all other nodes are not proper expressions
+		p.errorExpected(x.Pos(), "expression")
+		x = &ast.BadExpr{x.Pos(), x.End()}
+	}
+	return x
+}
+
+
+// isTypeName returns true iff x is a (qualified) TypeName.
+func isTypeName(x ast.Expr) bool {
+	switch t := x.(type) {
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.SelectorExpr:
+		_, isIdent := t.X.(*ast.Ident)
+		return isIdent
+	default:
+		return false // all other nodes are not type names
+	}
+	return true
+}
+
+
+// isLiteralType returns true iff x is a legal composite literal type.
+func isLiteralType(x ast.Expr) bool {
+	switch t := x.(type) {
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.SelectorExpr:
+		_, isIdent := t.X.(*ast.Ident)
+		return isIdent
+	case *ast.ArrayType:
+	case *ast.StructType:
+	case *ast.MapType:
+	default:
+		return false // all other nodes are not legal composite literal types
+	}
+	return true
+}
+
+
+// If x is of the form *T, deref returns T, otherwise it returns x.
+func deref(x ast.Expr) ast.Expr {
+	if p, isPtr := x.(*ast.StarExpr); isPtr {
+		x = p.X
+	}
+	return x
+}
+
+
+// If x is of the form (T), unparen returns unparen(T), otherwise it returns x.
+func unparen(x ast.Expr) ast.Expr {
+	if p, isParen := x.(*ast.ParenExpr); isParen {
+		x = unparen(p.X)
+	}
+	return x
+}
+
+
+// checkExprOrType checks that x is an expression or a type
+// (and not a raw type such as [...]T).
+//
+func (p *parser) checkExprOrType(x ast.Expr) ast.Expr {
+	switch t := unparen(x).(type) {
+	case *ast.ParenExpr:
+		panic("unreachable")
+	case *ast.UnaryExpr:
+		if t.Op == token.RANGE {
+			// the range operator is only allowed at the top of a for statement
+			p.errorExpected(x.Pos(), "expression")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	case *ast.ArrayType:
+		if len, isEllipsis := t.Len.(*ast.Ellipsis); isEllipsis {
+			p.error(len.Pos(), "expected array length, found '...'")
+			x = &ast.BadExpr{x.Pos(), x.End()}
+		}
+	}
+
+	// all other nodes are expressions or types
+	return x
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parsePrimaryExpr(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "PrimaryExpr"))
+	}
+
+	x := p.parseOperand(lhs)
+L:
+	for {
+		switch p.tok {
+		case token.PERIOD:
+			p.next()
+			if lhs {
+				p.resolve(x)
+			}
+			switch p.tok {
+			case token.IDENT:
+				x = p.parseSelector(p.checkExpr(x))
+			case token.LPAREN:
+				x = p.parseTypeAssertion(p.checkExpr(x))
+			default:
+				pos := p.pos
+				p.next() // make progress
+				p.errorExpected(pos, "selector or type assertion")
+				x = &ast.BadExpr{pos, p.pos}
+			}
+		case token.LBRACK:
+			if lhs {
+				p.resolve(x)
+			}
+			x = p.parseIndexOrSlice(p.checkExpr(x))
+		case token.LPAREN:
+			if lhs {
+				p.resolve(x)
+			}
+			x = p.parseCallOrConversion(p.checkExprOrType(x))
+		case token.LBRACE:
+			if isLiteralType(x) && (p.exprLev >= 0 || !isTypeName(x)) {
+				if lhs {
+					p.resolve(x)
+				}
+				x = p.parseLiteralValue(x)
+			} else {
+				break L
+			}
+		default:
+			break L
+		}
+		lhs = false // no need to try to resolve again
+	}
+
+	return x
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parseUnaryExpr(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "UnaryExpr"))
+	}
+
+	switch p.tok {
+	case token.ADD, token.SUB, token.NOT, token.XOR, token.AND, token.RANGE:
+		pos, op := p.pos, p.tok
+		p.next()
+		x := p.parseUnaryExpr(false)
+		return &ast.UnaryExpr{pos, op, p.checkExpr(x)}
+
+	case token.ARROW:
+		// channel type or receive expression
+		pos := p.pos
+		p.next()
+		if p.tok == token.CHAN {
+			p.next()
+			value := p.parseType()
+			return &ast.ChanType{pos, ast.RECV, value}
+		}
+
+		x := p.parseUnaryExpr(false)
+		return &ast.UnaryExpr{pos, token.ARROW, p.checkExpr(x)}
+
+	case token.MUL:
+		// pointer type or unary "*" expression
+		pos := p.pos
+		p.next()
+		x := p.parseUnaryExpr(false)
+		return &ast.StarExpr{pos, p.checkExprOrType(x)}
+	}
+
+	return p.parsePrimaryExpr(lhs)
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parseBinaryExpr(lhs bool, prec1 int) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "BinaryExpr"))
+	}
+
+	x := p.parseUnaryExpr(lhs)
+	for prec := p.tok.Precedence(); prec >= prec1; prec-- {
+		for p.tok.Precedence() == prec {
+			pos, op := p.pos, p.tok
+			p.next()
+			if lhs {
+				p.resolve(x)
+				lhs = false
+			}
+			y := p.parseBinaryExpr(false, prec+1)
+			x = &ast.BinaryExpr{p.checkExpr(x), pos, op, p.checkExpr(y)}
+		}
+	}
+
+	return x
+}
+
+
+// If lhs is set and the result is an identifier, it is not resolved.
+// TODO(gri): parseExpr may return a type or even a raw type ([..]int) -
+//            should reject when a type/raw type is obviously not allowed
+func (p *parser) parseExpr(lhs bool) ast.Expr {
+	if p.trace {
+		defer un(trace(p, "Expression"))
+	}
+
+	return p.parseBinaryExpr(lhs, token.LowestPrec+1)
+}
+
+
+func (p *parser) parseRhs() ast.Expr {
+	return p.parseExpr(false)
+}
+
+
+// ----------------------------------------------------------------------------
+// Statements
+
+func (p *parser) parseSimpleStmt(labelOk bool) ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "SimpleStmt"))
+	}
+
+	x := p.parseLhsList()
+
+	switch p.tok {
+	case
+		token.DEFINE, token.ASSIGN, token.ADD_ASSIGN,
+		token.SUB_ASSIGN, token.MUL_ASSIGN, token.QUO_ASSIGN,
+		token.REM_ASSIGN, token.AND_ASSIGN, token.OR_ASSIGN,
+		token.XOR_ASSIGN, token.SHL_ASSIGN, token.SHR_ASSIGN, token.AND_NOT_ASSIGN:
+		// assignment statement
+		pos, tok := p.pos, p.tok
+		p.next()
+		y := p.parseRhsList()
+		return &ast.AssignStmt{x, pos, tok, y}
+	}
+
+	if len(x) > 1 {
+		p.errorExpected(x[0].Pos(), "1 expression")
+		// continue with first expression
+	}
+
+	switch p.tok {
+	case token.COLON:
+		// labeled statement
+		colon := p.pos
+		p.next()
+		if label, isIdent := x[0].(*ast.Ident); labelOk && isIdent {
+			// Go spec: The scope of a label is the body of the function
+			// in which it is declared and excludes the body of any nested
+			// function.
+			stmt := &ast.LabeledStmt{label, colon, p.parseStmt()}
+			p.declare(stmt, p.labelScope, ast.Lbl, label)
+			return stmt
+		}
+		p.error(x[0].Pos(), "illegal label declaration")
+		return &ast.BadStmt{x[0].Pos(), colon + 1}
+
+	case token.ARROW:
+		// send statement
+		arrow := p.pos
+		p.next() // consume "<-"
+		y := p.parseRhs()
+		return &ast.SendStmt{x[0], arrow, y}
+
+	case token.INC, token.DEC:
+		// increment or decrement
+		s := &ast.IncDecStmt{x[0], p.pos, p.tok}
+		p.next() // consume "++" or "--"
+		return s
+	}
+
+	// expression
+	return &ast.ExprStmt{x[0]}
+}
+
+
+func (p *parser) parseCallExpr() *ast.CallExpr {
+	x := p.parseRhs()
+	if call, isCall := x.(*ast.CallExpr); isCall {
+		return call
+	}
+	p.errorExpected(x.Pos(), "function/method call")
+	return nil
+}
+
+
+func (p *parser) parseGoStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "GoStmt"))
+	}
+
+	pos := p.expect(token.GO)
+	call := p.parseCallExpr()
+	p.expectSemi()
+	if call == nil {
+		return &ast.BadStmt{pos, pos + 2} // len("go")
+	}
+
+	return &ast.GoStmt{pos, call}
+}
+
+
+func (p *parser) parseDeferStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "DeferStmt"))
+	}
+
+	pos := p.expect(token.DEFER)
+	call := p.parseCallExpr()
+	p.expectSemi()
+	if call == nil {
+		return &ast.BadStmt{pos, pos + 5} // len("defer")
+	}
+
+	return &ast.DeferStmt{pos, call}
+}
+
+
+func (p *parser) parseReturnStmt() *ast.ReturnStmt {
+	if p.trace {
+		defer un(trace(p, "ReturnStmt"))
+	}
+
+	pos := p.pos
+	p.expect(token.RETURN)
+	var x []ast.Expr
+	if p.tok != token.SEMICOLON && p.tok != token.RBRACE {
+		x = p.parseRhsList()
+	}
+	p.expectSemi()
+
+	return &ast.ReturnStmt{pos, x}
+}
+
+
+func (p *parser) parseBranchStmt(tok token.Token) *ast.BranchStmt {
+	if p.trace {
+		defer un(trace(p, "BranchStmt"))
+	}
+
+	pos := p.expect(tok)
+	var label *ast.Ident
+	if tok != token.FALLTHROUGH && p.tok == token.IDENT {
+		label = p.parseIdent()
+		// add to list of unresolved targets
+		n := len(p.targetStack) - 1
+		p.targetStack[n] = append(p.targetStack[n], label)
+	}
+	p.expectSemi()
+
+	return &ast.BranchStmt{pos, tok, label}
+}
+
+
+func (p *parser) makeExpr(s ast.Stmt) ast.Expr {
+	if s == nil {
+		return nil
+	}
+	if es, isExpr := s.(*ast.ExprStmt); isExpr {
+		return p.checkExpr(es.X)
+	}
+	p.error(s.Pos(), "expected condition, found simple statement")
+	return &ast.BadExpr{s.Pos(), s.End()}
+}
+
+
+func (p *parser) parseIfStmt() *ast.IfStmt {
+	if p.trace {
+		defer un(trace(p, "IfStmt"))
+	}
+
+	pos := p.expect(token.IF)
+	p.openScope()
+	defer p.closeScope()
+
+	var s ast.Stmt
+	var x ast.Expr
+	{
+		prevLev := p.exprLev
+		p.exprLev = -1
+		if p.tok == token.SEMICOLON {
+			p.next()
+			x = p.parseRhs()
+		} else {
+			s = p.parseSimpleStmt(false)
+			if p.tok == token.SEMICOLON {
+				p.next()
+				x = p.parseRhs()
+			} else {
+				x = p.makeExpr(s)
+				s = nil
+			}
+		}
+		p.exprLev = prevLev
+	}
+
+	body := p.parseBlockStmt()
+	var else_ ast.Stmt
+	if p.tok == token.ELSE {
+		p.next()
+		else_ = p.parseStmt()
+	} else {
+		p.expectSemi()
+	}
+
+	return &ast.IfStmt{pos, s, x, body, else_}
+}
+
+
+func (p *parser) parseTypeList() (list []ast.Expr) {
+	if p.trace {
+		defer un(trace(p, "TypeList"))
+	}
+
+	list = append(list, p.parseType())
+	for p.tok == token.COMMA {
+		p.next()
+		list = append(list, p.parseType())
+	}
+
+	return
+}
+
+
+func (p *parser) parseCaseClause(exprSwitch bool) *ast.CaseClause {
+	if p.trace {
+		defer un(trace(p, "CaseClause"))
+	}
+
+	pos := p.pos
+	var list []ast.Expr
+	if p.tok == token.CASE {
+		p.next()
+		if exprSwitch {
+			list = p.parseRhsList()
+		} else {
+			list = p.parseTypeList()
+		}
+	} else {
+		p.expect(token.DEFAULT)
+	}
+
+	colon := p.expect(token.COLON)
+	p.openScope()
+	body := p.parseStmtList()
+	p.closeScope()
+
+	return &ast.CaseClause{pos, list, colon, body}
+}
+
+
+func isExprSwitch(s ast.Stmt) bool {
+	if s == nil {
+		return true
+	}
+	if e, ok := s.(*ast.ExprStmt); ok {
+		if a, ok := e.X.(*ast.TypeAssertExpr); ok {
+			return a.Type != nil // regular type assertion
+		}
+		return true
+	}
+	return false
+}
+
+
+func (p *parser) parseSwitchStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "SwitchStmt"))
+	}
+
+	pos := p.expect(token.SWITCH)
+	p.openScope()
+	defer p.closeScope()
+
+	var s1, s2 ast.Stmt
+	if p.tok != token.LBRACE {
+		prevLev := p.exprLev
+		p.exprLev = -1
+		if p.tok != token.SEMICOLON {
+			s2 = p.parseSimpleStmt(false)
+		}
+		if p.tok == token.SEMICOLON {
+			p.next()
+			s1 = s2
+			s2 = nil
+			if p.tok != token.LBRACE {
+				s2 = p.parseSimpleStmt(false)
+			}
+		}
+		p.exprLev = prevLev
+	}
+
+	exprSwitch := isExprSwitch(s2)
+	lbrace := p.expect(token.LBRACE)
+	var list []ast.Stmt
+	for p.tok == token.CASE || p.tok == token.DEFAULT {
+		list = append(list, p.parseCaseClause(exprSwitch))
+	}
+	rbrace := p.expect(token.RBRACE)
+	p.expectSemi()
+	body := &ast.BlockStmt{lbrace, list, rbrace}
+
+	if exprSwitch {
+		return &ast.SwitchStmt{pos, s1, p.makeExpr(s2), body}
+	}
+	// type switch
+	// TODO(gri): do all the checks!
+	return &ast.TypeSwitchStmt{pos, s1, s2, body}
+}
+
+
+func (p *parser) parseCommClause() *ast.CommClause {
+	if p.trace {
+		defer un(trace(p, "CommClause"))
+	}
+
+	p.openScope()
+	pos := p.pos
+	var comm ast.Stmt
+	if p.tok == token.CASE {
+		p.next()
+		lhs := p.parseLhsList()
+		if p.tok == token.ARROW {
+			// SendStmt
+			if len(lhs) > 1 {
+				p.errorExpected(lhs[0].Pos(), "1 expression")
+				// continue with first expression
+			}
+			arrow := p.pos
+			p.next()
+			rhs := p.parseRhs()
+			comm = &ast.SendStmt{lhs[0], arrow, rhs}
+		} else {
+			// RecvStmt
+			pos := p.pos
+			tok := p.tok
+			var rhs ast.Expr
+			if tok == token.ASSIGN || tok == token.DEFINE {
+				// RecvStmt with assignment
+				if len(lhs) > 2 {
+					p.errorExpected(lhs[0].Pos(), "1 or 2 expressions")
+					// continue with first two expressions
+					lhs = lhs[0:2]
+				}
+				p.next()
+				rhs = p.parseRhs()
+			} else {
+				// rhs must be single receive operation
+				if len(lhs) > 1 {
+					p.errorExpected(lhs[0].Pos(), "1 expression")
+					// continue with first expression
+				}
+				rhs = lhs[0]
+				lhs = nil // there is no lhs
+			}
+			if x, isUnary := rhs.(*ast.UnaryExpr); !isUnary || x.Op != token.ARROW {
+				p.errorExpected(rhs.Pos(), "send or receive operation")
+				rhs = &ast.BadExpr{rhs.Pos(), rhs.End()}
+			}
+			if lhs != nil {
+				comm = &ast.AssignStmt{lhs, pos, tok, []ast.Expr{rhs}}
+			} else {
+				comm = &ast.ExprStmt{rhs}
+			}
+		}
+	} else {
+		p.expect(token.DEFAULT)
+	}
+
+	colon := p.expect(token.COLON)
+	body := p.parseStmtList()
+	p.closeScope()
+
+	return &ast.CommClause{pos, comm, colon, body}
+}
+
+
+func (p *parser) parseSelectStmt() *ast.SelectStmt {
+	if p.trace {
+		defer un(trace(p, "SelectStmt"))
+	}
+
+	pos := p.expect(token.SELECT)
+	lbrace := p.expect(token.LBRACE)
+	var list []ast.Stmt
+	for p.tok == token.CASE || p.tok == token.DEFAULT {
+		list = append(list, p.parseCommClause())
+	}
+	rbrace := p.expect(token.RBRACE)
+	p.expectSemi()
+	body := &ast.BlockStmt{lbrace, list, rbrace}
+
+	return &ast.SelectStmt{pos, body}
+}
+
+
+func (p *parser) parseForStmt() ast.Stmt {
+	if p.trace {
+		defer un(trace(p, "ForStmt"))
+	}
+
+	pos := p.expect(token.FOR)
+	p.openScope()
+	defer p.closeScope()
+
+	var s1, s2, s3 ast.Stmt
+	if p.tok != token.LBRACE {
+		prevLev := p.exprLev
+		p.exprLev = -1
+		if p.tok != token.SEMICOLON {
+			s2 = p.parseSimpleStmt(false)
+		}
+		if p.tok == token.SEMICOLON {
+			p.next()
+			s1 = s2
+			s2 = nil
+			if p.tok != token.SEMICOLON {
+				s2 = p.parseSimpleStmt(false)
+			}
+			p.expectSemi()
+			if p.tok != token.LBRACE {
+				s3 = p.parseSimpleStmt(false)
+			}
+		}
+		p.exprLev = prevLev
+	}
+
+	body := p.parseBlockStmt()
+	p.expectSemi()
+
+	if as, isAssign := s2.(*ast.AssignStmt); isAssign {
+		// possibly a for statement with a range clause; check assignment operator
+		if as.Tok != token.ASSIGN && as.Tok != token.DEFINE {
+			p.errorExpected(as.TokPos, "'=' or ':='")
+			return &ast.BadStmt{pos, body.End()}
+		}
+		// check lhs
+		var key, value ast.Expr
+		switch len(as.Lhs) {
+		case 2:
+			key, value = as.Lhs[0], as.Lhs[1]
+		case 1:
+			key = as.Lhs[0]
+		default:
+			p.errorExpected(as.Lhs[0].Pos(), "1 or 2 expressions")
+			return &ast.BadStmt{pos, body.End()}
+		}
+		// check rhs
+		if len(as.Rhs) != 1 {
+			p.errorExpected(as.Rhs[0].Pos(), "1 expression")
+			return &ast.BadStmt{pos, body.End()}
+		}
+		if rhs, isUnary := as.Rhs[0].(*ast.UnaryExpr); isUnary && rhs.Op == token.RANGE {
+			// rhs is range expression
+			// (any short variable declaration was handled by parseSimpleStat above)
+			return &ast.RangeStmt{pos, key, value, as.TokPos, as.Tok, rhs.X, body}
+		}
+		p.errorExpected(s2.Pos(), "range clause")
+		return &ast.BadStmt{pos, body.End()}
+	}
+
+	// regular for statement
+	return &ast.ForStmt{pos, s1, p.makeExpr(s2), s3, body}
+}
+
+
+func (p *parser) parseStmt() (s ast.Stmt) {
+	if p.trace {
+		defer un(trace(p, "Statement"))
+	}
+
+	switch p.tok {
+	case token.CONST, token.TYPE, token.VAR:
+		s = &ast.DeclStmt{p.parseDecl()}
+	case
+		// tokens that may start a top-level expression
+		token.IDENT, token.INT, token.FLOAT, token.CHAR, token.STRING, token.FUNC, token.LPAREN, // operand
+		token.LBRACK, token.STRUCT, // composite type
+		token.MUL, token.AND, token.ARROW, token.ADD, token.SUB, token.XOR: // unary operators
+		s = p.parseSimpleStmt(true)
+		// because of the required look-ahead, labeled statements are
+		// parsed by parseSimpleStmt - don't expect a semicolon after
+		// them
+		if _, isLabeledStmt := s.(*ast.LabeledStmt); !isLabeledStmt {
+			p.expectSemi()
+		}
+	case token.GO:
+		s = p.parseGoStmt()
+	case token.DEFER:
+		s = p.parseDeferStmt()
+	case token.RETURN:
+		s = p.parseReturnStmt()
+	case token.BREAK, token.CONTINUE, token.GOTO, token.FALLTHROUGH:
+		s = p.parseBranchStmt(p.tok)
+	case token.LBRACE:
+		s = p.parseBlockStmt()
+		p.expectSemi()
+	case token.IF:
+		s = p.parseIfStmt()
+	case token.SWITCH:
+		s = p.parseSwitchStmt()
+	case token.SELECT:
+		s = p.parseSelectStmt()
+	case token.FOR:
+		s = p.parseForStmt()
+	case token.SEMICOLON:
+		s = &ast.EmptyStmt{p.pos}
+		p.next()
+	case token.RBRACE:
+		// a semicolon may be omitted before a closing "}"
+		s = &ast.EmptyStmt{p.pos}
+	default:
+		// no statement found
+		pos := p.pos
+		p.errorExpected(pos, "statement")
+		p.next() // make progress
+		s = &ast.BadStmt{pos, p.pos}
+	}
+
+	return
+}
+
+
+// ----------------------------------------------------------------------------
+// Declarations
+
+type parseSpecFunction func(p *parser, doc *ast.CommentGroup, iota int) ast.Spec
+
+
+func parseImportSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "ImportSpec"))
+	}
+
+	var ident *ast.Ident
+	switch p.tok {
+	case token.PERIOD:
+		ident = &ast.Ident{p.pos, ".", nil}
+		p.next()
+	case token.IDENT:
+		ident = p.parseIdent()
+	}
+
+	var path *ast.BasicLit
+	if p.tok == token.STRING {
+		path = &ast.BasicLit{p.pos, p.tok, p.lit}
+		p.next()
+	} else {
+		p.expect(token.STRING) // use expect() error handling
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	// collect imports
+	spec := &ast.ImportSpec{doc, ident, path, p.lineComment}
+	p.imports = append(p.imports, spec)
+
+	return spec
+}
+
+
+func parseConstSpec(p *parser, doc *ast.CommentGroup, iota int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "ConstSpec"))
+	}
+
+	idents := p.parseIdentList()
+	typ := p.tryType()
+	var values []ast.Expr
+	if typ != nil || p.tok == token.ASSIGN || iota == 0 {
+		p.expect(token.ASSIGN)
+		values = p.parseRhsList()
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	// Go spec: The scope of a constant or variable identifier declared inside
+	// a function begins at the end of the ConstSpec or VarSpec and ends at
+	// the end of the innermost containing block.
+	// (Global identifiers are resolved in a separate phase after parsing.)
+	spec := &ast.ValueSpec{doc, idents, typ, values, p.lineComment}
+	p.declare(spec, p.topScope, ast.Con, idents...)
+
+	return spec
+}
+
+
+func parseTypeSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "TypeSpec"))
+	}
+
+	ident := p.parseIdent()
+
+	// Go spec: The scope of a type identifier declared inside a function begins
+	// at the identifier in the TypeSpec and ends at the end of the innermost
+	// containing block.
+	// (Global identifiers are resolved in a separate phase after parsing.)
+	spec := &ast.TypeSpec{doc, ident, nil, nil}
+	p.declare(spec, p.topScope, ast.Typ, ident)
+
+	spec.Type = p.parseType()
+	p.expectSemi() // call before accessing p.linecomment
+	spec.Comment = p.lineComment
+
+	return spec
+}
+
+
+func parseVarSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec {
+	if p.trace {
+		defer un(trace(p, "VarSpec"))
+	}
+
+	idents := p.parseIdentList()
+	typ := p.tryType()
+	var values []ast.Expr
+	if typ == nil || p.tok == token.ASSIGN {
+		p.expect(token.ASSIGN)
+		values = p.parseRhsList()
+	}
+	p.expectSemi() // call before accessing p.linecomment
+
+	// Go spec: The scope of a constant or variable identifier declared inside
+	// a function begins at the end of the ConstSpec or VarSpec and ends at
+	// the end of the innermost containing block.
+	// (Global identifiers are resolved in a separate phase after parsing.)
+	spec := &ast.ValueSpec{doc, idents, typ, values, p.lineComment}
+	p.declare(spec, p.topScope, ast.Var, idents...)
+
+	return spec
+}
+
+
+func (p *parser) parseGenDecl(keyword token.Token, f parseSpecFunction) *ast.GenDecl {
+	if p.trace {
+		defer un(trace(p, "GenDecl("+keyword.String()+")"))
+	}
+
+	doc := p.leadComment
+	pos := p.expect(keyword)
+	var lparen, rparen token.Pos
+	var list []ast.Spec
+	if p.tok == token.LPAREN {
+		lparen = p.pos
+		p.next()
+		for iota := 0; p.tok != token.RPAREN && p.tok != token.EOF; iota++ {
+			list = append(list, f(p, p.leadComment, iota))
+		}
+		rparen = p.expect(token.RPAREN)
+		p.expectSemi()
+	} else {
+		list = append(list, f(p, nil, 0))
+	}
+
+	return &ast.GenDecl{doc, pos, keyword, lparen, list, rparen}
+}
+
+
+func (p *parser) parseReceiver(scope *ast.Scope) *ast.FieldList {
+	if p.trace {
+		defer un(trace(p, "Receiver"))
+	}
+
+	pos := p.pos
+	par := p.parseParameters(scope, false)
+
+	// must have exactly one receiver
+	if par.NumFields() != 1 {
+		p.errorExpected(pos, "exactly one receiver")
+		// TODO determine a better range for BadExpr below
+		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{pos, pos}}}
+		return par
+	}
+
+	// recv type must be of the form ["*"] identifier
+	recv := par.List[0]
+	base := deref(recv.Type)
+	if _, isIdent := base.(*ast.Ident); !isIdent {
+		p.errorExpected(base.Pos(), "(unqualified) identifier")
+		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{recv.Pos(), recv.End()}}}
+	}
+
+	return par
+}
+
+
+func (p *parser) parseFuncDecl() *ast.FuncDecl {
+	if p.trace {
+		defer un(trace(p, "FunctionDecl"))
+	}
+
+	doc := p.leadComment
+	pos := p.expect(token.FUNC)
+	scope := ast.NewScope(p.topScope) // function scope
+
+	var recv *ast.FieldList
+	if p.tok == token.LPAREN {
+		recv = p.parseReceiver(scope)
+	}
+
+	ident := p.parseIdent()
+
+	params, results := p.parseSignature(scope)
+
+	var body *ast.BlockStmt
+	if p.tok == token.LBRACE {
+		body = p.parseBody(scope)
+	}
+	p.expectSemi()
+
+	decl := &ast.FuncDecl{doc, recv, ident, &ast.FuncType{pos, params, results}, body}
+	if recv == nil {
+		// Go spec: The scope of an identifier denoting a constant, type,
+		// variable, or function (but not method) declared at top level
+		// (outside any function) is the package block.
+		//
+		// init() functions cannot be referred to and there may
+		// be more than one - don't put them in the pkgScope
+		if ident.Name != "init" {
+			p.declare(decl, p.pkgScope, ast.Fun, ident)
+		}
+	}
+
+	return decl
+}
+
+
+func (p *parser) parseDecl() ast.Decl {
+	if p.trace {
+		defer un(trace(p, "Declaration"))
+	}
+
+	var f parseSpecFunction
+	switch p.tok {
+	case token.CONST:
+		f = parseConstSpec
+
+	case token.TYPE:
+		f = parseTypeSpec
+
+	case token.VAR:
+		f = parseVarSpec
+
+	case token.FUNC:
+		return p.parseFuncDecl()
+
+	default:
+		pos := p.pos
+		p.errorExpected(pos, "declaration")
+		p.next() // make progress
+		decl := &ast.BadDecl{pos, p.pos}
+		return decl
+	}
+
+	return p.parseGenDecl(p.tok, f)
+}
+
+
+func (p *parser) parseDeclList() (list []ast.Decl) {
+	if p.trace {
+		defer un(trace(p, "DeclList"))
+	}
+
+	for p.tok != token.EOF {
+		list = append(list, p.parseDecl())
+	}
+
+	return
+}
+
+
+// ----------------------------------------------------------------------------
+// Source files
+
+func (p *parser) parseFile() *ast.File {
+	if p.trace {
+		defer un(trace(p, "File"))
+	}
+
+	// package clause
+	doc := p.leadComment
+	pos := p.expect(token.PACKAGE)
+	// Go spec: The package clause is not a declaration;
+	// the package name does not appear in any scope.
+	ident := p.parseIdent()
+	if ident.Name == "_" {
+		p.error(p.pos, "invalid package name _")
+	}
+	p.expectSemi()
+
+	var decls []ast.Decl
+
+	// Don't bother parsing the rest if we had errors already.
+	// Likely not a Go source file at all.
+
+	if p.ErrorCount() == 0 && p.mode&PackageClauseOnly == 0 {
+		// import decls
+		for p.tok == token.IMPORT {
+			decls = append(decls, p.parseGenDecl(token.IMPORT, parseImportSpec))
+		}
+
+		if p.mode&ImportsOnly == 0 {
+			// rest of package body
+			for p.tok != token.EOF {
+				decls = append(decls, p.parseDecl())
+			}
+		}
+	}
+
+	assert(p.topScope == p.pkgScope, "imbalanced scopes")
+
+	// resolve global identifiers within the same file
+	i := 0
+	for _, ident := range p.unresolved {
+		// i <= index for current ident
+		assert(ident.Obj == unresolved, "object already resolved")
+		ident.Obj = p.pkgScope.Lookup(ident.Name) // also removes unresolved sentinel
+		if ident.Obj == nil {
+			p.unresolved[i] = ident
+			i++
+		}
+	}
+
+	// TODO(gri): store p.imports in AST
+	return &ast.File{doc, pos, ident, decls, p.pkgScope, p.imports, p.unresolved[0:i], p.comments}
+}