--- /dev/null
+// 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}
+}