--- /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.
+
+// A parser for Go source text. The input is a stream of lexical tokens
+// provided via the Scanner interface. The output is an abstract syntax
+// tree (AST) representing the Go source. The parser is invoked by calling
+// Parse.
+//
+package parser
+
+import (
+ "ast";
+ "fmt";
+ "io";
+ "scanner";
+ "token";
+ "vector";
+)
+
+
+// An implementation of an ErrorHandler may be provided to the parser.
+// If a syntax error is encountered and a handler was installed, Error
+// is called with a position and an error message. The position points
+// to the beginning of the offending token.
+//
+type ErrorHandler interface {
+ Error(pos token.Position, msg string);
+}
+
+
+type interval struct {
+ beg, end int;
+}
+
+
+// The parser structure holds the parser's internal state.
+type parser struct {
+ scanner scanner.Scanner;
+ err ErrorHandler; // nil if no handler installed
+ errorCount int;
+
+ // Tracing/debugging
+ mode uint; // parsing mode
+ trace bool; // == (mode & Trace != 0)
+ indent uint; // indentation used for tracing output
+
+ // Comments
+ comments vector.Vector; // list of collected, unassociated comments
+ last_doc interval; // last comments interval of consecutive comments
+
+ // The next token
+ pos token.Position; // token position
+ tok token.Token; // one token look-ahead
+ lit []byte; // token literal
+
+ // Non-syntactic parser control
+ opt_semi bool; // true if semicolon separator is optional in statement list
+ expr_lev int; // < 0: in control clause, >= 0: in expression
+};
+
+
+// noPos is used when there is no corresponding source position for a token
+var noPos token.Position;
+
+
+// ----------------------------------------------------------------------------
+// Parsing support
+
+func (p *parser) printTrace(a ...) {
+ const dots =
+ ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "
+ ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ";
+ const n = uint(len(dots));
+ fmt.Printf("%5d:%3d: ", p.pos.Line, p.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;
+}
+
+
+func un/*trace*/(p *parser) {
+ p.indent--;
+ p.printTrace(")");
+}
+
+
+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.Line == 0) is not initialized (it
+ // is token.ILLEGAL), so don't print it .
+ if p.trace && p.pos.Line > 0 {
+ s := p.tok.String();
+ switch {
+ case p.tok.IsLiteral():
+ p.printTrace(s, string(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();
+ p.opt_semi = false;
+}
+
+
+// Collect a comment in the parser's comment list and return the line
+// on which the comment ends.
+//
+func (p *parser) collectComment() int {
+ // For /*-style comments, the comment may end on a different line.
+ // Scan the comment for '\n' chars and adjust the end line accordingly.
+ // (Note that the position of the next token may be even further down
+ // as there may be more whitespace lines after the comment.)
+ endline := p.pos.Line;
+ if p.lit[1] == '*' {
+ for i, b := range p.lit {
+ if b == '\n' {
+ endline++;
+ }
+ }
+ }
+ p.comments.Push(&ast.Comment{p.pos, p.lit, endline});
+ p.next0();
+
+ return endline;
+}
+
+
+func (p *parser) getComments() interval {
+ // group adjacent comments, an empty line terminates a group
+ beg := p.comments.Len();
+ endline := p.pos.Line;
+ for p.tok == token.COMMENT && endline+1 >= p.pos.Line {
+ endline = p.collectComment();
+ }
+ end := p.comments.Len();
+ return interval {beg, end};
+}
+
+
+func (p *parser) getDoc() ast.Comments {
+ doc := p.last_doc;
+ n := doc.end - doc.beg;
+
+ if n <= 0 || p.comments.At(doc.end - 1).(*ast.Comment).EndLine + 1 < p.pos.Line {
+ // no comments or empty line between last comment and current token;
+ // do not use as documentation
+ return nil;
+ }
+
+ // found immediately adjacent comment interval;
+ // use as documentation
+ c := make(ast.Comments, n);
+ for i := 0; i < n; i++ {
+ c[i] = p.comments.At(doc.beg + i).(*ast.Comment);
+ }
+
+ // remove comments from the general list
+ p.comments.Cut(doc.beg, doc.end);
+
+ return c;
+}
+
+
+func (p *parser) next() {
+ p.next0();
+ p.last_doc = interval{0, 0};
+ for p.tok == token.COMMENT {
+ p.last_doc = p.getComments();
+ }
+}
+
+
+func (p *parser) error(pos token.Position, msg string) {
+ if p.err != nil {
+ p.err.Error(pos, msg);
+ }
+ p.errorCount++;
+}
+
+
+func (p *parser) error_expected(pos token.Position, msg string) {
+ msg = "expected " + msg;
+ if pos.Offset == p.pos.Offset {
+ // the error happened at the current position;
+ // make the error message more specific
+ msg += ", found '" + p.tok.String() + "'";
+ if p.tok.IsLiteral() {
+ msg += " " + string(p.lit);
+ }
+ }
+ p.error(pos, msg);
+}
+
+
+func (p *parser) expect(tok token.Token) token.Position {
+ pos := p.pos;
+ if p.tok != tok {
+ p.error_expected(pos, "'" + tok.String() + "'");
+ }
+ p.next(); // make progress in any case
+ return pos;
+}
+
+
+// ----------------------------------------------------------------------------
+// Common productions
+
+func (p *parser) tryType() ast.Expr;
+func (p *parser) parseStringList(x *ast.StringLit) []*ast.StringLit
+func (p *parser) parseExpression() ast.Expr;
+func (p *parser) parseStatement() ast.Stmt;
+func (p *parser) parseDeclaration() ast.Decl;
+
+
+func (p *parser) parseIdent() *ast.Ident {
+ if p.tok == token.IDENT {
+ x := &ast.Ident{p.pos, p.lit};
+ p.next();
+ return x;
+ }
+ p.expect(token.IDENT); // use expect() error handling
+ return &ast.Ident{p.pos, [0]byte{}};
+}
+
+
+func (p *parser) parseIdentList(x ast.Expr) []*ast.Ident {
+ if p.trace {
+ defer un(trace(p, "IdentList"));
+ }
+
+ list := vector.New(0);
+ if x == nil {
+ x = p.parseIdent();
+ }
+ list.Push(x);
+ for p.tok == token.COMMA {
+ p.next();
+ list.Push(p.parseIdent());
+ }
+
+ // convert vector
+ idents := make([]*ast.Ident, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ idents[i] = list.At(i).(*ast.Ident);
+ }
+
+ return idents;
+}
+
+
+func (p *parser) parseExpressionList() []ast.Expr {
+ if p.trace {
+ defer un(trace(p, "ExpressionList"));
+ }
+
+ list := vector.New(0);
+ list.Push(p.parseExpression());
+ for p.tok == token.COMMA {
+ p.next();
+ list.Push(p.parseExpression());
+ }
+
+ // convert list
+ exprs := make([]ast.Expr, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ exprs[i] = list.At(i).(ast.Expr);
+ }
+
+ return exprs;
+}
+
+
+// ----------------------------------------------------------------------------
+// Types
+
+func (p *parser) parseType() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Type"));
+ }
+
+ typ := p.tryType();
+
+ if typ == nil {
+ p.error_expected(p.pos, "type");
+ return &ast.BadExpr{p.pos};
+ }
+
+ return typ;
+}
+
+
+func (p *parser) parseQualifiedIdent() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "QualifiedIdent"));
+ }
+
+ var x ast.Expr = p.parseIdent();
+ if p.tok == token.PERIOD {
+ // first identifier is a package identifier
+ p.next();
+ sel := p.parseIdent();
+ x = &ast.SelectorExpr{x, sel};
+ }
+ return x;
+}
+
+
+func (p *parser) parseTypeName() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "TypeName"));
+ }
+
+ return p.parseQualifiedIdent();
+}
+
+
+func (p *parser) parseArrayOrSliceType(ellipsis_ok bool) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "ArrayOrSliceType"));
+ }
+
+ lbrack := p.expect(token.LBRACK);
+ var len ast.Expr;
+ if ellipsis_ok && p.tok == token.ELLIPSIS {
+ len = &ast.Ellipsis{p.pos};
+ p.next();
+ } else if p.tok != token.RBRACK {
+ len = p.parseExpression();
+ }
+ p.expect(token.RBRACK);
+ elt := p.parseType();
+
+ if len != nil {
+ return &ast.ArrayType{lbrack, len, elt};
+ }
+
+ return &ast.SliceType{lbrack, elt};
+}
+
+
+func (p *parser) makeIdentList(list *vector.Vector) []*ast.Ident {
+ idents := make([]*ast.Ident, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ ident, is_ident := list.At(i).(*ast.Ident);
+ if !is_ident {
+ pos := list.At(i).(ast.Expr).Pos();
+ p.error_expected(pos, "identifier");
+ idents[i] = &ast.Ident{pos, []byte{}};
+ }
+ idents[i] = ident;
+ }
+ return idents;
+}
+
+
+func (p *parser) parseFieldDecl() *ast.Field {
+ if p.trace {
+ defer un(trace(p, "FieldDecl"));
+ }
+
+ doc := p.getDoc();
+
+ // a list of identifiers looks like a list of type names
+ list := vector.New(0);
+ for {
+ // TODO do not allow ()'s here
+ list.Push(p.parseType());
+ if p.tok == token.COMMA {
+ p.next();
+ } else {
+ break;
+ }
+ }
+
+ // if we had a list of identifiers, it must be followed by a type
+ typ := p.tryType();
+
+ // optional tag
+ var tag []*ast.StringLit;
+ if p.tok == token.STRING {
+ tag = p.parseStringList(nil);
+ }
+
+ // analyze case
+ var idents []*ast.Ident;
+ if typ != nil {
+ // IdentifierList Type
+ idents = p.makeIdentList(list);
+ } else {
+ // Type (anonymous field)
+ if list.Len() == 1 {
+ // TODO check that this looks like a type
+ typ = list.At(0).(ast.Expr);
+ } else {
+ p.error_expected(p.pos, "anonymous field");
+ typ = &ast.BadExpr{p.pos};
+ }
+ }
+
+ return &ast.Field{doc, idents, typ, tag};
+}
+
+
+func (p *parser) parseStructType() *ast.StructType {
+ if p.trace {
+ defer un(trace(p, "StructType"));
+ }
+
+ pos := p.expect(token.STRUCT);
+ var lbrace, rbrace token.Position;
+ var fields []*ast.Field;
+ if p.tok == token.LBRACE {
+ lbrace = p.pos;
+ p.next();
+
+ list := vector.New(0);
+ for p.tok != token.RBRACE && p.tok != token.EOF {
+ list.Push(p.parseFieldDecl());
+ if p.tok == token.SEMICOLON {
+ p.next();
+ } else {
+ break;
+ }
+ }
+ if p.tok == token.SEMICOLON {
+ p.next();
+ }
+
+ rbrace = p.expect(token.RBRACE);
+ p.opt_semi = true;
+
+ // convert vector
+ fields = make([]*ast.Field, list.Len());
+ for i := list.Len() - 1; i >= 0; i-- {
+ fields[i] = list.At(i).(*ast.Field);
+ }
+ }
+
+ return &ast.StructType{pos, lbrace, fields, rbrace};
+}
+
+
+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) tryParameterType(ellipsis_ok bool) ast.Expr {
+ if ellipsis_ok && p.tok == token.ELLIPSIS {
+ pos := p.pos;
+ p.next();
+ if p.tok != token.RPAREN {
+ // "..." always must be at the very end of a parameter list
+ p.error(pos, "expected type, found '...'");
+ }
+ return &ast.Ellipsis{pos};
+ }
+ return p.tryType();
+}
+
+
+func (p *parser) parseParameterType(ellipsis_ok bool) ast.Expr {
+ typ := p.tryParameterType(ellipsis_ok);
+ if typ == nil {
+ p.error_expected(p.pos, "type");
+ typ = &ast.BadExpr{p.pos};
+ }
+ return typ;
+}
+
+
+func (p *parser) parseParameterDecl(ellipsis_ok bool) (*vector.Vector, ast.Expr) {
+ if p.trace {
+ defer un(trace(p, "ParameterDecl"));
+ }
+
+ // a list of identifiers looks like a list of type names
+ list := vector.New(0);
+ for {
+ // TODO do not allow ()'s here
+ list.Push(p.parseParameterType(ellipsis_ok));
+ if p.tok == token.COMMA {
+ p.next();
+ } else {
+ break;
+ }
+ }
+
+ // if we had a list of identifiers, it must be followed by a type
+ typ := p.tryParameterType(ellipsis_ok);
+
+ return list, typ;
+}
+
+
+func (p *parser) parseParameterList(ellipsis_ok bool) []*ast.Field {
+ if p.trace {
+ defer un(trace(p, "ParameterList"));
+ }
+
+ list, typ := p.parseParameterDecl(ellipsis_ok);
+ if typ != nil {
+ // IdentifierList Type
+ idents := p.makeIdentList(list);
+ list.Init(0);
+ list.Push(&ast.Field{nil, idents, typ, nil});
+
+ for p.tok == token.COMMA {
+ p.next();
+ idents := p.parseIdentList(nil);
+ typ := p.parseParameterType(ellipsis_ok);
+ list.Push(&ast.Field{nil, idents, typ, nil});
+ }
+
+ } else {
+ // Type { "," Type } (anonymous parameters)
+ // convert list of types into list of *Param
+ for i := 0; i < list.Len(); i++ {
+ list.Set(i, &ast.Field{nil, nil, list.At(i).(ast.Expr), nil});
+ }
+ }
+
+ // convert list
+ params := make([]*ast.Field, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ params[i] = list.At(i).(*ast.Field);
+ }
+
+ return params;
+}
+
+
+func (p *parser) parseParameters(ellipsis_ok bool) []*ast.Field {
+ if p.trace {
+ defer un(trace(p, "Parameters"));
+ }
+
+ var params []*ast.Field;
+ p.expect(token.LPAREN);
+ if p.tok != token.RPAREN {
+ params = p.parseParameterList(ellipsis_ok);
+ }
+ p.expect(token.RPAREN);
+
+ return params;
+}
+
+
+func (p *parser) parseResult() []*ast.Field {
+ if p.trace {
+ defer un(trace(p, "Result"));
+ }
+
+ var results []*ast.Field;
+ if p.tok == token.LPAREN {
+ results = p.parseParameters(false);
+ } else if p.tok != token.FUNC {
+ typ := p.tryType();
+ if typ != nil {
+ results = make([]*ast.Field, 1);
+ results[0] = &ast.Field{nil, nil, typ, nil};
+ }
+ }
+
+ return results;
+}
+
+
+func (p *parser) parseSignature() (params []*ast.Field, results []*ast.Field) {
+ if p.trace {
+ defer un(trace(p, "Signature"));
+ }
+
+ params = p.parseParameters(true);
+ results = p.parseResult();
+
+ return params, results;
+}
+
+
+func (p *parser) parseFuncType() *ast.FuncType {
+ if p.trace {
+ defer un(trace(p, "FuncType"));
+ }
+
+ pos := p.expect(token.FUNC);
+ params, results := p.parseSignature();
+
+ return &ast.FuncType{pos, params, results};
+}
+
+
+func (p *parser) parseMethodSpec() *ast.Field {
+ if p.trace {
+ defer un(trace(p, "MethodSpec"));
+ }
+
+ doc := p.getDoc();
+ var idents []*ast.Ident;
+ var typ ast.Expr;
+ x := p.parseQualifiedIdent();
+ if tmp, is_ident := x.(*ast.Ident); is_ident && (p.tok == token.COMMA || p.tok == token.LPAREN) {
+ // methods
+ idents = p.parseIdentList(x);
+ params, results := p.parseSignature();
+ typ = &ast.FuncType{noPos, params, results};
+ } else {
+ // embedded interface
+ typ = x;
+ }
+
+ return &ast.Field{doc, idents, typ, nil};
+}
+
+
+func (p *parser) parseInterfaceType() *ast.InterfaceType {
+ if p.trace {
+ defer un(trace(p, "InterfaceType"));
+ }
+
+ pos := p.expect(token.INTERFACE);
+ var lbrace, rbrace token.Position;
+ var methods []*ast.Field;
+ if p.tok == token.LBRACE {
+ lbrace = p.pos;
+ p.next();
+
+ list := vector.New(0);
+ for p.tok == token.IDENT {
+ list.Push(p.parseMethodSpec());
+ if p.tok != token.RBRACE {
+ p.expect(token.SEMICOLON);
+ }
+ }
+
+ rbrace = p.expect(token.RBRACE);
+ p.opt_semi = true;
+
+ // convert vector
+ methods = make([]*ast.Field, list.Len());
+ for i := list.Len() - 1; i >= 0; i-- {
+ methods[i] = list.At(i).(*ast.Field);
+ }
+ }
+
+ return &ast.InterfaceType{pos, lbrace, methods, rbrace};
+}
+
+
+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};
+}
+
+
+func (p *parser) tryRawType(ellipsis_ok bool) ast.Expr {
+ switch p.tok {
+ case token.IDENT: return p.parseTypeName();
+ case token.LBRACK: return p.parseArrayOrSliceType(ellipsis_ok);
+ case token.STRUCT: return p.parseStructType();
+ case token.MUL: return p.parsePointerType();
+ case token.FUNC: return p.parseFuncType();
+ 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 {
+ return p.tryRawType(false);
+}
+
+
+// ----------------------------------------------------------------------------
+// Blocks
+
+func makeStmtList(list *vector.Vector) []ast.Stmt {
+ stats := make([]ast.Stmt, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ stats[i] = list.At(i).(ast.Stmt);
+ }
+ return stats;
+}
+
+
+func (p *parser) parseStatementList() []ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "StatementList"));
+ }
+
+ list := vector.New(0);
+ expect_semi := false;
+ for p.tok != token.CASE && p.tok != token.DEFAULT && p.tok != token.RBRACE && p.tok != token.EOF {
+ if expect_semi {
+ p.expect(token.SEMICOLON);
+ expect_semi = false;
+ }
+ list.Push(p.parseStatement());
+ if p.tok == token.SEMICOLON {
+ p.next();
+ } else if p.opt_semi {
+ p.opt_semi = false; // "consume" optional semicolon
+ } else {
+ expect_semi = true;
+ }
+ }
+
+ return makeStmtList(list);
+}
+
+
+func (p *parser) parseBlockStmt() *ast.BlockStmt {
+ if p.trace {
+ defer un(trace(p, "BlockStmt"));
+ }
+
+ lbrace := p.expect(token.LBRACE);
+ list := p.parseStatementList();
+ rbrace := p.expect(token.RBRACE);
+ p.opt_semi = true;
+
+ return &ast.BlockStmt{lbrace, list, rbrace};
+}
+
+
+// ----------------------------------------------------------------------------
+// Expressions
+
+func (p *parser) parseStringList(x *ast.StringLit) []*ast.StringLit {
+ if p.trace {
+ defer un(trace(p, "StringList"));
+ }
+
+ list := vector.New(0);
+ if x != nil {
+ list.Push(x);
+ }
+
+ for p.tok == token.STRING {
+ list.Push(&ast.StringLit{p.pos, p.lit});
+ p.next();
+ }
+
+ // convert list
+ strings := make([]*ast.StringLit, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ strings[i] = list.At(i).(*ast.StringLit);
+ }
+
+ return strings;
+}
+
+
+func (p *parser) parseFuncLit() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "FuncLit"));
+ }
+
+ typ := p.parseFuncType();
+ p.expr_lev++;
+ body := p.parseBlockStmt();
+ p.expr_lev--;
+
+ 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.
+//
+func (p *parser) parseOperand() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Operand"));
+ }
+
+ switch p.tok {
+ case token.IDENT:
+ return p.parseIdent();
+
+ case token.INT:
+ x := &ast.IntLit{p.pos, p.lit};
+ p.next();
+ return x;
+
+ case token.FLOAT:
+ x := &ast.FloatLit{p.pos, p.lit};
+ p.next();
+ return x;
+
+ case token.CHAR:
+ x := &ast.CharLit{p.pos, p.lit};
+ p.next();
+ return x;
+
+ case token.STRING:
+ x := &ast.StringLit{p.pos, p.lit};
+ p.next();
+ if p.tok == token.STRING {
+ return &ast.StringList{p.parseStringList(x)};
+ }
+ return x;
+
+ case token.LPAREN:
+ lparen := p.pos;
+ p.next();
+ p.expr_lev++;
+ x := p.parseExpression();
+ p.expr_lev--;
+ rparen := p.expect(token.RPAREN);
+ return &ast.ParenExpr{lparen, x, rparen};
+
+ case token.FUNC:
+ return p.parseFuncLit();
+
+ default:
+ t := p.tryRawType(true); // could be type for composite literal
+ if t != nil {
+ return t;
+ }
+ }
+
+ p.error_expected(p.pos, "operand");
+ p.next(); // make progress
+ return &ast.BadExpr{p.pos};
+}
+
+
+func (p *parser) parseSelectorOrTypeAssertion(x ast.Expr) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "SelectorOrTypeAssertion"));
+ }
+
+ p.expect(token.PERIOD);
+ if p.tok == token.IDENT {
+ // selector
+ sel := p.parseIdent();
+ return &ast.SelectorExpr{x, sel};
+ }
+
+ // type assertion
+ p.expect(token.LPAREN);
+ var typ ast.Expr;
+ if p.tok == token.TYPE {
+ // special case for type switch
+ typ = &ast.Ident{p.pos, p.lit};
+ 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"));
+ }
+
+ p.expect(token.LBRACK);
+ p.expr_lev++;
+ begin := p.parseExpression();
+ var end ast.Expr;
+ if p.tok == token.COLON {
+ p.next();
+ end = p.parseExpression();
+ }
+ p.expr_lev--;
+ p.expect(token.RBRACK);
+
+ if end != nil {
+ return &ast.SliceExpr{x, begin, end};
+ }
+
+ return &ast.IndexExpr{x, begin};
+}
+
+
+func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
+ if p.trace {
+ defer un(trace(p, "CallOrConversion"));
+ }
+
+ lparen := p.expect(token.LPAREN);
+ var args []ast.Expr;
+ if p.tok != token.RPAREN {
+ args = p.parseExpressionList();
+ }
+ rparen := p.expect(token.RPAREN);
+
+ return &ast.CallExpr{fun, lparen, args, rparen};
+}
+
+
+func (p *parser) parseKeyValueExpr() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "KeyValueExpr"));
+ }
+
+ key := p.parseExpression();
+
+ if p.tok == token.COLON {
+ colon := p.pos;
+ p.next();
+ value := p.parseExpression();
+ return &ast.KeyValueExpr{key, colon, value};
+ }
+
+ return key;
+}
+
+
+func isPair(x ast.Expr) bool {
+ tmp, is_pair := x.(*ast.KeyValueExpr);
+ return is_pair;
+}
+
+
+func (p *parser) parseExpressionOrKeyValueList() []ast.Expr {
+ if p.trace {
+ defer un(trace(p, "ExpressionOrKeyValueList"));
+ }
+
+ var pairs bool;
+ list := vector.New(0);
+ for p.tok != token.RBRACE && p.tok != token.EOF {
+ x := p.parseKeyValueExpr();
+
+ if list.Len() == 0 {
+ pairs = isPair(x);
+ } else {
+ // not the first element - check syntax
+ if pairs != isPair(x) {
+ p.error_expected(x.Pos(), "all single expressions or all key-value pairs");
+ }
+ }
+
+ list.Push(x);
+
+ if p.tok == token.COMMA {
+ p.next();
+ } else {
+ break;
+ }
+ }
+
+ // convert list
+ elts := make([]ast.Expr, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ elts[i] = list.At(i).(ast.Expr);
+ }
+
+ return elts;
+}
+
+
+func (p *parser) parseCompositeLit(typ ast.Expr) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "CompositeLit"));
+ }
+
+ lbrace := p.expect(token.LBRACE);
+ var elts []ast.Expr;
+ if p.tok != token.RBRACE {
+ elts = p.parseExpressionOrKeyValueList();
+ }
+ rbrace := p.expect(token.RBRACE);
+ return &ast.CompositeLit{typ, lbrace, elts, rbrace};
+}
+
+
+// TODO Consider different approach to checking syntax after parsing:
+// Provide a arguments (set of flags) to parsing functions
+// restricting what they are syupposed to accept depending
+// on context.
+
+// checkExpr checks that x is an expression (and not a type).
+func (p *parser) checkExpr(x ast.Expr) ast.Expr {
+ // TODO should provide predicate in AST nodes
+ switch t := x.(type) {
+ case *ast.BadExpr:
+ case *ast.Ident:
+ case *ast.IntLit:
+ case *ast.FloatLit:
+ case *ast.CharLit:
+ case *ast.StringLit:
+ case *ast.StringList:
+ case *ast.FuncLit:
+ case *ast.CompositeLit:
+ case *ast.ParenExpr:
+ case *ast.SelectorExpr:
+ case *ast.IndexExpr:
+ case *ast.SliceExpr:
+ case *ast.TypeAssertExpr:
+ 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.error_expected(x.Pos(), "expression");
+ x = &ast.BadExpr{x.Pos()};
+ }
+ case *ast.BinaryExpr:
+ default:
+ // all other nodes are not proper expressions
+ p.error_expected(x.Pos(), "expression");
+ x = &ast.BadExpr{x.Pos()};
+ }
+ return x;
+}
+
+
+// checkTypeName checks that x is type name.
+func (p *parser) checkTypeName(x ast.Expr) ast.Expr {
+ // TODO should provide predicate in AST nodes
+ switch t := x.(type) {
+ case *ast.BadExpr:
+ case *ast.Ident:
+ case *ast.ParenExpr: p.checkTypeName(t.X); // TODO should (TypeName) be illegal?
+ case *ast.SelectorExpr: p.checkTypeName(t.X);
+ default:
+ // all other nodes are not type names
+ p.error_expected(x.Pos(), "type name");
+ x = &ast.BadExpr{x.Pos()};
+ }
+ return x;
+}
+
+
+// checkCompositeLitType checks that x is a legal composite literal type.
+func (p *parser) checkCompositeLitType(x ast.Expr) ast.Expr {
+ // TODO should provide predicate in AST nodes
+ switch t := x.(type) {
+ case *ast.BadExpr: return x;
+ case *ast.Ident: return x;
+ case *ast.ParenExpr: p.checkCompositeLitType(t.X);
+ case *ast.SelectorExpr: p.checkTypeName(t.X);
+ case *ast.ArrayType: return x;
+ case *ast.SliceType: return x;
+ case *ast.StructType: return x;
+ case *ast.MapType: return x;
+ default:
+ // all other nodes are not legal composite literal types
+ p.error_expected(x.Pos(), "composite literal type");
+ x = &ast.BadExpr{x.Pos()};
+ }
+ 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 {
+ // TODO should provide predicate in AST nodes
+ switch t := x.(type) {
+ case *ast.UnaryExpr:
+ if t.Op == token.RANGE {
+ // the range operator is only allowed at the top of a for statement
+ p.error_expected(x.Pos(), "expression");
+ x = &ast.BadExpr{x.Pos()};
+ }
+ case *ast.ArrayType:
+ if len, is_ellipsis := t.Len.(*ast.Ellipsis); is_ellipsis {
+ p.error(len.Pos(), "expected array length, found '...'");
+ x = &ast.BadExpr{x.Pos()};
+ }
+ }
+
+ // all other nodes are expressions or types
+ return x;
+}
+
+
+func (p *parser) parsePrimaryExpr() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "PrimaryExpr"));
+ }
+
+ x := p.parseOperand();
+ for {
+ switch p.tok {
+ case token.PERIOD: x = p.parseSelectorOrTypeAssertion(p.checkExpr(x));
+ case token.LBRACK: x = p.parseIndexOrSlice(p.checkExpr(x));
+ case token.LPAREN: x = p.parseCallOrConversion(p.checkExprOrType(x));
+ case token.LBRACE:
+ if p.expr_lev >= 0 {
+ x = p.parseCompositeLit(p.checkCompositeLitType(x));
+ } else {
+ return p.checkExprOrType(x);
+ }
+ default:
+ return p.checkExprOrType(x);
+ }
+ }
+
+ panic(); // unreachable
+ return nil;
+}
+
+
+func (p *parser) parseUnaryExpr() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "UnaryExpr"));
+ }
+
+ switch p.tok {
+ case token.ADD, token.SUB, token.NOT, token.XOR, token.ARROW, token.AND, token.RANGE:
+ pos, op := p.pos, p.tok;
+ p.next();
+ x := p.parseUnaryExpr();
+ return &ast.UnaryExpr{pos, op, p.checkExpr(x)};
+
+ case token.MUL:
+ // unary "*" expression or pointer type
+ pos := p.pos;
+ p.next();
+ x := p.parseUnaryExpr();
+ return &ast.StarExpr{pos, p.checkExprOrType(x)};
+ }
+
+ return p.parsePrimaryExpr();
+}
+
+
+func (p *parser) parseBinaryExpr(prec1 int) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "BinaryExpr"));
+ }
+
+ x := p.parseUnaryExpr();
+ for prec := p.tok.Precedence(); prec >= prec1; prec-- {
+ for p.tok.Precedence() == prec {
+ pos, op := p.pos, p.tok;
+ p.next();
+ y := p.parseBinaryExpr(prec + 1);
+ x = &ast.BinaryExpr{p.checkExpr(x), pos, op, p.checkExpr(y)};
+ }
+ }
+
+ return x;
+}
+
+
+func (p *parser) parseExpression() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Expression"));
+ }
+
+ return p.parseBinaryExpr(token.LowestPrec + 1);
+}
+
+
+// ----------------------------------------------------------------------------
+// Statements
+
+
+func (p *parser) parseSimpleStmt(label_ok bool) ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "SimpleStmt"));
+ }
+
+ x := p.parseExpressionList();
+
+ switch p.tok {
+ case token.COLON:
+ // labeled statement
+ p.next();
+ if label_ok && len(x) == 1 {
+ if label, is_ident := x[0].(*ast.Ident); is_ident {
+ return &ast.LabeledStmt{label, p.parseStatement()};
+ }
+ }
+ p.error(x[0].Pos(), "illegal label declaration");
+ return &ast.BadStmt{x[0].Pos()};
+
+ 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:
+ // assignment statement
+ pos, tok := p.pos, p.tok;
+ p.next();
+ y := p.parseExpressionList();
+ if len(x) > 1 && len(y) > 1 && len(x) != len(y) {
+ p.error(x[0].Pos(), "arity of lhs doesn't match rhs");
+ }
+ return &ast.AssignStmt{x, pos, tok, y};
+ }
+
+ if len(x) > 1 {
+ p.error(x[0].Pos(), "only one expression allowed");
+ // continue with first expression
+ }
+
+ if p.tok == token.INC || p.tok == token.DEC {
+ // increment or decrement
+ s := &ast.IncDecStmt{x[0], p.tok};
+ p.next(); // consume "++" or "--"
+ return s;
+ }
+
+ // expression
+ return &ast.ExprStmt{x[0]};
+}
+
+
+func (p *parser) parseCallExpr() *ast.CallExpr {
+ x := p.parseExpression();
+ if call, is_call := x.(*ast.CallExpr); is_call {
+ return call;
+ }
+ p.error_expected(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();
+ if call != nil {
+ return &ast.GoStmt{pos, call};
+ }
+ return &ast.BadStmt{pos};
+}
+
+
+func (p *parser) parseDeferStmt() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "DeferStmt"));
+ }
+
+ pos := p.expect(token.DEFER);
+ call := p.parseCallExpr();
+ if call != nil {
+ return &ast.DeferStmt{pos, call};
+ }
+ return &ast.BadStmt{pos};
+}
+
+
+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.parseExpressionList();
+ }
+
+ return &ast.ReturnStmt{pos, x};
+}
+
+
+func (p *parser) parseBranchStmt(tok token.Token) *ast.BranchStmt {
+ if p.trace {
+ defer un(trace(p, "BranchStmt"));
+ }
+
+ s := &ast.BranchStmt{p.pos, tok, nil};
+ p.expect(tok);
+ if tok != token.FALLTHROUGH && p.tok == token.IDENT {
+ s.Label = p.parseIdent();
+ }
+
+ return s;
+}
+
+
+func (p *parser) isExpr(s ast.Stmt) bool {
+ if s == nil {
+ return true;
+ }
+ dummy, is_expr := s.(*ast.ExprStmt);
+ return is_expr;
+}
+
+
+func (p *parser) makeExpr(s ast.Stmt) ast.Expr {
+ if s == nil {
+ return nil;
+ }
+ if es, is_expr := s.(*ast.ExprStmt); is_expr {
+ return p.checkExpr(es.X);
+ }
+ p.error(s.Pos(), "expected condition, found simple statement");
+ return &ast.BadExpr{s.Pos()};
+}
+
+
+func (p *parser) parseControlClause(isForStmt bool) (s1, s2, s3 ast.Stmt) {
+ if p.tok != token.LBRACE {
+ prev_lev := p.expr_lev;
+ p.expr_lev = -1;
+
+ if p.tok != token.SEMICOLON {
+ s1 = p.parseSimpleStmt(false);
+ }
+ if p.tok == token.SEMICOLON {
+ p.next();
+ if p.tok != token.LBRACE && p.tok != token.SEMICOLON {
+ s2 = p.parseSimpleStmt(false);
+ }
+ if isForStmt {
+ // for statements have a 3rd section
+ p.expect(token.SEMICOLON);
+ if p.tok != token.LBRACE {
+ s3 = p.parseSimpleStmt(false);
+ }
+ }
+ } else {
+ s1, s2 = nil, s1;
+ }
+
+ p.expr_lev = prev_lev;
+ }
+
+ return s1, s2, s3;
+}
+
+
+func (p *parser) parseIfStmt() *ast.IfStmt {
+ if p.trace {
+ defer un(trace(p, "IfStmt"));
+ }
+
+ pos := p.expect(token.IF);
+ s1, s2, dummy := p.parseControlClause(false);
+ body := p.parseBlockStmt();
+ var else_ ast.Stmt;
+ if p.tok == token.ELSE {
+ p.next();
+ else_ = p.parseStatement();
+ }
+
+ return &ast.IfStmt{pos, s1, p.makeExpr(s2), body, else_};
+}
+
+
+func (p *parser) parseCaseClause() *ast.CaseClause {
+ if p.trace {
+ defer un(trace(p, "CaseClause"));
+ }
+
+ // SwitchCase
+ pos := p.pos;
+ var x []ast.Expr;
+ if p.tok == token.CASE {
+ p.next();
+ x = p.parseExpressionList();
+ } else {
+ p.expect(token.DEFAULT);
+ }
+
+ colon := p.expect(token.COLON);
+ body := p.parseStatementList();
+
+ return &ast.CaseClause{pos, x, colon, body};
+}
+
+
+func (p *parser) parseTypeCaseClause() *ast.TypeCaseClause {
+ if p.trace {
+ defer un(trace(p, "CaseClause"));
+ }
+
+ // TypeSwitchCase
+ pos := p.pos;
+ var typ ast.Expr;
+ if p.tok == token.CASE {
+ p.next();
+ typ = p.parseType();
+ } else {
+ p.expect(token.DEFAULT);
+ }
+
+ colon := p.expect(token.COLON);
+ body := p.parseStatementList();
+
+ return &ast.TypeCaseClause{pos, typ, colon, body};
+}
+
+
+func (p *parser) parseSwitchStmt() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "SwitchStmt"));
+ }
+
+ pos := p.expect(token.SWITCH);
+ s1, s2, dummy := p.parseControlClause(false);
+
+ if p.isExpr(s2) {
+ // expression switch
+ lbrace := p.expect(token.LBRACE);
+ cases := vector.New(0);
+ for p.tok == token.CASE || p.tok == token.DEFAULT {
+ cases.Push(p.parseCaseClause());
+ }
+ rbrace := p.expect(token.RBRACE);
+ p.opt_semi = true;
+ body := &ast.BlockStmt{lbrace, makeStmtList(cases), rbrace};
+ return &ast.SwitchStmt{pos, s1, p.makeExpr(s2), body};
+ }
+
+ // type switch
+ // TODO do all the checks!
+ lbrace := p.expect(token.LBRACE);
+ cases := vector.New(0);
+ for p.tok == token.CASE || p.tok == token.DEFAULT {
+ cases.Push(p.parseTypeCaseClause());
+ }
+ rbrace := p.expect(token.RBRACE);
+ p.opt_semi = true;
+ body := &ast.BlockStmt{lbrace, makeStmtList(cases), rbrace};
+ return &ast.TypeSwitchStmt{pos, s1, s2, body};
+}
+
+
+func (p *parser) parseCommClause() *ast.CommClause {
+ if p.trace {
+ defer un(trace(p, "CommClause"));
+ }
+
+ // CommCase
+ pos := p.pos;
+ var tok token.Token;
+ var lhs, rhs ast.Expr;
+ if p.tok == token.CASE {
+ p.next();
+ if p.tok == token.ARROW {
+ // RecvExpr without assignment
+ rhs = p.parseExpression();
+ } else {
+ // SendExpr or RecvExpr
+ rhs = p.parseExpression();
+ if p.tok == token.ASSIGN || p.tok == token.DEFINE {
+ // RecvExpr with assignment
+ tok = p.tok;
+ p.next();
+ lhs = rhs;
+ if p.tok == token.ARROW {
+ rhs = p.parseExpression();
+ } else {
+ p.expect(token.ARROW); // use expect() error handling
+ }
+ }
+ // else SendExpr
+ }
+ } else {
+ p.expect(token.DEFAULT);
+ }
+
+ colon := p.expect(token.COLON);
+ body := p.parseStatementList();
+
+ return &ast.CommClause{pos, tok, lhs, rhs, 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);
+ cases := vector.New(0);
+ for p.tok == token.CASE || p.tok == token.DEFAULT {
+ cases.Push(p.parseCommClause());
+ }
+ rbrace := p.expect(token.RBRACE);
+ p.opt_semi = true;
+ body := &ast.BlockStmt{lbrace, makeStmtList(cases), 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);
+ s1, s2, s3 := p.parseControlClause(true);
+ body := p.parseBlockStmt();
+
+ if as, is_as := s2.(*ast.AssignStmt); is_as {
+ // possibly a for statement with a range clause; check assignment operator
+ if as.Tok != token.ASSIGN && as.Tok != token.DEFINE {
+ p.error_expected(as.TokPos, "'=' or ':='");
+ return &ast.BadStmt{pos};
+ }
+ // check lhs
+ var key, value ast.Expr;
+ switch len(as.Lhs) {
+ case 2:
+ value = as.Lhs[1];
+ fallthrough;
+ case 1:
+ key = as.Lhs[0];
+ default:
+ p.error_expected(as.Lhs[0].Pos(), "1 or 2 expressions");
+ return &ast.BadStmt{pos};
+ }
+ // check rhs
+ if len(as.Rhs) != 1 {
+ p.error_expected(as.Rhs[0].Pos(), "1 expressions");
+ return &ast.BadStmt{pos};
+ }
+ if rhs, is_unary := as.Rhs[0].(*ast.UnaryExpr); is_unary && rhs.Op == token.RANGE {
+ // rhs is range expression; check lhs
+ return &ast.RangeStmt{pos, key, value, as.TokPos, as.Tok, rhs.X, body}
+ } else {
+ p.error_expected(s2.Pos(), "range clause");
+ return &ast.BadStmt{pos};
+ }
+ } else {
+ // regular for statement
+ return &ast.ForStmt{pos, s1, p.makeExpr(s2), s3, body};
+ }
+
+ panic(); // unreachable
+ return nil;
+}
+
+
+func (p *parser) parseStatement() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "Statement"));
+ }
+
+ switch p.tok {
+ case token.CONST, token.TYPE, token.VAR:
+ return &ast.DeclStmt{p.parseDeclaration()};
+ 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: // unary operators
+ return p.parseSimpleStmt(true);
+ case token.GO:
+ return p.parseGoStmt();
+ case token.DEFER:
+ return p.parseDeferStmt();
+ case token.RETURN:
+ return p.parseReturnStmt();
+ case token.BREAK, token.CONTINUE, token.GOTO, token.FALLTHROUGH:
+ return p.parseBranchStmt(p.tok);
+ case token.LBRACE:
+ return p.parseBlockStmt();
+ case token.IF:
+ return p.parseIfStmt();
+ case token.SWITCH:
+ return p.parseSwitchStmt();
+ case token.SELECT:
+ return p.parseSelectStmt();
+ case token.FOR:
+ return p.parseForStmt();
+ case token.SEMICOLON, token.RBRACE:
+ // don't consume the ";", it is the separator following the empty statement
+ return &ast.EmptyStmt{p.pos};
+ }
+
+ // no statement found
+ p.error_expected(p.pos, "statement");
+ return &ast.BadStmt{p.pos};
+}
+
+
+// ----------------------------------------------------------------------------
+// Declarations
+
+func (p *parser) parseImportSpec(pos token.Position, doc ast.Comments) *ast.ImportDecl {
+ if p.trace {
+ defer un(trace(p, "ImportSpec"));
+ }
+
+ var ident *ast.Ident;
+ if p.tok == token.PERIOD {
+ p.error(p.pos, `"import ." not yet handled properly`);
+ p.next();
+ } else if p.tok == token.IDENT {
+ ident = p.parseIdent();
+ }
+
+ var path []*ast.StringLit;
+ if p.tok == token.STRING {
+ path = p.parseStringList(nil);
+ } else {
+ p.expect(token.STRING); // use expect() error handling
+ }
+
+ return &ast.ImportDecl{doc, pos, ident, path};
+}
+
+
+func (p *parser) parseConstSpec(pos token.Position, doc ast.Comments) *ast.ConstDecl {
+ if p.trace {
+ defer un(trace(p, "ConstSpec"));
+ }
+
+ idents := p.parseIdentList(nil);
+ typ := p.tryType();
+ var values []ast.Expr;
+ if typ != nil || p.tok == token.ASSIGN {
+ p.expect(token.ASSIGN);
+ values = p.parseExpressionList();
+ }
+
+ return &ast.ConstDecl{doc, pos, idents, typ, values};
+}
+
+
+func (p *parser) parseTypeSpec(pos token.Position, doc ast.Comments) *ast.TypeDecl {
+ if p.trace {
+ defer un(trace(p, "TypeSpec"));
+ }
+
+ ident := p.parseIdent();
+ typ := p.parseType();
+
+ return &ast.TypeDecl{doc, pos, ident, typ};
+}
+
+
+func (p *parser) parseVarSpec(pos token.Position, doc ast.Comments) *ast.VarDecl {
+ if p.trace {
+ defer un(trace(p, "VarSpec"));
+ }
+
+ idents := p.parseIdentList(nil);
+ typ := p.tryType();
+ var values []ast.Expr;
+ if typ == nil || p.tok == token.ASSIGN {
+ p.expect(token.ASSIGN);
+ values = p.parseExpressionList();
+ }
+
+ return &ast.VarDecl{doc, pos, idents, typ, values};
+}
+
+
+func (p *parser) parseSpec(pos token.Position, doc ast.Comments, keyword int) ast.Decl {
+ switch keyword {
+ case token.IMPORT: return p.parseImportSpec(pos, doc);
+ case token.CONST: return p.parseConstSpec(pos, doc);
+ case token.TYPE: return p.parseTypeSpec(pos, doc);
+ case token.VAR: return p.parseVarSpec(pos, doc);
+ }
+
+ panic(); // unreachable
+ return nil;
+}
+
+
+func (p *parser) parseDecl(keyword int) ast.Decl {
+ if p.trace {
+ defer un(trace(p, "Decl"));
+ }
+
+ doc := p.getDoc();
+ pos := p.expect(keyword);
+ if p.tok == token.LPAREN {
+ lparen := p.pos;
+ p.next();
+ list := vector.New(0);
+ for p.tok != token.RPAREN && p.tok != token.EOF {
+ list.Push(p.parseSpec(noPos, nil, keyword));
+ if p.tok == token.SEMICOLON {
+ p.next();
+ } else {
+ break;
+ }
+ }
+ rparen := p.expect(token.RPAREN);
+ p.opt_semi = true;
+
+ // convert vector
+ decls := make([]ast.Decl, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ decls[i] = list.At(i).(ast.Decl);
+ }
+
+ return &ast.DeclList{doc, pos, keyword, lparen, decls, rparen};
+ }
+
+ return p.parseSpec(pos, doc, keyword);
+}
+
+
+func (p *parser) parseReceiver() *ast.Field {
+ if p.trace {
+ defer un(trace(p, "Receiver"));
+ }
+
+ pos := p.pos;
+ par := p.parseParameters(false);
+
+ // must have exactly one receiver
+ if len(par) != 1 || len(par) == 1 && len(par[0].Names) > 1 {
+ p.error_expected(pos, "exactly one receiver");
+ return &ast.Field{nil, nil, &ast.BadExpr{noPos}, nil};
+ }
+
+ recv := par[0];
+
+ // recv type must be TypeName or *TypeName
+ base := recv.Type;
+ if ptr, is_ptr := base.(*ast.StarExpr); is_ptr {
+ base = ptr.X;
+ }
+ p.checkTypeName(base);
+
+ return recv;
+}
+
+
+func (p *parser) parseFunctionDecl() *ast.FuncDecl {
+ if p.trace {
+ defer un(trace(p, "FunctionDecl"));
+ }
+
+ doc := p.getDoc();
+ pos := p.expect(token.FUNC);
+
+ var recv *ast.Field;
+ if p.tok == token.LPAREN {
+ recv = p.parseReceiver();
+ }
+
+ ident := p.parseIdent();
+ params, results := p.parseSignature();
+
+ var body *ast.BlockStmt;
+ if p.tok == token.LBRACE {
+ body = p.parseBlockStmt();
+ }
+
+ return &ast.FuncDecl{doc, recv, ident, &ast.FuncType{pos, params, results}, body};
+}
+
+
+func (p *parser) parseDeclaration() ast.Decl {
+ if p.trace {
+ defer un(trace(p, "Declaration"));
+ }
+
+ switch p.tok {
+ case token.CONST, token.TYPE, token.VAR:
+ return p.parseDecl(p.tok);
+ case token.FUNC:
+ return p.parseFunctionDecl();
+ }
+
+ pos := p.pos;
+ p.error_expected(pos, "declaration");
+ p.next(); // make progress
+ return &ast.BadDecl{pos};
+}
+
+
+// ----------------------------------------------------------------------------
+// Packages
+
+// The mode parameter to the Parse function 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
+)
+
+
+func (p *parser) parsePackage() *ast.Program {
+ if p.trace {
+ defer un(trace(p, "Program"));
+ }
+
+ // package clause
+ comment := p.getDoc();
+ pos := p.expect(token.PACKAGE);
+ ident := p.parseIdent();
+ if p.tok == token.SEMICOLON {
+ // common error
+ p.error(p.pos, "extra semicolon");
+ p.next();
+ }
+
+ var decls []ast.Decl;
+ if p.mode & PackageClauseOnly == 0 {
+ // import decls
+ list := vector.New(0);
+ for p.tok == token.IMPORT {
+ list.Push(p.parseDecl(token.IMPORT));
+ if p.tok == token.SEMICOLON {
+ p.next();
+ }
+ }
+
+ if p.mode & ImportsOnly == 0 {
+ // rest of package body
+ for p.tok != token.EOF {
+ list.Push(p.parseDeclaration());
+ if p.tok == token.SEMICOLON {
+ p.next();
+ }
+ }
+ }
+
+ // convert declaration list
+ decls = make([]ast.Decl, list.Len());
+ for i := 0; i < list.Len(); i++ {
+ decls[i] = list.At(i).(ast.Decl);
+ }
+ }
+
+ // convert comments list
+ comments := make([]*ast.Comment, p.comments.Len());
+ for i := 0; i < p.comments.Len(); i++ {
+ comments[i] = p.comments.At(i).(*ast.Comment);
+ }
+
+ return &ast.Program{comment, pos, ident, decls, comments};
+}
+
+
+// ----------------------------------------------------------------------------
+// Parsing of entire programs.
+
+func readSource(src interface{}, err ErrorHandler) []byte {
+ errmsg := "invalid input type (or nil)";
+
+ switch s := src.(type) {
+ case string:
+ return io.StringBytes(s);
+ case []byte:
+ return s;
+ case *io.ByteBuffer:
+ // is io.Read, but src is already available in []byte form
+ if s != nil {
+ return s.Data();
+ }
+ case io.Read:
+ var buf io.ByteBuffer;
+ n, os_err := io.Copy(s, &buf);
+ if os_err == nil {
+ return buf.Data();
+ }
+ errmsg = os_err.String();
+ }
+
+ if err != nil {
+ err.Error(noPos, errmsg);
+ }
+ return nil;
+}
+
+
+// Parse parses a Go program.
+//
+// The program source src may be provided in a variety of formats. At the
+// moment the following types are supported: string, []byte, and io.Read.
+//
+// The ErrorHandler err, if not nil, is invoked if src cannot be read and
+// for each syntax error found. The mode parameter controls the amount of
+// source text parsed and other optional parser functionality.
+//
+// Parse returns an AST and the boolean value true if no errors occured;
+// it returns a partial AST (or nil if the source couldn't be read) and
+// the boolean value false to indicate failure.
+//
+// If syntax errors were found, the AST may only be constructed partially,
+// with ast.BadX nodes representing the fragments of erroneous source code.
+//
+func Parse(src interface{}, err ErrorHandler, mode uint) (*ast.Program, bool) {
+ data := readSource(src, err);
+
+ // initialize parser state
+ var p parser;
+ p.scanner.Init(data, err, mode & ParseComments != 0);
+ p.err = err;
+ p.mode = mode;
+ p.trace = mode & Trace != 0; // for convenience (p.trace is used frequently)
+ p.comments.Init(0);
+ p.next();
+
+ // parse program
+ prog := p.parsePackage();
+
+ return prog, p.scanner.ErrorCount == 0 && p.errorCount == 0;
+}