Significant parser cleanup:

- commented public interface
- much better and very precise error messages
- much better tracing output
- many more checks (still permits more than just syntactically legal
  programs, but much more is checked that can be checked w/o semantic information)
- updated with respect to updated AST
- general cleanup throughout

Parser almost ready for move into lib/go.

R=r
OCL=26853
CL=26855

usr/gri/pretty/compilation.go

@@ -97,11 +97,11 @@ func Compile(src_file string, flags *Flags) (*ast.Package, ErrorList) {
 	var scanner scanner.Scanner;
 	scanner.Init(src, &err, true);
 
-	pflags := uint(0);
+	mode := uint(0);
 	if flags.Verbose {
-		pflags |= parser.Trace;
+		mode |= parser.Trace;
 	}
-	prog, nerrs := parser.Parse(&scanner, &err, parser.ParseEntirePackage, pflags);
+	prog, nerrs := parser.Parse(&scanner, &err, mode);
 
 	if err.errors.Len() == 0 {
 		TypeChecker.CheckProgram(&err, prog);

usr/gri/pretty/printer.go

@@ -591,6 +591,15 @@ func (P *Printer) DoBinaryExpr(x *ast.BinaryExpr) {
 }
 
 
+func (P *Printer) DoKeyValueExpr(x *ast.KeyValueExpr) {
+	P.Expr(x.Key);
+	P.separator = blank;
+	P.Token(x.Colon, token.COLON);
+	P.separator = blank;
+	P.Expr(x.Value);
+}
+
+
 func (P *Printer) DoStarExpr(x *ast.StarExpr) {
 	P.Token(x.Pos(), token.MUL);
 	P.Expr(x.X);
@@ -721,9 +730,14 @@ func (P *Printer) DoEllipsis(x *ast.Ellipsis) {
 
 func (P *Printer) DoArrayType(x *ast.ArrayType) {
 	P.Token(x.Pos(), token.LBRACK);
-	if x.Len != nil {
-		P.Expr(x.Len);
-	}
+	P.Expr(x.Len);
+	P.Token(nopos, token.RBRACK);
+	P.Expr(x.Elt);
+}
+
+
+func (P *Printer) DoSliceType(x *ast.SliceType) {
+	P.Token(x.Pos(), token.LBRACK);
 	P.Token(nopos, token.RBRACK);
 	P.Expr(x.Elt);
 }
@@ -751,11 +765,6 @@ func (P *Printer) DoInterfaceType(x *ast.InterfaceType) {
 }
 
 
-func (P *Printer) DoSliceType(x *ast.SliceType) {
-	unimplemented();
-}
-
-
 func (P *Printer) DoMapType(x *ast.MapType) {
 	P.Token(x.Pos(), token.MAP);
 	P.separator = blank;