Allowing a colon between the argument name and type

colon.patch.diff

diff -r 5bf1a8b3aeea src/cmd/gc/go.y
--- a/src/cmd/gc/go.y	Thu May 29 13:47:31 2014 -0400
+++ b/src/cmd/gc/go.y	Tue Jun 03 11:47:44 2014 +0900
@@ -43,6 +43,7 @@
 %token	<sym>	LIF LIMPORT LINTERFACE LMAP LNAME
 %token	<sym>	LPACKAGE LRANGE LRETURN LSELECT LSTRUCT LSWITCH
 %token	<sym>	LTYPE LVAR
+%token	<sym>	LRARROW
 
 %token		LANDAND LANDNOT LBODY LCOMM LDEC LEQ LGE LGT
 %token		LIGNORE LINC LLE LLSH LLT LNE LOROR LRSH
@@ -1446,19 +1447,22 @@
 			$$ = list1(nod(OEMPTY, N, N));
 	}
 
+orarrow:
+|	LRARROW
+
 fnres:
 	%prec NotParen
 	{
 		$$ = nil;
 	}
-|	fnret_type
+|	orarrow fnret_type
 	{
-		$$ = list1(nod(ODCLFIELD, N, $1));
+		$$ = list1(nod(ODCLFIELD, N, $2));
 	}
-|	'(' oarg_type_list_ocomma ')'
+|	orarrow '(' oarg_type_list_ocomma ')'
 	{
-		$2 = checkarglist($2, 0);
-		$$ = $2;
+		$3 = checkarglist($3, 0);
+		$$ = $3;
 	}
 
 fnlitdcl:
@@ -1655,6 +1659,12 @@
  */
 arg_type:
 	name_or_type
+|	sym ':' name_or_type
+	{
+		$$ = nod(ONONAME, N, N);
+		$$->sym = $1;
+		$$ = nod(OKEY, $$, $3);
+	}
 |	sym name_or_type
 	{
 		$$ = nod(ONONAME, N, N);
diff -r 5bf1a8b3aeea src/cmd/gc/lex.c
--- a/src/cmd/gc/lex.c	Thu May 29 13:47:31 2014 -0400
+++ b/src/cmd/gc/lex.c	Tue Jun 03 11:47:44 2014 +0900
@@ -1121,6 +1121,10 @@
 			c = OSUB;
 			goto asop;
 		}
+		if(c1 == '>') {
+			c = LRARROW;
+			goto lx;
+		}
 		break;
 
 	case '>':
@@ -2210,6 +2214,7 @@
 	LRANGE,		"RANGE",
 	LRETURN,	"RETURN",
 	LRSH,		"RSH",
+	LRARROW,	"->",
 	LSELECT,	"SELECT",
 	LSTRUCT,	"STRUCT",
 	LSWITCH,	"SWITCH",
@@ -2262,6 +2267,7 @@
 	"LPACKAGE",	"package",
 	"LRANGE",	"range",
 	"LRETURN",	"return",
+	"LRARROW",	"->",
 	"LSELECT",	"select",
 	"LSTRUCT",	"struct",
 	"LSWITCH",	"switch",