gc: fix parenthesization check

Cannot use paren field in Node because all
instances of a given symbol name use the same Node.

Fixes #1022.

R=ken2
CC=golang-dev
https://golang.org/cl/2015043

src/cmd/gc/go.h

@@ -209,7 +209,6 @@ struct	Node
 	uchar	dodata;		// compile literal assignment as data statement
 	uchar	used;
 	uchar	isddd;
-	uchar	paren;	// was parenthesized
 	uchar	pun;		// dont registerize variable ONAME
 
 	// most nodes
@@ -411,6 +410,7 @@ enum
 	OTINTER,
 	OTFUNC,
 	OTARRAY,
+	OTPAREN,
 
 	// misc
 	ODDD,

src/cmd/gc/go.y

@@ -58,7 +58,7 @@
 %type	<node>	name_or_type non_expr_type
 %type	<node>	new_name dcl_name oexpr typedclname
 %type	<node>	onew_name
-%type	<node>	osimple_stmt pexpr
+%type	<node>	osimple_stmt pexpr pexpr_no_paren
 %type	<node>	pseudocall range_stmt select_stmt
 %type	<node>	simple_stmt
 %type	<node>	switch_stmt uexpr
@@ -812,7 +812,7 @@ pseudocall:
 		$$->list = $3;
 	}
 
-pexpr:
+pexpr_no_paren:
 	LLITERAL
 	{
 		$$ = nodlit($1);
@@ -829,11 +829,6 @@ pexpr:
 		}
 		$$ = nod(OXDOT, $1, newname($3));
 	}
-|	'(' expr_or_type ')'
-	{
-		$$ = $2;
-		$$->paren++;
-	}
 |	pexpr '.' '(' expr_or_type ')'
 	{
 		$$ = nod(ODOTTYPE, $1, $4);
@@ -873,16 +868,28 @@ pexpr:
 		if($2 == LBODY)
 			loophack = 1;
 	}
-|	pexpr '{' braced_keyval_list '}'
+|	pexpr_no_paren '{' braced_keyval_list '}'
 	{
-		if($1->paren)
-			yyerror("cannot parenthesize type in composite literal");
 		// composite expression
 		$$ = nod(OCOMPLIT, N, $1);
 		$$->list = $3;
 	}
+|	'(' expr_or_type ')' '{' braced_keyval_list '}'
+	{
+		yyerror("cannot parenthesize type in composite literal");
+		// composite expression
+		$$ = nod(OCOMPLIT, N, $2);
+		$$->list = $5;
+	}
 |	fnliteral
 
+pexpr:
+	pexpr_no_paren
+|	'(' expr_or_type ')'
+	{
+		$$ = $2;
+	}
+
 expr_or_type:
 	expr
 |	non_expr_type	%prec PreferToRightParen
@@ -965,8 +972,7 @@ ntype:
 |	dotname
 |	'(' ntype ')'
 	{
-		$$ = $2;
-		$$->paren++;
+		$$ = nod(OTPAREN, $2, N);
 	}
 
 non_expr_type:
@@ -985,8 +991,7 @@ non_recvchantype:
 |	dotname
 |	'(' ntype ')'
 	{
-		$$ = $2;
-		$$->paren++;
+		$$ = nod(OTPAREN, $2, N);
 	}
 
 convtype:
@@ -1146,7 +1151,7 @@ fndcl:
 			yyerror("bad receiver in method");
 			break;
 		}
-		if(rcvr->right->paren || (rcvr->right->op == OIND && rcvr->right->left->paren))
+		if(rcvr->right->op == OTPAREN || (rcvr->right->op == OIND && rcvr->right->left->op == OTPAREN))
 			yyerror("cannot parenthesize receiver type");
 
 		$$ = nod(ODCLFUNC, N, N);

src/cmd/gc/print.c

@@ -66,6 +66,7 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OPLUS:
 	case ORECV:
 	case OCONVIFACE:
+	case OTPAREN:
 		nprec = 7;
 		break;
 
@@ -165,6 +166,12 @@ exprfmt(Fmt *f, Node *n, int prec)
 		fmtprint(f, "[]");
 		exprfmt(f, n->left, PFIXME);
 		break;
+	
+	case OTPAREN:
+		fmtprint(f, "(");
+		exprfmt(f, n->left, 0);
+		fmtprint(f, ")");
+		break;
 
 	case OTMAP:
 		fmtprint(f, "map[");

src/cmd/gc/typecheck.c

@@ -169,6 +169,16 @@ reswitch:
 			goto error;
 		break;
 
+	case OTPAREN:
+		ok |= Etype;
+		l = typecheck(&n->left, Etype);
+		if(l->type == T)
+			goto error;
+		n->op = OTYPE;
+		n->type = l->type;
+		n->left = N;
+		break;
+	
 	case OTARRAY:
 		ok |= Etype;
 		t = typ(TARRAY);