back to T{x}, stricter handling of T(x) vs x.(T)

R=ken
DELTA=131  (60 added, 41 deleted, 30 changed)
OCL=25617
CL=25633

src/cmd/gc/go.h

@@ -327,9 +327,9 @@ enum
 	ONOT, OCOM, OPLUS, OMINUS, OSEND, ORECV,
 	OLITERAL, OREGISTER, OINDREG,
 	OKEY, OPARAM,
+	OCOMPOS,
 	OCONV,
-	OCONVDOT,
-	OCONVPAREN,
+	ODOTTYPE,
 	OBAD,
 
 	OEXTEND,	// 6g internal

src/cmd/gc/go.y

@@ -51,7 +51,7 @@
 %type	<node>		stmt_list_r Astmt_list_r Bstmt_list_r
 %type	<node>		Astmt Bstmt
 %type	<node>		for_stmt for_body for_header
-%type	<node>		if_stmt if_body if_header select_stmt
+%type	<node>		if_stmt if_body if_header select_stmt condition
 %type	<node>		simple_stmt osimple_stmt range_stmt semi_stmt
 %type	<node>		expr uexpr pexpr expr_list oexpr oexpr_list expr_list_r
 %type	<node>		exprsym3_list_r exprsym3
@@ -89,6 +89,13 @@
 %left			'+' '-' '|' '^'
 %left			'*' '/' '%' '&' LLSH LRSH
 
+/*
+ * resolve { vs condition in favor of condition
+ */
+%left			'{'
+%left			Condition
+
+
 %%
 file:
 	package import_there imports oxdcl_list
@@ -562,7 +569,7 @@ for_header:
 		$$->ntest = $3;
 		$$->nincr = $5;
 	}
-|	osimple_stmt
+|	condition
 	{
 		// normal test
 		$$ = nod(OFOR, N, N);
@@ -591,15 +598,30 @@ for_stmt:
 		$$ = $2;
 	}
 
+/*
+ * using cond instead of osimple_stmt creates
+ * a shift/reduce conflict on an input like
+ *
+ *	if x == []int { true } { true }
+ *
+ * at the first {, giving us an opportunity
+ * to resolve it by reduce, which implements
+ * the rule about { } inside if conditions
+ * needing parens.
+ */
+condition:
+	osimple_stmt	%prec Condition
+
+
 if_header:
-	osimple_stmt
+	condition
 	{
 		// test
 		$$ = nod(OIF, N, N);
 		$$->ninit = N;
 		$$->ntest = $1;
 	}
-|	osimple_stmt ';' osimple_stmt
+|	osimple_stmt ';' condition
 	{
 		// init ; test
 		$$ = nod(OIF, N, N);
@@ -791,7 +813,7 @@ pexpr:
 	}
 |	pexpr '.' '(' type ')'
 	{
-		$$ = nod(OCONVDOT, $1, N);
+		$$ = nod(ODOTTYPE, $1, N);
 		$$->type = $4;
 	}
 |	pexpr '[' expr ']'
@@ -841,24 +863,22 @@ pexpr:
 		$$ = nod(OMAKE, $5, N);
 		$$->type = $3;
 	}
-|	convtype '(' braced_keyexpr_list ')'
+|	convtype '(' expr ')'
 	{
-		// typed literal
+		// conversion
 		$$ = rev($3);
 		if($$ == N)
 			$$ = nod(OEMPTY, N, N);
-		$$ = nod(OCONVPAREN, $$, N);
+		$$ = nod(OCONV, $$, N);
 		$$->type = $1;
 	}
 |	convtype '{' braced_keyexpr_list '}'
 	{
-		if(!debug['{'])
-			warn("braces should now be parens");
-		// composite literal
+		// composite expression
 		$$ = rev($3);
 		if($$ == N)
 			$$ = nod(OEMPTY, N, N);
-		$$ = nod(OCONVPAREN, $$, N);
+		$$ = nod(OCOMPOS, $$, N);
 		$$->type = $1;
 	}
 |	fnliteral

src/cmd/gc/subr.c

@@ -634,9 +634,9 @@ opnames[] =
 	[OXCASE]	= "XCASE",
 	[OCMP]		= "CMP",
 	[OFALL]		= "FALL",
+	[OCOMPOS]	= "COMPOS",
+	[ODOTTYPE]		= "DOTTYPE",
 	[OCONV]	= "CONV",
-	[OCONVDOT]		= "CONVDOT",
-	[OCONVPAREN]	= "CONVPAREN",
 	[OCOM]		= "COM",
 	[OCONST]	= "CONST",
 	[OCONTINUE]	= "CONTINUE",

src/cmd/gc/walk.c

@@ -510,7 +510,7 @@ loop:
 			}
 			break;
 
-		case OCONVDOT:
+		case ODOTTYPE:
 			if(cl == 2 && cr == 1) {
 				// a,b = i.(T)
 				walktype(r->left, Erv);
@@ -593,13 +593,41 @@ loop:
 		goto ret;
 
 	case OCONV:
-	case OCONVDOT:
-	case OCONVPAREN:
+	case ODOTTYPE:
 		if(top != Erv)
 			goto nottop;
 		walkconv(n);
 		goto ret;
 
+	case OCOMPOS:
+		t = n->type;
+		if(t == T)
+			goto ret;
+		l = n->left;
+		if(l == N)
+			goto ret;
+		walktype(l, Erv);
+	
+		// structure literal
+		if(t->etype == TSTRUCT) {
+			indir(n, structlit(n, N));
+			goto ret;
+		}
+
+		// array literal
+		if(t->etype == TARRAY) {
+			indir(n, arraylit(n, N));
+			goto ret;
+		}
+
+		// map literal
+		if(t->etype == TMAP) {
+			indir(n, maplit(n, N));
+			goto ret;
+		}
+		yyerror("invalid type for composite literal: %T", t);
+		goto ret;
+
 	case ORETURN:
 		if(top != Etop)
 			goto nottop;
@@ -887,11 +915,7 @@ loop:
 	case OADDR:
 		if(top != Erv)
 			goto nottop;
-		if(n->left->op == OCONVPAREN && n->left->type != T)
-		switch(n->left->type->etype) {
-		case TSTRUCT:
-		case TARRAY:
-		case TMAP:
+		if(n->left->op == OCOMPOS && n->left->type != T) {
 			// turn &Point(1, 2) or &[]int(1, 2) or &[...]int(1, 2) into allocation.
 			// initialize with
 			//	nvar := new(*Point);
@@ -920,13 +944,14 @@ loop:
 				maplit(n->left, nstar);
 				break;
 			default:
-				fatal("addr lit %T", n->left->type);
+				goto badlit;
 			}
 
 			indir(n, nvar);
 			goto ret;
 		}
 
+	badlit:
 		if(istype(n->left->type, TFUNC) && n->left->class == PFUNC) {
 			if(!n->diag) {
 				n->diag = 1;
@@ -1130,10 +1155,12 @@ walkbool(Node *n)
 			yyerror("IF and FOR require a boolean type");
 }
 
+
+
 void
 walkconv(Node *n)
 {
-	int et, op;
+	int et;
 	Type *t;
 	Node *l;
 
@@ -1145,17 +1172,20 @@ walkconv(Node *n)
 		return;
 	walktype(l, Erv);
 
-	switch(t->etype) {
-	case TSTRUCT:
-	case TMAP:
-	case TARRAY:
-		break;
-	default:
-		convlit1(l, t, 1);
+	convlit1(l, t, 1);
+
+	// if using .(T), interface assertion.
+	if(n->op == ODOTTYPE) {
+		// interface conversion
+		et = ifaceas(n->type, l->type, 1);
+		if(et != Inone) {
+			indir(n, ifaceop(n->type, l, et));
+			return;
+		}
+		goto bad;
 	}
 
-	op = n->op;
-	n->op = OCONV;	// generic conversion
+	// otherwise, conversion.
 
 	// nil conversion
 	if(eqtype(t, l->type, 0)) {
@@ -1218,37 +1248,7 @@ walkconv(Node *n)
 			return;
 	}
 
-	// possible interface conversion if using .(T)
-	if(op == OCONVDOT) {
-		// interface conversion
-		et = ifaceas(n->type, l->type, 1);
-		if(et != Inone) {
-			indir(n, ifaceop(n->type, l, et));
-			return;
-		}
-	}
-
-	// possible composite literal if using T()
-	if(op == OCONVPAREN) {
-		// structure literal
-		if(t->etype == TSTRUCT) {
-			indir(n, structlit(n, N));
-			return;
-		}
-
-		// array literal
-		if(t->etype == TARRAY) {
-			indir(n, arraylit(n, N));
-			return;
-		}
-
-		// map literal
-		if(t->etype == TMAP) {
-			indir(n, maplit(n, N));
-			return;
-		}
-	}
-
+bad:
 	if(l->type != T)
 		yyerror("invalid conversion: %T to %T", l->type, t);
 	else if(n->left->op == OLIST)
@@ -1256,7 +1256,6 @@ walkconv(Node *n)
 }
 
 
-
 /*
  * return the first type
  */
@@ -3146,7 +3145,7 @@ multi:
 		n = list(n, a);
 		break;
 
-	case OCONVDOT:
+	case ODOTTYPE:
 		// a,b := i.(T)
 		if(cl != 2)
 			goto badt;