gc: don't print implicit type on struct literal in export

As pointed out in the discussion around 2678.

R=rsc
CC=golang-dev
https://golang.org/cl/5534077

src/cmd/gc/fmt.c

@@ -1150,11 +1150,16 @@ exprfmt(Fmt *f, Node *n, int prec)
 		return fmtprint(f, "%N{ %,H }", n->right, n->list);
 
 	case OPTRLIT:
+		if (fmtmode == FExp && n->left->right->implicit == Implicit) 
+			return fmtprint(f, "%N", n->left);
 		return fmtprint(f, "&%N", n->left);
 
 	case OSTRUCTLIT:
 		if (fmtmode == FExp) {   // requires special handling of field names
-			fmtprint(f, "%T{", n->type);
+			if(n->right->implicit == Implicit)
+				fmtstrcpy(f, "{");
+			else 
+				fmtprint(f, "%T{", n->type);
 			for(l=n->list; l; l=l->next) {
 				// another special case: if n->left is an embedded field of builtin type,
 				// it needs to be non-qualified.  Can't figure that out in %S, so do it here
@@ -1411,7 +1416,7 @@ nodedump(Fmt *fp, Node *n)
 		fmtprint(fp, "%O-%O%J", n->op, n->etype, n);
 		break;
 	case OTYPE:
-		fmtprint(fp, "%O %S type=%T", n->op, n->sym, n->type);
+		fmtprint(fp, "%O %S%J type=%T", n->op, n->sym, n, n->type);
 		if(recur && n->type == T && n->ntype) {
 			indent(fp);
 			fmtprint(fp, "%O-ntype%N", n->op, n->ntype);

src/cmd/gc/go.h

@@ -217,6 +217,13 @@ enum
 	EscNever,
 };
 
+enum
+{
+	Explicit,
+	Implicit,  // don't print in output
+	ImplPtr,   // OIND added by &T{ ... } literal
+};
+
 struct	Node
 {
 	// Tree structure.
@@ -252,7 +259,7 @@ struct	Node
 	uchar	used;
 	uchar	isddd;
 	uchar	readonly;
-	uchar	implicit;	// don't show in printout
+	uchar	implicit;	// Explicit, Implicit, ImplPtr. 
 	uchar	addrtaken;	// address taken, even if not moved to heap
 	uchar	dupok;	// duplicate definitions ok (for func)
 

src/cmd/gc/go.y

@@ -808,7 +808,7 @@ uexpr:
 			// Special case for &T{...}: turn into (*T){...}.
 			$$ = $2;
 			$$->right = nod(OIND, $$->right, N);
-			$$->right->implicit = 1;
+			$$->right->implicit = ImplPtr;
 		} else {
 			$$ = nod(OADDR, $2, N);
 		}

src/cmd/gc/typecheck.c

@@ -2047,10 +2047,9 @@ typecheckcomplit(Node **np)
 	n->type = t;
 	
 	if(isptr[t->etype]) {
-		// For better or worse, we don't allow pointers as
+		// For better or worse, we don't allow pointers as the composite literal type,
-		// the composite literal type, except when using
+		// except when using the &T syntax, which sets implicit to ImplPtr.
-		// the &T syntax, which sets implicit.
+		if(n->right->implicit == Explicit) {
-		if(!n->right->implicit) {
 			yyerror("invalid pointer type %T for composite literal (use &%T instead)", t, t->type);
 			goto error;
 		}

src/cmd/gc/y.tab.c

@@ -3232,7 +3232,7 @@ yyreduce:
 			// Special case for &T{...}: turn into (*T){...}.
 			(yyval.node) = (yyvsp[(2) - (2)].node);
 			(yyval.node)->right = nod(OIND, (yyval.node)->right, N);
-			(yyval.node)->right->implicit = 1;
+			(yyval.node)->right->implicit = ImplPtr;
 		} else {
 			(yyval.node) = nod(OADDR, (yyvsp[(2) - (2)].node), N);
 		}

test/fixedbugs/bug392.dir/one.go

@@ -20,3 +20,22 @@ func F3() (ret []int) { return append(ret, 1) }
 // Call of inlined method with blank receiver.
 func (_ *T) M() int { return 1 }
 func (t *T) MM() int { return t.M() }
+
+
+// One more like issue 2678
+type S struct { x, y int }
+type U []S
+
+func F4(S int) U { return U{{S,S}} }
+
+func F5() []*S {
+	return []*S{ {1,2}, { 3, 4} }
+}
+
+func F6(S int) *U {
+	return &U{{S,S}}
+}
+
+
+
+

test/fixedbugs/bug392.dir/two.go

@@ -13,6 +13,7 @@ func use() {
 	one.F1(nil)
 	one.F2(nil)
 	one.F3()
+	one.F4(1)
 
 	var t *one.T
 	t.M()