cmd/gc: silence redundant error prints for misuse of [...]int

Fixes #4452.

R=ken2
CC=golang-dev
https://golang.org/cl/7241065

src/cmd/gc/align.c

@@ -253,8 +253,12 @@ dowidth(Type *t)
 			checkwidth(t->type);
 			t->align = widthptr;
 		}
-		else if(t->bound == -100)
-			yyerror("use of [...] array outside of array literal");
+		else if(t->bound == -100) {
+			if(!t->broke) {
+				yyerror("use of [...] array outside of array literal");
+				t->broke = 1;
+			}
+		}
 		else
 			fatal("dowidth %T", t);	// probably [...]T
 		break;

src/cmd/gc/const.c

@@ -240,7 +240,8 @@ convlit1(Node **np, Type *t, int explicit)
 
 bad:
 	if(!n->diag) {
-		yyerror("cannot convert %N to type %T", n, t);
+		if(!t->broke)
+			yyerror("cannot convert %N to type %T", n, t);
 		n->diag = 1;
 	}
 	if(isideal(n->type)) {

src/cmd/gc/typecheck.c

@@ -377,8 +377,11 @@ reswitch:
 			t->bound = -1;	// slice
 		} else if(l->op == ODDD) {
 			t->bound = -100;	// to be filled in
-			if(!(top&Ecomplit))
+			if(!(top&Ecomplit) && !n->diag) {
+				t->broke = 1;
+				n->diag = 1;
 				yyerror("use of [...] array outside of array literal");
+			}
 		} else {
 			l = typecheck(&n->left, Erv);
 			switch(consttype(l)) {
@@ -1028,8 +1031,11 @@ reswitch:
 		defaultlit(&n->left, T);
 		l = n->left;
 		if(l->op == OTYPE) {
-			if(n->isddd || l->type->bound == -100)
-				yyerror("invalid use of ... in type conversion", l);
+			if(n->isddd || l->type->bound == -100) {
+				if(!l->type->broke)
+					yyerror("invalid use of ... in type conversion", l);
+				n->diag = 1;
+			}
 			// pick off before type-checking arguments
 			ok |= Erv;
 			// turn CALL(type, arg) into CONV(arg) w/ type
@@ -1335,7 +1341,10 @@ reswitch:
 		if((t = n->left->type) == T || n->type == T)
 			goto error;
 		if((n->op = convertop(t, n->type, &why)) == 0) {
-			yyerror("cannot convert %lN to type %T%s", n->left, n->type, why);
+			if(!n->diag && !n->type->broke) {
+				yyerror("cannot convert %lN to type %T%s", n->left, n->type, why);
+				n->diag = 1;
+			}
 			n->op = OCONV;
 		}
 		switch(n->op) {

test/fixedbugs/issue4452.go

+// errorcheck
+
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 4452. Used to print many errors, now just one.
+
+package main
+
+func main() {
+	_ = [...]int(4) // ERROR "use of \[\.\.\.\] array outside of array literal"
+}