Gracefully handle returning NIL though a bad type.

tools/qfcc/source/expr.c

@@ -2138,6 +2138,8 @@ return_expr (function_t *f, expr_t *e)
 		if (e->type == ex_nil) {
 			t = f->def->type->aux_type;
 			e->type = expr_types[t->type];
+			if (e->type == ex_nil)
+				return error (e, "invalid return type for NIL");
 		} else {
 			if (!options.traditional)
 				return error (e, "void value not ignored as it ought to be");

tools/qfcc/test/nil.r

@@ -1 +1,18 @@
 Class x = NIL;
+
+struct Size {
+	integer x;
+	integer y;
+};
+typedef struct Size Size;
+
+@interface foo
+-(Size) bar;
+@end
+@implementation foo
+-(Size) bar
+{
+	local Size s;
+	return NIL;
+}
+@end