Fix parsing bug on `bit_set[;x]`

src/parser.cpp

@@ -2885,6 +2885,10 @@ gb_internal Ast *parse_operand(AstFile *f, bool lhs) {
 		elem = parse_expr(f, true);
 		f->allow_range = prev_allow_range;
 
+		if (elem == nullptr) {
+			syntax_error(token, "Expected a type or range, got nothing");
+		}
+
 		if (allow_token(f, Token_Semicolon)) {
 			underlying = parse_type(f);
 		} else if (allow_token(f, Token_Comma)) {
@@ -2894,6 +2898,7 @@ gb_internal Ast *parse_operand(AstFile *f, bool lhs) {
 			underlying = parse_type(f);
 		}
 
+
 		expect_token(f, Token_CloseBracket);
 		return ast_bit_set_type(f, token, elem, underlying);
 	}