Improve `matrix` conversion rules

src/check_expr.cpp

@@ -818,6 +818,10 @@ i64 check_distance_between_types(CheckerContext *c, Operand *operand, Type *type
 	}
 	
 	if (is_type_matrix(dst)) {
+		if (are_types_identical(src, dst)) {
+			return 5;
+		}
+
 		Type *dst_elem = base_array_type(dst);
 		i64 distance = check_distance_between_types(c, operand, dst_elem);
 		if (distance >= 0) {