message: remove `is_noop`
diff: match $intrinsic {
  $(
  sym::$name => {
  - assert!($substs.is_noop());
  + assert!($substs.is_empty());
  if let [$(ref $arg),*] = *$args {
  let ($($arg,)*) = (
  $(codegen_operand($fx, $arg),)*
  