error: lifetime parameters must be declared prior to type and const parameters
  --> $DIR/issue-80512-param-reordering-with-defaults.rs:3:18
   |
LL | struct S<T = (), 'a>(&'a T);
   |         ---------^^- help: reorder the parameters: lifetimes, then consts and types: `<'a, T = ()>`

error: aborting due to previous error