Macro solver_exhaustiveness_check 

macro_rules! solver_exhaustiveness_check {
    (
        $dollar:tt, $solver_ty:ident, $id_ty:ident,
        [ $($id_tys:ident),* ]

        $( $lang_item:ident, $target:ident $(, $solver:ident)?; )*
    ) => { ... };
}