mir: add `used_generic_parameters_needs_subst`
Fixes#74636.
This PR adds a `used_generic_parameters_needs_subst` helper function which checks whether a type needs substitution, but only for parameters that the `unused_generic_params` query considers used. This is used in the MIR interpreter to make the check for some pointer casts and for reflection intrinsics more precise.
I've opened this as a draft PR because this might not be the approach we want to fix this issue and we have to decide what to do about the reflection case.
r? @eddyb
cc @lcnr @wesleywiser
This commit adds a `ensure_monomorphic_enough` utility function which
checks whether a type needs substitution, but only for parameters
that the `unused_generic_params` query considers used.
`ensure_monomorphic_enough` is then used throughout interpret where
`needs_subst` checks previously existed (in particular, for some
pointer casts and for reflection intrinsics more precise).
Signed-off-by: David Wood <david@davidtw.co>
This commit disables polymorphisation to resolve regressions related to
closures which inherit unused generic parameters and are then used in
casts or reflection.
Signed-off-by: David Wood <david@davidtw.co>
This commit introduces a `FiniteBitSet` type which replaces the manual
bit manipulation which was being performed in polymorphization.
Signed-off-by: David Wood <david@davidtw.co>
This commit replaces the `-Z polymorphize-errors` debugging flag with a
`#[rustc_polymorphize_error]` attribute for use on functions.
Signed-off-by: David Wood <david@davidtw.co>
This commit normalizes function signatures for instances before
substituting, a workaround for polymorphization considering
parameters unused when they show up in the signature, but not the
body (due to being normalized).
Unfortunately, this causes test output to change with the parallel
compiler only.
Signed-off-by: David Wood <david@davidtw.co>
This commit implements the `unused_generic_params` query, an initial
version of polymorphization which detects when an item does not use
generic parameters and is being needlessly monomorphized as a result.
Signed-off-by: David Wood <david@davidtw.co>
