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Don't codegen impossible to satisfy impls

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This commit is contained in:
Michael Goulet 2023-03-14 01:08:48 +00:00
parent f1b1ed7e18
commit b36bbb0266
2 changed files with 28 additions and 0 deletions
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15
compiler/rustc_monomorphize/src/collector.rs
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@ -1326,6 +1326,21 @@ fn create_mono_items_for_default_impls<'tcx>(
return;
}
// Unlike 'lazy' monomorphization that begins by collecting items transitively
// called by `main` or other global items, when eagerly monomorphizing impl
// items, we never actually check that the predicates of this impl are satisfied
// in a empty reveal-all param env (i.e. with no assumptions).
//
// Even though this impl has no substitutions, because we don't consider higher-
// ranked predicates such as `for<'a> &'a mut [u8]: Copy` to be trivially false,
// we must now check that the impl has no impossible-to-satisfy predicates.
if tcx.subst_and_check_impossible_predicates((
item.owner_id.to_def_id(),
&InternalSubsts::identity_for_item(tcx, item.owner_id.to_def_id()),
)) {
return;
}
let Some(trait_ref) = tcx.impl_trait_ref(item.owner_id) else {
return;
};