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Rollup merge of #95471 - oli-obk:tait_ice, r=estebank

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Don't ICE when opaque types get their hidden type constrained again.

Contrary to popular belief, `codegen_fulfill_obligation` does not get used solely in codegen, so we cannot rely on `param_env` being set to RevealAll and thus revealing the hidden types instead of constraining them.

Fixes #89312 (for real this time)
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Dylan DPC 2022-03-31 04:57:26 +02:00 • committed by GitHub
commit 64a3767fee
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2 changed files with 30 additions and 13 deletions
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19
compiler/rustc_trait_selection/src/traits/codegen.rs
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@ -19,6 +19,7 @@ use rustc_middle::ty::{self, TyCtxt};
/// obligations *could be* resolved if we wanted to.
///
/// This also expects that `trait_ref` is fully normalized.
#[instrument(level = "debug", skip(tcx))]
pub fn codegen_fulfill_obligation<'tcx>(
tcx: TyCtxt<'tcx>,
(param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
@ -27,11 +28,6 @@ pub fn codegen_fulfill_obligation<'tcx>(
let trait_ref = tcx.erase_regions(trait_ref);
// We expect the input to be fully normalized.
debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));
debug!(
"codegen_fulfill_obligation(trait_ref={:?}, def_id={:?})",
(param_env, trait_ref),
trait_ref.def_id()
);
// Do the initial selection for the obligation. This yields the
// shallow result we are looking for -- that is, what specific impl.
@ -80,25 +76,22 @@ pub fn codegen_fulfill_obligation<'tcx>(
}
};
debug!("fulfill_obligation: selection={:?}", selection);
debug!(?selection);
// Currently, we use a fulfillment context to completely resolve
// all nested obligations. This is because they can inform the
// inference of the impl's type parameters.
let mut fulfill_cx = FulfillmentContext::new();
let impl_source = selection.map(|predicate| {
debug!("fulfill_obligation: register_predicate_obligation {:?}", predicate);
fulfill_cx.register_predicate_obligation(&infcx, predicate);
});
let impl_source = drain_fulfillment_cx_or_panic(&infcx, &mut fulfill_cx, impl_source);
// There should be no opaque types during codegen, they all get revealed.
let opaque_types = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
if !opaque_types.is_empty() {
bug!("{:#?}", opaque_types);
}
// Opaque types may have gotten their hidden types constrained, but we can ignore them safely
// as they will get constrained elsewhere, too.
let _opaque_types = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
debug!("Cache miss: {:?} => {:?}", trait_ref, impl_source);
debug!("Cache miss: {trait_ref:?} => {impl_source:?}");
Ok(&*tcx.arena.alloc(impl_source))
})
}