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.
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@ -19,6 +19,7 @@ use rustc_middle::ty::{self, TyCtxt};
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/// obligations *could be* resolved if we wanted to.
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/// obligations *could be* resolved if we wanted to.
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///
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///
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/// This also expects that `trait_ref` is fully normalized.
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/// This also expects that `trait_ref` is fully normalized.
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#[instrument(level = "debug", skip(tcx))]
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pub fn codegen_fulfill_obligation<'tcx>(
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pub fn codegen_fulfill_obligation<'tcx>(
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tcx: TyCtxt<'tcx>,
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tcx: TyCtxt<'tcx>,
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(param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
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(param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
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@ -27,11 +28,6 @@ pub fn codegen_fulfill_obligation<'tcx>(
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let trait_ref = tcx.erase_regions(trait_ref);
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let trait_ref = tcx.erase_regions(trait_ref);
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// We expect the input to be fully normalized.
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// We expect the input to be fully normalized.
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debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));
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debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));
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debug!(
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"codegen_fulfill_obligation(trait_ref={:?}, def_id={:?})",
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(param_env, trait_ref),
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trait_ref.def_id()
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);
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// Do the initial selection for the obligation. This yields the
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// Do the initial selection for the obligation. This yields the
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// shallow result we are looking for -- that is, what specific impl.
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// shallow result we are looking for -- that is, what specific impl.
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@ -80,25 +76,22 @@ pub fn codegen_fulfill_obligation<'tcx>(
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}
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}
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};
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};
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debug!("fulfill_obligation: selection={:?}", selection);
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debug!(?selection);
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// Currently, we use a fulfillment context to completely resolve
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// Currently, we use a fulfillment context to completely resolve
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// all nested obligations. This is because they can inform the
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// all nested obligations. This is because they can inform the
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// inference of the impl's type parameters.
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// inference of the impl's type parameters.
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let mut fulfill_cx = FulfillmentContext::new();
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let mut fulfill_cx = FulfillmentContext::new();
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let impl_source = selection.map(|predicate| {
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let impl_source = selection.map(|predicate| {
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debug!("fulfill_obligation: register_predicate_obligation {:?}", predicate);
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fulfill_cx.register_predicate_obligation(&infcx, predicate);
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fulfill_cx.register_predicate_obligation(&infcx, predicate);
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});
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});
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let impl_source = drain_fulfillment_cx_or_panic(&infcx, &mut fulfill_cx, impl_source);
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let impl_source = drain_fulfillment_cx_or_panic(&infcx, &mut fulfill_cx, impl_source);
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// There should be no opaque types during codegen, they all get revealed.
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// Opaque types may have gotten their hidden types constrained, but we can ignore them safely
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let opaque_types = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
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// as they will get constrained elsewhere, too.
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if !opaque_types.is_empty() {
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let _opaque_types = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
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bug!("{:#?}", opaque_types);
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}
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debug!("Cache miss: {:?} => {:?}", trait_ref, impl_source);
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debug!("Cache miss: {trait_ref:?} => {impl_source:?}");
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Ok(&*tcx.arena.alloc(impl_source))
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Ok(&*tcx.arena.alloc(impl_source))
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})
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})
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}
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}
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24
src/test/ui/type-alias-impl-trait/assoc-projection-ice.rs
Normal file
24
src/test/ui/type-alias-impl-trait/assoc-projection-ice.rs
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@ -0,0 +1,24 @@
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#![feature(type_alias_impl_trait)]
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// build-pass
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trait T { type Item; }
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type Alias<'a> = impl T<Item = &'a ()>;
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struct S;
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impl<'a> T for &'a S {
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type Item = &'a ();
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}
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fn filter_positive<'a>() -> Alias<'a> {
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&S
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}
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fn with_positive(fun: impl Fn(Alias<'_>)) {
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fun(filter_positive());
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}
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fn main() {
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with_positive(|_| ());
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}
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