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Rollup merge of #112781 - compiler-errors:new-solver-tait-overlaps-hidden, r=lcnr

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Don't consider TAIT normalizable to hidden ty if it would result in impossible item bounds

See test for example where we shouldn't consider it possible to alias-relate a TAIT and hidden type.

r? `@lcnr`
This commit is contained in:
Michael Goulet 2023-06-19 17:53:35 -07:00 • committed by GitHub
commit 3171c989ef
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GPG key ID: 4AEE18F83AFDEB23
5 changed files with 39 additions and 13 deletions
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13
compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
View file

@ -835,13 +835,15 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn add_item_bounds_for_hidden_type(
&mut self,
opaque_type_key: OpaqueTypeKey<'tcx>,
opaque_def_id: DefId,
opaque_substs: ty::SubstsRef<'tcx>,
param_env: ty::ParamEnv<'tcx>,
hidden_ty: Ty<'tcx>,
) {
let mut obligations = Vec::new();
self.infcx.add_item_bounds_for_hidden_type(
opaque_type_key,
opaque_def_id,
opaque_substs,
ObligationCause::dummy(),
param_env,
hidden_ty,
@ -872,7 +874,12 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
ecx.eq(param_env, a, b)?;
}
ecx.eq(param_env, candidate_ty, ty)?;
ecx.add_item_bounds_for_hidden_type(candidate_key, param_env, candidate_ty);
ecx.add_item_bounds_for_hidden_type(
candidate_key.def_id.to_def_id(),
candidate_key.substs,
param_env,
candidate_ty,
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
},
|r| CandidateKind::Candidate { name: "opaque type storage".into(), result: *r },

24
compiler/rustc_trait_selection/src/solve/opaques.rs
View file

@ -20,8 +20,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
let Some(opaque_ty_def_id) = opaque_ty.def_id.as_local() else {
return Err(NoSolution);
};
let opaque_ty =
ty::OpaqueTypeKey { def_id: opaque_ty_def_id, substs: opaque_ty.substs };
// FIXME: at some point we should call queries without defining
// new opaque types but having the existing opaque type definitions.
// This will require moving this below "Prefer opaques registered already".
@ -41,7 +39,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
Ok(()) => {}
}
// Prefer opaques registered already.
let matches = self.unify_existing_opaque_tys(goal.param_env, opaque_ty, expected);
let opaque_type_key =
ty::OpaqueTypeKey { def_id: opaque_ty_def_id, substs: opaque_ty.substs };
let matches =
self.unify_existing_opaque_tys(goal.param_env, opaque_type_key, expected);
if !matches.is_empty() {
if let Some(response) = self.try_merge_responses(&matches) {
return Ok(response);
@ -50,11 +51,24 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
}
// Otherwise, define a new opaque type
self.insert_hidden_type(opaque_ty, goal.param_env, expected)?;
self.add_item_bounds_for_hidden_type(opaque_ty, goal.param_env, expected);
self.insert_hidden_type(opaque_type_key, goal.param_env, expected)?;
self.add_item_bounds_for_hidden_type(
opaque_ty.def_id,
opaque_ty.substs,
goal.param_env,
expected,
);
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
(Reveal::UserFacing, SolverMode::Coherence) => {
// An impossible opaque type bound is the only way this goal will fail
// e.g. assigning `impl Copy := NotCopy`
self.add_item_bounds_for_hidden_type(
opaque_ty.def_id,
opaque_ty.substs,
goal.param_env,
expected,
);
self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
}
(Reveal::All, _) => {