introduce enter_forall
This commit is contained in:
Boxy
@@ -31,103 +31,109 @@ impl<'tcx> InferCtxtSelectExt<'tcx> for InferCtxt<'tcx> {
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) -> SelectionResult<'tcx, Selection<'tcx>> {
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assert!(self.next_trait_solver());
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let trait_goal = Goal::new(
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self.tcx,
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obligation.param_env,
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self.instantiate_binder_with_placeholders(obligation.predicate),
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);
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// FIXME(tree_universes): leaking universes?
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self.enter_forall(obligation.predicate, |pred| {
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let trait_goal = Goal::new(self.tcx, obligation.param_env, pred);
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let (result, _) = EvalCtxt::enter_root(self, GenerateProofTree::Never, |ecx| {
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let goal = Goal::new(ecx.tcx(), trait_goal.param_env, trait_goal.predicate);
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let (orig_values, canonical_goal) = ecx.canonicalize_goal(goal);
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let mut candidates = ecx.compute_canonical_trait_candidates(canonical_goal);
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let (result, _) = EvalCtxt::enter_root(self, GenerateProofTree::Never, |ecx| {
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let goal = Goal::new(ecx.tcx(), trait_goal.param_env, trait_goal.predicate);
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let (orig_values, canonical_goal) = ecx.canonicalize_goal(goal);
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let mut candidates = ecx.compute_canonical_trait_candidates(canonical_goal);
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// pseudo-winnow
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if candidates.len() == 0 {
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return Err(SelectionError::Unimplemented);
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} else if candidates.len() > 1 {
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let mut i = 0;
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while i < candidates.len() {
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let should_drop_i = (0..candidates.len()).filter(|&j| i != j).any(|j| {
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candidate_should_be_dropped_in_favor_of(
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ecx.tcx(),
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&candidates[i],
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&candidates[j],
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)
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});
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if should_drop_i {
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candidates.swap_remove(i);
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} else {
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i += 1;
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if i > 1 {
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return Ok(None);
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// pseudo-winnow
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if candidates.len() == 0 {
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return Err(SelectionError::Unimplemented);
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} else if candidates.len() > 1 {
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let mut i = 0;
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while i < candidates.len() {
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let should_drop_i = (0..candidates.len()).filter(|&j| i != j).any(|j| {
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candidate_should_be_dropped_in_favor_of(
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ecx.tcx(),
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&candidates[i],
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&candidates[j],
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)
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});
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if should_drop_i {
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candidates.swap_remove(i);
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} else {
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i += 1;
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if i > 1 {
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return Ok(None);
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}
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}
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}
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}
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let candidate = candidates.pop().unwrap();
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let (certainty, nested_goals) = ecx
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.instantiate_and_apply_query_response(
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trait_goal.param_env,
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orig_values,
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candidate.result,
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)
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.map_err(|_| SelectionError::Unimplemented)?;
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Ok(Some((candidate, certainty, nested_goals)))
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});
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let (candidate, certainty, nested_goals) = match result {
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Ok(Some((candidate, certainty, nested_goals))) => {
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(candidate, certainty, nested_goals)
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}
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Ok(None) => return Ok(None),
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Err(e) => return Err(e),
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};
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let nested_obligations: Vec<_> = nested_goals
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.into_iter()
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.map(|goal| {
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Obligation::new(
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self.tcx,
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ObligationCause::dummy(),
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goal.param_env,
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goal.predicate,
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)
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})
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.collect();
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let goal = self.resolve_vars_if_possible(trait_goal);
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match (certainty, candidate.source) {
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// Rematching the implementation will instantiate the same nested goals that
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// would have caused the ambiguity, so we can still make progress here regardless.
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(_, CandidateSource::Impl(def_id)) => {
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rematch_impl(self, goal, def_id, nested_obligations)
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}
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// If an unsize goal is ambiguous, then we can manually rematch it to make
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// selection progress for coercion during HIR typeck. If it is *not* ambiguous,
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// but is `BuiltinImplSource::Misc`, it may have nested `Unsize` goals,
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// and we need to rematch those to detect tuple unsizing and trait upcasting.
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// FIXME: This will be wrong if we have param-env or where-clause bounds
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// with the unsize goal -- we may need to mark those with different impl
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// sources.
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(Certainty::Maybe(_), CandidateSource::BuiltinImpl(src))
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| (Certainty::Yes, CandidateSource::BuiltinImpl(src @ BuiltinImplSource::Misc))
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if self.tcx.lang_items().unsize_trait() == Some(goal.predicate.def_id()) =>
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{
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rematch_unsize(self, goal, nested_obligations, src, certainty)
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}
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// Technically some builtin impls have nested obligations, but if
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// `Certainty::Yes`, then they should've all been verified and don't
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// need re-checking.
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(Certainty::Yes, CandidateSource::BuiltinImpl(src)) => {
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Ok(Some(ImplSource::Builtin(src, nested_obligations)))
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}
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// It's fine not to do anything to rematch these, since there are no
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// nested obligations.
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(Certainty::Yes, CandidateSource::ParamEnv(_) | CandidateSource::AliasBound) => {
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Ok(Some(ImplSource::Param(nested_obligations)))
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}
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(Certainty::Maybe(_), _) => Ok(None),
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}
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let candidate = candidates.pop().unwrap();
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let (certainty, nested_goals) = ecx
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.instantiate_and_apply_query_response(
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trait_goal.param_env,
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orig_values,
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candidate.result,
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)
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.map_err(|_| SelectionError::Unimplemented)?;
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Ok(Some((candidate, certainty, nested_goals)))
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});
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let (candidate, certainty, nested_goals) = match result {
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Ok(Some((candidate, certainty, nested_goals))) => (candidate, certainty, nested_goals),
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Ok(None) => return Ok(None),
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Err(e) => return Err(e),
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};
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let nested_obligations: Vec<_> = nested_goals
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.into_iter()
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.map(|goal| {
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Obligation::new(self.tcx, ObligationCause::dummy(), goal.param_env, goal.predicate)
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})
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.collect();
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let goal = self.resolve_vars_if_possible(trait_goal);
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match (certainty, candidate.source) {
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// Rematching the implementation will instantiate the same nested goals that
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// would have caused the ambiguity, so we can still make progress here regardless.
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(_, CandidateSource::Impl(def_id)) => {
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rematch_impl(self, goal, def_id, nested_obligations)
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}
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// If an unsize goal is ambiguous, then we can manually rematch it to make
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// selection progress for coercion during HIR typeck. If it is *not* ambiguous,
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// but is `BuiltinImplSource::Misc`, it may have nested `Unsize` goals,
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// and we need to rematch those to detect tuple unsizing and trait upcasting.
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// FIXME: This will be wrong if we have param-env or where-clause bounds
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// with the unsize goal -- we may need to mark those with different impl
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// sources.
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(Certainty::Maybe(_), CandidateSource::BuiltinImpl(src))
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| (Certainty::Yes, CandidateSource::BuiltinImpl(src @ BuiltinImplSource::Misc))
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if self.tcx.lang_items().unsize_trait() == Some(goal.predicate.def_id()) =>
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{
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rematch_unsize(self, goal, nested_obligations, src, certainty)
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}
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// Technically some builtin impls have nested obligations, but if
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// `Certainty::Yes`, then they should've all been verified and don't
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// need re-checking.
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(Certainty::Yes, CandidateSource::BuiltinImpl(src)) => {
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Ok(Some(ImplSource::Builtin(src, nested_obligations)))
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}
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// It's fine not to do anything to rematch these, since there are no
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// nested obligations.
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(Certainty::Yes, CandidateSource::ParamEnv(_) | CandidateSource::AliasBound) => {
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Ok(Some(ImplSource::Param(nested_obligations)))
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}
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(Certainty::Maybe(_), _) => Ok(None),
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}
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})
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}
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}
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