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Get rid of subst-relate incompleteness in new solver

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This commit is contained in:
Michael Goulet 2023-07-20 20:02:56 +00:00
parent 8164cdb9ee
commit e32011209d
1 changed files with 12 additions and 9 deletions
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21
compiler/rustc_trait_selection/src/solve/alias_relate.rs
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@ -66,24 +66,27 @@ pub(super) fn compute_alias_relate_goal(
Invert::Yes,
));
// Relate via args
let subst_relate_response = self
.assemble_subst_relate_candidate(param_env, alias_lhs, alias_rhs, direction);
candidates.extend(subst_relate_response);
candidates.extend(
self.assemble_subst_relate_candidate(
param_env, alias_lhs, alias_rhs, direction,
),
);
debug!(?candidates);
if let Some(merged) = self.try_merge_responses(&candidates) {
Ok(merged)
} else {
// When relating two aliases and we have ambiguity, we prefer
// relating the generic arguments of the aliases over normalizing
// them. This is necessary for inference during typeck.
// When relating two aliases and we have ambiguity, if both
// aliases can be normalized to something, we prefer
// "bidirectionally normalizing" both of them within the same
// candidate.
//
// See <https://github.com/rust-lang/trait-system-refactor-initiative/issues/25>.
//
// As this is incomplete, we must not do so during coherence.
match self.solver_mode() {
SolverMode::Normal => {
if let Ok(subst_relate_response) = subst_relate_response {
Ok(subst_relate_response)
} else if let Ok(bidirectional_normalizes_to_response) = self
if let Ok(bidirectional_normalizes_to_response) = self
.assemble_bidirectional_normalizes_to_candidate(
param_env, lhs, rhs, direction,
)