bjoernager/rust
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Rollup merge of #114117 - compiler-errors:return-to-uniq, r=lcnr

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Restore region uniquification in the new solver 🎉

All of the bugs that were "due" to uniquification have been settled via other means (e.g. bidirectional alias-relate, param-env incompleteness, etc).

Firstly, revert the functional changes in #110180. 😸

Secondly, we need to ignore regions when considering if a goal has changed (the "has_changed" boolean returned from `evaluate_goal`) -- otherwise, because we're doing region uniquification, we may perpetually consider a goal to be changed. See the UI test I committed for an explanation.
This commit is contained in:
Guillaume Gomez 2023-07-27 16:05:15 +02:00 • committed by GitHub
commit 0bebfa39cc
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4 changed files with 48 additions and 13 deletions
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25
compiler/rustc_trait_selection/src/solve/canonicalize.rs
View file

@ -125,9 +125,8 @@ impl<'a, 'tcx> Canonicalizer<'a, 'tcx> {
// - var_infos: [E0, U1, E1, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 6
// - var_infos: [E0, U1, E1, U1, E1, E2, U2], curr_compressed_uv: 2, next_orig_uv: -
//
// This algorithm runs in `O(nm)` where `n` is the number of different universe
// indices in the input and `m` is the number of canonical variables.
// This should be fine as both `n` and `m` are expected to be small.
// This algorithm runs in `O(n²)` where `n` is the number of different universe
// indices in the input. This should be fine as `n` is expected to be small.
let mut curr_compressed_uv = ty::UniverseIndex::ROOT;
let mut existential_in_new_uv = false;
let mut next_orig_uv = Some(ty::UniverseIndex::ROOT);
@ -263,14 +262,18 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
ty::ReError(_) => return r,
};
let var = ty::BoundVar::from(
self.variables.iter().position(|&v| v == r.into()).unwrap_or_else(|| {
let var = self.variables.len();
self.variables.push(r.into());
self.primitive_var_infos.push(CanonicalVarInfo { kind });
var
}),
);
let existing_bound_var = match self.canonicalize_mode {
CanonicalizeMode::Input => None,
CanonicalizeMode::Response { .. } => {
self.variables.iter().position(|&v| v == r.into()).map(ty::BoundVar::from)
}
};
let var = existing_bound_var.unwrap_or_else(|| {
let var = ty::BoundVar::from(self.variables.len());
self.variables.push(r.into());
self.primitive_var_infos.push(CanonicalVarInfo { kind });
var
});
let br = ty::BoundRegion { var, kind: BrAnon(None) };
ty::Region::new_late_bound(self.interner(), self.binder_index, br)
}

2
compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
View file

@ -344,7 +344,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
Ok(response) => response,
};
let has_changed = !canonical_response.value.var_values.is_identity()
let has_changed = !canonical_response.value.var_values.is_identity_modulo_regions()
|| !canonical_response.value.external_constraints.opaque_types.is_empty();
let (certainty, nested_goals) = match self.instantiate_and_apply_query_response(
goal.param_env,