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Bubble up nested goals from equation in predicates_for_object_candidate

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This commit is contained in:
Michael Goulet 2023-07-26 22:29:52 +00:00
parent 4734ac0943
commit 57407a3555
3 changed files with 44 additions and 23 deletions
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31
compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
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@ -3,6 +3,7 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_hir::{def_id::DefId, Movability, Mutability};
use rustc_infer::traits::query::NoSolution;
use rustc_middle::traits::solve::Goal;
use rustc_middle::ty::{
self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
};
@ -345,7 +346,7 @@ pub(in crate::solve) fn predicates_for_object_candidate<'tcx>(
param_env: ty::ParamEnv<'tcx>,
trait_ref: ty::TraitRef<'tcx>,
object_bound: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Vec<ty::Clause<'tcx>> {
) -> Vec<Goal<'tcx, ty::Predicate<'tcx>>> {
let tcx = ecx.tcx();
let mut requirements = vec![];
requirements.extend(
@ -376,17 +377,22 @@ pub(in crate::solve) fn predicates_for_object_candidate<'tcx>(
}
}
requirements.fold_with(&mut ReplaceProjectionWith {
ecx,
param_env,
mapping: replace_projection_with,
})
let mut folder =
ReplaceProjectionWith { ecx, param_env, mapping: replace_projection_with, nested: vec![] };
let folded_requirements = requirements.fold_with(&mut folder);
folder
.nested
.into_iter()
.chain(folded_requirements.into_iter().map(|clause| Goal::new(tcx, param_env, clause)))
.collect()
}
struct ReplaceProjectionWith<'a, 'tcx> {
ecx: &'a EvalCtxt<'a, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
mapping: FxHashMap<DefId, ty::PolyProjectionPredicate<'tcx>>,
nested: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceProjectionWith<'_, 'tcx> {
@ -402,13 +408,12 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceProjectionWith<'_, 'tcx> {
// but the where clauses we instantiated are not. We can solve this by instantiating
// the binder at the usage site.
let proj = self.ecx.instantiate_binder_with_infer(*replacement);
// FIXME: Technically this folder could be fallible?
let nested = self
.ecx
.eq_and_get_goals(self.param_env, alias_ty, proj.projection_ty)
.expect("expected to be able to unify goal projection with dyn's projection");
// FIXME: Technically we could register these too..
assert!(nested.is_empty(), "did not expect unification to have any nested goals");
// FIXME: Technically this equate could be fallible...
self.nested.extend(
self.ecx
.eq_and_get_goals(self.param_env, alias_ty, proj.projection_ty)
.expect("expected to be able to unify goal projection with dyn's projection"),
);
proj.term.ty().unwrap()
} else {
ty.super_fold_with(self)