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Don't install default opaque projection predicates in RPITIT associated type's param-env

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This commit is contained in:
Michael Goulet 2023-03-16 01:11:04 +00:00
parent 0949da8f4e
commit ff7c3b854d
12 changed files with 78 additions and 21 deletions
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22
compiler/rustc_ty_utils/src/ty.rs
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@ -117,16 +117,22 @@ fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
/// See `ParamEnv` struct definition for details.
fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
// When computing the param_env of an RPITIT, copy param_env of the containing function. The
// synthesized associated type doesn't have extra predicates to assume.
if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
return tcx.param_env(fn_def_id);
}
// Compute the bounds on Self and the type parameters.
let ty::InstantiatedPredicates { mut predicates, .. } =
tcx.predicates_of(def_id).instantiate_identity(tcx);
// When computing the param_env of an RPITIT, use predicates of the containing function,
// *except* for the additional assumption that the RPITIT normalizes to the trait method's
// default opaque type. This is needed to properly check the item bounds of the assoc
// type hold (`check_type_bounds`), since that method already installs a similar projection
// bound, so they will conflict.
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): I don't like this, we should
// at least be making sure that the generics in RPITITs and their parent fn don't
// get out of alignment, or else we do actually need to substitute these predicates.
if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
predicates = tcx.predicates_of(fn_def_id).instantiate_identity(tcx).predicates;
}
// Finally, we have to normalize the bounds in the environment, in
// case they contain any associated type projections. This process
// can yield errors if the put in illegal associated types, like
@ -160,7 +166,9 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
}
let local_did = def_id.as_local();
let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): This isn't correct for
// RPITITs in const trait fn.
let hir_id = local_did.and_then(|def_id| tcx.opt_local_def_id_to_hir_id(def_id));
// FIXME(consts): This is not exactly in line with the constness query.
let constness = match hir_id {