bjoernager/rust
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Rewrite dropck

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This commit is contained in:
Boxy 2024-07-01 21:43:00 +01:00
parent 1f41fbe0ef
commit 6a00008276
10 changed files with 265 additions and 367 deletions
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34
compiler/rustc_hir_analysis/src/check/dropck.rs
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@ -6,10 +6,10 @@ use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{codes::*, struct_span_code_err, ErrorGuaranteed};
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
use rustc_infer::traits::ObligationCauseCode;
use rustc_infer::traits::{ObligationCause, ObligationCauseCode};
use rustc_middle::ty::util::CheckRegions;
use rustc_middle::ty::GenericArgsRef;
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::ty::{GenericArgsRef, Ty};
use rustc_trait_selection::regions::InferCtxtRegionExt;
use rustc_trait_selection::traits::{self, ObligationCtxt};
@ -115,8 +115,9 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
Err(err.emit())
}
/// Confirms that every predicate imposed by dtor_predicates is
/// implied by assuming the predicates attached to self_type_did.
/// Confirms that all predicates defined on the `Drop` impl (`drop_impl_def_id`) are able to be
/// proven from within `adt_def_id`'s environment. I.e. all the predicates on the impl are
/// implied by the ADT being well formed.
fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
tcx: TyCtxt<'tcx>,
drop_impl_def_id: LocalDefId,
@ -126,6 +127,8 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
let infcx = tcx.infer_ctxt().build();
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
let impl_span = tcx.def_span(drop_impl_def_id.to_def_id());
// Take the param-env of the adt and instantiate the args that show up in
// the implementation's self type. This gives us the assumptions that the
// self ty of the implementation is allowed to know just from it being a
@ -135,14 +138,27 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
// We don't need to normalize this param-env or anything, since we're only
// instantiating it with free params, so no additional param-env normalization
// can occur on top of what has been done in the param_env query itself.
let param_env =
//
// Note: Ideally instead of instantiating the `ParamEnv` with the arguments from the impl ty we
// could instead use identity args for the adt. Unfortunately this would cause any errors to
// reference the params from the ADT instead of from the impl which is bad UX. To resolve
// this we "rename" the ADT's params to be the impl's params which should not affect behaviour.
let impl_adt_ty = Ty::new_adt(tcx, tcx.adt_def(adt_def_id), adt_to_impl_args);
let adt_env =
ty::EarlyBinder::bind(tcx.param_env(adt_def_id)).instantiate(tcx, adt_to_impl_args);
for (pred, span) in tcx.predicates_of(drop_impl_def_id).instantiate_identity(tcx) {
let fresh_impl_args = infcx.fresh_args_for_item(impl_span, drop_impl_def_id.to_def_id());
let fresh_adt_ty =
tcx.impl_trait_ref(drop_impl_def_id).unwrap().instantiate(tcx, fresh_impl_args).self_ty();
ocx.eq(&ObligationCause::dummy_with_span(impl_span), adt_env, fresh_adt_ty, impl_adt_ty)
.unwrap();
for (clause, span) in tcx.predicates_of(drop_impl_def_id).instantiate(tcx, fresh_impl_args) {
let normalize_cause = traits::ObligationCause::misc(span, adt_def_id);
let pred = ocx.normalize(&normalize_cause, param_env, pred);
let pred = ocx.normalize(&normalize_cause, adt_env, clause);
let cause = traits::ObligationCause::new(span, adt_def_id, ObligationCauseCode::DropImpl);
ocx.register_obligation(traits::Obligation::new(tcx, cause, param_env, pred));
ocx.register_obligation(traits::Obligation::new(tcx, cause, adt_env, pred));
}
// All of the custom error reporting logic is to preserve parity with the old
@ -176,7 +192,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
return Err(guar.unwrap());
}
let errors = ocx.infcx.resolve_regions(&OutlivesEnvironment::new(param_env));
let errors = ocx.infcx.resolve_regions(&OutlivesEnvironment::new(adt_env));
if !errors.is_empty() {
let mut guar = None;
for error in errors {