bjoernager/rust
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Auto merge of #111029 - Nilstrieb:when-the-errs-are-too-big, r=petrochenkov

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Shrink `SelectionError` a lot

`SelectionError` used to be 80 bytes (on 64 bit). That's quite big. Especially because the selection cache contained `Result<_, SelectionError>. The Ok type is only 32 bytes, so the 80 bytes significantly inflate the size of the cache.

Most variants of the `SelectionError` seem to be hard errors, only `Unimplemented` shows up in practice (for cranelift-codegen, it occupies 23.4% of all cache entries). We can just box away the biggest variant, `OutputTypeParameterMismatch`, to get the size down to 16 bytes, well within the size of the Ok type inside the cache.
This commit is contained in:
bors 2023-05-11 08:43:38 +00:00
commit f8d8ffa2eb
5 changed files with 32 additions and 14 deletions
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13
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View file

@ -28,6 +28,7 @@ use rustc_hir::{GenericParam, Item, Node};
use rustc_infer::infer::error_reporting::TypeErrCtxt;
use rustc_infer::infer::{InferOk, TypeTrace};
use rustc_middle::traits::select::OverflowError;
use rustc_middle::traits::SelectionOutputTypeParameterMismatch;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
@ -1087,17 +1088,21 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}
}
OutputTypeParameterMismatch(
OutputTypeParameterMismatch(box SelectionOutputTypeParameterMismatch {
found_trait_ref,
expected_trait_ref,
terr @ TypeError::CyclicTy(_),
) => self.report_type_parameter_mismatch_cyclic_type_error(
terr: terr @ TypeError::CyclicTy(_),
}) => self.report_type_parameter_mismatch_cyclic_type_error(
&obligation,
found_trait_ref,
expected_trait_ref,
terr,
),
OutputTypeParameterMismatch(found_trait_ref, expected_trait_ref, _) => {
OutputTypeParameterMismatch(box SelectionOutputTypeParameterMismatch {
found_trait_ref,
expected_trait_ref,
terr: _,
}) => {
match self.report_type_parameter_mismatch_error(
&obligation,
span,

13
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -10,6 +10,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir::lang_items::LangItem;
use rustc_infer::infer::LateBoundRegionConversionTime::HigherRankedType;
use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
use rustc_middle::traits::SelectionOutputTypeParameterMismatch;
use rustc_middle::ty::{
self, Binder, GenericParamDefKind, InternalSubsts, SubstsRef, ToPolyTraitRef, ToPredicate,
TraitRef, Ty, TyCtxt, TypeVisitableExt,
@ -811,7 +812,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
fn confirm_poly_trait_refs(
&mut self,
obligation: &TraitObligation<'tcx>,
expected_trait_ref: ty::PolyTraitRef<'tcx>,
self_ty_trait_ref: ty::PolyTraitRef<'tcx>,
) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
let obligation_trait_ref = obligation.predicate.to_poly_trait_ref();
// Normalize the obligation and expected trait refs together, because why not
@ -822,7 +823,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
(obligation_trait_ref, expected_trait_ref),
(obligation_trait_ref, self_ty_trait_ref),
)
});
@ -834,7 +835,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligations.extend(nested);
obligations
})
.map_err(|e| OutputTypeParameterMismatch(expected_trait_ref, obligation_trait_ref, e))
.map_err(|terr| {
OutputTypeParameterMismatch(Box::new(SelectionOutputTypeParameterMismatch {
expected_trait_ref: obligation_trait_ref,
found_trait_ref: expected_trait_ref,
terr,
}))
})
}
fn confirm_trait_upcasting_unsize_candidate(