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Rollup merge of #129725 - compiler-errors:predicates-of, r=fmease

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Stop using `ty::GenericPredicates` for non-predicates_of queries

`GenericPredicates` is a struct of several parts: A list of of an item's own predicates, and a parent def id (and some effects related stuff, but ignore that since it's kinda irrelevant). When instantiating these generic predicates, it calls `predicates_of` on the parent and instantiates its predicates, and appends the item's own instantiated predicates too:

acb4e8b625/compiler/rustc_middle/src/ty/generics.rs (L407-L413)

Notice how this should result in a recursive set of calls to `predicates_of`... However, `GenericPredicates` is *also* misused by a bunch of *other* queries as a convenient way of passing around a list of predicates. For these queries, we don't ever set the parent def id of the `GenericPredicates`, but if we did, then this would be very easy to mistakenly call `predicates_of` instead of some other intended parent query.

Given that footgun, and the fact that we don't ever even *use* the parent def id in the `GenericPredicates` returned from queries like `explicit_super_predicates_of`, It really has no benefit over just returning `&'tcx [(Clause<'tcx>, Span)]`.

This PR additionally opts to wrap the results of `EarlyBinder`, as we've tended to use that in the return type of these kinds of queries to properly convey that the user has params to deal with, and it also gives a convenient way of iterating over a slice of things after instantiating.
This commit is contained in:
Matthias Krüger 2024-08-31 10:08:57 +02:00 • committed by GitHub
commit 5f10a99c7a
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20 changed files with 101 additions and 98 deletions
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18
compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
View file

@ -76,6 +76,24 @@ impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>> ProcessQueryValue<'
}
}
impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>>
ProcessQueryValue<'tcx, ty::EarlyBinder<'tcx, &'tcx [T]>>
for Option<DecodeIterator<'a, 'tcx, T>>
{
#[inline(always)]
fn process_decoded(
self,
tcx: TyCtxt<'tcx>,
_err: impl Fn() -> !,
) -> ty::EarlyBinder<'tcx, &'tcx [T]> {
ty::EarlyBinder::bind(if let Some(iter) = self {
tcx.arena.alloc_from_iter(iter)
} else {
&[]
})
}
}
impl<'a, 'tcx, T: Copy + Decodable<DecodeContext<'a, 'tcx>>>
ProcessQueryValue<'tcx, Option<&'tcx [T]>> for Option<DecodeIterator<'a, 'tcx, T>>
{

12
compiler/rustc_metadata/src/rmeta/encoder.rs
View file

@ -1446,8 +1446,10 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
}
if let DefKind::Trait = def_kind {
record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
record!(self.tables.explicit_super_predicates_of[def_id] <- self.tcx.explicit_super_predicates_of(def_id));
record!(self.tables.explicit_implied_predicates_of[def_id] <- self.tcx.explicit_implied_predicates_of(def_id));
record_array!(self.tables.explicit_super_predicates_of[def_id] <-
self.tcx.explicit_super_predicates_of(def_id).skip_binder());
record_array!(self.tables.explicit_implied_predicates_of[def_id] <-
self.tcx.explicit_implied_predicates_of(def_id).skip_binder());
let module_children = self.tcx.module_children_local(local_id);
record_array!(self.tables.module_children_non_reexports[def_id] <-
@ -1455,8 +1457,10 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
}
if let DefKind::TraitAlias = def_kind {
record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
record!(self.tables.explicit_super_predicates_of[def_id] <- self.tcx.explicit_super_predicates_of(def_id));
record!(self.tables.explicit_implied_predicates_of[def_id] <- self.tcx.explicit_implied_predicates_of(def_id));
record_array!(self.tables.explicit_super_predicates_of[def_id] <-
self.tcx.explicit_super_predicates_of(def_id).skip_binder());
record_array!(self.tables.explicit_implied_predicates_of[def_id] <-
self.tcx.explicit_implied_predicates_of(def_id).skip_binder());
}
if let DefKind::Trait | DefKind::Impl { .. } = def_kind {
let associated_item_def_ids = self.tcx.associated_item_def_ids(def_id);

4
compiler/rustc_metadata/src/rmeta/mod.rs
View file

@ -419,10 +419,10 @@ define_tables! {
lookup_deprecation_entry: Table<DefIndex, LazyValue<attr::Deprecation>>,
explicit_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
generics_of: Table<DefIndex, LazyValue<ty::Generics>>,
explicit_super_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
explicit_super_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
// As an optimization, we only store this for trait aliases,
// since it's identical to explicit_super_predicates_of for traits.
explicit_implied_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
explicit_implied_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
type_of: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, Ty<'static>>>>,
variances_of: Table<DefIndex, LazyArray<ty::Variance>>,
fn_sig: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, ty::PolyFnSig<'static>>>>,