Repository: rust-lang/rust
Pull request: Overhaul `Erasable` impls

This PR removes many unused `Erasable` impls, converts many of the hand-written impls to macro-generated impls, and sorts the macro's inputs. This cuts over 200 lines of code and fixes three FIXME comments.

r? @petrochenkov 

Changed files:
filename: compiler/rustc_middle/src/query/erase.rs
patch: @@ -10,13 +10,12 @@ use std::intrinsics::transmute_unchecked;
 use std::mem::MaybeUninit;
 
 use rustc_ast::tokenstream::TokenStream;
+use rustc_data_structures::steal::Steal;
 use rustc_span::{ErrorGuaranteed, Spanned};
 
-use crate::mir::interpret::EvalToValTreeResult;
 use crate::mir::mono::{MonoItem, NormalizationErrorInMono};
-use crate::traits::solve;
 use crate::ty::{self, Ty, TyCtxt};
-use crate::{mir, traits};
+use crate::{mir, thir, traits};
 
 /// Internal implementation detail of [`Erased`].
 #[derive(Copy, Clone)]
@@ -101,192 +100,42 @@ pub fn restore_val<T: Erasable>(erased_value: Erased<T>) -> T {
 // FIXME(#151565): Using `T: ?Sized` here should let us remove the separate
 // impls for fat reference types.
 impl<T> Erasable for &'_ T {
-    type Storage = [u8; size_of::<&'static ()>()];
+    type Storage = [u8; size_of::<&'_ ()>()];
 }
 
 impl<T> Erasable for &'_ [T] {
-    type Storage = [u8; size_of::<&'static [()]>()];
-}
-
-impl Erasable for &'_ OsStr {
-    type Storage = [u8; size_of::<&'static OsStr>()];
+    type Storage = [u8; size_of::<&'_ [()]>()];
 }
 
 impl<T> Erasable for &'_ ty::List<T> {
-    type Storage = [u8; size_of::<&'static ty::List<()>>()];
+    type Storage = [u8; size_of::<&'_ ty::List<()>>()];
 }
 
 impl<T> Erasable for &'_ ty::ListWithCachedTypeInfo<T> {
-    type Storage = [u8; size_of::<&'static ty::ListWithCachedTypeInfo<()>>()];
-}
-
-impl<I: rustc_index::Idx, T> Erasable for &'_ rustc_index::IndexSlice<I, T> {
-    type Storage = [u8; size_of::<&'static rustc_index::IndexSlice<u32, ()>>()];
+    type Storage = [u8; size_of::<&'_ ty::ListWithCachedTypeInfo<()>>()];
 }
 
 impl<T> Erasable for Result<&'_ T, traits::query::NoSolution> {
-    type Storage = [u8; size_of::<Result<&'static (), traits::query::NoSolution>>()];
-}
-
-impl<T> Erasable for Result<&'_ [T], traits::query::NoSolution> {
-    type Storage = [u8; size_of::<Result<&'static [()], traits::query::NoSolution>>()];
-}
-
-impl<T> Erasable for Result<&'_ T, rustc_errors::ErrorGuaranteed> {
-    type Storage = [u8; size_of::<Result<&'static (), rustc_errors::ErrorGuaranteed>>()];
-}
-
-impl<T> Erasable for Result<&'_ [T], rustc_errors::ErrorGuaranteed> {
-    type Storage = [u8; size_of::<Result<&'static [()], rustc_errors::ErrorGuaranteed>>()];
-}
-
-impl<T> Erasable for Result<&'_ T, traits::CodegenObligationError> {
-    type Storage = [u8; size_of::<Result<&'static (), traits::CodegenObligationError>>()];
-}
-
-impl<T> Erasable for Result<&'_ T, &'_ ty::layout::FnAbiError<'_>> {
-    type Storage = [u8; size_of::<Result<&'static (), &'static ty::layout::FnAbiError<'static>>>()];
-}
-
-impl<T> Erasable for Result<(&'_ T, crate::thir::ExprId), rustc_errors::ErrorGuaranteed> {
-    type Storage = [u8; size_of::<
-        Result<(&'static (), crate::thir::ExprId), rustc_errors::ErrorGuaranteed>,
-    >()];
-}
-
-impl Erasable for Result<Option<ty::Instance<'_>>, rustc_errors::ErrorGuaranteed> {
-    type Storage =
-        [u8; size_of::<Result<Option<ty::Instance<'static>>, rustc_errors::ErrorGuaranteed>>()];
-}
-
-impl Erasable
-    for Result<Option<ty::EarlyBinder<'_, ty::Const<'_>>>, rustc_errors::ErrorGuaranteed>
-{
-    type Storage = [u8; size_of::<
-        Result<Option<ty::EarlyBinder<'static, ty::Const<'static>>>, rustc_errors::ErrorGuaranteed>,
-    >()];
-}
-
-impl Erasable for Result<ty::GenericArg<'_>, traits::query::NoSolution> {
-    type Storage = [u8; size_of::<Result<ty::GenericArg<'static>, traits::query::NoSolution>>()];
-}
-
-impl Erasable for Result<bool, &ty::layout::LayoutError<'_>> {
-    type Storage = [u8; size_of::<Result<bool, &'static ty::layout::LayoutError<'static>>>()];
+    type Storage = [u8; size_of::<Result<&'_ (), traits::query::NoSolution>>()];
 }
 
-impl Erasable for Result<rustc_abi::TyAndLayout<'_, Ty<'_>>, &ty::layout::LayoutError<'_>> {
-    type Storage = [u8; size_of::<
-        Result<
-            rustc_abi::TyAndLayout<'static, Ty<'static>>,
-            &'static ty::layout::LayoutError<'static>,
-        >,
-    >()];
-}
-
-impl Erasable for Result<mir::ConstAlloc<'_>, mir::interpret::ErrorHandled> {
-    type Storage =
-        [u8; size_of::<Result<mir::ConstAlloc<'static>, mir::interpret::ErrorHandled>>()];
-}
-
-impl Erasable for Option<(mir::ConstValue, Ty<'_>)> {
-    type Storage = [u8; size_of::<Option<(mir::ConstValue, Ty<'_>)>>()];
-}
-
-impl Erasable for EvalToValTreeResult<'_> {
-    type Storage = [u8; size_of::<EvalToValTreeResult<'static>>()];
-}
-
-impl Erasable for Result<&'_ ty::List<Ty<'_>>, ty::util::AlwaysRequiresDrop> {
-    type Storage =
-        [u8; size_of::<Result<&'static ty::List<Ty<'static>>, ty::util::AlwaysRequiresDrop>>()];
-}
-
-impl Erasable
-    for Result<(&'_ [Spanned<MonoItem<'_>>], &'_ [Spanned<MonoItem<'_>>]), NormalizationErrorInMono>
-{
-    type Storage = [u8; size_of::<
-        Result<
-            (&'static [Spanned<MonoItem<'static>>], &'static [Spanned<MonoItem<'static>>]),
-            NormalizationErrorInMono,
-        >,
-    >()];
-}
-
-impl Erasable for Result<&'_ TokenStream, ()> {
-    type Storage = [u8; size_of::<Result<&'static TokenStream, ()>>()];
+impl<T> Erasable for Result<&'_ T, ErrorGuaranteed> {
+    type Storage = [u8; size_of::<Result<&'_ (), ErrorGuaranteed>>()];
 }
 
 impl<T> Erasable for Option<&'_ T> {
-    type Storage = [u8; size_of::<Option<&'static ()>>()];
-}
-
-impl<T> Erasable for Option<&'_ [T]> {
-    type Storage = [u8; size_of::<Option<&'static [()]>>()];
-}
-
-impl Erasable for Option<&'_ OsStr> {
-    type Storage = [u8; size_of::<Option<&'static OsStr>>()];
-}
-
-impl Erasable for Option<mir::DestructuredConstant<'_>> {
-    type Storage = [u8; size_of::<Option<mir::DestructuredConstant<'static>>>()];
-}
-
-impl Erasable for ty::ImplTraitHeader<'_> {
-    type Storage = [u8; size_of::<ty::ImplTraitHeader<'static>>()];
-}
-
-impl Erasable for Option<ty::EarlyBinder<'_, Ty<'_>>> {
-    type Storage = [u8; size_of::<Option<ty::EarlyBinder<'static, Ty<'static>>>>()];
-}
-
-impl Erasable for Option<ty::Value<'_>> {
-    type Storage = [u8; size_of::<Option<ty::Value<'static>>>()];
-}
-
-impl Erasable for rustc_hir::MaybeOwner<'_> {
-    type Storage = [u8; size_of::<rustc_hir::MaybeOwner<'static>>()];
+    type Storage = [u8; size_of::<Option<&'_ ()>>()];
 }
 
 impl<T: Erasable> Erasable for ty::EarlyBinder<'_, T> {
     type Storage = T::Storage;
 }
 
-impl Erasable for ty::Binder<'_, ty::FnSig<'_>> {
-    type Storage = [u8; size_of::<ty::Binder<'static, ty::FnSig<'static>>>()];
-}
-
-impl Erasable for ty::Binder<'_, ty::CoroutineWitnessTypes<TyCtxt<'_>>> {
-    type Storage =
-        [u8; size_of::<ty::Binder<'static, ty::CoroutineWitnessTypes<TyCtxt<'static>>>>()];
-}
-
-impl Erasable for ty::Binder<'_, &'_ ty::List<Ty<'_>>> {
-    type Storage = [u8; size_of::<ty::Binder<'static, &'static ty::List<Ty<'static>>>>()];
-}
-
 impl<T0, T1> Erasable for (&'_ T0, &'_ T1) {
-    type Storage = [u8; size_of::<(&'static (), &'static ())>()];
-}
-
-impl<T0> Erasable for (solve::QueryResult<'_>, &'_ T0) {
-    type Storage = [u8; size_of::<(solve::QueryResult<'static>, &'static ())>()];
-}
-
-impl<T0, T1> Erasable for (&'_ T0, &'_ [T1]) {
-    type Storage = [u8; size_of::<(&'static (), &'static [()])>()];
+    type Storage = [u8; size_of::<(&'_ (), &'_ ())>()];
 }
 
-impl<T0, T1> Erasable for (&'_ [T0], &'_ [T1]) {
-    type Storage = [u8; size_of::<(&'static [()], &'static [()])>()];
-}
-
-impl<T0> Erasable for (&'_ T0, Result<(), ErrorGuaranteed>) {
-    type Storage = [u8; size_of::<(&'static (), Result<(), ErrorGuaranteed>)>()];
-}
-
-macro_rules! impl_erasable_for_simple_types {
+macro_rules! impl_erasable_for_types_with_no_type_params {
     ($($ty:ty),+ $(,)?) => {
         $(
             impl Erasable for $ty {
@@ -296,171 +145,96 @@ macro_rules! impl_erasable_for_simple_types {
     }
 }
 
-// For concrete types with no lifetimes, the erased storage for `Foo` is
-// `[u8; size_of::<Foo>()]`.
-impl_erasable_for_simple_types! {
-    // FIXME(#151565): Add `tidy-alphabetical-{start,end}` and sort this.
+// For types with no type parameters the erased storage for `Foo` is
+// `[u8; size_of::<Foo>()]`. ('_ lifetimes are allowed.)
+impl_erasable_for_types_with_no_type_params! {
+    // tidy-alphabetical-start
+    (&'_ ty::CrateInherentImpls, Result<(), ErrorGuaranteed>),
     (),
-    bool,
+    (traits::solve::QueryResult<'_>, &'_ traits::solve::inspect::Probe<TyCtxt<'_>>),
+    Option<&'_ OsStr>,
+    Option<&'_ [rustc_hir::PreciseCapturingArgKind<rustc_span::Symbol, rustc_span::Symbol>]>,
+    Option<(mir::ConstValue, Ty<'_>)>,
     Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
+    Option<rustc_abi::Align>,
     Option<rustc_ast::expand::allocator::AllocatorKind>,
+    Option<rustc_data_structures::svh::Svh>,
     Option<rustc_hir::ConstStability>,
+    Option<rustc_hir::CoroutineKind>,
     Option<rustc_hir::DefaultBodyStability>,
     Option<rustc_hir::Stability>,
-    Option<rustc_data_structures::svh::Svh>,
-    Option<rustc_hir::def::DefKind>,
-    Option<rustc_hir::CoroutineKind>,
-    Option<rustc_hir::HirId>,
     Option<rustc_middle::middle::stability::DeprecationEntry>,
     Option<rustc_middle::ty::AsyncDestructor>,
     Option<rustc_middle::ty::Destructor>,
-    Option<rustc_middle::ty::ImplTraitInTraitData>,
+    Option<rustc_middle::ty::IntrinsicDef>,
     Option<rustc_middle::ty::ScalarInt>,
+    Option<rustc_span::Span>,
     Option<rustc_span::def_id::CrateNum>,
     Option<rustc_span::def_id::DefId>,
     Option<rustc_span::def_id::LocalDefId>,
-    Option<rustc_span::Span>,
-    Option<rustc_abi::FieldIdx>,
     Option<rustc_target::spec::PanicStrategy>,
+    Option<ty::EarlyBinder<'_, Ty<'_>>>,
+    Option<ty::Value<'_>>,
     Option<usize>,
-    Option<rustc_middle::ty::IntrinsicDef>,
-    Option<rustc_abi::Align>,
-    Result<(), rustc_errors::ErrorGuaranteed>,
-    Result<(), rustc_middle::traits::query::NoSolution>,
-    Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
-    Result<rustc_middle::ty::adjustment::CoerceUnsizedInfo, rustc_errors::ErrorGuaranteed>,
+    Result<&'_ TokenStream, ()>,
+    Result<&'_ rustc_target::callconv::FnAbi<'_, Ty<'_>>, &'_ ty::layout::FnAbiError<'_>>,
+    Result<&'_ traits::ImplSource<'_, ()>, traits::CodegenObligationError>,
+    Result<&'_ ty::List<Ty<'_>>, ty::util::AlwaysRequiresDrop>,
+    Result<(&'_ Steal<thir::Thir<'_>>, thir::ExprId), ErrorGuaranteed>,
+    Result<(&'_ [Spanned<MonoItem<'_>>], &'_ [Spanned<MonoItem<'_>>]), NormalizationErrorInMono>,
+    Result<(), ErrorGuaranteed>,
+    Result<Option<ty::EarlyBinder<'_, ty::Const<'_>>>, ErrorGuaranteed>,
+    Result<Option<ty::Instance<'_>>, ErrorGuaranteed>,
+    Result<bool, &ty::layout::LayoutError<'_>>,
+    Result<mir::ConstAlloc<'_>, mir::interpret::ErrorHandled>,
     Result<mir::ConstValue, mir::interpret::ErrorHandled>,
-    rustc_abi::ReprOptions,
-    rustc_ast::expand::allocator::AllocatorKind,
-    rustc_hir::DefaultBodyStability,
-    rustc_hir::attrs::Deprecation,
-    rustc_hir::attrs::EiiDecl,
-    rustc_hir::attrs::EiiImpl,
+    Result<rustc_abi::TyAndLayout<'_, Ty<'_>>, &ty::layout::LayoutError<'_>>,
+    Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
+    Result<rustc_middle::ty::adjustment::CoerceUnsizedInfo, ErrorGuaranteed>,
+    Result<ty::GenericArg<'_>, traits::query::NoSolution>,
+    Ty<'_>,
+    bool,
     rustc_data_structures::svh::Svh,
-    rustc_errors::ErrorGuaranteed,
     rustc_hir::Constness,
-    rustc_hir::ConstStability,
-    rustc_hir::def_id::DefId,
-    rustc_hir::def_id::DefIndex,
-    rustc_hir::def_id::LocalDefId,
-    rustc_hir::def_id::LocalModDefId,
-    rustc_hir::def::DefKind,
     rustc_hir::Defaultness,
-    rustc_hir::definitions::DefKey,
-    rustc_hir::CoroutineKind,
     rustc_hir::HirId,
-    rustc_hir::IsAsync,
-    rustc_hir::ItemLocalId,
-    rustc_hir::LangItem,
+    rustc_hir::MaybeOwner<'_>,
     rustc_hir::OpaqueTyOrigin<rustc_hir::def_id::DefId>,
-    rustc_hir::OwnerId,
-    rustc_hir::Stability,
-    rustc_hir::Upvar,
-    rustc_middle::middle::deduced_param_attrs::DeducedParamAttrs,
-    rustc_middle::middle::dependency_format::Linkage,
-    rustc_middle::middle::exported_symbols::SymbolExportInfo,
+    rustc_hir::def::DefKind,
+    rustc_hir::def_id::DefId,
+    rustc_middle::middle::codegen_fn_attrs::SanitizerFnAttrs,
     rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault,
-    rustc_middle::middle::resolve_bound_vars::ResolvedArg,
-    rustc_middle::middle::stability::DeprecationEntry,
     rustc_middle::mir::ConstQualifs,
     rustc_middle::mir::ConstValue,
     rustc_middle::mir::interpret::AllocId,
-    rustc_middle::mir::interpret::CtfeProvenance,
-    rustc_middle::mir::interpret::ErrorHandled,
-    rustc_middle::thir::ExprId,
-    rustc_middle::traits::CodegenObligationError,
-    rustc_middle::traits::EvaluationResult,
-    rustc_middle::traits::OverflowError,
-    rustc_middle::traits::query::NoSolution,
-    rustc_middle::traits::WellFormedLoc,
-    rustc_middle::ty::adjustment::CoerceUnsizedInfo,
+    rustc_middle::mir::interpret::EvalStaticInitializerRawResult<'_>,
+    rustc_middle::mir::interpret::EvalToValTreeResult<'_>,
+    rustc_middle::mir::mono::MonoItemPartitions<'_>,
+    rustc_middle::traits::query::MethodAutoderefStepsResult<'_>,
+    rustc_middle::ty::AdtDef<'_>,
+    rustc_middle::ty::AnonConstKind,
     rustc_middle::ty::AssocItem,
-    rustc_middle::ty::AssocContainer,
     rustc_middle::ty::Asyncness,
-    rustc_middle::ty::AsyncDestructor,
-    rustc_middle::ty::AnonConstKind,
-    rustc_middle::ty::Destructor,
-    rustc_middle::ty::fast_reject::SimplifiedType,
-    rustc_middle::ty::ImplPolarity,
-    rustc_middle::ty::util::AlwaysRequiresDrop,
+    rustc_middle::ty::Binder<'_, ty::CoroutineWitnessTypes<TyCtxt<'_>>>,
+    rustc_middle::ty::Binder<'_, ty::FnSig<'_>>,
+    rustc_middle::ty::ClosureTypeInfo<'_>,
+    rustc_middle::ty::Const<'_>,
+    rustc_middle::ty::ConstConditions<'_>,
+    rustc_middle::ty::GenericPredicates<'_>,
+    rustc_middle::ty::ImplTraitHeader<'_>,
+    rustc_middle::ty::ParamEnv<'_>,
+    rustc_middle::ty::SymbolName<'_>,
+    rustc_middle::ty::TypingEnv<'_>,
     rustc_middle::ty::Visibility<rustc_span::def_id::DefId>,
-    rustc_middle::middle::codegen_fn_attrs::SanitizerFnAttrs,
-    rustc_session::config::CrateType,
-    rustc_session::config::EntryFnType,
+    rustc_middle::ty::inhabitedness::InhabitedPredicate<'_>,
+    rustc_session::Limits,
     rustc_session::config::OptLevel,
     rustc_session::config::SymbolManglingVersion,
     rustc_session::cstore::CrateDepKind,
-    rustc_session::cstore::ExternCrate,
-    rustc_session::cstore::LinkagePreference,
-    rustc_session::Limits,
-    rustc_session::lint::LintExpectationId,
-    rustc_span::def_id::CrateNum,
-    rustc_span::def_id::DefPathHash,
-    rustc_span::ExpnHash,
     rustc_span::ExpnId,
     rustc_span::Span,
     rustc_span::Symbol,
-    rustc_span::Ident,
     rustc_target::spec::PanicStrategy,
-    rustc_type_ir::Variance,
-    u32,
     usize,
-}
-
-macro_rules! impl_erasable_for_single_lifetime_types {
-    ($($($fake_path:ident)::+),+ $(,)?) => {
-        $(
-            impl<'tcx> Erasable for $($fake_path)::+<'tcx> {
-                type Storage = [u8; size_of::<$($fake_path)::+<'static>>()];
-            }
-        )*
-    }
-}
-
-// For types containing a single lifetime and no other generics, e.g.
-// `Foo<'tcx>`, the erased storage is `[u8; size_of::<Foo<'static>>()]`.
-//
-// FIXME(#151565): Some of the hand-written impls above that only use one
-// lifetime can probably be migrated here.
-impl_erasable_for_single_lifetime_types! {
-    // FIXME(#151565): Add `tidy-alphabetical-{start,end}` and sort this.
-    rustc_middle::middle::exported_symbols::ExportedSymbol,
-    rustc_middle::mir::Const,
-    rustc_middle::mir::DestructuredConstant,
-    rustc_middle::mir::ConstAlloc,
-    rustc_middle::mir::interpret::GlobalId,
-    rustc_middle::mir::interpret::EvalStaticInitializerRawResult,
-    rustc_middle::mir::mono::MonoItemPartitions,
-    rustc_middle::traits::query::MethodAutoderefStepsResult,
-    rustc_middle::traits::query::type_op::AscribeUserType,
-    rustc_middle::traits::query::type_op::Eq,
-    rustc_middle::traits::query::type_op::ProvePredicate,
-    rustc_middle::traits::query::type_op::Subtype,
-    rustc_middle::ty::AdtDef,
-    rustc_middle::ty::AliasTy,
-    rustc_middle::ty::ClauseKind,
-    rustc_middle::ty::ClosureTypeInfo,
-    rustc_middle::ty::Const,
-    rustc_middle::ty::DestructuredAdtConst,
-    rustc_middle::ty::ExistentialTraitRef,
-    rustc_middle::ty::FnSig,
-    rustc_middle::ty::GenericArg,
-    rustc_middle::ty::GenericPredicates,
-    rustc_middle::ty::ConstConditions,
-    rustc_middle::ty::inhabitedness::InhabitedPredicate,
-    rustc_middle::ty::Instance,
-    rustc_middle::ty::BoundVariableKind,
-    rustc_middle::ty::InstanceKind,
-    rustc_middle::ty::layout::FnAbiError,
-    rustc_middle::ty::layout::LayoutError,
-    rustc_middle::ty::LitToConstInput,
-    rustc_middle::ty::ParamEnv,
-    rustc_middle::ty::TypingEnv,
-    rustc_middle::ty::Predicate,
-    rustc_middle::ty::SymbolName,
-    rustc_middle::ty::TraitRef,
-    rustc_middle::ty::Ty,
-    rustc_middle::ty::UnevaluatedConst,
-    rustc_middle::ty::ValTree,
-    rustc_middle::ty::VtblEntry,
+    // tidy-alphabetical-end
 }