rustc_middle/query/
erase.rs

1use std::ffi::OsStr;
2use std::intrinsics::transmute_unchecked;
3use std::mem::MaybeUninit;
4
5use rustc_span::ErrorGuaranteed;
6
7use crate::mir::interpret::EvalToValTreeResult;
8use crate::query::CyclePlaceholder;
9use crate::traits::solve;
10use crate::ty::adjustment::CoerceUnsizedInfo;
11use crate::ty::{self, Ty, TyCtxt};
12use crate::{mir, traits};
13
14#[derive(Copy, Clone)]
15pub struct Erased<T: Copy> {
16    // We use `MaybeUninit` here so we can store any value
17    // in `data` since we aren't actually storing a `T`.
18    data: MaybeUninit<T>,
19}
20
21pub trait EraseType: Copy {
22    type Result: Copy;
23}
24
25// Allow `type_alias_bounds` since compilation will fail without `EraseType`.
26#[allow(type_alias_bounds)]
27pub type Erase<T: EraseType> = Erased<impl Copy>;
28
29#[inline(always)]
30#[define_opaque(Erase)]
31pub fn erase<T: EraseType>(src: T) -> Erase<T> {
32    // Ensure the sizes match
33    const {
34        if size_of::<T>() != size_of::<T::Result>() {
35            panic!("size of T must match erased type T::Result")
36        }
37    };
38
39    Erased::<<T as EraseType>::Result> {
40        // `transmute_unchecked` is needed here because it does not have `transmute`'s size check
41        // (and thus allows to transmute between `T` and `MaybeUninit<T::Result>`) (we do the size
42        // check ourselves in the `const` block above).
43        //
44        // `transmute_copy` is also commonly used for this (and it would work here since
45        // `EraseType: Copy`), but `transmute_unchecked` better explains the intent.
46        //
47        // SAFETY: It is safe to transmute to MaybeUninit for types with the same sizes.
48        data: unsafe { transmute_unchecked::<T, MaybeUninit<T::Result>>(src) },
49    }
50}
51
52/// Restores an erased value.
53#[inline(always)]
54#[define_opaque(Erase)]
55pub fn restore<T: EraseType>(value: Erase<T>) -> T {
56    let value: Erased<<T as EraseType>::Result> = value;
57    // See comment in `erase` for why we use `transmute_unchecked`.
58    //
59    // SAFETY: Due to the use of impl Trait in `Erase` the only way to safely create an instance
60    // of `Erase` is to call `erase`, so we know that `value.data` is a valid instance of `T` of
61    // the right size.
62    unsafe { transmute_unchecked::<MaybeUninit<T::Result>, T>(value.data) }
63}
64
65impl<T> EraseType for &'_ T {
66    type Result = [u8; size_of::<&'static ()>()];
67}
68
69impl<T> EraseType for &'_ [T] {
70    type Result = [u8; size_of::<&'static [()]>()];
71}
72
73impl EraseType for &'_ OsStr {
74    type Result = [u8; size_of::<&'static OsStr>()];
75}
76
77impl<T> EraseType for &'_ ty::List<T> {
78    type Result = [u8; size_of::<&'static ty::List<()>>()];
79}
80
81impl<T> EraseType for &'_ ty::ListWithCachedTypeInfo<T> {
82    type Result = [u8; size_of::<&'static ty::ListWithCachedTypeInfo<()>>()];
83}
84
85impl<I: rustc_index::Idx, T> EraseType for &'_ rustc_index::IndexSlice<I, T> {
86    type Result = [u8; size_of::<&'static rustc_index::IndexSlice<u32, ()>>()];
87}
88
89impl<T> EraseType for Result<&'_ T, traits::query::NoSolution> {
90    type Result = [u8; size_of::<Result<&'static (), traits::query::NoSolution>>()];
91}
92
93impl<T> EraseType for Result<&'_ [T], traits::query::NoSolution> {
94    type Result = [u8; size_of::<Result<&'static [()], traits::query::NoSolution>>()];
95}
96
97impl<T> EraseType for Result<&'_ T, rustc_errors::ErrorGuaranteed> {
98    type Result = [u8; size_of::<Result<&'static (), rustc_errors::ErrorGuaranteed>>()];
99}
100
101impl<T> EraseType for Result<&'_ [T], rustc_errors::ErrorGuaranteed> {
102    type Result = [u8; size_of::<Result<&'static [()], rustc_errors::ErrorGuaranteed>>()];
103}
104
105impl<T> EraseType for Result<&'_ T, traits::CodegenObligationError> {
106    type Result = [u8; size_of::<Result<&'static (), traits::CodegenObligationError>>()];
107}
108
109impl<T> EraseType for Result<&'_ T, &'_ ty::layout::FnAbiError<'_>> {
110    type Result = [u8; size_of::<Result<&'static (), &'static ty::layout::FnAbiError<'static>>>()];
111}
112
113impl<T> EraseType for Result<(&'_ T, crate::thir::ExprId), rustc_errors::ErrorGuaranteed> {
114    type Result = [u8; size_of::<
115        Result<(&'static (), crate::thir::ExprId), rustc_errors::ErrorGuaranteed>,
116    >()];
117}
118
119impl EraseType for Result<Option<ty::Instance<'_>>, rustc_errors::ErrorGuaranteed> {
120    type Result =
121        [u8; size_of::<Result<Option<ty::Instance<'static>>, rustc_errors::ErrorGuaranteed>>()];
122}
123
124impl EraseType for Result<CoerceUnsizedInfo, rustc_errors::ErrorGuaranteed> {
125    type Result = [u8; size_of::<Result<CoerceUnsizedInfo, rustc_errors::ErrorGuaranteed>>()];
126}
127
128impl EraseType
129    for Result<Option<ty::EarlyBinder<'_, ty::Const<'_>>>, rustc_errors::ErrorGuaranteed>
130{
131    type Result = [u8; size_of::<
132        Result<Option<ty::EarlyBinder<'static, ty::Const<'static>>>, rustc_errors::ErrorGuaranteed>,
133    >()];
134}
135
136impl EraseType for Result<ty::GenericArg<'_>, traits::query::NoSolution> {
137    type Result = [u8; size_of::<Result<ty::GenericArg<'static>, traits::query::NoSolution>>()];
138}
139
140impl EraseType for Result<bool, &ty::layout::LayoutError<'_>> {
141    type Result = [u8; size_of::<Result<bool, &'static ty::layout::LayoutError<'static>>>()];
142}
143
144impl EraseType for Result<rustc_abi::TyAndLayout<'_, Ty<'_>>, &ty::layout::LayoutError<'_>> {
145    type Result = [u8; size_of::<
146        Result<
147            rustc_abi::TyAndLayout<'static, Ty<'static>>,
148            &'static ty::layout::LayoutError<'static>,
149        >,
150    >()];
151}
152
153impl EraseType for Result<mir::ConstAlloc<'_>, mir::interpret::ErrorHandled> {
154    type Result = [u8; size_of::<Result<mir::ConstAlloc<'static>, mir::interpret::ErrorHandled>>()];
155}
156
157impl EraseType for Result<mir::ConstValue, mir::interpret::ErrorHandled> {
158    type Result = [u8; size_of::<Result<mir::ConstValue, mir::interpret::ErrorHandled>>()];
159}
160
161impl EraseType for EvalToValTreeResult<'_> {
162    type Result = [u8; size_of::<EvalToValTreeResult<'static>>()];
163}
164
165impl EraseType for Result<&'_ ty::List<Ty<'_>>, ty::util::AlwaysRequiresDrop> {
166    type Result =
167        [u8; size_of::<Result<&'static ty::List<Ty<'static>>, ty::util::AlwaysRequiresDrop>>()];
168}
169
170impl EraseType for Result<ty::EarlyBinder<'_, Ty<'_>>, CyclePlaceholder> {
171    type Result = [u8; size_of::<Result<ty::EarlyBinder<'static, Ty<'_>>, CyclePlaceholder>>()];
172}
173
174impl<T> EraseType for Option<&'_ T> {
175    type Result = [u8; size_of::<Option<&'static ()>>()];
176}
177
178impl<T> EraseType for Option<&'_ [T]> {
179    type Result = [u8; size_of::<Option<&'static [()]>>()];
180}
181
182impl EraseType for Option<&'_ OsStr> {
183    type Result = [u8; size_of::<Option<&'static OsStr>>()];
184}
185
186impl EraseType for Option<mir::DestructuredConstant<'_>> {
187    type Result = [u8; size_of::<Option<mir::DestructuredConstant<'static>>>()];
188}
189
190impl EraseType for Option<ty::ImplTraitHeader<'_>> {
191    type Result = [u8; size_of::<Option<ty::ImplTraitHeader<'static>>>()];
192}
193
194impl EraseType for Option<ty::EarlyBinder<'_, Ty<'_>>> {
195    type Result = [u8; size_of::<Option<ty::EarlyBinder<'static, Ty<'static>>>>()];
196}
197
198impl EraseType for rustc_hir::MaybeOwner<'_> {
199    type Result = [u8; size_of::<rustc_hir::MaybeOwner<'static>>()];
200}
201
202impl<T: EraseType> EraseType for ty::EarlyBinder<'_, T> {
203    type Result = T::Result;
204}
205
206impl EraseType for ty::Binder<'_, ty::FnSig<'_>> {
207    type Result = [u8; size_of::<ty::Binder<'static, ty::FnSig<'static>>>()];
208}
209
210impl EraseType for ty::Binder<'_, ty::CoroutineWitnessTypes<TyCtxt<'_>>> {
211    type Result =
212        [u8; size_of::<ty::Binder<'static, ty::CoroutineWitnessTypes<TyCtxt<'static>>>>()];
213}
214
215impl EraseType for ty::Binder<'_, &'_ ty::List<Ty<'_>>> {
216    type Result = [u8; size_of::<ty::Binder<'static, &'static ty::List<Ty<'static>>>>()];
217}
218
219impl<T0, T1> EraseType for (&'_ T0, &'_ T1) {
220    type Result = [u8; size_of::<(&'static (), &'static ())>()];
221}
222
223impl<T0> EraseType for (solve::QueryResult<'_>, &'_ T0) {
224    type Result = [u8; size_of::<(solve::QueryResult<'static>, &'static ())>()];
225}
226
227impl<T0, T1> EraseType for (&'_ T0, &'_ [T1]) {
228    type Result = [u8; size_of::<(&'static (), &'static [()])>()];
229}
230
231impl<T0, T1> EraseType for (&'_ [T0], &'_ [T1]) {
232    type Result = [u8; size_of::<(&'static [()], &'static [()])>()];
233}
234
235impl<T0> EraseType for (&'_ T0, Result<(), ErrorGuaranteed>) {
236    type Result = [u8; size_of::<(&'static (), Result<(), ErrorGuaranteed>)>()];
237}
238
239macro_rules! trivial {
240    ($($ty:ty),+ $(,)?) => {
241        $(
242            impl EraseType for $ty {
243                type Result = [u8; size_of::<$ty>()];
244            }
245        )*
246    }
247}
248
249trivial! {
250    (),
251    bool,
252    Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
253    Option<rustc_ast::expand::allocator::AllocatorKind>,
254    Option<rustc_hir::ConstStability>,
255    Option<rustc_hir::DefaultBodyStability>,
256    Option<rustc_hir::Stability>,
257    Option<rustc_data_structures::svh::Svh>,
258    Option<rustc_hir::def::DefKind>,
259    Option<rustc_hir::CoroutineKind>,
260    Option<rustc_hir::HirId>,
261    Option<rustc_middle::middle::stability::DeprecationEntry>,
262    Option<rustc_middle::ty::AsyncDestructor>,
263    Option<rustc_middle::ty::Destructor>,
264    Option<rustc_middle::ty::ImplTraitInTraitData>,
265    Option<rustc_middle::ty::ScalarInt>,
266    Option<rustc_span::def_id::CrateNum>,
267    Option<rustc_span::def_id::DefId>,
268    Option<rustc_span::def_id::LocalDefId>,
269    Option<rustc_span::Span>,
270    Option<rustc_abi::FieldIdx>,
271    Option<rustc_target::spec::PanicStrategy>,
272    Option<usize>,
273    Option<rustc_middle::ty::IntrinsicDef>,
274    Option<rustc_abi::Align>,
275    Result<(), rustc_errors::ErrorGuaranteed>,
276    Result<(), rustc_middle::traits::query::NoSolution>,
277    Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
278    rustc_abi::ReprOptions,
279    rustc_ast::expand::allocator::AllocatorKind,
280    rustc_hir::DefaultBodyStability,
281    rustc_hir::attrs::Deprecation,
282    rustc_data_structures::svh::Svh,
283    rustc_errors::ErrorGuaranteed,
284    rustc_hir::Constness,
285    rustc_hir::ConstStability,
286    rustc_hir::def_id::DefId,
287    rustc_hir::def_id::DefIndex,
288    rustc_hir::def_id::LocalDefId,
289    rustc_hir::def_id::LocalModDefId,
290    rustc_hir::def::DefKind,
291    rustc_hir::Defaultness,
292    rustc_hir::definitions::DefKey,
293    rustc_hir::CoroutineKind,
294    rustc_hir::HirId,
295    rustc_hir::IsAsync,
296    rustc_hir::ItemLocalId,
297    rustc_hir::LangItem,
298    rustc_hir::OpaqueTyOrigin<rustc_hir::def_id::DefId>,
299    rustc_hir::OwnerId,
300    rustc_hir::Stability,
301    rustc_hir::Upvar,
302    rustc_index::bit_set::FiniteBitSet<u32>,
303    rustc_middle::middle::dependency_format::Linkage,
304    rustc_middle::middle::exported_symbols::SymbolExportInfo,
305    rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault,
306    rustc_middle::middle::resolve_bound_vars::ResolvedArg,
307    rustc_middle::middle::stability::DeprecationEntry,
308    rustc_middle::mir::ConstQualifs,
309    rustc_middle::mir::ConstValue,
310    rustc_middle::mir::interpret::AllocId,
311    rustc_middle::mir::interpret::CtfeProvenance,
312    rustc_middle::mir::interpret::ErrorHandled,
313    rustc_middle::thir::ExprId,
314    rustc_middle::traits::CodegenObligationError,
315    rustc_middle::traits::EvaluationResult,
316    rustc_middle::traits::OverflowError,
317    rustc_middle::traits::query::NoSolution,
318    rustc_middle::traits::WellFormedLoc,
319    rustc_middle::ty::adjustment::CoerceUnsizedInfo,
320    rustc_middle::ty::AssocItem,
321    rustc_middle::ty::AssocItemContainer,
322    rustc_middle::ty::Asyncness,
323    rustc_middle::ty::AsyncDestructor,
324    rustc_middle::ty::BoundVariableKind,
325    rustc_middle::ty::AnonConstKind,
326    rustc_middle::ty::DeducedParamAttrs,
327    rustc_middle::ty::Destructor,
328    rustc_middle::ty::fast_reject::SimplifiedType,
329    rustc_middle::ty::ImplPolarity,
330    rustc_middle::ty::Representability,
331    rustc_middle::ty::UnusedGenericParams,
332    rustc_middle::ty::util::AlwaysRequiresDrop,
333    rustc_middle::ty::Visibility<rustc_span::def_id::DefId>,
334    rustc_session::config::CrateType,
335    rustc_session::config::EntryFnType,
336    rustc_session::config::OptLevel,
337    rustc_session::config::SymbolManglingVersion,
338    rustc_session::cstore::CrateDepKind,
339    rustc_session::cstore::ExternCrate,
340    rustc_session::cstore::LinkagePreference,
341    rustc_session::Limits,
342    rustc_session::lint::LintExpectationId,
343    rustc_span::def_id::CrateNum,
344    rustc_span::def_id::DefPathHash,
345    rustc_span::ExpnHash,
346    rustc_span::ExpnId,
347    rustc_span::Span,
348    rustc_span::Symbol,
349    rustc_span::Ident,
350    rustc_target::spec::PanicStrategy,
351    rustc_target::spec::SanitizerSet,
352    rustc_type_ir::Variance,
353    u32,
354    usize,
355}
356
357macro_rules! tcx_lifetime {
358    ($($($fake_path:ident)::+),+ $(,)?) => {
359        $(
360            impl<'tcx> EraseType for $($fake_path)::+<'tcx> {
361                type Result = [u8; size_of::<$($fake_path)::+<'static>>()];
362            }
363        )*
364    }
365}
366
367tcx_lifetime! {
368    rustc_middle::middle::exported_symbols::ExportedSymbol,
369    rustc_middle::mir::Const,
370    rustc_middle::mir::DestructuredConstant,
371    rustc_middle::mir::ConstAlloc,
372    rustc_middle::mir::interpret::GlobalId,
373    rustc_middle::mir::interpret::LitToConstInput,
374    rustc_middle::mir::interpret::EvalStaticInitializerRawResult,
375    rustc_middle::mir::mono::MonoItemPartitions,
376    rustc_middle::traits::query::MethodAutoderefStepsResult,
377    rustc_middle::traits::query::type_op::AscribeUserType,
378    rustc_middle::traits::query::type_op::Eq,
379    rustc_middle::traits::query::type_op::ProvePredicate,
380    rustc_middle::traits::query::type_op::Subtype,
381    rustc_middle::ty::AdtDef,
382    rustc_middle::ty::AliasTy,
383    rustc_middle::ty::ClauseKind,
384    rustc_middle::ty::ClosureTypeInfo,
385    rustc_middle::ty::Const,
386    rustc_middle::ty::DestructuredConst,
387    rustc_middle::ty::ExistentialTraitRef,
388    rustc_middle::ty::FnSig,
389    rustc_middle::ty::GenericArg,
390    rustc_middle::ty::GenericPredicates,
391    rustc_middle::ty::ConstConditions,
392    rustc_middle::ty::inhabitedness::InhabitedPredicate,
393    rustc_middle::ty::Instance,
394    rustc_middle::ty::InstanceKind,
395    rustc_middle::ty::layout::FnAbiError,
396    rustc_middle::ty::layout::LayoutError,
397    rustc_middle::ty::ParamEnv,
398    rustc_middle::ty::TypingEnv,
399    rustc_middle::ty::Predicate,
400    rustc_middle::ty::SymbolName,
401    rustc_middle::ty::TraitRef,
402    rustc_middle::ty::Ty,
403    rustc_middle::ty::UnevaluatedConst,
404    rustc_middle::ty::ValTree,
405    rustc_middle::ty::VtblEntry,
406}
rustc_middle/query/erase.rs

rustc_middle/query/
erase.rs
