1 use crate::middle
::codegen_fn_attrs
::CodegenFnAttrFlags
;
2 use crate::ty
::print
::{FmtPrinter, Printer}
;
3 use crate::ty
::subst
::InternalSubsts
;
4 use crate::ty
::{self, SubstsRef, Ty, TyCtxt, TypeFoldable}
;
5 use rustc_errors
::ErrorReported
;
6 use rustc_hir
::def
::Namespace
;
7 use rustc_hir
::def_id
::{CrateNum, DefId}
;
8 use rustc_hir
::lang_items
::LangItem
;
9 use rustc_macros
::HashStable
;
13 /// A monomorphized `InstanceDef`.
15 /// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
16 /// simply couples a potentially generic `InstanceDef` with some substs, and codegen and const eval
17 /// will do all required substitution as they run.
18 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
19 #[derive(HashStable, Lift)]
20 pub struct Instance
<'tcx
> {
21 pub def
: InstanceDef
<'tcx
>,
22 pub substs
: SubstsRef
<'tcx
>,
25 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable, HashStable)]
26 pub enum InstanceDef
<'tcx
> {
27 /// A user-defined callable item.
33 Item(ty
::WithOptConstParam
<DefId
>),
35 /// An intrinsic `fn` item (with `"rust-intrinsic"` or `"platform-intrinsic"` ABI).
37 /// Alongside `Virtual`, this is the only `InstanceDef` that does not have its own callable MIR.
38 /// Instead, codegen and const eval "magically" evaluate calls to intrinsics purely in the
42 /// `<T as Trait>::method` where `method` receives unsizeable `self: Self` (part of the
43 /// `unsized_locals` feature).
45 /// The generated shim will take `Self` via `*mut Self` - conceptually this is `&owned Self` -
46 /// and dereference the argument to call the original function.
49 /// `fn()` pointer where the function itself cannot be turned into a pointer.
51 /// One example is `<dyn Trait as Trait>::fn`, where the shim contains
52 /// a virtual call, which codegen supports only via a direct call to the
53 /// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
55 /// Another example is functions annotated with `#[track_caller]`, which
56 /// must have their implicit caller location argument populated for a call.
57 /// Because this is a required part of the function's ABI but can't be tracked
58 /// as a property of the function pointer, we use a single "caller location"
59 /// (the definition of the function itself).
62 /// `<fn() as FnTrait>::call_*` (generated `FnTrait` implementation for `fn()` pointers).
64 /// `DefId` is `FnTrait::call_*`.
66 /// NB: the (`fn` pointer) type must currently be monomorphic to avoid double substitution
67 /// problems with the MIR shim bodies. `Instance::resolve` enforces this.
68 // FIXME(#69925) support polymorphic MIR shim bodies properly instead.
69 FnPtrShim(DefId
, Ty
<'tcx
>),
71 /// Dynamic dispatch to `<dyn Trait as Trait>::fn`.
73 /// This `InstanceDef` does not have callable MIR. Calls to `Virtual` instances must be
74 /// codegen'd as virtual calls through the vtable.
76 /// If this is reified to a `fn` pointer, a `ReifyShim` is used (see `ReifyShim` above for more
78 Virtual(DefId
, usize),
80 /// `<[FnMut closure] as FnOnce>::call_once`.
82 /// The `DefId` is the ID of the `call_once` method in `FnOnce`.
83 ClosureOnceShim { call_once: DefId }
,
85 /// `core::ptr::drop_in_place::<T>`.
87 /// The `DefId` is for `core::ptr::drop_in_place`.
88 /// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
91 /// NB: the type must currently be monomorphic to avoid double substitution
92 /// problems with the MIR shim bodies. `Instance::resolve` enforces this.
93 // FIXME(#69925) support polymorphic MIR shim bodies properly instead.
94 DropGlue(DefId
, Option
<Ty
<'tcx
>>),
96 /// Compiler-generated `<T as Clone>::clone` implementation.
98 /// For all types that automatically implement `Copy`, a trivial `Clone` impl is provided too.
99 /// Additionally, arrays, tuples, and closures get a `Clone` shim even if they aren't `Copy`.
101 /// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
103 /// NB: the type must currently be monomorphic to avoid double substitution
104 /// problems with the MIR shim bodies. `Instance::resolve` enforces this.
105 // FIXME(#69925) support polymorphic MIR shim bodies properly instead.
106 CloneShim(DefId
, Ty
<'tcx
>),
109 impl<'tcx
> Instance
<'tcx
> {
110 /// Returns the `Ty` corresponding to this `Instance`, with generic substitutions applied and
111 /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
112 pub fn ty(&self, tcx
: TyCtxt
<'tcx
>, param_env
: ty
::ParamEnv
<'tcx
>) -> Ty
<'tcx
> {
113 let ty
= tcx
.type_of(self.def
.def_id());
114 tcx
.subst_and_normalize_erasing_regions(self.substs
, param_env
, &ty
)
117 /// Finds a crate that contains a monomorphization of this instance that
118 /// can be linked to from the local crate. A return value of `None` means
119 /// no upstream crate provides such an exported monomorphization.
121 /// This method already takes into account the global `-Zshare-generics`
122 /// setting, always returning `None` if `share-generics` is off.
123 pub fn upstream_monomorphization(&self, tcx
: TyCtxt
<'tcx
>) -> Option
<CrateNum
> {
124 // If we are not in share generics mode, we don't link to upstream
125 // monomorphizations but always instantiate our own internal versions
127 if !tcx
.sess
.opts
.share_generics() {
131 // If this is an item that is defined in the local crate, no upstream
132 // crate can know about it/provide a monomorphization.
133 if self.def_id().is_local() {
137 // If this a non-generic instance, it cannot be a shared monomorphization.
138 self.substs
.non_erasable_generics().next()?
;
141 InstanceDef
::Item(def
) => tcx
142 .upstream_monomorphizations_for(def
.did
)
143 .and_then(|monos
| monos
.get(&self.substs
).cloned()),
144 InstanceDef
::DropGlue(_
, Some(_
)) => tcx
.upstream_drop_glue_for(self.substs
),
150 impl<'tcx
> InstanceDef
<'tcx
> {
152 pub fn def_id(self) -> DefId
{
154 InstanceDef
::Item(def
) => def
.did
,
155 InstanceDef
::VtableShim(def_id
)
156 | InstanceDef
::ReifyShim(def_id
)
157 | InstanceDef
::FnPtrShim(def_id
, _
)
158 | InstanceDef
::Virtual(def_id
, _
)
159 | InstanceDef
::Intrinsic(def_id
)
160 | InstanceDef
::ClosureOnceShim { call_once: def_id }
161 | InstanceDef
::DropGlue(def_id
, _
)
162 | InstanceDef
::CloneShim(def_id
, _
) => def_id
,
167 pub fn with_opt_param(self) -> ty
::WithOptConstParam
<DefId
> {
169 InstanceDef
::Item(def
) => def
,
170 InstanceDef
::VtableShim(def_id
)
171 | InstanceDef
::ReifyShim(def_id
)
172 | InstanceDef
::FnPtrShim(def_id
, _
)
173 | InstanceDef
::Virtual(def_id
, _
)
174 | InstanceDef
::Intrinsic(def_id
)
175 | InstanceDef
::ClosureOnceShim { call_once: def_id }
176 | InstanceDef
::DropGlue(def_id
, _
)
177 | InstanceDef
::CloneShim(def_id
, _
) => ty
::WithOptConstParam
::unknown(def_id
),
182 pub fn attrs(&self, tcx
: TyCtxt
<'tcx
>) -> ty
::Attributes
<'tcx
> {
183 tcx
.get_attrs(self.def_id())
186 /// Returns `true` if the LLVM version of this instance is unconditionally
187 /// marked with `inline`. This implies that a copy of this instance is
188 /// generated in every codegen unit.
189 /// Note that this is only a hint. See the documentation for
190 /// `generates_cgu_internal_copy` for more information.
191 pub fn requires_inline(&self, tcx
: TyCtxt
<'tcx
>) -> bool
{
192 use rustc_hir
::definitions
::DefPathData
;
193 let def_id
= match *self {
194 ty
::InstanceDef
::Item(def
) => def
.did
,
195 ty
::InstanceDef
::DropGlue(_
, Some(_
)) => return false,
198 match tcx
.def_key(def_id
).disambiguated_data
.data
{
199 DefPathData
::Ctor
| DefPathData
::ClosureExpr
=> true,
204 /// Returns `true` if the machine code for this instance is instantiated in
205 /// each codegen unit that references it.
206 /// Note that this is only a hint! The compiler can globally decide to *not*
207 /// do this in order to speed up compilation. CGU-internal copies are
208 /// only exist to enable inlining. If inlining is not performed (e.g. at
209 /// `-Copt-level=0`) then the time for generating them is wasted and it's
210 /// better to create a single copy with external linkage.
211 pub fn generates_cgu_internal_copy(&self, tcx
: TyCtxt
<'tcx
>) -> bool
{
212 if self.requires_inline(tcx
) {
215 if let ty
::InstanceDef
::DropGlue(.., Some(ty
)) = *self {
216 // Drop glue generally wants to be instantiated at every codegen
217 // unit, but without an #[inline] hint. We should make this
218 // available to normal end-users.
219 if tcx
.sess
.opts
.incremental
.is_none() {
222 // When compiling with incremental, we can generate a *lot* of
223 // codegen units. Including drop glue into all of them has a
224 // considerable compile time cost.
226 // We include enums without destructors to allow, say, optimizing
227 // drops of `Option::None` before LTO. We also respect the intent of
228 // `#[inline]` on `Drop::drop` implementations.
229 return ty
.ty_adt_def().map_or(true, |adt_def
| {
230 adt_def
.destructor(tcx
).map_or(adt_def
.is_enum(), |dtor
| {
231 tcx
.codegen_fn_attrs(dtor
.did
).requests_inline()
235 tcx
.codegen_fn_attrs(self.def_id()).requests_inline()
238 pub fn requires_caller_location(&self, tcx
: TyCtxt
<'_
>) -> bool
{
240 InstanceDef
::Item(def
) => {
241 tcx
.codegen_fn_attrs(def
.did
).flags
.contains(CodegenFnAttrFlags
::TRACK_CALLER
)
248 impl<'tcx
> fmt
::Display
for Instance
<'tcx
> {
249 fn fmt(&self, f
: &mut fmt
::Formatter
<'_
>) -> fmt
::Result
{
250 ty
::tls
::with(|tcx
| {
251 let substs
= tcx
.lift(&self.substs
).expect("could not lift for printing");
252 FmtPrinter
::new(tcx
, &mut *f
, Namespace
::ValueNS
)
253 .print_def_path(self.def_id(), substs
)?
;
258 InstanceDef
::Item(_
) => Ok(()),
259 InstanceDef
::VtableShim(_
) => write
!(f
, " - shim(vtable)"),
260 InstanceDef
::ReifyShim(_
) => write
!(f
, " - shim(reify)"),
261 InstanceDef
::Intrinsic(_
) => write
!(f
, " - intrinsic"),
262 InstanceDef
::Virtual(_
, num
) => write
!(f
, " - virtual#{}", num
),
263 InstanceDef
::FnPtrShim(_
, ty
) => write
!(f
, " - shim({:?})", ty
),
264 InstanceDef
::ClosureOnceShim { .. }
=> write
!(f
, " - shim"),
265 InstanceDef
::DropGlue(_
, ty
) => write
!(f
, " - shim({:?})", ty
),
266 InstanceDef
::CloneShim(_
, ty
) => write
!(f
, " - shim({:?})", ty
),
271 impl<'tcx
> Instance
<'tcx
> {
272 pub fn new(def_id
: DefId
, substs
: SubstsRef
<'tcx
>) -> Instance
<'tcx
> {
274 !substs
.has_escaping_bound_vars(),
275 "substs of instance {:?} not normalized for codegen: {:?}",
279 Instance { def: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)), substs }
282 pub fn mono(tcx
: TyCtxt
<'tcx
>, def_id
: DefId
) -> Instance
<'tcx
> {
283 Instance
::new(def_id
, tcx
.empty_substs_for_def_id(def_id
))
287 pub fn def_id(&self) -> DefId
{
291 /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
292 /// this is used to find the precise code that will run for a trait method invocation,
295 /// Returns `Ok(None)` if we cannot resolve `Instance` to a specific instance.
296 /// For example, in a context like this,
299 /// fn foo<T: Debug>(t: T) { ... }
302 /// trying to resolve `Debug::fmt` applied to `T` will yield `Ok(None)`, because we do not
303 /// know what code ought to run. (Note that this setting is also affected by the
304 /// `RevealMode` in the parameter environment.)
306 /// Presuming that coherence and type-check have succeeded, if this method is invoked
307 /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
308 /// `Ok(Some(instance))`.
310 /// Returns `Err(ErrorReported)` when the `Instance` resolution process
311 /// couldn't complete due to errors elsewhere - this is distinct
312 /// from `Ok(None)` to avoid misleading diagnostics when an error
313 /// has already been/will be emitted, for the original cause
316 param_env
: ty
::ParamEnv
<'tcx
>,
318 substs
: SubstsRef
<'tcx
>,
319 ) -> Result
<Option
<Instance
<'tcx
>>, ErrorReported
> {
320 Instance
::resolve_opt_const_arg(
323 ty
::WithOptConstParam
::unknown(def_id
),
328 // This should be kept up to date with `resolve`.
329 pub fn resolve_opt_const_arg(
331 param_env
: ty
::ParamEnv
<'tcx
>,
332 def
: ty
::WithOptConstParam
<DefId
>,
333 substs
: SubstsRef
<'tcx
>,
334 ) -> Result
<Option
<Instance
<'tcx
>>, ErrorReported
> {
335 // All regions in the result of this query are erased, so it's
336 // fine to erase all of the input regions.
338 // HACK(eddyb) erase regions in `substs` first, so that `param_env.and(...)`
339 // below is more likely to ignore the bounds in scope (e.g. if the only
340 // generic parameters mentioned by `substs` were lifetime ones).
341 let substs
= tcx
.erase_regions(&substs
);
343 // FIXME(eddyb) should this always use `param_env.with_reveal_all()`?
344 if let Some((did
, param_did
)) = def
.as_const_arg() {
345 tcx
.resolve_instance_of_const_arg(
346 tcx
.erase_regions(¶m_env
.and((did
, param_did
, substs
))),
349 tcx
.resolve_instance(tcx
.erase_regions(¶m_env
.and((def
.did
, substs
))))
353 pub fn resolve_for_fn_ptr(
355 param_env
: ty
::ParamEnv
<'tcx
>,
357 substs
: SubstsRef
<'tcx
>,
358 ) -> Option
<Instance
<'tcx
>> {
359 debug
!("resolve(def_id={:?}, substs={:?})", def_id
, substs
);
360 Instance
::resolve(tcx
, param_env
, def_id
, substs
).ok().flatten().map(|mut resolved
| {
362 InstanceDef
::Item(def
) if resolved
.def
.requires_caller_location(tcx
) => {
363 debug
!(" => fn pointer created for function with #[track_caller]");
364 resolved
.def
= InstanceDef
::ReifyShim(def
.did
);
366 InstanceDef
::Virtual(def_id
, _
) => {
367 debug
!(" => fn pointer created for virtual call");
368 resolved
.def
= InstanceDef
::ReifyShim(def_id
);
377 pub fn resolve_for_vtable(
379 param_env
: ty
::ParamEnv
<'tcx
>,
381 substs
: SubstsRef
<'tcx
>,
382 ) -> Option
<Instance
<'tcx
>> {
383 debug
!("resolve(def_id={:?}, substs={:?})", def_id
, substs
);
384 let fn_sig
= tcx
.fn_sig(def_id
);
385 let is_vtable_shim
= !fn_sig
.inputs().skip_binder().is_empty()
386 && fn_sig
.input(0).skip_binder().is_param(0)
387 && tcx
.generics_of(def_id
).has_self
;
389 debug
!(" => associated item with unsizeable self: Self");
390 Some(Instance { def: InstanceDef::VtableShim(def_id), substs }
)
392 Instance
::resolve_for_fn_ptr(tcx
, param_env
, def_id
, substs
)
396 pub fn resolve_closure(
399 substs
: ty
::SubstsRef
<'tcx
>,
400 requested_kind
: ty
::ClosureKind
,
401 ) -> Instance
<'tcx
> {
402 let actual_kind
= substs
.as_closure().kind();
404 match needs_fn_once_adapter_shim(actual_kind
, requested_kind
) {
405 Ok(true) => Instance
::fn_once_adapter_instance(tcx
, def_id
, substs
),
406 _
=> Instance
::new(def_id
, substs
),
410 pub fn resolve_drop_in_place(tcx
: TyCtxt
<'tcx
>, ty
: Ty
<'tcx
>) -> ty
::Instance
<'tcx
> {
411 let def_id
= tcx
.require_lang_item(LangItem
::DropInPlace
, None
);
412 let substs
= tcx
.intern_substs(&[ty
.into()]);
413 Instance
::resolve(tcx
, ty
::ParamEnv
::reveal_all(), def_id
, substs
).unwrap().unwrap()
416 pub fn fn_once_adapter_instance(
419 substs
: ty
::SubstsRef
<'tcx
>,
420 ) -> Instance
<'tcx
> {
421 debug
!("fn_once_adapter_shim({:?}, {:?})", closure_did
, substs
);
422 let fn_once
= tcx
.require_lang_item(LangItem
::FnOnce
, None
);
424 .associated_items(fn_once
)
425 .in_definition_order()
426 .find(|it
| it
.kind
== ty
::AssocKind
::Fn
)
429 let def
= ty
::InstanceDef
::ClosureOnceShim { call_once }
;
431 let self_ty
= tcx
.mk_closure(closure_did
, substs
);
433 let sig
= substs
.as_closure().sig();
434 let sig
= tcx
.normalize_erasing_late_bound_regions(ty
::ParamEnv
::reveal_all(), &sig
);
435 assert_eq
!(sig
.inputs().len(), 1);
436 let substs
= tcx
.mk_substs_trait(self_ty
, &[sig
.inputs()[0].into()]);
438 debug
!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty
, sig
);
439 Instance { def, substs }
442 /// FIXME(#69925) Depending on the kind of `InstanceDef`, the MIR body associated with an
443 /// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
444 /// cases the MIR body is expressed in terms of the types found in the substitution array.
445 /// In the former case, we want to substitute those generic types and replace them with the
446 /// values from the substs when monomorphizing the function body. But in the latter case, we
447 /// don't want to do that substitution, since it has already been done effectively.
449 /// This function returns `Some(substs)` in the former case and None otherwise -- i.e., if
450 /// this function returns `None`, then the MIR body does not require substitution during
451 /// monomorphization.
452 pub fn substs_for_mir_body(&self) -> Option
<SubstsRef
<'tcx
>> {
454 InstanceDef
::CloneShim(..)
455 | InstanceDef
::DropGlue(_
, Some(_
)) => None
,
456 InstanceDef
::ClosureOnceShim { .. }
457 | InstanceDef
::DropGlue(..)
458 // FIXME(#69925): `FnPtrShim` should be in the other branch.
459 | InstanceDef
::FnPtrShim(..)
460 | InstanceDef
::Item(_
)
461 | InstanceDef
::Intrinsic(..)
462 | InstanceDef
::ReifyShim(..)
463 | InstanceDef
::Virtual(..)
464 | InstanceDef
::VtableShim(..) => Some(self.substs
),
468 /// Returns a new `Instance` where generic parameters in `instance.substs` are replaced by
469 /// identify parameters if they are determined to be unused in `instance.def`.
470 pub fn polymorphize(self, tcx
: TyCtxt
<'tcx
>) -> Self {
471 debug
!("polymorphize: running polymorphization analysis");
472 if !tcx
.sess
.opts
.debugging_opts
.polymorphize
{
476 if let InstanceDef
::Item(def
) = self.def
{
477 let polymorphized_substs
= polymorphize(tcx
, def
.did
, self.substs
);
478 debug
!("polymorphize: self={:?} polymorphized_substs={:?}", self, polymorphized_substs
);
479 Self { def: self.def, substs: polymorphized_substs }
486 fn polymorphize
<'tcx
>(
489 substs
: SubstsRef
<'tcx
>,
490 ) -> SubstsRef
<'tcx
> {
491 debug
!("polymorphize({:?}, {:?})", def_id
, substs
);
492 let unused
= tcx
.unused_generic_params(def_id
);
493 debug
!("polymorphize: unused={:?}", unused
);
495 // If this is a closure or generator then we need to handle the case where another closure
496 // from the function is captured as an upvar and hasn't been polymorphized. In this case,
497 // the unpolymorphized upvar closure would result in a polymorphized closure producing
498 // multiple mono items (and eventually symbol clashes).
499 let upvars_ty
= if tcx
.is_closure(def_id
) {
500 Some(substs
.as_closure().tupled_upvars_ty())
501 } else if tcx
.type_of(def_id
).is_generator() {
502 Some(substs
.as_generator().tupled_upvars_ty())
506 let has_upvars
= upvars_ty
.map(|ty
| ty
.tuple_fields().count() > 0).unwrap_or(false);
507 debug
!("polymorphize: upvars_ty={:?} has_upvars={:?}", upvars_ty
, has_upvars
);
509 struct PolymorphizationFolder
<'tcx
> {
513 impl ty
::TypeFolder
<'tcx
> for PolymorphizationFolder
<'tcx
> {
514 fn tcx
<'a
>(&'a
self) -> TyCtxt
<'tcx
> {
518 fn fold_ty(&mut self, ty
: Ty
<'tcx
>) -> Ty
<'tcx
> {
519 debug
!("fold_ty: ty={:?}", ty
);
521 ty
::Closure(def_id
, substs
) => {
522 let polymorphized_substs
= polymorphize(self.tcx
, def_id
, substs
);
523 if substs
== polymorphized_substs
{
526 self.tcx
.mk_closure(def_id
, polymorphized_substs
)
529 ty
::Generator(def_id
, substs
, movability
) => {
530 let polymorphized_substs
= polymorphize(self.tcx
, def_id
, substs
);
531 if substs
== polymorphized_substs
{
534 self.tcx
.mk_generator(def_id
, polymorphized_substs
, movability
)
537 _
=> ty
.super_fold_with(self),
542 InternalSubsts
::for_item(tcx
, def_id
, |param
, _
| {
543 let is_unused
= unused
.contains(param
.index
).unwrap_or(false);
544 debug
!("polymorphize: param={:?} is_unused={:?}", param
, is_unused
);
546 // Upvar case: If parameter is a type parameter..
547 ty
::GenericParamDefKind
::Type { .. }
if
548 // ..and has upvars..
550 // ..and this param has the same type as the tupled upvars..
551 upvars_ty
== Some(substs
[param
.index
as usize].expect_ty()) => {
552 // ..then double-check that polymorphization marked it used..
553 debug_assert
!(!is_unused
);
554 // ..and polymorphize any closures/generators captured as upvars.
555 let upvars_ty
= upvars_ty
.unwrap();
556 let polymorphized_upvars_ty
= upvars_ty
.fold_with(
557 &mut PolymorphizationFolder { tcx }
);
558 debug
!("polymorphize: polymorphized_upvars_ty={:?}", polymorphized_upvars_ty
);
559 ty
::GenericArg
::from(polymorphized_upvars_ty
)
562 // Simple case: If parameter is a const or type parameter..
563 ty
::GenericParamDefKind
::Const
| ty
::GenericParamDefKind
::Type { .. }
if
564 // ..and is within range and unused..
565 unused
.contains(param
.index
).unwrap_or(false) =>
566 // ..then use the identity for this parameter.
567 tcx
.mk_param_from_def(param
),
569 // Otherwise, use the parameter as before.
570 _
=> substs
[param
.index
as usize],
575 fn needs_fn_once_adapter_shim(
576 actual_closure_kind
: ty
::ClosureKind
,
577 trait_closure_kind
: ty
::ClosureKind
,
578 ) -> Result
<bool
, ()> {
579 match (actual_closure_kind
, trait_closure_kind
) {
580 (ty
::ClosureKind
::Fn
, ty
::ClosureKind
::Fn
)
581 | (ty
::ClosureKind
::FnMut
, ty
::ClosureKind
::FnMut
)
582 | (ty
::ClosureKind
::FnOnce
, ty
::ClosureKind
::FnOnce
) => {
583 // No adapter needed.
586 (ty
::ClosureKind
::Fn
, ty
::ClosureKind
::FnMut
) => {
587 // The closure fn `llfn` is a `fn(&self, ...)`. We want a
588 // `fn(&mut self, ...)`. In fact, at codegen time, these are
589 // basically the same thing, so we can just return llfn.
592 (ty
::ClosureKind
::Fn
| ty
::ClosureKind
::FnMut
, ty
::ClosureKind
::FnOnce
) => {
593 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
594 // self, ...)`. We want a `fn(self, ...)`. We can produce
595 // this by doing something like:
597 // fn call_once(self, ...) { call_mut(&self, ...) }
598 // fn call_once(mut self, ...) { call_mut(&mut self, ...) }
600 // These are both the same at codegen time.
603 (ty
::ClosureKind
::FnMut
| ty
::ClosureKind
::FnOnce
, _
) => Err(()),