1 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
2 use crate::ty::print::{FmtPrinter, Printer};
3 use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitable};
4 use crate::ty::{EarlyBinder, InternalSubsts, SubstsRef};
5 use rustc_errors::ErrorGuaranteed;
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;
10 use rustc_middle::ty::normalize_erasing_regions::NormalizationError;
11 use rustc_span::Symbol;
15 /// A monomorphized `InstanceDef`.
17 /// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
18 /// simply couples a potentially generic `InstanceDef` with some substs, and codegen and const eval
19 /// will do all required substitution as they run.
20 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
21 #[derive(HashStable, Lift, TypeFoldable, TypeVisitable)]
22 pub struct Instance<'tcx> {
23 pub def: InstanceDef<'tcx>,
24 pub substs: SubstsRef<'tcx>,
27 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
28 #[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable, Lift)]
29 pub enum InstanceDef<'tcx> {
30 /// A user-defined callable item.
36 Item(ty::WithOptConstParam<DefId>),
38 /// An intrinsic `fn` item (with `"rust-intrinsic"` or `"platform-intrinsic"` ABI).
40 /// Alongside `Virtual`, this is the only `InstanceDef` that does not have its own callable MIR.
41 /// Instead, codegen and const eval "magically" evaluate calls to intrinsics purely in the
45 /// `<T as Trait>::method` where `method` receives unsizeable `self: Self` (part of the
46 /// `unsized_locals` feature).
48 /// The generated shim will take `Self` via `*mut Self` - conceptually this is `&owned Self` -
49 /// and dereference the argument to call the original function.
52 /// `fn()` pointer where the function itself cannot be turned into a pointer.
54 /// One example is `<dyn Trait as Trait>::fn`, where the shim contains
55 /// a virtual call, which codegen supports only via a direct call to the
56 /// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
58 /// Another example is functions annotated with `#[track_caller]`, which
59 /// must have their implicit caller location argument populated for a call.
60 /// Because this is a required part of the function's ABI but can't be tracked
61 /// as a property of the function pointer, we use a single "caller location"
62 /// (the definition of the function itself).
65 /// `<fn() as FnTrait>::call_*` (generated `FnTrait` implementation for `fn()` pointers).
67 /// `DefId` is `FnTrait::call_*`.
68 FnPtrShim(DefId, Ty<'tcx>),
70 /// Dynamic dispatch to `<dyn Trait as Trait>::fn`.
72 /// This `InstanceDef` does not have callable MIR. Calls to `Virtual` instances must be
73 /// codegen'd as virtual calls through the vtable.
75 /// If this is reified to a `fn` pointer, a `ReifyShim` is used (see `ReifyShim` above for more
77 Virtual(DefId, usize),
79 /// `<[FnMut closure] as FnOnce>::call_once`.
81 /// The `DefId` is the ID of the `call_once` method in `FnOnce`.
82 ClosureOnceShim { call_once: DefId, track_caller: bool },
84 /// `core::ptr::drop_in_place::<T>`.
86 /// The `DefId` is for `core::ptr::drop_in_place`.
87 /// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
89 DropGlue(DefId, Option<Ty<'tcx>>),
91 /// Compiler-generated `<T as Clone>::clone` implementation.
93 /// For all types that automatically implement `Copy`, a trivial `Clone` impl is provided too.
94 /// Additionally, arrays, tuples, and closures get a `Clone` shim even if they aren't `Copy`.
96 /// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
97 CloneShim(DefId, Ty<'tcx>),
100 impl<'tcx> Instance<'tcx> {
101 /// Returns the `Ty` corresponding to this `Instance`, with generic substitutions applied and
102 /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
103 pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
104 let ty = tcx.type_of(self.def.def_id());
105 tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty)
108 /// Finds a crate that contains a monomorphization of this instance that
109 /// can be linked to from the local crate. A return value of `None` means
110 /// no upstream crate provides such an exported monomorphization.
112 /// This method already takes into account the global `-Zshare-generics`
113 /// setting, always returning `None` if `share-generics` is off.
114 pub fn upstream_monomorphization(&self, tcx: TyCtxt<'tcx>) -> Option<CrateNum> {
115 // If we are not in share generics mode, we don't link to upstream
116 // monomorphizations but always instantiate our own internal versions
118 if !tcx.sess.opts.share_generics() {
122 // If this is an item that is defined in the local crate, no upstream
123 // crate can know about it/provide a monomorphization.
124 if self.def_id().is_local() {
128 // If this a non-generic instance, it cannot be a shared monomorphization.
129 self.substs.non_erasable_generics().next()?;
132 InstanceDef::Item(def) => tcx
133 .upstream_monomorphizations_for(def.did)
134 .and_then(|monos| monos.get(&self.substs).cloned()),
135 InstanceDef::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.substs),
141 impl<'tcx> InstanceDef<'tcx> {
143 pub fn def_id(self) -> DefId {
145 InstanceDef::Item(def) => def.did,
146 InstanceDef::VTableShim(def_id)
147 | InstanceDef::ReifyShim(def_id)
148 | InstanceDef::FnPtrShim(def_id, _)
149 | InstanceDef::Virtual(def_id, _)
150 | InstanceDef::Intrinsic(def_id)
151 | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
152 | InstanceDef::DropGlue(def_id, _)
153 | InstanceDef::CloneShim(def_id, _) => def_id,
157 /// Returns the `DefId` of instances which might not require codegen locally.
158 pub fn def_id_if_not_guaranteed_local_codegen(self) -> Option<DefId> {
160 ty::InstanceDef::Item(def) => Some(def.did),
161 ty::InstanceDef::DropGlue(def_id, Some(_)) => Some(def_id),
162 InstanceDef::VTableShim(..)
163 | InstanceDef::ReifyShim(..)
164 | InstanceDef::FnPtrShim(..)
165 | InstanceDef::Virtual(..)
166 | InstanceDef::Intrinsic(..)
167 | InstanceDef::ClosureOnceShim { .. }
168 | InstanceDef::DropGlue(..)
169 | InstanceDef::CloneShim(..) => None,
174 pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
176 InstanceDef::Item(def) => def,
177 InstanceDef::VTableShim(def_id)
178 | InstanceDef::ReifyShim(def_id)
179 | InstanceDef::FnPtrShim(def_id, _)
180 | InstanceDef::Virtual(def_id, _)
181 | InstanceDef::Intrinsic(def_id)
182 | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
183 | InstanceDef::DropGlue(def_id, _)
184 | InstanceDef::CloneShim(def_id, _) => ty::WithOptConstParam::unknown(def_id),
189 pub fn get_attrs(&self, tcx: TyCtxt<'tcx>, attr: Symbol) -> ty::Attributes<'tcx> {
190 tcx.get_attrs(self.def_id(), attr)
193 /// Returns `true` if the LLVM version of this instance is unconditionally
194 /// marked with `inline`. This implies that a copy of this instance is
195 /// generated in every codegen unit.
196 /// Note that this is only a hint. See the documentation for
197 /// `generates_cgu_internal_copy` for more information.
198 pub fn requires_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
199 use rustc_hir::definitions::DefPathData;
200 let def_id = match *self {
201 ty::InstanceDef::Item(def) => def.did,
202 ty::InstanceDef::DropGlue(_, Some(_)) => return false,
206 tcx.def_key(def_id).disambiguated_data.data,
207 DefPathData::Ctor | DefPathData::ClosureExpr
211 /// Returns `true` if the machine code for this instance is instantiated in
212 /// each codegen unit that references it.
213 /// Note that this is only a hint! The compiler can globally decide to *not*
214 /// do this in order to speed up compilation. CGU-internal copies are
215 /// only exist to enable inlining. If inlining is not performed (e.g. at
216 /// `-Copt-level=0`) then the time for generating them is wasted and it's
217 /// better to create a single copy with external linkage.
218 pub fn generates_cgu_internal_copy(&self, tcx: TyCtxt<'tcx>) -> bool {
219 if self.requires_inline(tcx) {
222 if let ty::InstanceDef::DropGlue(.., Some(ty)) = *self {
223 // Drop glue generally wants to be instantiated at every codegen
224 // unit, but without an #[inline] hint. We should make this
225 // available to normal end-users.
226 if tcx.sess.opts.incremental.is_none() {
229 // When compiling with incremental, we can generate a *lot* of
230 // codegen units. Including drop glue into all of them has a
231 // considerable compile time cost.
233 // We include enums without destructors to allow, say, optimizing
234 // drops of `Option::None` before LTO. We also respect the intent of
235 // `#[inline]` on `Drop::drop` implementations.
236 return ty.ty_adt_def().map_or(true, |adt_def| {
237 adt_def.destructor(tcx).map_or_else(
238 || adt_def.is_enum(),
239 |dtor| tcx.codegen_fn_attrs(dtor.did).requests_inline(),
243 tcx.codegen_fn_attrs(self.def_id()).requests_inline()
246 pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
248 InstanceDef::Item(ty::WithOptConstParam { did: def_id, .. })
249 | InstanceDef::Virtual(def_id, _) => {
250 tcx.body_codegen_attrs(def_id).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
252 InstanceDef::ClosureOnceShim { call_once: _, track_caller } => track_caller,
257 /// Returns `true` when the MIR body associated with this instance should be monomorphized
258 /// by its users (e.g. codegen or miri) by substituting the `substs` from `Instance` (see
259 /// `Instance::substs_for_mir_body`).
261 /// Otherwise, returns `false` only for some kinds of shims where the construction of the MIR
262 /// body should perform necessary substitutions.
263 pub fn has_polymorphic_mir_body(&self) -> bool {
265 InstanceDef::CloneShim(..)
266 | InstanceDef::FnPtrShim(..)
267 | InstanceDef::DropGlue(_, Some(_)) => false,
268 InstanceDef::ClosureOnceShim { .. }
269 | InstanceDef::DropGlue(..)
270 | InstanceDef::Item(_)
271 | InstanceDef::Intrinsic(..)
272 | InstanceDef::ReifyShim(..)
273 | InstanceDef::Virtual(..)
274 | InstanceDef::VTableShim(..) => true,
280 f: &mut fmt::Formatter<'_>,
281 instance: &Instance<'_>,
282 type_length: rustc_session::Limit,
284 ty::tls::with(|tcx| {
285 let substs = tcx.lift(instance.substs).expect("could not lift for printing");
287 let s = FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
288 .print_def_path(instance.def_id(), substs)?
294 InstanceDef::Item(_) => Ok(()),
295 InstanceDef::VTableShim(_) => write!(f, " - shim(vtable)"),
296 InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
297 InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
298 InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
299 InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
300 InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
301 InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
302 InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
303 InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
307 pub struct ShortInstance<'a, 'tcx>(pub &'a Instance<'tcx>, pub usize);
309 impl<'a, 'tcx> fmt::Display for ShortInstance<'a, 'tcx> {
310 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
311 fmt_instance(f, self.0, rustc_session::Limit(self.1))
315 impl<'tcx> fmt::Display for Instance<'tcx> {
316 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
317 ty::tls::with(|tcx| fmt_instance(f, self, tcx.type_length_limit()))
321 impl<'tcx> Instance<'tcx> {
322 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx> {
324 !substs.has_escaping_bound_vars(),
325 "substs of instance {:?} not normalized for codegen: {:?}",
329 Instance { def: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)), substs }
332 pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
333 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
334 ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
335 ty::GenericParamDefKind::Type { .. } => {
336 bug!("Instance::mono: {:?} has type parameters", def_id)
338 ty::GenericParamDefKind::Const { .. } => {
339 bug!("Instance::mono: {:?} has const parameters", def_id)
343 Instance::new(def_id, substs)
347 pub fn def_id(&self) -> DefId {
351 /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
352 /// this is used to find the precise code that will run for a trait method invocation,
355 /// Returns `Ok(None)` if we cannot resolve `Instance` to a specific instance.
356 /// For example, in a context like this,
358 /// ```ignore (illustrative)
359 /// fn foo<T: Debug>(t: T) { ... }
362 /// trying to resolve `Debug::fmt` applied to `T` will yield `Ok(None)`, because we do not
363 /// know what code ought to run. (Note that this setting is also affected by the
364 /// `RevealMode` in the parameter environment.)
366 /// Presuming that coherence and type-check have succeeded, if this method is invoked
367 /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
368 /// `Ok(Some(instance))`.
370 /// Returns `Err(ErrorGuaranteed)` when the `Instance` resolution process
371 /// couldn't complete due to errors elsewhere - this is distinct
372 /// from `Ok(None)` to avoid misleading diagnostics when an error
373 /// has already been/will be emitted, for the original cause
376 param_env: ty::ParamEnv<'tcx>,
378 substs: SubstsRef<'tcx>,
379 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
380 Instance::resolve_opt_const_arg(
383 ty::WithOptConstParam::unknown(def_id),
388 // This should be kept up to date with `resolve`.
389 pub fn resolve_opt_const_arg(
391 param_env: ty::ParamEnv<'tcx>,
392 def: ty::WithOptConstParam<DefId>,
393 substs: SubstsRef<'tcx>,
394 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
395 // All regions in the result of this query are erased, so it's
396 // fine to erase all of the input regions.
398 // HACK(eddyb) erase regions in `substs` first, so that `param_env.and(...)`
399 // below is more likely to ignore the bounds in scope (e.g. if the only
400 // generic parameters mentioned by `substs` were lifetime ones).
401 let substs = tcx.erase_regions(substs);
403 // FIXME(eddyb) should this always use `param_env.with_reveal_all()`?
404 if let Some((did, param_did)) = def.as_const_arg() {
405 tcx.resolve_instance_of_const_arg(
406 tcx.erase_regions(param_env.and((did, param_did, substs))),
409 tcx.resolve_instance(tcx.erase_regions(param_env.and((def.did, substs))))
413 pub fn resolve_for_fn_ptr(
415 param_env: ty::ParamEnv<'tcx>,
417 substs: SubstsRef<'tcx>,
418 ) -> Option<Instance<'tcx>> {
419 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
420 // Use either `resolve_closure` or `resolve_for_vtable`
421 assert!(!tcx.is_closure(def_id), "Called `resolve_for_fn_ptr` on closure: {:?}", def_id);
422 Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
424 InstanceDef::Item(def) if resolved.def.requires_caller_location(tcx) => {
425 debug!(" => fn pointer created for function with #[track_caller]");
426 resolved.def = InstanceDef::ReifyShim(def.did);
428 InstanceDef::Virtual(def_id, _) => {
429 debug!(" => fn pointer created for virtual call");
430 resolved.def = InstanceDef::ReifyShim(def_id);
439 pub fn resolve_for_vtable(
441 param_env: ty::ParamEnv<'tcx>,
443 substs: SubstsRef<'tcx>,
444 ) -> Option<Instance<'tcx>> {
445 debug!("resolve_for_vtable(def_id={:?}, substs={:?})", def_id, substs);
446 let fn_sig = tcx.fn_sig(def_id);
447 let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
448 && fn_sig.input(0).skip_binder().is_param(0)
449 && tcx.generics_of(def_id).has_self;
451 debug!(" => associated item with unsizeable self: Self");
452 Some(Instance { def: InstanceDef::VTableShim(def_id), substs })
454 Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
456 InstanceDef::Item(def) => {
457 // We need to generate a shim when we cannot guarantee that
458 // the caller of a trait object method will be aware of
459 // `#[track_caller]` - this ensures that the caller
460 // and callee ABI will always match.
462 // The shim is generated when all of these conditions are met:
464 // 1) The underlying method expects a caller location parameter
466 if resolved.def.requires_caller_location(tcx)
467 // 2) The caller location parameter comes from having `#[track_caller]`
468 // on the implementation, and *not* on the trait method.
469 && !tcx.should_inherit_track_caller(def.did)
470 // If the method implementation comes from the trait definition itself
471 // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`),
472 // then we don't need to generate a shim. This check is needed because
473 // `should_inherit_track_caller` returns `false` if our method
474 // implementation comes from the trait block, and not an impl block
476 tcx.opt_associated_item(def.did),
478 container: ty::AssocItemContainer::TraitContainer,
483 if tcx.is_closure(def.did) {
484 debug!(" => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
485 def.did, def_id, substs);
487 // Create a shim for the `FnOnce/FnMut/Fn` method we are calling
488 // - unlike functions, invoking a closure always goes through a
490 resolved = Instance { def: InstanceDef::ReifyShim(def_id), substs };
493 " => vtable fn pointer created for function with #[track_caller]: {:?}", def.did
495 resolved.def = InstanceDef::ReifyShim(def.did);
499 InstanceDef::Virtual(def_id, _) => {
500 debug!(" => vtable fn pointer created for virtual call");
501 resolved.def = InstanceDef::ReifyShim(def_id);
511 pub fn resolve_closure(
514 substs: ty::SubstsRef<'tcx>,
515 requested_kind: ty::ClosureKind,
516 ) -> Option<Instance<'tcx>> {
517 let actual_kind = substs.as_closure().kind();
519 match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
520 Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
521 _ => Some(Instance::new(def_id, substs)),
525 pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
526 let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
527 let substs = tcx.intern_substs(&[ty.into()]);
528 Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap().unwrap()
531 #[instrument(level = "debug", skip(tcx), ret)]
532 pub fn fn_once_adapter_instance(
535 substs: ty::SubstsRef<'tcx>,
536 ) -> Option<Instance<'tcx>> {
537 let fn_once = tcx.require_lang_item(LangItem::FnOnce, None);
539 .associated_items(fn_once)
540 .in_definition_order()
541 .find(|it| it.kind == ty::AssocKind::Fn)
545 tcx.codegen_fn_attrs(closure_did).flags.contains(CodegenFnAttrFlags::TRACK_CALLER);
546 let def = ty::InstanceDef::ClosureOnceShim { call_once, track_caller };
548 let self_ty = tcx.mk_closure(closure_did, substs);
550 let sig = substs.as_closure().sig();
552 tcx.try_normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig).ok()?;
553 assert_eq!(sig.inputs().len(), 1);
554 let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
556 debug!(?self_ty, ?sig);
557 Some(Instance { def, substs })
560 /// Depending on the kind of `InstanceDef`, the MIR body associated with an
561 /// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
562 /// cases the MIR body is expressed in terms of the types found in the substitution array.
563 /// In the former case, we want to substitute those generic types and replace them with the
564 /// values from the substs when monomorphizing the function body. But in the latter case, we
565 /// don't want to do that substitution, since it has already been done effectively.
567 /// This function returns `Some(substs)` in the former case and `None` otherwise -- i.e., if
568 /// this function returns `None`, then the MIR body does not require substitution during
570 fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
571 if self.def.has_polymorphic_mir_body() { Some(self.substs) } else { None }
574 pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
576 T: TypeFoldable<'tcx> + Copy,
578 if let Some(substs) = self.substs_for_mir_body() {
579 EarlyBinder(*v).subst(tcx, substs)
586 pub fn subst_mir_and_normalize_erasing_regions<T>(
589 param_env: ty::ParamEnv<'tcx>,
593 T: TypeFoldable<'tcx> + Clone,
595 if let Some(substs) = self.substs_for_mir_body() {
596 tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
598 tcx.normalize_erasing_regions(param_env, v)
603 pub fn try_subst_mir_and_normalize_erasing_regions<T>(
606 param_env: ty::ParamEnv<'tcx>,
608 ) -> Result<T, NormalizationError<'tcx>>
610 T: TypeFoldable<'tcx> + Clone,
612 if let Some(substs) = self.substs_for_mir_body() {
613 tcx.try_subst_and_normalize_erasing_regions(substs, param_env, v)
615 tcx.try_normalize_erasing_regions(param_env, v)
619 /// Returns a new `Instance` where generic parameters in `instance.substs` are replaced by
620 /// identity parameters if they are determined to be unused in `instance.def`.
621 pub fn polymorphize(self, tcx: TyCtxt<'tcx>) -> Self {
622 debug!("polymorphize: running polymorphization analysis");
623 if !tcx.sess.opts.unstable_opts.polymorphize {
627 let polymorphized_substs = polymorphize(tcx, self.def, self.substs);
628 debug!("polymorphize: self={:?} polymorphized_substs={:?}", self, polymorphized_substs);
629 Self { def: self.def, substs: polymorphized_substs }
633 fn polymorphize<'tcx>(
635 instance: ty::InstanceDef<'tcx>,
636 substs: SubstsRef<'tcx>,
637 ) -> SubstsRef<'tcx> {
638 debug!("polymorphize({:?}, {:?})", instance, substs);
639 let unused = tcx.unused_generic_params(instance);
640 debug!("polymorphize: unused={:?}", unused);
642 // If this is a closure or generator then we need to handle the case where another closure
643 // from the function is captured as an upvar and hasn't been polymorphized. In this case,
644 // the unpolymorphized upvar closure would result in a polymorphized closure producing
645 // multiple mono items (and eventually symbol clashes).
646 let def_id = instance.def_id();
647 let upvars_ty = if tcx.is_closure(def_id) {
648 Some(substs.as_closure().tupled_upvars_ty())
649 } else if tcx.type_of(def_id).is_generator() {
650 Some(substs.as_generator().tupled_upvars_ty())
654 let has_upvars = upvars_ty.map_or(false, |ty| !ty.tuple_fields().is_empty());
655 debug!("polymorphize: upvars_ty={:?} has_upvars={:?}", upvars_ty, has_upvars);
657 struct PolymorphizationFolder<'tcx> {
661 impl<'tcx> ty::TypeFolder<'tcx> for PolymorphizationFolder<'tcx> {
662 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
666 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
667 debug!("fold_ty: ty={:?}", ty);
669 ty::Closure(def_id, substs) => {
670 let polymorphized_substs = polymorphize(
672 ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
675 if substs == polymorphized_substs {
678 self.tcx.mk_closure(def_id, polymorphized_substs)
681 ty::Generator(def_id, substs, movability) => {
682 let polymorphized_substs = polymorphize(
684 ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
687 if substs == polymorphized_substs {
690 self.tcx.mk_generator(def_id, polymorphized_substs, movability)
693 _ => ty.super_fold_with(self),
698 InternalSubsts::for_item(tcx, def_id, |param, _| {
699 let is_unused = unused.contains(param.index).unwrap_or(false);
700 debug!("polymorphize: param={:?} is_unused={:?}", param, is_unused);
702 // Upvar case: If parameter is a type parameter..
703 ty::GenericParamDefKind::Type { .. } if
704 // ..and has upvars..
706 // ..and this param has the same type as the tupled upvars..
707 upvars_ty == Some(substs[param.index as usize].expect_ty()) => {
708 // ..then double-check that polymorphization marked it used..
709 debug_assert!(!is_unused);
710 // ..and polymorphize any closures/generators captured as upvars.
711 let upvars_ty = upvars_ty.unwrap();
712 let polymorphized_upvars_ty = upvars_ty.fold_with(
713 &mut PolymorphizationFolder { tcx });
714 debug!("polymorphize: polymorphized_upvars_ty={:?}", polymorphized_upvars_ty);
715 ty::GenericArg::from(polymorphized_upvars_ty)
718 // Simple case: If parameter is a const or type parameter..
719 ty::GenericParamDefKind::Const { .. } | ty::GenericParamDefKind::Type { .. } if
720 // ..and is within range and unused..
721 unused.contains(param.index).unwrap_or(false) =>
722 // ..then use the identity for this parameter.
723 tcx.mk_param_from_def(param),
725 // Otherwise, use the parameter as before.
726 _ => substs[param.index as usize],
731 fn needs_fn_once_adapter_shim(
732 actual_closure_kind: ty::ClosureKind,
733 trait_closure_kind: ty::ClosureKind,
734 ) -> Result<bool, ()> {
735 match (actual_closure_kind, trait_closure_kind) {
736 (ty::ClosureKind::Fn, ty::ClosureKind::Fn)
737 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut)
738 | (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
739 // No adapter needed.
742 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
743 // The closure fn `llfn` is a `fn(&self, ...)`. We want a
744 // `fn(&mut self, ...)`. In fact, at codegen time, these are
745 // basically the same thing, so we can just return llfn.
748 (ty::ClosureKind::Fn | ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
749 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
750 // self, ...)`. We want a `fn(self, ...)`. We can produce
751 // this by doing something like:
753 // fn call_once(self, ...) { call_mut(&self, ...) }
754 // fn call_once(mut self, ...) { call_mut(&mut self, ...) }
756 // These are both the same at codegen time.
759 (ty::ClosureKind::FnMut | ty::ClosureKind::FnOnce, _) => Err(()),