1 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
2 use crate::middle::lang_items::DropInPlaceFnLangItem;
4 use crate::ty::print::{FmtPrinter, Printer};
5 use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
6 use rustc_hir::def::Namespace;
7 use rustc_hir::def_id::DefId;
8 use rustc_macros::HashStable;
9 use rustc_target::spec::abi::Abi;
13 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
14 #[derive(HashStable, Lift)]
15 pub struct Instance<'tcx> {
16 pub def: InstanceDef<'tcx>,
17 pub substs: SubstsRef<'tcx>,
20 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable, HashStable)]
21 pub enum InstanceDef<'tcx> {
25 /// `<T as Trait>::method` where `method` receives unsizeable `self: Self`.
28 /// `fn()` pointer where the function itself cannot be turned into a pointer.
30 /// One example is `<dyn Trait as Trait>::fn`, where the shim contains
31 /// a virtual call, which codegen supports only via a direct call to the
32 /// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
34 /// Another example is functions annotated with `#[track_caller]`, which
35 /// must have their implicit caller location argument populated for a call.
36 /// Because this is a required part of the function's ABI but can't be tracked
37 /// as a property of the function pointer, we use a single "caller location"
38 /// (the definition of the function itself).
41 /// `<fn() as FnTrait>::call_*`
42 /// `DefId` is `FnTrait::call_*`.
43 FnPtrShim(DefId, Ty<'tcx>),
45 /// `<dyn Trait as Trait>::fn`, "direct calls" of which are implicitly
46 /// codegen'd as virtual calls.
48 /// NB: if this is reified to a `fn` pointer, a `ReifyShim` is used
49 /// (see `ReifyShim` above for more details on that).
50 Virtual(DefId, usize),
52 /// `<[mut closure] as FnOnce>::call_once`
57 /// `drop_in_place::<T>; None` for empty drop glue.
58 DropGlue(DefId, Option<Ty<'tcx>>),
60 ///`<T as Clone>::clone` shim.
61 CloneShim(DefId, Ty<'tcx>),
64 impl<'tcx> Instance<'tcx> {
65 /// Returns the `Ty` corresponding to this `Instance`,
66 /// with generic substitutions applied and lifetimes erased.
68 /// This method can only be called when the 'substs' for this Instance
69 /// are fully monomorphic (no `ty::Param`'s are present).
70 /// This is usually the case (e.g. during codegen).
71 /// However, during constant evaluation, we may want
72 /// to try to resolve a `Instance` using generic parameters
73 /// (e.g. when we are attempting to to do const-propagation).
74 /// In this case, `Instance.ty_env` should be used to provide
75 /// the `ParamEnv` for our generic context.
76 pub fn monomorphic_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
77 let ty = tcx.type_of(self.def.def_id());
78 // There shouldn't be any params - if there are, then
79 // Instance.ty_env should have been used to provide the proper
81 if self.substs.has_param_types() {
82 bug!("Instance.ty called for type {:?} with params in substs: {:?}", ty, self.substs);
84 tcx.subst_and_normalize_erasing_regions(self.substs, ty::ParamEnv::reveal_all(), &ty)
87 /// Like `Instance.ty`, but allows a `ParamEnv` to be specified for use during
88 /// normalization. This method is only really useful during constant evaluation,
89 /// where we are dealing with potentially generic types.
90 pub fn ty_env(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
91 let ty = tcx.type_of(self.def.def_id());
92 tcx.subst_and_normalize_erasing_regions(self.substs, param_env, &ty)
96 impl<'tcx> InstanceDef<'tcx> {
98 pub fn def_id(&self) -> DefId {
100 InstanceDef::Item(def_id)
101 | InstanceDef::VtableShim(def_id)
102 | InstanceDef::ReifyShim(def_id)
103 | InstanceDef::FnPtrShim(def_id, _)
104 | InstanceDef::Virtual(def_id, _)
105 | InstanceDef::Intrinsic(def_id)
106 | InstanceDef::ClosureOnceShim { call_once: def_id }
107 | InstanceDef::DropGlue(def_id, _)
108 | InstanceDef::CloneShim(def_id, _) => def_id,
113 pub fn attrs(&self, tcx: TyCtxt<'tcx>) -> ty::Attributes<'tcx> {
114 tcx.get_attrs(self.def_id())
117 pub fn is_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
118 use crate::hir::map::DefPathData;
119 let def_id = match *self {
120 ty::InstanceDef::Item(def_id) => def_id,
121 ty::InstanceDef::DropGlue(_, Some(_)) => return false,
124 match tcx.def_key(def_id).disambiguated_data.data {
125 DefPathData::Ctor | DefPathData::ClosureExpr => true,
130 pub fn requires_local(&self, tcx: TyCtxt<'tcx>) -> bool {
131 if self.is_inline(tcx) {
134 if let ty::InstanceDef::DropGlue(..) = *self {
135 // Drop glue wants to be instantiated at every codegen
136 // unit, but without an #[inline] hint. We should make this
137 // available to normal end-users.
140 tcx.codegen_fn_attrs(self.def_id()).requests_inline()
143 pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
145 InstanceDef::Item(def_id) => {
146 tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
153 impl<'tcx> fmt::Display for Instance<'tcx> {
154 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
155 ty::tls::with(|tcx| {
156 let substs = tcx.lift(&self.substs).expect("could not lift for printing");
157 FmtPrinter::new(tcx, &mut *f, Namespace::ValueNS)
158 .print_def_path(self.def_id(), substs)?;
163 InstanceDef::Item(_) => Ok(()),
164 InstanceDef::VtableShim(_) => write!(f, " - shim(vtable)"),
165 InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
166 InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
167 InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
168 InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({:?})", ty),
169 InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
170 InstanceDef::DropGlue(_, ty) => write!(f, " - shim({:?})", ty),
171 InstanceDef::CloneShim(_, ty) => write!(f, " - shim({:?})", ty),
176 impl<'tcx> Instance<'tcx> {
177 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx> {
179 !substs.has_escaping_bound_vars(),
180 "substs of instance {:?} not normalized for codegen: {:?}",
184 Instance { def: InstanceDef::Item(def_id), substs: substs }
187 pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
188 Instance::new(def_id, tcx.empty_substs_for_def_id(def_id))
192 pub fn def_id(&self) -> DefId {
196 /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
197 /// this is used to find the precise code that will run for a trait method invocation,
200 /// Returns `None` if we cannot resolve `Instance` to a specific instance.
201 /// For example, in a context like this,
204 /// fn foo<T: Debug>(t: T) { ... }
207 /// trying to resolve `Debug::fmt` applied to `T` will yield `None`, because we do not
208 /// know what code ought to run. (Note that this setting is also affected by the
209 /// `RevealMode` in the parameter environment.)
211 /// Presuming that coherence and type-check have succeeded, if this method is invoked
212 /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
216 param_env: ty::ParamEnv<'tcx>,
218 substs: SubstsRef<'tcx>,
219 ) -> Option<Instance<'tcx>> {
220 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
221 let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
222 debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
223 let item = tcx.associated_item(def_id);
224 resolve_associated_item(tcx, &item, param_env, trait_def_id, substs)
226 let ty = tcx.type_of(def_id);
227 let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, &ty);
229 let def = match item_type.kind {
232 let f = item_type.fn_sig(tcx);
233 f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic
236 debug!(" => intrinsic");
237 ty::InstanceDef::Intrinsic(def_id)
240 if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
241 let ty = substs.type_at(0);
242 if ty.needs_drop(tcx, ty::ParamEnv::reveal_all()) {
243 debug!(" => nontrivial drop glue");
244 ty::InstanceDef::DropGlue(def_id, Some(ty))
246 debug!(" => trivial drop glue");
247 ty::InstanceDef::DropGlue(def_id, None)
250 debug!(" => free item");
251 ty::InstanceDef::Item(def_id)
255 Some(Instance { def: def, substs: substs })
257 debug!("resolve(def_id={:?}, substs={:?}) = {:?}", def_id, substs, result);
261 pub fn resolve_for_fn_ptr(
263 param_env: ty::ParamEnv<'tcx>,
265 substs: SubstsRef<'tcx>,
266 ) -> Option<Instance<'tcx>> {
267 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
268 Instance::resolve(tcx, param_env, def_id, substs).map(|mut resolved| {
270 InstanceDef::Item(def_id) if resolved.def.requires_caller_location(tcx) => {
271 debug!(" => fn pointer created for function with #[track_caller]");
272 resolved.def = InstanceDef::ReifyShim(def_id);
274 InstanceDef::Virtual(def_id, _) => {
275 debug!(" => fn pointer created for virtual call");
276 resolved.def = InstanceDef::ReifyShim(def_id);
285 pub fn resolve_for_vtable(
287 param_env: ty::ParamEnv<'tcx>,
289 substs: SubstsRef<'tcx>,
290 ) -> Option<Instance<'tcx>> {
291 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
292 let fn_sig = tcx.fn_sig(def_id);
293 let is_vtable_shim = fn_sig.inputs().skip_binder().len() > 0
294 && fn_sig.input(0).skip_binder().is_param(0)
295 && tcx.generics_of(def_id).has_self;
297 debug!(" => associated item with unsizeable self: Self");
298 Some(Instance { def: InstanceDef::VtableShim(def_id), substs })
300 Instance::resolve(tcx, param_env, def_id, substs)
304 pub fn resolve_closure(
307 substs: ty::SubstsRef<'tcx>,
308 requested_kind: ty::ClosureKind,
309 ) -> Instance<'tcx> {
310 let actual_kind = substs.as_closure().kind(def_id, tcx);
312 match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
313 Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
314 _ => Instance::new(def_id, substs),
318 pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
319 let def_id = tcx.require_lang_item(DropInPlaceFnLangItem, None);
320 let substs = tcx.intern_substs(&[ty.into()]);
321 Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap()
324 pub fn fn_once_adapter_instance(
327 substs: ty::SubstsRef<'tcx>,
328 ) -> Instance<'tcx> {
329 debug!("fn_once_adapter_shim({:?}, {:?})", closure_did, substs);
330 let fn_once = tcx.lang_items().fn_once_trait().unwrap();
332 .associated_items(fn_once)
333 .find(|it| it.kind == ty::AssocKind::Method)
336 let def = ty::InstanceDef::ClosureOnceShim { call_once };
338 let self_ty = tcx.mk_closure(closure_did, substs);
340 let sig = substs.as_closure().sig(closure_did, tcx);
341 let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
342 assert_eq!(sig.inputs().len(), 1);
343 let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
345 debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
346 Instance { def, substs }
349 pub fn is_vtable_shim(&self) -> bool {
350 if let InstanceDef::VtableShim(..) = self.def { true } else { false }
354 fn resolve_associated_item<'tcx>(
356 trait_item: &ty::AssocItem,
357 param_env: ty::ParamEnv<'tcx>,
359 rcvr_substs: SubstsRef<'tcx>,
360 ) -> Option<Instance<'tcx>> {
361 let def_id = trait_item.def_id;
363 "resolve_associated_item(trait_item={:?}, \
367 def_id, param_env, trait_id, rcvr_substs
370 let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
371 let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref)));
373 // Now that we know which impl is being used, we can dispatch to
374 // the actual function:
376 traits::VtableImpl(impl_data) => {
377 let (def_id, substs) =
378 traits::find_associated_item(tcx, param_env, trait_item, rcvr_substs, &impl_data);
380 let resolved_item = tcx.associated_item(def_id);
382 // Since this is a trait item, we need to see if the item is either a trait default item
383 // or a specialization because we can't resolve those unless we can `Reveal::All`.
384 // NOTE: This should be kept in sync with the similar code in
385 // `rustc::traits::project::assemble_candidates_from_impls()`.
386 let eligible = if !resolved_item.defaultness.is_default() {
388 } else if param_env.reveal == traits::Reveal::All {
389 !trait_ref.needs_subst()
398 let substs = tcx.erase_regions(&substs);
399 Some(ty::Instance::new(def_id, substs))
401 traits::VtableGenerator(generator_data) => Some(Instance {
402 def: ty::InstanceDef::Item(generator_data.generator_def_id),
403 substs: generator_data.substs,
405 traits::VtableClosure(closure_data) => {
406 let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
407 Some(Instance::resolve_closure(
409 closure_data.closure_def_id,
414 traits::VtableFnPointer(ref data) => Some(Instance {
415 def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
418 traits::VtableObject(ref data) => {
419 let index = traits::get_vtable_index_of_object_method(tcx, data, def_id);
420 Some(Instance { def: ty::InstanceDef::Virtual(def_id, index), substs: rcvr_substs })
422 traits::VtableBuiltin(..) => {
423 if tcx.lang_items().clone_trait().is_some() {
425 def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
432 traits::VtableAutoImpl(..) | traits::VtableParam(..) | traits::VtableTraitAlias(..) => None,
436 fn needs_fn_once_adapter_shim(
437 actual_closure_kind: ty::ClosureKind,
438 trait_closure_kind: ty::ClosureKind,
439 ) -> Result<bool, ()> {
440 match (actual_closure_kind, trait_closure_kind) {
441 (ty::ClosureKind::Fn, ty::ClosureKind::Fn)
442 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut)
443 | (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
444 // No adapter needed.
447 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
448 // The closure fn `llfn` is a `fn(&self, ...)`. We want a
449 // `fn(&mut self, ...)`. In fact, at codegen time, these are
450 // basically the same thing, so we can just return llfn.
453 (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce)
454 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
455 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
456 // self, ...)`. We want a `fn(self, ...)`. We can produce
457 // this by doing something like:
459 // fn call_once(self, ...) { call_mut(&self, ...) }
460 // fn call_once(mut self, ...) { call_mut(&mut self, ...) }
462 // These are both the same at codegen time.
465 (ty::ClosureKind::FnMut, _) | (ty::ClosureKind::FnOnce, _) => Err(()),