src/librustc/ty/instance.rs

   1 use crate::hir::CodegenFnAttrFlags;
   2 use crate::hir::Unsafety;
   3 use crate::hir::def::Namespace;
   4 use crate::hir::def_id::DefId;
   5 use crate::ty::{self, Ty, PolyFnSig, TypeFoldable, SubstsRef, TyCtxt};
   6 use crate::ty::print::{FmtPrinter, Printer};
   7 use crate::traits;
   8 use crate::middle::lang_items::DropInPlaceFnLangItem;
   9 use rustc_target::spec::abi::Abi;
  10 use rustc_macros::HashStable;
  11
  12 use std::fmt;
  13 use std::iter;
  14
  15 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
  16 #[derive(HashStable, Lift)]
  17 pub struct Instance<'tcx> {
  18     pub def: InstanceDef<'tcx>,
  19     pub substs: SubstsRef<'tcx>,
  20 }
  21
  22 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable, HashStable)]
  23 pub enum InstanceDef<'tcx> {
  24     Item(DefId),
  25     Intrinsic(DefId),
  26
  27     /// `<T as Trait>::method` where `method` receives unsizeable `self: Self`.
  28     VtableShim(DefId),
  29
  30     /// `fn()` pointer where the function itself cannot be turned into a pointer.
  31     ///
  32     /// One example in the compiler today is functions annotated with `#[track_caller]`, which
  33     /// must have their implicit caller location argument populated for a call. Because this is a
  34     /// required part of the function's ABI but can't be tracked as a property of the function
  35     /// pointer, we create a single "caller location" at the site where the function is reified.
  36     ReifyShim(DefId),
  37
  38     /// `<fn() as FnTrait>::call_*`
  39     /// `DefId` is `FnTrait::call_*`
  40     FnPtrShim(DefId, Ty<'tcx>),
  41
  42     /// `<Trait as Trait>::fn`
  43     Virtual(DefId, usize),
  44
  45     /// `<[mut closure] as FnOnce>::call_once`
  46     ClosureOnceShim { call_once: DefId },
  47
  48     /// `drop_in_place::<T>; None` for empty drop glue.
  49     DropGlue(DefId, Option<Ty<'tcx>>),
  50
  51     ///`<T as Clone>::clone` shim.
  52     CloneShim(DefId, Ty<'tcx>),
  53 }
  54
  55 impl<'tcx> Instance<'tcx> {
  56     pub fn ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
  57         let ty = tcx.type_of(self.def.def_id());
  58         tcx.subst_and_normalize_erasing_regions(
  59             self.substs,
  60             ty::ParamEnv::reveal_all(),
  61             &ty,
  62         )
  63     }
  64
  65     fn fn_sig_noadjust(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
  66         let ty = self.ty(tcx);
  67         match ty.kind {
  68             ty::FnDef(..) |
  69             // Shims currently have type FnPtr. Not sure this should remain.
  70             ty::FnPtr(_) => ty.fn_sig(tcx),
  71             ty::Closure(def_id, substs) => {
  72                 let sig = substs.as_closure().sig(def_id, tcx);
  73
  74                 let env_ty = tcx.closure_env_ty(def_id, substs).unwrap();
  75                 sig.map_bound(|sig| tcx.mk_fn_sig(
  76                     iter::once(*env_ty.skip_binder()).chain(sig.inputs().iter().cloned()),
  77                     sig.output(),
  78                     sig.c_variadic,
  79                     sig.unsafety,
  80                     sig.abi
  81                 ))
  82             }
  83             ty::Generator(def_id, substs, _) => {
  84                 let sig = substs.as_generator().poly_sig(def_id, tcx);
  85
  86                 let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv);
  87                 let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
  88
  89                 let pin_did = tcx.lang_items().pin_type().unwrap();
  90                 let pin_adt_ref = tcx.adt_def(pin_did);
  91                 let pin_substs = tcx.intern_substs(&[env_ty.into()]);
  92                 let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs);
  93
  94                 sig.map_bound(|sig| {
  95                     let state_did = tcx.lang_items().gen_state().unwrap();
  96                     let state_adt_ref = tcx.adt_def(state_did);
  97                     let state_substs = tcx.intern_substs(&[
  98                         sig.yield_ty.into(),
  99                         sig.return_ty.into(),
 100                     ]);
 101                     let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
 102
 103                     tcx.mk_fn_sig(iter::once(env_ty),
 104                         ret_ty,
 105                         false,
 106                         Unsafety::Normal,
 107                         Abi::Rust
 108                     )
 109                 })
 110             }
 111             _ => bug!("unexpected type {:?} in Instance::fn_sig_noadjust", ty)
 112         }
 113     }
 114
 115     pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> ty::PolyFnSig<'tcx> {
 116         let mut fn_sig = self.fn_sig_noadjust(tcx);
 117         if let InstanceDef::VtableShim(..) = self.def {
 118             // Modify fn(self, ...) to fn(self: *mut Self, ...)
 119             fn_sig = fn_sig.map_bound(|mut fn_sig| {
 120                 let mut inputs_and_output = fn_sig.inputs_and_output.to_vec();
 121                 inputs_and_output[0] = tcx.mk_mut_ptr(inputs_and_output[0]);
 122                 fn_sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output);
 123                 fn_sig
 124             });
 125         }
 126         fn_sig
 127     }
 128 }
 129
 130 impl<'tcx> InstanceDef<'tcx> {
 131     #[inline]
 132     pub fn def_id(&self) -> DefId {
 133         match *self {
 134             InstanceDef::Item(def_id) |
 135             InstanceDef::VtableShim(def_id) |
 136             InstanceDef::ReifyShim(def_id) |
 137             InstanceDef::FnPtrShim(def_id, _) |
 138             InstanceDef::Virtual(def_id, _) |
 139             InstanceDef::Intrinsic(def_id, ) |
 140             InstanceDef::ClosureOnceShim { call_once: def_id } |
 141             InstanceDef::DropGlue(def_id, _) |
 142             InstanceDef::CloneShim(def_id, _) => def_id
 143         }
 144     }
 145
 146     #[inline]
 147     pub fn attrs(&self, tcx: TyCtxt<'tcx>) -> ty::Attributes<'tcx> {
 148         tcx.get_attrs(self.def_id())
 149     }
 150
 151     pub fn is_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
 152         use crate::hir::map::DefPathData;
 153         let def_id = match *self {
 154             ty::InstanceDef::Item(def_id) => def_id,
 155             ty::InstanceDef::DropGlue(_, Some(_)) => return false,
 156             _ => return true
 157         };
 158         match tcx.def_key(def_id).disambiguated_data.data {
 159             DefPathData::Ctor | DefPathData::ClosureExpr => true,
 160             _ => false
 161         }
 162     }
 163
 164     pub fn requires_local(&self, tcx: TyCtxt<'tcx>) -> bool {
 165         if self.is_inline(tcx) {
 166             return true
 167         }
 168         if let ty::InstanceDef::DropGlue(..) = *self {
 169             // Drop glue wants to be instantiated at every codegen
 170             // unit, but without an #[inline] hint. We should make this
 171             // available to normal end-users.
 172             return true
 173         }
 174         tcx.codegen_fn_attrs(self.def_id()).requests_inline()
 175     }
 176 }
 177
 178 impl<'tcx> fmt::Display for Instance<'tcx> {
 179     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 180         ty::tls::with(|tcx| {
 181             let substs = tcx.lift(&self.substs).expect("could not lift for printing");
 182             FmtPrinter::new(tcx, &mut *f, Namespace::ValueNS)
 183                 .print_def_path(self.def_id(), substs)?;
 184             Ok(())
 185         })?;
 186
 187         match self.def {
 188             InstanceDef::Item(_) => Ok(()),
 189             InstanceDef::VtableShim(_) => {
 190                 write!(f, " - shim(vtable)")
 191             }
 192             InstanceDef::ReifyShim(_) => {
 193                 write!(f, " - shim(reify)")
 194             }
 195             InstanceDef::Intrinsic(_) => {
 196                 write!(f, " - intrinsic")
 197             }
 198             InstanceDef::Virtual(_, num) => {
 199                 write!(f, " - shim(#{})", num)
 200             }
 201             InstanceDef::FnPtrShim(_, ty) => {
 202                 write!(f, " - shim({:?})", ty)
 203             }
 204             InstanceDef::ClosureOnceShim { .. } => {
 205                 write!(f, " - shim")
 206             }
 207             InstanceDef::DropGlue(_, ty) => {
 208                 write!(f, " - shim({:?})", ty)
 209             }
 210             InstanceDef::CloneShim(_, ty) => {
 211                 write!(f, " - shim({:?})", ty)
 212             }
 213         }
 214     }
 215 }
 216
 217 impl<'tcx> Instance<'tcx> {
 218     pub fn new(def_id: DefId, substs: SubstsRef<'tcx>)
 219                -> Instance<'tcx> {
 220         assert!(!substs.has_escaping_bound_vars(),
 221                 "substs of instance {:?} not normalized for codegen: {:?}",
 222                 def_id, substs);
 223         Instance { def: InstanceDef::Item(def_id), substs: substs }
 224     }
 225
 226     pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
 227         Instance::new(def_id, tcx.empty_substs_for_def_id(def_id))
 228     }
 229
 230     #[inline]
 231     pub fn def_id(&self) -> DefId {
 232         self.def.def_id()
 233     }
 234
 235     /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
 236     /// this is used to find the precise code that will run for a trait method invocation,
 237     /// if known.
 238     ///
 239     /// Returns `None` if we cannot resolve `Instance` to a specific instance.
 240     /// For example, in a context like this,
 241     ///
 242     /// ```
 243     /// fn foo<T: Debug>(t: T) { ... }
 244     /// ```
 245     ///
 246     /// trying to resolve `Debug::fmt` applied to `T` will yield `None`, because we do not
 247     /// know what code ought to run. (Note that this setting is also affected by the
 248     /// `RevealMode` in the parameter environment.)
 249     ///
 250     /// Presuming that coherence and type-check have succeeded, if this method is invoked
 251     /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
 252     /// `Some`.
 253     pub fn resolve(
 254         tcx: TyCtxt<'tcx>,
 255         param_env: ty::ParamEnv<'tcx>,
 256         def_id: DefId,
 257         substs: SubstsRef<'tcx>,
 258     ) -> Option<Instance<'tcx>> {
 259         debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
 260         let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
 261             debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
 262             let item = tcx.associated_item(def_id);
 263             resolve_associated_item(tcx, &item, param_env, trait_def_id, substs)
 264         } else {
 265             let ty = tcx.type_of(def_id);
 266             let item_type = tcx.subst_and_normalize_erasing_regions(
 267                 substs,
 268                 param_env,
 269                 &ty,
 270             );
 271
 272             let def = match item_type.kind {
 273                 ty::FnDef(..) if {
 274                     let f = item_type.fn_sig(tcx);
 275                     f.abi() == Abi::RustIntrinsic ||
 276                         f.abi() == Abi::PlatformIntrinsic
 277                 } =>
 278                 {
 279                     debug!(" => intrinsic");
 280                     ty::InstanceDef::Intrinsic(def_id)
 281                 }
 282                 _ => {
 283                     if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
 284                         let ty = substs.type_at(0);
 285                         if ty.needs_drop(tcx, ty::ParamEnv::reveal_all()) {
 286                             debug!(" => nontrivial drop glue");
 287                             ty::InstanceDef::DropGlue(def_id, Some(ty))
 288                         } else {
 289                             debug!(" => trivial drop glue");
 290                             ty::InstanceDef::DropGlue(def_id, None)
 291                         }
 292                     } else {
 293                         debug!(" => free item");
 294                         ty::InstanceDef::Item(def_id)
 295                     }
 296                 }
 297             };
 298             Some(Instance {
 299                 def: def,
 300                 substs: substs
 301             })
 302         };
 303         debug!("resolve(def_id={:?}, substs={:?}) = {:?}", def_id, substs, result);
 304         result
 305     }
 306
 307     pub fn resolve_for_fn_ptr(
 308         tcx: TyCtxt<'tcx>,
 309         param_env: ty::ParamEnv<'tcx>,
 310         def_id: DefId,
 311         substs: SubstsRef<'tcx>,
 312     ) -> Option<Instance<'tcx>> {
 313         debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
 314         Instance::resolve(tcx, param_env, def_id, substs).map(|resolved| {
 315             let has_track_caller = |def| tcx.codegen_fn_attrs(def).flags
 316                 .contains(CodegenFnAttrFlags::TRACK_CALLER);
 317
 318             match resolved.def {
 319                 InstanceDef::Item(def_id) if has_track_caller(def_id) => {
 320                     debug!(" => fn pointer created for function with #[track_caller]");
 321                     Instance {
 322                         def: InstanceDef::ReifyShim(def_id),
 323                         substs,
 324                     }
 325                 },
 326                 _ => resolved,
 327             }
 328         })
 329     }
 330
 331     pub fn resolve_for_vtable(
 332         tcx: TyCtxt<'tcx>,
 333         param_env: ty::ParamEnv<'tcx>,
 334         def_id: DefId,
 335         substs: SubstsRef<'tcx>,
 336     ) -> Option<Instance<'tcx>> {
 337         debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
 338         let fn_sig = tcx.fn_sig(def_id);
 339         let is_vtable_shim = fn_sig.inputs().skip_binder().len() > 0
 340             && fn_sig.input(0).skip_binder().is_param(0)
 341             && tcx.generics_of(def_id).has_self;
 342         if is_vtable_shim {
 343             debug!(" => associated item with unsizeable self: Self");
 344             Some(Instance {
 345                 def: InstanceDef::VtableShim(def_id),
 346                 substs,
 347             })
 348         } else {
 349             Instance::resolve(tcx, param_env, def_id, substs)
 350         }
 351     }
 352
 353     pub fn resolve_closure(
 354         tcx: TyCtxt<'tcx>,
 355         def_id: DefId,
 356         substs: ty::SubstsRef<'tcx>,
 357         requested_kind: ty::ClosureKind,
 358     ) -> Instance<'tcx> {
 359         let actual_kind = substs.as_closure().kind(def_id, tcx);
 360
 361         match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
 362             Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
 363             _ => Instance::new(def_id, substs)
 364         }
 365     }
 366
 367     pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
 368         let def_id = tcx.require_lang_item(DropInPlaceFnLangItem, None);
 369         let substs = tcx.intern_substs(&[ty.into()]);
 370         Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap()
 371     }
 372
 373     pub fn fn_once_adapter_instance(
 374         tcx: TyCtxt<'tcx>,
 375         closure_did: DefId,
 376         substs: ty::SubstsRef<'tcx>,
 377     ) -> Instance<'tcx> {
 378         debug!("fn_once_adapter_shim({:?}, {:?})",
 379                closure_did,
 380                substs);
 381         let fn_once = tcx.lang_items().fn_once_trait().unwrap();
 382         let call_once = tcx.associated_items(fn_once)
 383             .find(|it| it.kind == ty::AssocKind::Method)
 384             .unwrap().def_id;
 385         let def = ty::InstanceDef::ClosureOnceShim { call_once };
 386
 387         let self_ty = tcx.mk_closure(closure_did, substs);
 388
 389         let sig = substs.as_closure().sig(closure_did, tcx);
 390         let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
 391         assert_eq!(sig.inputs().len(), 1);
 392         let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
 393
 394         debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
 395         Instance { def, substs }
 396     }
 397
 398     pub fn is_vtable_shim(&self) -> bool {
 399         if let InstanceDef::VtableShim(..) = self.def {
 400             true
 401         } else {
 402             false
 403         }
 404     }
 405 }
 406
 407 fn resolve_associated_item<'tcx>(
 408     tcx: TyCtxt<'tcx>,
 409     trait_item: &ty::AssocItem,
 410     param_env: ty::ParamEnv<'tcx>,
 411     trait_id: DefId,
 412     rcvr_substs: SubstsRef<'tcx>,
 413 ) -> Option<Instance<'tcx>> {
 414     let def_id = trait_item.def_id;
 415     debug!("resolve_associated_item(trait_item={:?}, \
 416             param_env={:?}, \
 417             trait_id={:?}, \
 418             rcvr_substs={:?})",
 419             def_id, param_env, trait_id, rcvr_substs);
 420
 421     let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
 422     let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref)));
 423
 424     // Now that we know which impl is being used, we can dispatch to
 425     // the actual function:
 426     match vtbl {
 427         traits::VtableImpl(impl_data) => {
 428             let (def_id, substs) = traits::find_associated_item(
 429                 tcx, param_env, trait_item, rcvr_substs, &impl_data);
 430             let substs = tcx.erase_regions(&substs);
 431             Some(ty::Instance::new(def_id, substs))
 432         }
 433         traits::VtableGenerator(generator_data) => {
 434             Some(Instance {
 435                 def: ty::InstanceDef::Item(generator_data.generator_def_id),
 436                 substs: generator_data.substs
 437             })
 438         }
 439         traits::VtableClosure(closure_data) => {
 440             let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
 441             Some(Instance::resolve_closure(tcx, closure_data.closure_def_id, closure_data.substs,
 442                                            trait_closure_kind))
 443         }
 444         traits::VtableFnPointer(ref data) => {
 445             Some(Instance {
 446                 def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
 447                 substs: rcvr_substs
 448             })
 449         }
 450         traits::VtableObject(ref data) => {
 451             let index = tcx.get_vtable_index_of_object_method(data, def_id);
 452             Some(Instance {
 453                 def: ty::InstanceDef::Virtual(def_id, index),
 454                 substs: rcvr_substs
 455             })
 456         }
 457         traits::VtableBuiltin(..) => {
 458             if tcx.lang_items().clone_trait().is_some() {
 459                 Some(Instance {
 460                     def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
 461                     substs: rcvr_substs
 462                 })
 463             } else {
 464                 None
 465             }
 466         }
 467         traits::VtableAutoImpl(..) |
 468         traits::VtableParam(..) |
 469         traits::VtableTraitAlias(..) => None
 470     }
 471 }
 472
 473 fn needs_fn_once_adapter_shim(
 474     actual_closure_kind: ty::ClosureKind,
 475     trait_closure_kind: ty::ClosureKind,
 476 ) -> Result<bool, ()> {
 477     match (actual_closure_kind, trait_closure_kind) {
 478         (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
 479             (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
 480             (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
 481                 // No adapter needed.
 482                 Ok(false)
 483             }
 484         (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
 485             // The closure fn `llfn` is a `fn(&self, ...)`.  We want a
 486             // `fn(&mut self, ...)`. In fact, at codegen time, these are
 487             // basically the same thing, so we can just return llfn.
 488             Ok(false)
 489         }
 490         (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
 491             (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
 492                 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
 493                 // self, ...)`.  We want a `fn(self, ...)`. We can produce
 494                 // this by doing something like:
 495                 //
 496                 //     fn call_once(self, ...) { call_mut(&self, ...) }
 497                 //     fn call_once(mut self, ...) { call_mut(&mut self, ...) }
 498                 //
 499                 // These are both the same at codegen time.
 500                 Ok(true)
 501         }
 502         (ty::ClosureKind::FnMut, _) |
 503         (ty::ClosureKind::FnOnce, _) => Err(())
 504     }
 505 }