src/librustc/ty/instance.rs

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