src/librustc/ty/instance.rs

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