src/librustc/ty/instance.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use hir::Unsafety;
  12 use hir::def_id::DefId;
  13 use ty::{self, Ty, PolyFnSig, TypeFoldable, Substs, TyCtxt};
  14 use traits;
  15 use rustc_target::spec::abi::Abi;
  16 use util::ppaux;
  17
  18 use std::fmt;
  19 use std::iter;
  20
  21 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
  22 pub struct Instance<'tcx> {
  23     pub def: InstanceDef<'tcx>,
  24     pub substs: &'tcx Substs<'tcx>,
  25 }
  26
  27 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
  28 pub enum InstanceDef<'tcx> {
  29     Item(DefId),
  30     Intrinsic(DefId),
  31
  32     /// `<T as Trait>::method` where `method` receives unsizeable `self: Self`.
  33     VtableShim(DefId),
  34
  35     /// \<fn() as FnTrait>::call_*
  36     /// def-id is FnTrait::call_*
  37     FnPtrShim(DefId, Ty<'tcx>),
  38
  39     /// <Trait as Trait>::fn
  40     Virtual(DefId, usize),
  41
  42     /// <[mut closure] as FnOnce>::call_once
  43     ClosureOnceShim { call_once: DefId },
  44
  45     /// drop_in_place::<T>; None for empty drop glue.
  46     DropGlue(DefId, Option<Ty<'tcx>>),
  47
  48     ///`<T as Clone>::clone` shim.
  49     CloneShim(DefId, Ty<'tcx>),
  50 }
  51
  52 impl<'a, 'tcx> Instance<'tcx> {
  53     pub fn ty(&self,
  54               tcx: TyCtxt<'a, 'tcx, 'tcx>)
  55               -> Ty<'tcx>
  56     {
  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<'a, 'tcx, 'tcx>) -> PolyFnSig<'tcx> {
  66         let ty = self.ty(tcx);
  67         match ty.sty {
  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.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.variadic,
  79                     sig.unsafety,
  80                     sig.abi
  81                 ))
  82             }
  83             ty::Generator(def_id, substs, _) => {
  84                 let sig = substs.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                 sig.map_bound(|sig| {
  90                     let state_did = tcx.lang_items().gen_state().unwrap();
  91                     let state_adt_ref = tcx.adt_def(state_did);
  92                     let state_substs = tcx.intern_substs(&[
  93                         sig.yield_ty.into(),
  94                         sig.return_ty.into(),
  95                     ]);
  96                     let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
  97
  98                     tcx.mk_fn_sig(iter::once(env_ty),
  99                         ret_ty,
 100                         false,
 101                         Unsafety::Normal,
 102                         Abi::Rust
 103                     )
 104                 })
 105             }
 106             _ => bug!("unexpected type {:?} in Instance::fn_sig_noadjust", ty)
 107         }
 108     }
 109
 110     pub fn fn_sig(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::PolyFnSig<'tcx> {
 111         let mut fn_sig = self.fn_sig_noadjust(tcx);
 112         if let InstanceDef::VtableShim(..) = self.def {
 113             // Modify fn(self, ...) to fn(self: *mut Self, ...)
 114             fn_sig = fn_sig.map_bound(|mut fn_sig| {
 115                 let mut inputs_and_output = fn_sig.inputs_and_output.to_vec();
 116                 inputs_and_output[0] = tcx.mk_mut_ptr(inputs_and_output[0]);
 117                 fn_sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output);
 118                 fn_sig
 119             });
 120         }
 121         fn_sig
 122     }
 123 }
 124
 125 impl<'tcx> InstanceDef<'tcx> {
 126     #[inline]
 127     pub fn def_id(&self) -> DefId {
 128         match *self {
 129             InstanceDef::Item(def_id) |
 130             InstanceDef::VtableShim(def_id) |
 131             InstanceDef::FnPtrShim(def_id, _) |
 132             InstanceDef::Virtual(def_id, _) |
 133             InstanceDef::Intrinsic(def_id, ) |
 134             InstanceDef::ClosureOnceShim { call_once: def_id } |
 135             InstanceDef::DropGlue(def_id, _) |
 136             InstanceDef::CloneShim(def_id, _) => def_id
 137         }
 138     }
 139
 140     #[inline]
 141     pub fn attrs<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::Attributes<'tcx> {
 142         tcx.get_attrs(self.def_id())
 143     }
 144
 145     pub fn is_inline<'a>(
 146         &self,
 147         tcx: TyCtxt<'a, 'tcx, 'tcx>
 148     ) -> bool {
 149         use hir::map::DefPathData;
 150         let def_id = match *self {
 151             ty::InstanceDef::Item(def_id) => def_id,
 152             ty::InstanceDef::DropGlue(_, Some(_)) => return false,
 153             _ => return true
 154         };
 155         match tcx.def_key(def_id).disambiguated_data.data {
 156             DefPathData::StructCtor |
 157             DefPathData::EnumVariant(..) |
 158             DefPathData::ClosureExpr => true,
 159             _ => false
 160         }
 161     }
 162
 163     pub fn requires_local<'a>(
 164         &self,
 165         tcx: TyCtxt<'a, 'tcx, 'tcx>
 166     ) -> bool {
 167         if self.is_inline(tcx) {
 168             return true
 169         }
 170         if let ty::InstanceDef::DropGlue(..) = *self {
 171             // Drop glue wants to be instantiated at every codegen
 172             // unit, but without an #[inline] hint. We should make this
 173             // available to normal end-users.
 174             return true
 175         }
 176         let codegen_fn_attrs = tcx.codegen_fn_attrs(self.def_id());
 177         // need to use `is_const_fn_raw` since we don't really care if the user can use it as a
 178         // const fn, just whether the function should be inlined
 179         codegen_fn_attrs.requests_inline() || tcx.is_const_fn_raw(self.def_id())
 180     }
 181 }
 182
 183 impl<'tcx> fmt::Display for Instance<'tcx> {
 184     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 185         ppaux::parameterized(f, self.substs, self.def_id(), &[])?;
 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: &'tcx Substs<'tcx>)
 215                -> Instance<'tcx> {
 216         assert!(!substs.has_escaping_regions(),
 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     /// Resolve 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: &'tcx Substs<'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: &'tcx Substs<'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: &'tcx Substs<'tcx>,
 350 ) -> Option<Instance<'tcx>> {
 351     let def_id = trait_item.def_id;
 352     debug!("resolve_associated_item(trait_item={:?}, \
 353             trait_id={:?}, \
 354             rcvr_substs={:?})",
 355            def_id, trait_id, rcvr_substs);
 356
 357     let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
 358     let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref)));
 359
 360     // Now that we know which impl is being used, we can dispatch to
 361     // the actual function:
 362     match vtbl {
 363         traits::VtableImpl(impl_data) => {
 364             let (def_id, substs) = traits::find_associated_item(
 365                 tcx, trait_item, rcvr_substs, &impl_data);
 366             let substs = tcx.erase_regions(&substs);
 367             Some(ty::Instance::new(def_id, substs))
 368         }
 369         traits::VtableGenerator(generator_data) => {
 370             Some(Instance {
 371                 def: ty::InstanceDef::Item(generator_data.generator_def_id),
 372                 substs: generator_data.substs.substs
 373             })
 374         }
 375         traits::VtableClosure(closure_data) => {
 376             let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
 377             Some(Instance::resolve_closure(tcx, closure_data.closure_def_id, closure_data.substs,
 378                                            trait_closure_kind))
 379         }
 380         traits::VtableFnPointer(ref data) => {
 381             Some(Instance {
 382                 def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
 383                 substs: rcvr_substs
 384             })
 385         }
 386         traits::VtableObject(ref data) => {
 387             let index = tcx.get_vtable_index_of_object_method(data, def_id);
 388             Some(Instance {
 389                 def: ty::InstanceDef::Virtual(def_id, index),
 390                 substs: rcvr_substs
 391             })
 392         }
 393         traits::VtableBuiltin(..) => {
 394             if tcx.lang_items().clone_trait().is_some() {
 395                 Some(Instance {
 396                     def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
 397                     substs: rcvr_substs
 398                 })
 399             } else {
 400                 None
 401             }
 402         }
 403         traits::VtableAutoImpl(..) | traits::VtableParam(..) => None
 404     }
 405 }
 406
 407 fn needs_fn_once_adapter_shim<'a, 'tcx>(actual_closure_kind: ty::ClosureKind,
 408                                         trait_closure_kind: ty::ClosureKind)
 409     -> Result<bool, ()>
 410 {
 411     match (actual_closure_kind, trait_closure_kind) {
 412         (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
 413             (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
 414             (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
 415                 // No adapter needed.
 416                 Ok(false)
 417             }
 418         (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
 419             // The closure fn `llfn` is a `fn(&self, ...)`.  We want a
 420             // `fn(&mut self, ...)`. In fact, at codegen time, these are
 421             // basically the same thing, so we can just return llfn.
 422             Ok(false)
 423         }
 424         (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
 425             (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
 426                 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
 427                 // self, ...)`.  We want a `fn(self, ...)`. We can produce
 428                 // this by doing something like:
 429                 //
 430                 //     fn call_once(self, ...) { call_mut(&self, ...) }
 431                 //     fn call_once(mut self, ...) { call_mut(&mut self, ...) }
 432                 //
 433                 // These are both the same at codegen time.
 434                 Ok(true)
 435         }
 436         (ty::ClosureKind::FnMut, _) |
 437         (ty::ClosureKind::FnOnce, _) => Err(())
 438     }
 439 }
 440
 441 fn fn_once_adapter_instance<'a, 'tcx>(
 442     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 443     closure_did: DefId,
 444     substs: ty::ClosureSubsts<'tcx>)
 445     -> Instance<'tcx>
 446 {
 447     debug!("fn_once_adapter_shim({:?}, {:?})",
 448            closure_did,
 449            substs);
 450     let fn_once = tcx.lang_items().fn_once_trait().unwrap();
 451     let call_once = tcx.associated_items(fn_once)
 452         .find(|it| it.kind == ty::AssociatedKind::Method)
 453         .unwrap().def_id;
 454     let def = ty::InstanceDef::ClosureOnceShim { call_once };
 455
 456     let self_ty = tcx.mk_closure(closure_did, substs);
 457
 458     let sig = substs.closure_sig(closure_did, tcx);
 459     let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
 460     assert_eq!(sig.inputs().len(), 1);
 461     let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
 462
 463     debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
 464     Instance { def, substs }
 465 }