src/librustc/ty/util.rs

   1 // Copyright 2012-2015 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 //! misc. type-system utilities too small to deserve their own file
  12
  13 use hir::def_id::{DefId, LOCAL_CRATE};
  14 use hir::map::DefPathData;
  15 use infer::InferCtxt;
  16 use ich::{StableHashingContext, NodeIdHashingMode};
  17 use traits::{self, Reveal};
  18 use ty::{self, Ty, TyCtxt, TypeFoldable};
  19 use ty::fold::TypeVisitor;
  20 use ty::layout::{Layout, LayoutError};
  21 use ty::subst::{Subst, Kind};
  22 use ty::TypeVariants::*;
  23 use util::common::ErrorReported;
  24 use middle::lang_items;
  25
  26 use rustc_const_math::{ConstInt, ConstIsize, ConstUsize};
  27 use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
  28                                            HashStable};
  29 use std::cmp;
  30 use std::hash::Hash;
  31 use std::intrinsics;
  32 use syntax::ast::{self, Name};
  33 use syntax::attr::{self, SignedInt, UnsignedInt};
  34 use syntax_pos::{Span, DUMMY_SP};
  35
  36 type Disr = ConstInt;
  37
  38 pub trait IntTypeExt {
  39     fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx>;
  40     fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Disr>)
  41                            -> Option<Disr>;
  42     fn assert_ty_matches(&self, val: Disr);
  43     fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Disr;
  44 }
  45
  46
  47 macro_rules! typed_literal {
  48     ($tcx:expr, $ty:expr, $lit:expr) => {
  49         match $ty {
  50             SignedInt(ast::IntTy::I8)    => ConstInt::I8($lit),
  51             SignedInt(ast::IntTy::I16)   => ConstInt::I16($lit),
  52             SignedInt(ast::IntTy::I32)   => ConstInt::I32($lit),
  53             SignedInt(ast::IntTy::I64)   => ConstInt::I64($lit),
  54             SignedInt(ast::IntTy::I128)   => ConstInt::I128($lit),
  55             SignedInt(ast::IntTy::Is) => match $tcx.sess.target.int_type {
  56                 ast::IntTy::I16 => ConstInt::Isize(ConstIsize::Is16($lit)),
  57                 ast::IntTy::I32 => ConstInt::Isize(ConstIsize::Is32($lit)),
  58                 ast::IntTy::I64 => ConstInt::Isize(ConstIsize::Is64($lit)),
  59                 _ => bug!(),
  60             },
  61             UnsignedInt(ast::UintTy::U8)  => ConstInt::U8($lit),
  62             UnsignedInt(ast::UintTy::U16) => ConstInt::U16($lit),
  63             UnsignedInt(ast::UintTy::U32) => ConstInt::U32($lit),
  64             UnsignedInt(ast::UintTy::U64) => ConstInt::U64($lit),
  65             UnsignedInt(ast::UintTy::U128) => ConstInt::U128($lit),
  66             UnsignedInt(ast::UintTy::Us) => match $tcx.sess.target.uint_type {
  67                 ast::UintTy::U16 => ConstInt::Usize(ConstUsize::Us16($lit)),
  68                 ast::UintTy::U32 => ConstInt::Usize(ConstUsize::Us32($lit)),
  69                 ast::UintTy::U64 => ConstInt::Usize(ConstUsize::Us64($lit)),
  70                 _ => bug!(),
  71             },
  72         }
  73     }
  74 }
  75
  76 impl IntTypeExt for attr::IntType {
  77     fn to_ty<'a, 'gcx, 'tcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
  78         match *self {
  79             SignedInt(ast::IntTy::I8)      => tcx.types.i8,
  80             SignedInt(ast::IntTy::I16)     => tcx.types.i16,
  81             SignedInt(ast::IntTy::I32)     => tcx.types.i32,
  82             SignedInt(ast::IntTy::I64)     => tcx.types.i64,
  83             SignedInt(ast::IntTy::I128)     => tcx.types.i128,
  84             SignedInt(ast::IntTy::Is)   => tcx.types.isize,
  85             UnsignedInt(ast::UintTy::U8)    => tcx.types.u8,
  86             UnsignedInt(ast::UintTy::U16)   => tcx.types.u16,
  87             UnsignedInt(ast::UintTy::U32)   => tcx.types.u32,
  88             UnsignedInt(ast::UintTy::U64)   => tcx.types.u64,
  89             UnsignedInt(ast::UintTy::U128)   => tcx.types.u128,
  90             UnsignedInt(ast::UintTy::Us) => tcx.types.usize,
  91         }
  92     }
  93
  94     fn initial_discriminant<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Disr {
  95         typed_literal!(tcx, *self, 0)
  96     }
  97
  98     fn assert_ty_matches(&self, val: Disr) {
  99         match (*self, val) {
 100             (SignedInt(ast::IntTy::I8), ConstInt::I8(_)) => {},
 101             (SignedInt(ast::IntTy::I16), ConstInt::I16(_)) => {},
 102             (SignedInt(ast::IntTy::I32), ConstInt::I32(_)) => {},
 103             (SignedInt(ast::IntTy::I64), ConstInt::I64(_)) => {},
 104             (SignedInt(ast::IntTy::I128), ConstInt::I128(_)) => {},
 105             (SignedInt(ast::IntTy::Is), ConstInt::Isize(_)) => {},
 106             (UnsignedInt(ast::UintTy::U8), ConstInt::U8(_)) => {},
 107             (UnsignedInt(ast::UintTy::U16), ConstInt::U16(_)) => {},
 108             (UnsignedInt(ast::UintTy::U32), ConstInt::U32(_)) => {},
 109             (UnsignedInt(ast::UintTy::U64), ConstInt::U64(_)) => {},
 110             (UnsignedInt(ast::UintTy::U128), ConstInt::U128(_)) => {},
 111             (UnsignedInt(ast::UintTy::Us), ConstInt::Usize(_)) => {},
 112             _ => bug!("disr type mismatch: {:?} vs {:?}", self, val),
 113         }
 114     }
 115
 116     fn disr_incr<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, val: Option<Disr>)
 117                            -> Option<Disr> {
 118         if let Some(val) = val {
 119             self.assert_ty_matches(val);
 120             (val + typed_literal!(tcx, *self, 1)).ok()
 121         } else {
 122             Some(self.initial_discriminant(tcx))
 123         }
 124     }
 125 }
 126
 127
 128 #[derive(Copy, Clone)]
 129 pub enum CopyImplementationError<'tcx> {
 130     InfrigingField(&'tcx ty::FieldDef),
 131     NotAnAdt,
 132     HasDestructor,
 133 }
 134
 135 /// Describes whether a type is representable. For types that are not
 136 /// representable, 'SelfRecursive' and 'ContainsRecursive' are used to
 137 /// distinguish between types that are recursive with themselves and types that
 138 /// contain a different recursive type. These cases can therefore be treated
 139 /// differently when reporting errors.
 140 ///
 141 /// The ordering of the cases is significant. They are sorted so that cmp::max
 142 /// will keep the "more erroneous" of two values.
 143 #[derive(Clone, PartialOrd, Ord, Eq, PartialEq, Debug)]
 144 pub enum Representability {
 145     Representable,
 146     ContainsRecursive,
 147     SelfRecursive(Vec<Span>),
 148 }
 149
 150 impl<'tcx> ty::ParamEnv<'tcx> {
 151     /// Construct a trait environment suitable for contexts where
 152     /// there are no where clauses in scope.
 153     pub fn empty() -> Self {
 154         Self::new(ty::Slice::empty())
 155     }
 156
 157     /// Construct a trait environment with the given set of predicates.
 158     pub fn new(caller_bounds: &'tcx ty::Slice<ty::Predicate<'tcx>>) -> Self {
 159         ty::ParamEnv { caller_bounds }
 160     }
 161
 162     pub fn can_type_implement_copy<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
 163                                        self_type: Ty<'tcx>, span: Span)
 164                                        -> Result<(), CopyImplementationError> {
 165         // FIXME: (@jroesch) float this code up
 166         tcx.infer_ctxt(self.clone(), Reveal::UserFacing).enter(|infcx| {
 167             let (adt, substs) = match self_type.sty {
 168                 ty::TyAdt(adt, substs) => (adt, substs),
 169                 _ => return Err(CopyImplementationError::NotAnAdt),
 170             };
 171
 172             let field_implements_copy = |field: &ty::FieldDef| {
 173                 let cause = traits::ObligationCause::dummy();
 174                 match traits::fully_normalize(&infcx, cause, &field.ty(tcx, substs)) {
 175                     Ok(ty) => !infcx.type_moves_by_default(ty, span),
 176                     Err(..) => false,
 177                 }
 178             };
 179
 180             for variant in &adt.variants {
 181                 for field in &variant.fields {
 182                     if !field_implements_copy(field) {
 183                         return Err(CopyImplementationError::InfrigingField(field));
 184                     }
 185                 }
 186             }
 187
 188             if adt.has_dtor(tcx) {
 189                 return Err(CopyImplementationError::HasDestructor);
 190             }
 191
 192             Ok(())
 193         })
 194     }
 195 }
 196
 197 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
 198     /// Creates a hash of the type `Ty` which will be the same no matter what crate
 199     /// context it's calculated within. This is used by the `type_id` intrinsic.
 200     pub fn type_id_hash(self, ty: Ty<'tcx>) -> u64 {
 201         let mut hasher = StableHasher::new();
 202         let mut hcx = StableHashingContext::new(self);
 203
 204         hcx.while_hashing_spans(false, |hcx| {
 205             hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
 206                 ty.hash_stable(hcx, &mut hasher);
 207             });
 208         });
 209         hasher.finish()
 210     }
 211 }
 212
 213 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 214     pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
 215         match ty.sty {
 216             ty::TyAdt(def, substs) => {
 217                 for field in def.all_fields() {
 218                     let field_ty = field.ty(self, substs);
 219                     if let TyError = field_ty.sty {
 220                         return true;
 221                     }
 222                 }
 223             }
 224             _ => (),
 225         }
 226         false
 227     }
 228
 229     /// Returns the type of element at index `i` in tuple or tuple-like type `t`.
 230     /// For an enum `t`, `variant` is None only if `t` is a univariant enum.
 231     pub fn positional_element_ty(self,
 232                                  ty: Ty<'tcx>,
 233                                  i: usize,
 234                                  variant: Option<DefId>) -> Option<Ty<'tcx>> {
 235         match (&ty.sty, variant) {
 236             (&TyAdt(adt, substs), Some(vid)) => {
 237                 adt.variant_with_id(vid).fields.get(i).map(|f| f.ty(self, substs))
 238             }
 239             (&TyAdt(adt, substs), None) => {
 240                 // Don't use `struct_variant`, this may be a univariant enum.
 241                 adt.variants[0].fields.get(i).map(|f| f.ty(self, substs))
 242             }
 243             (&TyTuple(ref v, _), None) => v.get(i).cloned(),
 244             _ => None,
 245         }
 246     }
 247
 248     /// Returns the type of element at field `n` in struct or struct-like type `t`.
 249     /// For an enum `t`, `variant` must be some def id.
 250     pub fn named_element_ty(self,
 251                             ty: Ty<'tcx>,
 252                             n: Name,
 253                             variant: Option<DefId>) -> Option<Ty<'tcx>> {
 254         match (&ty.sty, variant) {
 255             (&TyAdt(adt, substs), Some(vid)) => {
 256                 adt.variant_with_id(vid).find_field_named(n).map(|f| f.ty(self, substs))
 257             }
 258             (&TyAdt(adt, substs), None) => {
 259                 adt.struct_variant().find_field_named(n).map(|f| f.ty(self, substs))
 260             }
 261             _ => return None
 262         }
 263     }
 264
 265     /// Returns the deeply last field of nested structures, or the same type,
 266     /// if not a structure at all. Corresponds to the only possible unsized
 267     /// field, and its type can be used to determine unsizing strategy.
 268     pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
 269         loop {
 270             match ty.sty {
 271                 ty::TyAdt(def, substs) => {
 272                     if !def.is_struct() {
 273                         break;
 274                     }
 275                     match def.struct_variant().fields.last() {
 276                         Some(f) => ty = f.ty(self, substs),
 277                         None => break,
 278                     }
 279                 }
 280
 281                 ty::TyTuple(tys, _) => {
 282                     if let Some((&last_ty, _)) = tys.split_last() {
 283                         ty = last_ty;
 284                     } else {
 285                         break;
 286                     }
 287                 }
 288
 289                 _ => {
 290                     break;
 291                 }
 292             }
 293         }
 294         ty
 295     }
 296
 297     /// Same as applying struct_tail on `source` and `target`, but only
 298     /// keeps going as long as the two types are instances of the same
 299     /// structure definitions.
 300     /// For `(Foo<Foo<T>>, Foo<Trait>)`, the result will be `(Foo<T>, Trait)`,
 301     /// whereas struct_tail produces `T`, and `Trait`, respectively.
 302     pub fn struct_lockstep_tails(self,
 303                                  source: Ty<'tcx>,
 304                                  target: Ty<'tcx>)
 305                                  -> (Ty<'tcx>, Ty<'tcx>) {
 306         let (mut a, mut b) = (source, target);
 307         while let (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs)) = (&a.sty, &b.sty) {
 308             if a_def != b_def || !a_def.is_struct() {
 309                 break;
 310             }
 311             match a_def.struct_variant().fields.last() {
 312                 Some(f) => {
 313                     a = f.ty(self, a_substs);
 314                     b = f.ty(self, b_substs);
 315                 }
 316                 _ => break,
 317             }
 318         }
 319         (a, b)
 320     }
 321
 322     /// Given a set of predicates that apply to an object type, returns
 323     /// the region bounds that the (erased) `Self` type must
 324     /// outlive. Precisely *because* the `Self` type is erased, the
 325     /// parameter `erased_self_ty` must be supplied to indicate what type
 326     /// has been used to represent `Self` in the predicates
 327     /// themselves. This should really be a unique type; `FreshTy(0)` is a
 328     /// popular choice.
 329     ///
 330     /// NB: in some cases, particularly around higher-ranked bounds,
 331     /// this function returns a kind of conservative approximation.
 332     /// That is, all regions returned by this function are definitely
 333     /// required, but there may be other region bounds that are not
 334     /// returned, as well as requirements like `for<'a> T: 'a`.
 335     ///
 336     /// Requires that trait definitions have been processed so that we can
 337     /// elaborate predicates and walk supertraits.
 338     ///
 339     /// FIXME callers may only have a &[Predicate], not a Vec, so that's
 340     /// what this code should accept.
 341     pub fn required_region_bounds(self,
 342                                   erased_self_ty: Ty<'tcx>,
 343                                   predicates: Vec<ty::Predicate<'tcx>>)
 344                                   -> Vec<ty::Region<'tcx>>    {
 345         debug!("required_region_bounds(erased_self_ty={:?}, predicates={:?})",
 346                erased_self_ty,
 347                predicates);
 348
 349         assert!(!erased_self_ty.has_escaping_regions());
 350
 351         traits::elaborate_predicates(self, predicates)
 352             .filter_map(|predicate| {
 353                 match predicate {
 354                     ty::Predicate::Projection(..) |
 355                     ty::Predicate::Trait(..) |
 356                     ty::Predicate::Equate(..) |
 357                     ty::Predicate::Subtype(..) |
 358                     ty::Predicate::WellFormed(..) |
 359                     ty::Predicate::ObjectSafe(..) |
 360                     ty::Predicate::ClosureKind(..) |
 361                     ty::Predicate::RegionOutlives(..) => {
 362                         None
 363                     }
 364                     ty::Predicate::TypeOutlives(ty::Binder(ty::OutlivesPredicate(t, r))) => {
 365                         // Search for a bound of the form `erased_self_ty
 366                         // : 'a`, but be wary of something like `for<'a>
 367                         // erased_self_ty : 'a` (we interpret a
 368                         // higher-ranked bound like that as 'static,
 369                         // though at present the code in `fulfill.rs`
 370                         // considers such bounds to be unsatisfiable, so
 371                         // it's kind of a moot point since you could never
 372                         // construct such an object, but this seems
 373                         // correct even if that code changes).
 374                         if t == erased_self_ty && !r.has_escaping_regions() {
 375                             Some(r)
 376                         } else {
 377                             None
 378                         }
 379                     }
 380                 }
 381             })
 382             .collect()
 383     }
 384
 385     /// Calculate the destructor of a given type.
 386     pub fn calculate_dtor(
 387         self,
 388         adt_did: DefId,
 389         validate: &mut FnMut(Self, DefId) -> Result<(), ErrorReported>
 390     ) -> Option<ty::Destructor> {
 391         let drop_trait = if let Some(def_id) = self.lang_items.drop_trait() {
 392             def_id
 393         } else {
 394             return None;
 395         };
 396
 397         self.coherent_trait((LOCAL_CRATE, drop_trait));
 398
 399         let mut dtor_did = None;
 400         let ty = self.type_of(adt_did);
 401         self.trait_def(drop_trait).for_each_relevant_impl(self, ty, |impl_did| {
 402             if let Some(item) = self.associated_items(impl_did).next() {
 403                 if let Ok(()) = validate(self, impl_did) {
 404                     dtor_did = Some(item.def_id);
 405                 }
 406             }
 407         });
 408
 409         let dtor_did = match dtor_did {
 410             Some(dtor) => dtor,
 411             None => return None,
 412         };
 413
 414         Some(ty::Destructor { did: dtor_did })
 415     }
 416
 417     /// Return the set of types that are required to be alive in
 418     /// order to run the destructor of `def` (see RFCs 769 and
 419     /// 1238).
 420     ///
 421     /// Note that this returns only the constraints for the
 422     /// destructor of `def` itself. For the destructors of the
 423     /// contents, you need `adt_dtorck_constraint`.
 424     pub fn destructor_constraints(self, def: &'tcx ty::AdtDef)
 425                                   -> Vec<ty::subst::Kind<'tcx>>
 426     {
 427         let dtor = match def.destructor(self) {
 428             None => {
 429                 debug!("destructor_constraints({:?}) - no dtor", def.did);
 430                 return vec![]
 431             }
 432             Some(dtor) => dtor.did
 433         };
 434
 435         // RFC 1238: if the destructor method is tagged with the
 436         // attribute `unsafe_destructor_blind_to_params`, then the
 437         // compiler is being instructed to *assume* that the
 438         // destructor will not access borrowed data,
 439         // even if such data is otherwise reachable.
 440         //
 441         // Such access can be in plain sight (e.g. dereferencing
 442         // `*foo.0` of `Foo<'a>(&'a u32)`) or indirectly hidden
 443         // (e.g. calling `foo.0.clone()` of `Foo<T:Clone>`).
 444         if self.has_attr(dtor, "unsafe_destructor_blind_to_params") {
 445             debug!("destructor_constraint({:?}) - blind", def.did);
 446             return vec![];
 447         }
 448
 449         let impl_def_id = self.associated_item(dtor).container.id();
 450         let impl_generics = self.generics_of(impl_def_id);
 451
 452         // We have a destructor - all the parameters that are not
 453         // pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
 454         // must be live.
 455
 456         // We need to return the list of parameters from the ADTs
 457         // generics/substs that correspond to impure parameters on the
 458         // impl's generics. This is a bit ugly, but conceptually simple:
 459         //
 460         // Suppose our ADT looks like the following
 461         //
 462         //     struct S<X, Y, Z>(X, Y, Z);
 463         //
 464         // and the impl is
 465         //
 466         //     impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
 467         //
 468         // We want to return the parameters (X, Y). For that, we match
 469         // up the item-substs <X, Y, Z> with the substs on the impl ADT,
 470         // <P1, P2, P0>, and then look up which of the impl substs refer to
 471         // parameters marked as pure.
 472
 473         let impl_substs = match self.type_of(impl_def_id).sty {
 474             ty::TyAdt(def_, substs) if def_ == def => substs,
 475             _ => bug!()
 476         };
 477
 478         let item_substs = match self.type_of(def.did).sty {
 479             ty::TyAdt(def_, substs) if def_ == def => substs,
 480             _ => bug!()
 481         };
 482
 483         let result = item_substs.iter().zip(impl_substs.iter())
 484             .filter(|&(_, &k)| {
 485                 if let Some(&ty::RegionKind::ReEarlyBound(ref ebr)) = k.as_region() {
 486                     !impl_generics.region_param(ebr).pure_wrt_drop
 487                 } else if let Some(&ty::TyS {
 488                     sty: ty::TypeVariants::TyParam(ref pt), ..
 489                 }) = k.as_type() {
 490                     !impl_generics.type_param(pt).pure_wrt_drop
 491                 } else {
 492                     // not a type or region param - this should be reported
 493                     // as an error.
 494                     false
 495                 }
 496             }).map(|(&item_param, _)| item_param).collect();
 497         debug!("destructor_constraint({:?}) = {:?}", def.did, result);
 498         result
 499     }
 500
 501     /// Return a set of constraints that needs to be satisfied in
 502     /// order for `ty` to be valid for destruction.
 503     pub fn dtorck_constraint_for_ty(self,
 504                                     span: Span,
 505                                     for_ty: Ty<'tcx>,
 506                                     depth: usize,
 507                                     ty: Ty<'tcx>)
 508                                     -> Result<ty::DtorckConstraint<'tcx>, ErrorReported>
 509     {
 510         debug!("dtorck_constraint_for_ty({:?}, {:?}, {:?}, {:?})",
 511                span, for_ty, depth, ty);
 512
 513         if depth >= self.sess.recursion_limit.get() {
 514             let mut err = struct_span_err!(
 515                 self.sess, span, E0320,
 516                 "overflow while adding drop-check rules for {}", for_ty);
 517             err.note(&format!("overflowed on {}", ty));
 518             err.emit();
 519             return Err(ErrorReported);
 520         }
 521
 522         let result = match ty.sty {
 523             ty::TyBool | ty::TyChar | ty::TyInt(_) | ty::TyUint(_) |
 524             ty::TyFloat(_) | ty::TyStr | ty::TyNever |
 525             ty::TyRawPtr(..) | ty::TyRef(..) | ty::TyFnDef(..) | ty::TyFnPtr(_) => {
 526                 // these types never have a destructor
 527                 Ok(ty::DtorckConstraint::empty())
 528             }
 529
 530             ty::TyArray(ety, _) | ty::TySlice(ety) => {
 531                 // single-element containers, behave like their element
 532                 self.dtorck_constraint_for_ty(span, for_ty, depth+1, ety)
 533             }
 534
 535             ty::TyTuple(tys, _) => {
 536                 tys.iter().map(|ty| {
 537                     self.dtorck_constraint_for_ty(span, for_ty, depth+1, ty)
 538                 }).collect()
 539             }
 540
 541             ty::TyClosure(def_id, substs) => {
 542                 substs.upvar_tys(def_id, self).map(|ty| {
 543                     self.dtorck_constraint_for_ty(span, for_ty, depth+1, ty)
 544                 }).collect()
 545             }
 546
 547             ty::TyAdt(def, substs) => {
 548                 let ty::DtorckConstraint {
 549                     dtorck_types, outlives
 550                 } = self.at(span).adt_dtorck_constraint(def.did);
 551                 Ok(ty::DtorckConstraint {
 552                     // FIXME: we can try to recursively `dtorck_constraint_on_ty`
 553                     // there, but that needs some way to handle cycles.
 554                     dtorck_types: dtorck_types.subst(self, substs),
 555                     outlives: outlives.subst(self, substs)
 556                 })
 557             }
 558
 559             // Objects must be alive in order for their destructor
 560             // to be called.
 561             ty::TyDynamic(..) => Ok(ty::DtorckConstraint {
 562                 outlives: vec![Kind::from(ty)],
 563                 dtorck_types: vec![],
 564             }),
 565
 566             // Types that can't be resolved. Pass them forward.
 567             ty::TyProjection(..) | ty::TyAnon(..) | ty::TyParam(..) => {
 568                 Ok(ty::DtorckConstraint {
 569                     outlives: vec![],
 570                     dtorck_types: vec![ty],
 571                 })
 572             }
 573
 574             ty::TyInfer(..) | ty::TyError => {
 575                 self.sess.delay_span_bug(span, "unresolved type in dtorck");
 576                 Err(ErrorReported)
 577             }
 578         };
 579
 580         debug!("dtorck_constraint_for_ty({:?}) = {:?}", ty, result);
 581         result
 582     }
 583
 584     pub fn closure_base_def_id(self, def_id: DefId) -> DefId {
 585         let mut def_id = def_id;
 586         while self.def_key(def_id).disambiguated_data.data == DefPathData::ClosureExpr {
 587             def_id = self.parent_def_id(def_id).unwrap_or_else(|| {
 588                 bug!("closure {:?} has no parent", def_id);
 589             });
 590         }
 591         def_id
 592     }
 593
 594     /// Given the def-id of some item that has no type parameters, make
 595     /// a suitable "empty substs" for it.
 596     pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx ty::Substs<'tcx> {
 597         ty::Substs::for_item(self, item_def_id,
 598                              |_, _| self.types.re_erased,
 599                              |_, _| {
 600             bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
 601         })
 602     }
 603
 604     pub fn const_usize(&self, val: u16) -> ConstInt {
 605         match self.sess.target.uint_type {
 606             ast::UintTy::U16 => ConstInt::Usize(ConstUsize::Us16(val as u16)),
 607             ast::UintTy::U32 => ConstInt::Usize(ConstUsize::Us32(val as u32)),
 608             ast::UintTy::U64 => ConstInt::Usize(ConstUsize::Us64(val as u64)),
 609             _ => bug!(),
 610         }
 611     }
 612 }
 613
 614 pub struct TypeIdHasher<'a, 'gcx: 'a+'tcx, 'tcx: 'a, W> {
 615     tcx: TyCtxt<'a, 'gcx, 'tcx>,
 616     state: StableHasher<W>,
 617 }
 618
 619 impl<'a, 'gcx, 'tcx, W> TypeIdHasher<'a, 'gcx, 'tcx, W>
 620     where W: StableHasherResult
 621 {
 622     pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Self {
 623         TypeIdHasher { tcx: tcx, state: StableHasher::new() }
 624     }
 625
 626     pub fn finish(self) -> W {
 627         self.state.finish()
 628     }
 629
 630     pub fn hash<T: Hash>(&mut self, x: T) {
 631         x.hash(&mut self.state);
 632     }
 633
 634     fn hash_discriminant_u8<T>(&mut self, x: &T) {
 635         let v = unsafe {
 636             intrinsics::discriminant_value(x)
 637         };
 638         let b = v as u8;
 639         assert_eq!(v, b as u64);
 640         self.hash(b)
 641     }
 642
 643     fn def_id(&mut self, did: DefId) {
 644         // Hash the DefPath corresponding to the DefId, which is independent
 645         // of compiler internal state. We already have a stable hash value of
 646         // all DefPaths available via tcx.def_path_hash(), so we just feed that
 647         // into the hasher.
 648         let hash = self.tcx.def_path_hash(did);
 649         self.hash(hash);
 650     }
 651 }
 652
 653 impl<'a, 'gcx, 'tcx, W> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tcx, W>
 654     where W: StableHasherResult
 655 {
 656     fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
 657         // Distinguish between the Ty variants uniformly.
 658         self.hash_discriminant_u8(&ty.sty);
 659
 660         match ty.sty {
 661             TyInt(i) => self.hash(i),
 662             TyUint(u) => self.hash(u),
 663             TyFloat(f) => self.hash(f),
 664             TyArray(_, n) => self.hash(n),
 665             TyRawPtr(m) |
 666             TyRef(_, m) => self.hash(m.mutbl),
 667             TyClosure(def_id, _) |
 668             TyAnon(def_id, _) |
 669             TyFnDef(def_id, ..) => self.def_id(def_id),
 670             TyAdt(d, _) => self.def_id(d.did),
 671             TyFnPtr(f) => {
 672                 self.hash(f.unsafety());
 673                 self.hash(f.abi());
 674                 self.hash(f.variadic());
 675                 self.hash(f.inputs().skip_binder().len());
 676             }
 677             TyDynamic(ref data, ..) => {
 678                 if let Some(p) = data.principal() {
 679                     self.def_id(p.def_id());
 680                 }
 681                 for d in data.auto_traits() {
 682                     self.def_id(d);
 683                 }
 684             }
 685             TyTuple(tys, defaulted) => {
 686                 self.hash(tys.len());
 687                 self.hash(defaulted);
 688             }
 689             TyParam(p) => {
 690                 self.hash(p.idx);
 691                 self.hash(p.name.as_str());
 692             }
 693             TyProjection(ref data) => {
 694                 self.def_id(data.trait_ref.def_id);
 695                 self.hash(data.item_name.as_str());
 696             }
 697             TyNever |
 698             TyBool |
 699             TyChar |
 700             TyStr |
 701             TySlice(_) => {}
 702
 703             TyError |
 704             TyInfer(_) => bug!("TypeIdHasher: unexpected type {}", ty)
 705         }
 706
 707         ty.super_visit_with(self)
 708     }
 709
 710     fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
 711         self.hash_discriminant_u8(r);
 712         match *r {
 713             ty::ReErased |
 714             ty::ReStatic |
 715             ty::ReEmpty => {
 716                 // No variant fields to hash for these ...
 717             }
 718             ty::ReLateBound(db, ty::BrAnon(i)) => {
 719                 self.hash(db.depth);
 720                 self.hash(i);
 721             }
 722             ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
 723                 self.def_id(def_id);
 724             }
 725             ty::ReLateBound(..) |
 726             ty::ReFree(..) |
 727             ty::ReScope(..) |
 728             ty::ReVar(..) |
 729             ty::ReSkolemized(..) => {
 730                 bug!("TypeIdHasher: unexpected region {:?}", r)
 731             }
 732         }
 733         false
 734     }
 735
 736     fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, x: &ty::Binder<T>) -> bool {
 737         // Anonymize late-bound regions so that, for example:
 738         // `for<'a, b> fn(&'a &'b T)` and `for<'a, b> fn(&'b &'a T)`
 739         // result in the same TypeId (the two types are equivalent).
 740         self.tcx.anonymize_late_bound_regions(x).super_visit_with(self)
 741     }
 742 }
 743
 744 impl<'a, 'tcx> ty::TyS<'tcx> {
 745     pub fn moves_by_default(&'tcx self,
 746                             tcx: TyCtxt<'a, 'tcx, 'tcx>,
 747                             param_env: ty::ParamEnv<'tcx>,
 748                             span: Span)
 749                             -> bool {
 750         !tcx.at(span).is_copy_raw(param_env.and(self))
 751     }
 752
 753     pub fn is_sized(&'tcx self,
 754                     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 755                     param_env: ty::ParamEnv<'tcx>,
 756                     span: Span)-> bool
 757     {
 758         tcx.at(span).is_sized_raw(param_env.and(self))
 759     }
 760
 761     pub fn is_freeze(&'tcx self,
 762                      tcx: TyCtxt<'a, 'tcx, 'tcx>,
 763                      param_env: ty::ParamEnv<'tcx>,
 764                      span: Span)-> bool
 765     {
 766         tcx.at(span).is_freeze_raw(param_env.and(self))
 767     }
 768
 769     /// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
 770     /// non-copy and *might* have a destructor attached; if it returns
 771     /// `false`, then `ty` definitely has no destructor (i.e. no drop glue).
 772     ///
 773     /// (Note that this implies that if `ty` has a destructor attached,
 774     /// then `needs_drop` will definitely return `true` for `ty`.)
 775     #[inline]
 776     pub fn needs_drop(&'tcx self,
 777                       tcx: TyCtxt<'a, 'tcx, 'tcx>,
 778                       param_env: ty::ParamEnv<'tcx>)
 779                       -> bool {
 780         tcx.needs_drop_raw(param_env.and(self))
 781     }
 782
 783     #[inline]
 784     pub fn layout<'lcx>(&'tcx self, infcx: &InferCtxt<'a, 'tcx, 'lcx>)
 785                         -> Result<&'tcx Layout, LayoutError<'tcx>> {
 786         let tcx = infcx.tcx.global_tcx();
 787         let can_cache = !self.has_param_types() && !self.has_self_ty();
 788         if can_cache {
 789             if let Some(&cached) = tcx.layout_cache.borrow().get(&self) {
 790                 return Ok(cached);
 791             }
 792         }
 793
 794         let rec_limit = tcx.sess.recursion_limit.get();
 795         let depth = tcx.layout_depth.get();
 796         if depth > rec_limit {
 797             tcx.sess.fatal(
 798                 &format!("overflow representing the type `{}`", self));
 799         }
 800
 801         tcx.layout_depth.set(depth+1);
 802         let layout = Layout::compute_uncached(self, infcx);
 803         tcx.layout_depth.set(depth);
 804         let layout = layout?;
 805         if can_cache {
 806             tcx.layout_cache.borrow_mut().insert(self, layout);
 807         }
 808         Ok(layout)
 809     }
 810
 811
 812     /// Check whether a type is representable. This means it cannot contain unboxed
 813     /// structural recursion. This check is needed for structs and enums.
 814     pub fn is_representable(&'tcx self,
 815                             tcx: TyCtxt<'a, 'tcx, 'tcx>,
 816                             sp: Span)
 817                             -> Representability {
 818
 819         // Iterate until something non-representable is found
 820         fn fold_repr<It: Iterator<Item=Representability>>(iter: It) -> Representability {
 821             iter.fold(Representability::Representable, |r1, r2| {
 822                 match (r1, r2) {
 823                     (Representability::SelfRecursive(v1),
 824                      Representability::SelfRecursive(v2)) => {
 825                         Representability::SelfRecursive(v1.iter().map(|s| *s).chain(v2).collect())
 826                     }
 827                     (r1, r2) => cmp::max(r1, r2)
 828                 }
 829             })
 830         }
 831
 832         fn are_inner_types_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span,
 833                                                seen: &mut Vec<Ty<'tcx>>, ty: Ty<'tcx>)
 834                                                -> Representability {
 835             match ty.sty {
 836                 TyTuple(ref ts, _) => {
 837                     // Find non representable
 838                     fold_repr(ts.iter().map(|ty| {
 839                         is_type_structurally_recursive(tcx, sp, seen, ty)
 840                     }))
 841                 }
 842                 // Fixed-length vectors.
 843                 // FIXME(#11924) Behavior undecided for zero-length vectors.
 844                 TyArray(ty, _) => {
 845                     is_type_structurally_recursive(tcx, sp, seen, ty)
 846                 }
 847                 TyAdt(def, substs) => {
 848                     // Find non representable fields with their spans
 849                     fold_repr(def.all_fields().map(|field| {
 850                         let ty = field.ty(tcx, substs);
 851                         let span = tcx.hir.span_if_local(field.did).unwrap_or(sp);
 852                         match is_type_structurally_recursive(tcx, span, seen, ty) {
 853                             Representability::SelfRecursive(_) => {
 854                                 Representability::SelfRecursive(vec![span])
 855                             }
 856                             x => x,
 857                         }
 858                     }))
 859                 }
 860                 TyClosure(..) => {
 861                     // this check is run on type definitions, so we don't expect
 862                     // to see closure types
 863                     bug!("requires check invoked on inapplicable type: {:?}", ty)
 864                 }
 865                 _ => Representability::Representable,
 866             }
 867         }
 868
 869         fn same_struct_or_enum<'tcx>(ty: Ty<'tcx>, def: &'tcx ty::AdtDef) -> bool {
 870             match ty.sty {
 871                 TyAdt(ty_def, _) => {
 872                      ty_def == def
 873                 }
 874                 _ => false
 875             }
 876         }
 877
 878         fn same_type<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
 879             match (&a.sty, &b.sty) {
 880                 (&TyAdt(did_a, substs_a), &TyAdt(did_b, substs_b)) => {
 881                     if did_a != did_b {
 882                         return false;
 883                     }
 884
 885                     substs_a.types().zip(substs_b.types()).all(|(a, b)| same_type(a, b))
 886                 }
 887                 _ => a == b,
 888             }
 889         }
 890
 891         // Does the type `ty` directly (without indirection through a pointer)
 892         // contain any types on stack `seen`?
 893         fn is_type_structurally_recursive<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 894                                                     sp: Span,
 895                                                     seen: &mut Vec<Ty<'tcx>>,
 896                                                     ty: Ty<'tcx>) -> Representability {
 897             debug!("is_type_structurally_recursive: {:?} {:?}", ty, sp);
 898
 899             match ty.sty {
 900                 TyAdt(def, _) => {
 901                     {
 902                         // Iterate through stack of previously seen types.
 903                         let mut iter = seen.iter();
 904
 905                         // The first item in `seen` is the type we are actually curious about.
 906                         // We want to return SelfRecursive if this type contains itself.
 907                         // It is important that we DON'T take generic parameters into account
 908                         // for this check, so that Bar<T> in this example counts as SelfRecursive:
 909                         //
 910                         // struct Foo;
 911                         // struct Bar<T> { x: Bar<Foo> }
 912
 913                         if let Some(&seen_type) = iter.next() {
 914                             if same_struct_or_enum(seen_type, def) {
 915                                 debug!("SelfRecursive: {:?} contains {:?}",
 916                                        seen_type,
 917                                        ty);
 918                                 return Representability::SelfRecursive(vec![sp]);
 919                             }
 920                         }
 921
 922                         // We also need to know whether the first item contains other types
 923                         // that are structurally recursive. If we don't catch this case, we
 924                         // will recurse infinitely for some inputs.
 925                         //
 926                         // It is important that we DO take generic parameters into account
 927                         // here, so that code like this is considered SelfRecursive, not
 928                         // ContainsRecursive:
 929                         //
 930                         // struct Foo { Option<Option<Foo>> }
 931
 932                         for &seen_type in iter {
 933                             if same_type(ty, seen_type) {
 934                                 debug!("ContainsRecursive: {:?} contains {:?}",
 935                                        seen_type,
 936                                        ty);
 937                                 return Representability::ContainsRecursive;
 938                             }
 939                         }
 940                     }
 941
 942                     // For structs and enums, track all previously seen types by pushing them
 943                     // onto the 'seen' stack.
 944                     seen.push(ty);
 945                     let out = are_inner_types_recursive(tcx, sp, seen, ty);
 946                     seen.pop();
 947                     out
 948                 }
 949                 _ => {
 950                     // No need to push in other cases.
 951                     are_inner_types_recursive(tcx, sp, seen, ty)
 952                 }
 953             }
 954         }
 955
 956         debug!("is_type_representable: {:?}", self);
 957
 958         // To avoid a stack overflow when checking an enum variant or struct that
 959         // contains a different, structurally recursive type, maintain a stack
 960         // of seen types and check recursion for each of them (issues #3008, #3779).
 961         let mut seen: Vec<Ty> = Vec::new();
 962         let r = is_type_structurally_recursive(tcx, sp, &mut seen, self);
 963         debug!("is_type_representable: {:?} is {:?}", self, r);
 964         r
 965     }
 966 }
 967
 968 fn is_copy_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 969                          query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
 970                          -> bool
 971 {
 972     let (param_env, ty) = query.into_parts();
 973     let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem);
 974     tcx.infer_ctxt(param_env, Reveal::UserFacing)
 975        .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
 976 }
 977
 978 fn is_sized_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 979                           query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
 980                           -> bool
 981 {
 982     let (param_env, ty) = query.into_parts();
 983     let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem);
 984     tcx.infer_ctxt(param_env, Reveal::UserFacing)
 985        .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
 986 }
 987
 988 fn is_freeze_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 989                            query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
 990                            -> bool
 991 {
 992     let (param_env, ty) = query.into_parts();
 993     let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem);
 994     tcx.infer_ctxt(param_env, Reveal::UserFacing)
 995        .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
 996 }
 997
 998 fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 999                             query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
1000                             -> bool
1001 {
1002     let (param_env, ty) = query.into_parts();
1003
1004     let needs_drop = |ty: Ty<'tcx>| -> bool {
1005         match ty::queries::needs_drop_raw::try_get(tcx, DUMMY_SP, param_env.and(ty)) {
1006             Ok(v) => v,
1007             Err(_) => {
1008                 // Cycles should be reported as an error by `check_representable`.
1009                 //
1010                 // Consider the type as not needing drop in the meanwhile to avoid
1011                 // further errors.
1012                 false
1013             }
1014         }
1015     };
1016
1017     assert!(!ty.needs_infer());
1018
1019     match ty.sty {
1020         // Fast-path for primitive types
1021         ty::TyInfer(ty::FreshIntTy(_)) | ty::TyInfer(ty::FreshFloatTy(_)) |
1022         ty::TyBool | ty::TyInt(_) | ty::TyUint(_) | ty::TyFloat(_) | ty::TyNever |
1023         ty::TyFnDef(..) | ty::TyFnPtr(_) | ty::TyChar |
1024         ty::TyRawPtr(_) | ty::TyRef(..) | ty::TyStr => false,
1025
1026         // Issue #22536: We first query type_moves_by_default.  It sees a
1027         // normalized version of the type, and therefore will definitely
1028         // know whether the type implements Copy (and thus needs no
1029         // cleanup/drop/zeroing) ...
1030         _ if !ty.moves_by_default(tcx, param_env, DUMMY_SP) => false,
1031
1032         // ... (issue #22536 continued) but as an optimization, still use
1033         // prior logic of asking for the structural "may drop".
1034
1035         // FIXME(#22815): Note that this is a conservative heuristic;
1036         // it may report that the type "may drop" when actual type does
1037         // not actually have a destructor associated with it. But since
1038         // the type absolutely did not have the `Copy` bound attached
1039         // (see above), it is sound to treat it as having a destructor.
1040
1041         // User destructors are the only way to have concrete drop types.
1042         ty::TyAdt(def, _) if def.has_dtor(tcx) => true,
1043
1044         // Can refer to a type which may drop.
1045         // FIXME(eddyb) check this against a ParamEnv.
1046         ty::TyDynamic(..) | ty::TyProjection(..) | ty::TyParam(_) |
1047         ty::TyAnon(..) | ty::TyInfer(_) | ty::TyError => true,
1048
1049         // Structural recursion.
1050         ty::TyArray(ty, _) | ty::TySlice(ty) => needs_drop(ty),
1051
1052         ty::TyClosure(def_id, ref substs) => substs.upvar_tys(def_id, tcx).any(needs_drop),
1053
1054         ty::TyTuple(ref tys, _) => tys.iter().cloned().any(needs_drop),
1055
1056         // unions don't have destructors regardless of the child types
1057         ty::TyAdt(def, _) if def.is_union() => false,
1058
1059         ty::TyAdt(def, substs) =>
1060             def.variants.iter().any(
1061                 |variant| variant.fields.iter().any(
1062                     |field| needs_drop(field.ty(tcx, substs)))),
1063     }
1064 }
1065
1066
1067 pub fn provide(providers: &mut ty::maps::Providers) {
1068     *providers = ty::maps::Providers {
1069         is_copy_raw,
1070         is_sized_raw,
1071         is_freeze_raw,
1072         needs_drop_raw,
1073         ..*providers
1074     };
1075 }