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.
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.
11 //! This module contains TypeVariants and its major components
13 use hir::def_id::DefId;
16 use ty::subst::Substs;
17 use ty::{self, AdtDef, TypeFlags, Ty, TyCtxt, TypeFoldable};
23 use std::cmp::Ordering;
25 use syntax::ast::{self, Name};
26 use syntax::symbol::{keywords, InternedString};
27 use util::nodemap::FxHashMap;
34 use self::TypeVariants::*;
36 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
37 pub struct TypeAndMut<'tcx> {
39 pub mutbl: hir::Mutability,
42 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash,
43 RustcEncodable, RustcDecodable, Copy)]
44 /// A "free" region `fr` can be interpreted as "some region
45 /// at least as big as the scope `fr.scope`".
46 pub struct FreeRegion {
48 pub bound_region: BoundRegion,
51 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash,
52 RustcEncodable, RustcDecodable, Copy)]
53 pub enum BoundRegion {
54 /// An anonymous region parameter for a given fn (&T)
57 /// Named region parameters for functions (a in &'a T)
59 /// The def-id is needed to distinguish free regions in
60 /// the event of shadowing.
63 /// Fresh bound identifiers created during GLB computations.
66 /// Anonymous region for the implicit env pointer parameter
72 pub fn is_named(&self) -> bool {
74 BoundRegion::BrNamed(..) => true,
80 /// When a region changed from late-bound to early-bound when #32330
81 /// was fixed, its `RegionParameterDef` will have one of these
82 /// structures that we can use to give nicer errors.
83 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, Ord, Hash,
84 RustcEncodable, RustcDecodable)]
85 pub struct Issue32330 {
86 /// fn where is region declared
89 /// name of region; duplicates the info in BrNamed but convenient
90 /// to have it here, and this code is only temporary
91 pub region_name: ast::Name,
94 /// NB: If you change this, you'll probably want to change the corresponding
95 /// AST structure in libsyntax/ast.rs as well.
96 #[derive(Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
97 pub enum TypeVariants<'tcx> {
98 /// The primitive boolean type. Written as `bool`.
101 /// The primitive character type; holds a Unicode scalar value
102 /// (a non-surrogate code point). Written as `char`.
105 /// A primitive signed integer type. For example, `i32`.
108 /// A primitive unsigned integer type. For example, `u32`.
111 /// A primitive floating-point type. For example, `f64`.
112 TyFloat(ast::FloatTy),
114 /// Structures, enumerations and unions.
116 /// Substs here, possibly against intuition, *may* contain `TyParam`s.
117 /// That is, even after substitution it is possible that there are type
118 /// variables. This happens when the `TyAdt` corresponds to an ADT
119 /// definition and not a concrete use of it.
120 TyAdt(&'tcx AdtDef, &'tcx Substs<'tcx>),
122 /// The pointee of a string slice. Written as `str`.
125 /// An array with the given length. Written as `[T; n]`.
126 TyArray(Ty<'tcx>, usize),
128 /// The pointee of an array slice. Written as `[T]`.
131 /// A raw pointer. Written as `*mut T` or `*const T`
132 TyRawPtr(TypeAndMut<'tcx>),
134 /// A reference; a pointer with an associated lifetime. Written as
135 /// `&'a mut T` or `&'a T`.
136 TyRef(Region<'tcx>, TypeAndMut<'tcx>),
138 /// The anonymous type of a function declaration/definition. Each
139 /// function has a unique type.
140 TyFnDef(DefId, &'tcx Substs<'tcx>, PolyFnSig<'tcx>),
142 /// A pointer to a function. Written as `fn() -> i32`.
143 /// FIXME: This is currently also used to represent the callee of a method;
144 /// see ty::MethodCallee etc.
145 TyFnPtr(PolyFnSig<'tcx>),
147 /// A trait, defined with `trait`.
148 TyDynamic(Binder<&'tcx Slice<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
150 /// The anonymous type of a closure. Used to represent the type of
152 TyClosure(DefId, ClosureSubsts<'tcx>),
154 /// The never type `!`
157 /// A tuple type. For example, `(i32, bool)`.
158 /// The bool indicates whether this is a unit tuple and was created by
159 /// defaulting a diverging type variable with feature(never_type) disabled.
160 /// It's only purpose is for raising future-compatibility warnings for when
161 /// diverging type variables start defaulting to ! instead of ().
162 TyTuple(&'tcx Slice<Ty<'tcx>>, bool),
164 /// The projection of an associated type. For example,
165 /// `<T as Trait<..>>::N`.
166 TyProjection(ProjectionTy<'tcx>),
168 /// Anonymized (`impl Trait`) type found in a return type.
169 /// The DefId comes from the `impl Trait` ast::Ty node, and the
170 /// substitutions are for the generics of the function in question.
171 /// After typeck, the concrete type can be found in the `types` map.
172 TyAnon(DefId, &'tcx Substs<'tcx>),
174 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
177 /// A type variable used during type-checking.
180 /// A placeholder for a type which could not be computed; this is
181 /// propagated to avoid useless error messages.
185 /// A closure can be modeled as a struct that looks like:
187 /// struct Closure<'l0...'li, T0...Tj, U0...Uk> {
193 /// where 'l0...'li and T0...Tj are the lifetime and type parameters
194 /// in scope on the function that defined the closure, and U0...Uk are
195 /// type parameters representing the types of its upvars (borrowed, if
198 /// So, for example, given this function:
200 /// fn foo<'a, T>(data: &'a mut T) {
201 /// do(|| data.count += 1)
204 /// the type of the closure would be something like:
206 /// struct Closure<'a, T, U0> {
210 /// Note that the type of the upvar is not specified in the struct.
211 /// You may wonder how the impl would then be able to use the upvar,
212 /// if it doesn't know it's type? The answer is that the impl is
213 /// (conceptually) not fully generic over Closure but rather tied to
214 /// instances with the expected upvar types:
216 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, &'b mut &'a mut T> {
220 /// You can see that the *impl* fully specified the type of the upvar
221 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
222 /// (Here, I am assuming that `data` is mut-borrowed.)
224 /// Now, the last question you may ask is: Why include the upvar types
225 /// as extra type parameters? The reason for this design is that the
226 /// upvar types can reference lifetimes that are internal to the
227 /// creating function. In my example above, for example, the lifetime
228 /// `'b` represents the extent of the closure itself; this is some
229 /// subset of `foo`, probably just the extent of the call to the to
230 /// `do()`. If we just had the lifetime/type parameters from the
231 /// enclosing function, we couldn't name this lifetime `'b`. Note that
232 /// there can also be lifetimes in the types of the upvars themselves,
233 /// if one of them happens to be a reference to something that the
234 /// creating fn owns.
236 /// OK, you say, so why not create a more minimal set of parameters
237 /// that just includes the extra lifetime parameters? The answer is
238 /// primarily that it would be hard --- we don't know at the time when
239 /// we create the closure type what the full types of the upvars are,
240 /// nor do we know which are borrowed and which are not. In this
241 /// design, we can just supply a fresh type parameter and figure that
244 /// All right, you say, but why include the type parameters from the
245 /// original function then? The answer is that trans may need them
246 /// when monomorphizing, and they may not appear in the upvars. A
247 /// closure could capture no variables but still make use of some
248 /// in-scope type parameter with a bound (e.g., if our example above
249 /// had an extra `U: Default`, and the closure called `U::default()`).
251 /// There is another reason. This design (implicitly) prohibits
252 /// closures from capturing themselves (except via a trait
253 /// object). This simplifies closure inference considerably, since it
254 /// means that when we infer the kind of a closure or its upvars, we
255 /// don't have to handle cycles where the decisions we make for
256 /// closure C wind up influencing the decisions we ought to make for
257 /// closure C (which would then require fixed point iteration to
258 /// handle). Plus it fixes an ICE. :P
259 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
260 pub struct ClosureSubsts<'tcx> {
261 /// Lifetime and type parameters from the enclosing function,
262 /// concatenated with the types of the upvars.
264 /// These are separated out because trans wants to pass them around
265 /// when monomorphizing.
266 pub substs: &'tcx Substs<'tcx>,
269 impl<'a, 'gcx, 'acx, 'tcx> ClosureSubsts<'tcx> {
271 pub fn upvar_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'acx>) ->
272 impl Iterator<Item=Ty<'tcx>> + 'tcx
274 let generics = tcx.generics_of(def_id);
275 self.substs[self.substs.len()-generics.own_count()..].iter().map(
276 |t| t.as_type().expect("unexpected region in upvars"))
280 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
281 pub enum ExistentialPredicate<'tcx> {
283 Trait(ExistentialTraitRef<'tcx>),
284 /// e.g. Iterator::Item = T
285 Projection(ExistentialProjection<'tcx>),
290 impl<'a, 'gcx, 'tcx> ExistentialPredicate<'tcx> {
291 pub fn cmp(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, other: &Self) -> Ordering {
292 use self::ExistentialPredicate::*;
293 match (*self, *other) {
294 (Trait(_), Trait(_)) => Ordering::Equal,
295 (Projection(ref a), Projection(ref b)) => a.sort_key(tcx).cmp(&b.sort_key(tcx)),
296 (AutoTrait(ref a), AutoTrait(ref b)) =>
297 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash),
298 (Trait(_), _) => Ordering::Less,
299 (Projection(_), Trait(_)) => Ordering::Greater,
300 (Projection(_), _) => Ordering::Less,
301 (AutoTrait(_), _) => Ordering::Greater,
307 impl<'a, 'gcx, 'tcx> Binder<ExistentialPredicate<'tcx>> {
308 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
309 -> ty::Predicate<'tcx> {
311 match *self.skip_binder() {
312 ExistentialPredicate::Trait(tr) => Binder(tr).with_self_ty(tcx, self_ty).to_predicate(),
313 ExistentialPredicate::Projection(p) =>
314 ty::Predicate::Projection(Binder(p.with_self_ty(tcx, self_ty))),
315 ExistentialPredicate::AutoTrait(did) => {
316 let trait_ref = Binder(ty::TraitRef {
318 substs: tcx.mk_substs_trait(self_ty, &[]),
320 trait_ref.to_predicate()
326 impl<'tcx> serialize::UseSpecializedDecodable for &'tcx Slice<ExistentialPredicate<'tcx>> {}
328 impl<'tcx> Slice<ExistentialPredicate<'tcx>> {
329 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
331 Some(&ExistentialPredicate::Trait(tr)) => Some(tr),
337 pub fn projection_bounds<'a>(&'a self) ->
338 impl Iterator<Item=ExistentialProjection<'tcx>> + 'a {
339 self.iter().filter_map(|predicate| {
341 ExistentialPredicate::Projection(p) => Some(p),
348 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
349 self.iter().filter_map(|predicate| {
351 ExistentialPredicate::AutoTrait(d) => Some(d),
358 impl<'tcx> Binder<&'tcx Slice<ExistentialPredicate<'tcx>>> {
359 pub fn principal(&self) -> Option<PolyExistentialTraitRef<'tcx>> {
360 self.skip_binder().principal().map(Binder)
364 pub fn projection_bounds<'a>(&'a self) ->
365 impl Iterator<Item=PolyExistentialProjection<'tcx>> + 'a {
366 self.skip_binder().projection_bounds().map(Binder)
370 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
371 self.skip_binder().auto_traits()
374 pub fn iter<'a>(&'a self)
375 -> impl DoubleEndedIterator<Item=Binder<ExistentialPredicate<'tcx>>> + 'tcx {
376 self.skip_binder().iter().cloned().map(Binder)
380 /// A complete reference to a trait. These take numerous guises in syntax,
381 /// but perhaps the most recognizable form is in a where clause:
385 /// This would be represented by a trait-reference where the def-id is the
386 /// def-id for the trait `Foo` and the substs define `T` as parameter 0,
387 /// and `U` as parameter 1.
389 /// Trait references also appear in object types like `Foo<U>`, but in
390 /// that case the `Self` parameter is absent from the substitutions.
392 /// Note that a `TraitRef` introduces a level of region binding, to
393 /// account for higher-ranked trait bounds like `T : for<'a> Foo<&'a
394 /// U>` or higher-ranked object types.
395 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
396 pub struct TraitRef<'tcx> {
398 pub substs: &'tcx Substs<'tcx>,
401 impl<'tcx> TraitRef<'tcx> {
402 pub fn new(def_id: DefId, substs: &'tcx Substs<'tcx>) -> TraitRef<'tcx> {
403 TraitRef { def_id: def_id, substs: substs }
406 pub fn self_ty(&self) -> Ty<'tcx> {
407 self.substs.type_at(0)
410 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
411 // Select only the "input types" from a trait-reference. For
412 // now this is all the types that appear in the
413 // trait-reference, but it should eventually exclude
419 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
421 impl<'tcx> PolyTraitRef<'tcx> {
422 pub fn self_ty(&self) -> Ty<'tcx> {
426 pub fn def_id(&self) -> DefId {
430 pub fn substs(&self) -> &'tcx Substs<'tcx> {
431 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
435 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
436 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
440 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
441 // Note that we preserve binding levels
442 Binder(ty::TraitPredicate { trait_ref: self.0.clone() })
446 /// An existential reference to a trait, where `Self` is erased.
447 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
449 /// exists T. T: Trait<'a, 'b, X, Y>
451 /// The substitutions don't include the erased `Self`, only trait
452 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
453 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
454 pub struct ExistentialTraitRef<'tcx> {
456 pub substs: &'tcx Substs<'tcx>,
459 impl<'a, 'gcx, 'tcx> ExistentialTraitRef<'tcx> {
460 pub fn input_types<'b>(&'b self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'b {
461 // Select only the "input types" from a trait-reference. For
462 // now this is all the types that appear in the
463 // trait-reference, but it should eventually exclude
468 /// Object types don't have a self-type specified. Therefore, when
469 /// we convert the principal trait-ref into a normal trait-ref,
470 /// you must give *some* self-type. A common choice is `mk_err()`
471 /// or some skolemized type.
472 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
473 -> ty::TraitRef<'tcx> {
474 // otherwise the escaping regions would be captured by the binder
475 assert!(!self_ty.has_escaping_regions());
479 substs: tcx.mk_substs(
480 iter::once(Kind::from(self_ty)).chain(self.substs.iter().cloned()))
485 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
487 impl<'tcx> PolyExistentialTraitRef<'tcx> {
488 pub fn def_id(&self) -> DefId {
492 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
493 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
498 /// Binder is a binder for higher-ranked lifetimes. It is part of the
499 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
500 /// (which would be represented by the type `PolyTraitRef ==
501 /// Binder<TraitRef>`). Note that when we skolemize, instantiate,
502 /// erase, or otherwise "discharge" these bound regions, we change the
503 /// type from `Binder<T>` to just `T` (see
504 /// e.g. `liberate_late_bound_regions`).
505 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
506 pub struct Binder<T>(pub T);
509 /// Skips the binder and returns the "bound" value. This is a
510 /// risky thing to do because it's easy to get confused about
511 /// debruijn indices and the like. It is usually better to
512 /// discharge the binder using `no_late_bound_regions` or
513 /// `replace_late_bound_regions` or something like
514 /// that. `skip_binder` is only valid when you are either
515 /// extracting data that has nothing to do with bound regions, you
516 /// are doing some sort of test that does not involve bound
517 /// regions, or you are being very careful about your depth
520 /// Some examples where `skip_binder` is reasonable:
521 /// - extracting the def-id from a PolyTraitRef;
522 /// - comparing the self type of a PolyTraitRef to see if it is equal to
523 /// a type parameter `X`, since the type `X` does not reference any regions
524 pub fn skip_binder(&self) -> &T {
528 pub fn as_ref(&self) -> Binder<&T> {
532 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
533 where F: FnOnce(&T) -> U
535 self.as_ref().map_bound(f)
538 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
539 where F: FnOnce(T) -> U
541 ty::Binder(f(self.0))
545 impl fmt::Debug for TypeFlags {
546 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
547 write!(f, "{:x}", self.bits)
551 /// Represents the projection of an associated type. In explicit UFCS
552 /// form this would be written `<T as Trait<..>>::N`.
553 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
554 pub struct ProjectionTy<'tcx> {
555 /// The trait reference `T as Trait<..>`.
556 pub trait_ref: ty::TraitRef<'tcx>,
558 /// The name `N` of the associated type.
561 /// Signature of a function type, which I have arbitrarily
562 /// decided to use to refer to the input/output types.
564 /// - `inputs` is the list of arguments and their modes.
565 /// - `output` is the return type.
566 /// - `variadic` indicates whether this is a variadic function. (only true for foreign fns)
567 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
568 pub struct FnSig<'tcx> {
569 pub inputs_and_output: &'tcx Slice<Ty<'tcx>>,
571 pub unsafety: hir::Unsafety,
575 impl<'tcx> FnSig<'tcx> {
576 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
577 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
580 pub fn output(&self) -> Ty<'tcx> {
581 self.inputs_and_output[self.inputs_and_output.len() - 1]
585 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
587 impl<'tcx> PolyFnSig<'tcx> {
588 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
589 Binder(self.skip_binder().inputs())
591 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
592 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
594 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
595 self.map_bound_ref(|fn_sig| fn_sig.output().clone())
597 pub fn variadic(&self) -> bool {
598 self.skip_binder().variadic
600 pub fn unsafety(&self) -> hir::Unsafety {
601 self.skip_binder().unsafety
603 pub fn abi(&self) -> abi::Abi {
604 self.skip_binder().abi
608 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
614 impl<'a, 'gcx, 'tcx> ParamTy {
615 pub fn new(index: u32, name: Name) -> ParamTy {
616 ParamTy { idx: index, name: name }
619 pub fn for_self() -> ParamTy {
620 ParamTy::new(0, keywords::SelfType.name())
623 pub fn for_def(def: &ty::TypeParameterDef) -> ParamTy {
624 ParamTy::new(def.index, def.name)
627 pub fn to_ty(self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
628 tcx.mk_param(self.idx, self.name)
631 pub fn is_self(&self) -> bool {
632 if self.name == keywords::SelfType.name() {
633 assert_eq!(self.idx, 0);
641 /// A [De Bruijn index][dbi] is a standard means of representing
642 /// regions (and perhaps later types) in a higher-ranked setting. In
643 /// particular, imagine a type like this:
645 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
648 /// | +------------+ 1 | |
650 /// +--------------------------------+ 2 |
652 /// +------------------------------------------+ 1
654 /// In this type, there are two binders (the outer fn and the inner
655 /// fn). We need to be able to determine, for any given region, which
656 /// fn type it is bound by, the inner or the outer one. There are
657 /// various ways you can do this, but a De Bruijn index is one of the
658 /// more convenient and has some nice properties. The basic idea is to
659 /// count the number of binders, inside out. Some examples should help
660 /// clarify what I mean.
662 /// Let's start with the reference type `&'b isize` that is the first
663 /// argument to the inner function. This region `'b` is assigned a De
664 /// Bruijn index of 1, meaning "the innermost binder" (in this case, a
665 /// fn). The region `'a` that appears in the second argument type (`&'a
666 /// isize`) would then be assigned a De Bruijn index of 2, meaning "the
667 /// second-innermost binder". (These indices are written on the arrays
670 /// What is interesting is that De Bruijn index attached to a particular
671 /// variable will vary depending on where it appears. For example,
672 /// the final type `&'a char` also refers to the region `'a` declared on
673 /// the outermost fn. But this time, this reference is not nested within
674 /// any other binders (i.e., it is not an argument to the inner fn, but
675 /// rather the outer one). Therefore, in this case, it is assigned a
676 /// De Bruijn index of 1, because the innermost binder in that location
679 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
680 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, Copy)]
681 pub struct DebruijnIndex {
682 /// We maintain the invariant that this is never 0. So 1 indicates
683 /// the innermost binder. To ensure this, create with `DebruijnIndex::new`.
687 pub type Region<'tcx> = &'tcx RegionKind;
689 /// Representation of regions.
691 /// Unlike types, most region variants are "fictitious", not concrete,
692 /// regions. Among these, `ReStatic`, `ReEmpty` and `ReScope` are the only
693 /// ones representing concrete regions.
697 /// These are regions that are stored behind a binder and must be substituted
698 /// with some concrete region before being used. There are 2 kind of
699 /// bound regions: early-bound, which are bound in an item's Generics,
700 /// and are substituted by a Substs, and late-bound, which are part of
701 /// higher-ranked types (e.g. `for<'a> fn(&'a ())`) and are substituted by
702 /// the likes of `liberate_late_bound_regions`. The distinction exists
703 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
705 /// Unlike TyParam-s, bound regions are not supposed to exist "in the wild"
706 /// outside their binder, e.g. in types passed to type inference, and
707 /// should first be substituted (by skolemized regions, free regions,
708 /// or region variables).
710 /// ## Skolemized and Free Regions
712 /// One often wants to work with bound regions without knowing their precise
713 /// identity. For example, when checking a function, the lifetime of a borrow
714 /// can end up being assigned to some region parameter. In these cases,
715 /// it must be ensured that bounds on the region can't be accidentally
716 /// assumed without being checked.
718 /// The process of doing that is called "skolemization". The bound regions
719 /// are replaced by skolemized markers, which don't satisfy any relation
720 /// not explicity provided.
722 /// There are 2 kinds of skolemized regions in rustc: `ReFree` and
723 /// `ReSkolemized`. When checking an item's body, `ReFree` is supposed
724 /// to be used. These also support explicit bounds: both the internally-stored
725 /// *scope*, which the region is assumed to outlive, as well as other
726 /// relations stored in the `FreeRegionMap`. Note that these relations
727 /// aren't checked when you `make_subregion` (or `eq_types`), only by
728 /// `resolve_regions_and_report_errors`.
730 /// When working with higher-ranked types, some region relations aren't
731 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
732 /// `ReSkolemized` is designed for this purpose. In these contexts,
733 /// there's also the risk that some inference variable laying around will
734 /// get unified with your skolemized region: if you want to check whether
735 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
736 /// with a skolemized region `'%a`, the variable `'_` would just be
737 /// instantiated to the skolemized region `'%a`, which is wrong because
738 /// the inference variable is supposed to satisfy the relation
739 /// *for every value of the skolemized region*. To ensure that doesn't
740 /// happen, you can use `leak_check`. This is more clearly explained
741 /// by infer/higher_ranked/README.md.
743 /// [1] http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
744 /// [2] http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
745 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable)]
746 pub enum RegionKind {
747 // Region bound in a type or fn declaration which will be
748 // substituted 'early' -- that is, at the same time when type
749 // parameters are substituted.
750 ReEarlyBound(EarlyBoundRegion),
752 // Region bound in a function scope, which will be substituted when the
753 // function is called.
754 ReLateBound(DebruijnIndex, BoundRegion),
756 /// When checking a function body, the types of all arguments and so forth
757 /// that refer to bound region parameters are modified to refer to free
758 /// region parameters.
761 /// A concrete region naming some statically determined extent
762 /// (e.g. an expression or sequence of statements) within the
763 /// current function.
764 ReScope(region::CodeExtent),
766 /// Static data that has an "infinite" lifetime. Top in the region lattice.
769 /// A region variable. Should not exist after typeck.
772 /// A skolemized region - basically the higher-ranked version of ReFree.
773 /// Should not exist after typeck.
774 ReSkolemized(SkolemizedRegionVid, BoundRegion),
776 /// Empty lifetime is for data that is never accessed.
777 /// Bottom in the region lattice. We treat ReEmpty somewhat
778 /// specially; at least right now, we do not generate instances of
779 /// it during the GLB computations, but rather
780 /// generate an error instead. This is to improve error messages.
781 /// The only way to get an instance of ReEmpty is to have a region
782 /// variable with no constraints.
785 /// Erased region, used by trait selection, in MIR and during trans.
789 impl<'tcx> serialize::UseSpecializedDecodable for Region<'tcx> {}
791 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
792 pub struct EarlyBoundRegion {
798 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
803 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
808 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
809 pub struct FloatVid {
813 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
814 pub struct RegionVid {
818 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
819 pub struct SkolemizedRegionVid {
823 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
829 /// A `FreshTy` is one that is generated as a replacement for an
830 /// unbound type variable. This is convenient for caching etc. See
831 /// `infer::freshen` for more details.
837 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
838 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
839 pub struct ExistentialProjection<'tcx> {
840 pub trait_ref: ExistentialTraitRef<'tcx>,
845 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
847 impl<'a, 'tcx, 'gcx> ExistentialProjection<'tcx> {
848 pub fn item_name(&self) -> Name {
849 self.item_name // safe to skip the binder to access a name
852 pub fn sort_key(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> (u64, InternedString) {
853 // We want something here that is stable across crate boundaries.
854 // The DefId isn't but the `deterministic_hash` of the corresponding
856 let trait_def = tcx.trait_def(self.trait_ref.def_id);
857 let def_path_hash = trait_def.def_path_hash;
859 // An `ast::Name` is also not stable (it's just an index into an
860 // interning table), so map to the corresponding `InternedString`.
861 let item_name = self.item_name.as_str();
862 (def_path_hash, item_name)
865 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
867 -> ty::ProjectionPredicate<'tcx>
869 // otherwise the escaping regions would be captured by the binders
870 assert!(!self_ty.has_escaping_regions());
872 ty::ProjectionPredicate {
873 projection_ty: ty::ProjectionTy {
874 trait_ref: self.trait_ref.with_self_ty(tcx, self_ty),
875 item_name: self.item_name,
882 impl<'a, 'tcx, 'gcx> PolyExistentialProjection<'tcx> {
883 pub fn item_name(&self) -> Name {
884 self.skip_binder().item_name()
887 pub fn sort_key(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> (u64, InternedString) {
888 self.skip_binder().sort_key(tcx)
891 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
892 -> ty::PolyProjectionPredicate<'tcx> {
893 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
898 pub fn new(depth: u32) -> DebruijnIndex {
900 DebruijnIndex { depth: depth }
903 pub fn shifted(&self, amount: u32) -> DebruijnIndex {
904 DebruijnIndex { depth: self.depth + amount }
910 pub fn is_late_bound(&self) -> bool {
912 ty::ReLateBound(..) => true,
917 pub fn needs_infer(&self) -> bool {
919 ty::ReVar(..) | ty::ReSkolemized(..) => true,
924 pub fn escapes_depth(&self, depth: u32) -> bool {
926 ty::ReLateBound(debruijn, _) => debruijn.depth > depth,
931 /// Returns the depth of `self` from the (1-based) binding level `depth`
932 pub fn from_depth(&self, depth: u32) -> RegionKind {
934 ty::ReLateBound(debruijn, r) => ty::ReLateBound(DebruijnIndex {
935 depth: debruijn.depth - (depth - 1)
941 pub fn type_flags(&self) -> TypeFlags {
942 let mut flags = TypeFlags::empty();
946 flags = flags | TypeFlags::HAS_RE_INFER;
947 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
949 ty::ReSkolemized(..) => {
950 flags = flags | TypeFlags::HAS_RE_INFER;
951 flags = flags | TypeFlags::HAS_RE_SKOL;
952 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
954 ty::ReLateBound(..) => { }
955 ty::ReEarlyBound(..) => { flags = flags | TypeFlags::HAS_RE_EARLY_BOUND; }
956 ty::ReStatic | ty::ReErased => { }
957 _ => { flags = flags | TypeFlags::HAS_FREE_REGIONS; }
961 ty::ReStatic | ty::ReEmpty | ty::ReErased => (),
962 _ => flags = flags | TypeFlags::HAS_LOCAL_NAMES,
965 debug!("type_flags({:?}) = {:?}", self, flags);
972 impl<'a, 'gcx, 'tcx> TyS<'tcx> {
973 pub fn as_opt_param_ty(&self) -> Option<ty::ParamTy> {
975 ty::TyParam(ref d) => Some(d.clone()),
980 pub fn is_nil(&self) -> bool {
982 TyTuple(ref tys, _) => tys.is_empty(),
987 pub fn is_never(&self) -> bool {
994 /// Test whether this is a `()` which was produced by defaulting a
995 /// diverging type variable with feature(never_type) disabled.
996 pub fn is_defaulted_unit(&self) -> bool {
998 TyTuple(_, true) => true,
1003 /// Checks whether a type is visibly uninhabited from a particular module.
1009 /// pub struct SecretlyUninhabited {
1016 /// pub struct AlsoSecretlyUninhabited {
1024 /// x: a::b::SecretlyUninhabited,
1025 /// y: c::AlsoSecretlyUninhabited,
1028 /// In this code, the type `Foo` will only be visibly uninhabited inside the
1029 /// modules b, c and d. This effects pattern-matching on `Foo` or types that
1034 /// let foo_result: Result<T, Foo> = ... ;
1035 /// let Ok(t) = foo_result;
1037 /// This code should only compile in modules where the uninhabitedness of Foo is
1039 pub fn is_uninhabited_from(&self, module: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
1040 let mut visited = FxHashMap::default();
1041 let forest = self.uninhabited_from(&mut visited, tcx);
1043 // To check whether this type is uninhabited at all (not just from the
1044 // given node) you could check whether the forest is empty.
1046 // forest.is_empty()
1048 forest.contains(tcx, module)
1051 pub fn is_primitive(&self) -> bool {
1053 TyBool | TyChar | TyInt(_) | TyUint(_) | TyFloat(_) => true,
1058 pub fn is_ty_var(&self) -> bool {
1060 TyInfer(TyVar(_)) => true,
1065 pub fn is_phantom_data(&self) -> bool {
1066 if let TyAdt(def, _) = self.sty {
1067 def.is_phantom_data()
1073 pub fn is_bool(&self) -> bool { self.sty == TyBool }
1075 pub fn is_param(&self, index: u32) -> bool {
1077 ty::TyParam(ref data) => data.idx == index,
1082 pub fn is_self(&self) -> bool {
1084 TyParam(ref p) => p.is_self(),
1089 pub fn is_slice(&self) -> bool {
1091 TyRawPtr(mt) | TyRef(_, mt) => match mt.ty.sty {
1092 TySlice(_) | TyStr => true,
1099 pub fn is_structural(&self) -> bool {
1101 TyAdt(..) | TyTuple(..) | TyArray(..) | TyClosure(..) => true,
1102 _ => self.is_slice() | self.is_trait(),
1107 pub fn is_simd(&self) -> bool {
1109 TyAdt(def, _) => def.repr.simd(),
1114 pub fn sequence_element_type(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
1116 TyArray(ty, _) | TySlice(ty) => ty,
1117 TyStr => tcx.mk_mach_uint(ast::UintTy::U8),
1118 _ => bug!("sequence_element_type called on non-sequence value: {}", self),
1122 pub fn simd_type(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
1124 TyAdt(def, substs) => {
1125 def.struct_variant().fields[0].ty(tcx, substs)
1127 _ => bug!("simd_type called on invalid type")
1131 pub fn simd_size(&self, _cx: TyCtxt) -> usize {
1133 TyAdt(def, _) => def.struct_variant().fields.len(),
1134 _ => bug!("simd_size called on invalid type")
1138 pub fn is_region_ptr(&self) -> bool {
1145 pub fn is_mutable_pointer(&self) -> bool {
1147 TyRawPtr(tnm) | TyRef(_, tnm) => if let hir::Mutability::MutMutable = tnm.mutbl {
1156 pub fn is_unsafe_ptr(&self) -> bool {
1158 TyRawPtr(_) => return true,
1163 pub fn is_box(&self) -> bool {
1165 TyAdt(def, _) => def.is_box(),
1170 /// panics if called on any type other than `Box<T>`
1171 pub fn boxed_ty(&self) -> Ty<'tcx> {
1173 TyAdt(def, substs) if def.is_box() => substs.type_at(0),
1174 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1178 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1179 /// (A TyRawPtr is scalar because it represents a non-managed pointer, so its
1180 /// contents are abstract to rustc.)
1181 pub fn is_scalar(&self) -> bool {
1183 TyBool | TyChar | TyInt(_) | TyFloat(_) | TyUint(_) |
1184 TyInfer(IntVar(_)) | TyInfer(FloatVar(_)) |
1185 TyFnDef(..) | TyFnPtr(_) | TyRawPtr(_) => true,
1190 /// Returns true if this type is a floating point type and false otherwise.
1191 pub fn is_floating_point(&self) -> bool {
1194 TyInfer(FloatVar(_)) => true,
1199 pub fn is_trait(&self) -> bool {
1201 TyDynamic(..) => true,
1206 pub fn is_closure(&self) -> bool {
1208 TyClosure(..) => true,
1213 pub fn is_integral(&self) -> bool {
1215 TyInfer(IntVar(_)) | TyInt(_) | TyUint(_) => true,
1220 pub fn is_fresh(&self) -> bool {
1222 TyInfer(FreshTy(_)) => true,
1223 TyInfer(FreshIntTy(_)) => true,
1224 TyInfer(FreshFloatTy(_)) => true,
1229 pub fn is_uint(&self) -> bool {
1231 TyInfer(IntVar(_)) | TyUint(ast::UintTy::Us) => true,
1236 pub fn is_char(&self) -> bool {
1243 pub fn is_fp(&self) -> bool {
1245 TyInfer(FloatVar(_)) | TyFloat(_) => true,
1250 pub fn is_numeric(&self) -> bool {
1251 self.is_integral() || self.is_fp()
1254 pub fn is_signed(&self) -> bool {
1261 pub fn is_machine(&self) -> bool {
1263 TyInt(ast::IntTy::Is) | TyUint(ast::UintTy::Us) => false,
1264 TyInt(..) | TyUint(..) | TyFloat(..) => true,
1269 pub fn has_concrete_skeleton(&self) -> bool {
1271 TyParam(_) | TyInfer(_) | TyError => false,
1276 /// Returns the type and mutability of *ty.
1278 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1279 /// Some types---notably unsafe ptrs---can only be dereferenced explicitly.
1280 pub fn builtin_deref(&self, explicit: bool, pref: ty::LvaluePreference)
1281 -> Option<TypeAndMut<'tcx>>
1284 TyAdt(def, _) if def.is_box() => {
1286 ty: self.boxed_ty(),
1287 mutbl: if pref == ty::PreferMutLvalue {
1294 TyRef(_, mt) => Some(mt),
1295 TyRawPtr(mt) if explicit => Some(mt),
1300 /// Returns the type of ty[i]
1301 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
1303 TyArray(ty, _) | TySlice(ty) => Some(ty),
1308 pub fn fn_sig(&self) -> PolyFnSig<'tcx> {
1310 TyFnDef(.., f) | TyFnPtr(f) => f,
1311 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self)
1315 /// Type accessors for substructures of types
1316 pub fn fn_args(&self) -> ty::Binder<&'tcx [Ty<'tcx>]> {
1317 self.fn_sig().inputs()
1320 pub fn fn_ret(&self) -> Binder<Ty<'tcx>> {
1321 self.fn_sig().output()
1324 pub fn is_fn(&self) -> bool {
1326 TyFnDef(..) | TyFnPtr(_) => true,
1331 pub fn ty_to_def_id(&self) -> Option<DefId> {
1333 TyDynamic(ref tt, ..) => tt.principal().map(|p| p.def_id()),
1334 TyAdt(def, _) => Some(def.did),
1335 TyClosure(id, _) => Some(id),
1340 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
1342 TyAdt(adt, _) => Some(adt),
1347 /// Returns the regions directly referenced from this type (but
1348 /// not types reachable from this type via `walk_tys`). This
1349 /// ignores late-bound regions binders.
1350 pub fn regions(&self) -> Vec<ty::Region<'tcx>> {
1352 TyRef(region, _) => {
1355 TyDynamic(ref obj, region) => {
1356 let mut v = vec![region];
1357 if let Some(p) = obj.principal() {
1358 v.extend(p.skip_binder().substs.regions());
1362 TyAdt(_, substs) | TyAnon(_, substs) => {
1363 substs.regions().collect()
1365 TyClosure(_, ref substs) => {
1366 substs.substs.regions().collect()
1368 TyProjection(ref data) => {
1369 data.trait_ref.substs.regions().collect()