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`".
47 /// If `fr.scope` is None, then this is in some context (e.g., an
48 /// impl) where lifetimes are more abstract and the notion of the
49 /// caller/callee stack frames are not applicable.
50 pub struct FreeRegion<'tcx> {
51 pub scope: Option<region::CodeExtent<'tcx>>,
52 pub bound_region: BoundRegion,
55 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash,
56 RustcEncodable, RustcDecodable, Copy)]
57 pub enum BoundRegion {
58 /// An anonymous region parameter for a given fn (&T)
61 /// Named region parameters for functions (a in &'a T)
63 /// The def-id is needed to distinguish free regions in
64 /// the event of shadowing.
67 /// Fresh bound identifiers created during GLB computations.
70 /// Anonymous region for the implicit env pointer parameter
76 pub fn is_named(&self) -> bool {
78 BoundRegion::BrNamed(..) => true,
84 /// When a region changed from late-bound to early-bound when #32330
85 /// was fixed, its `RegionParameterDef` will have one of these
86 /// structures that we can use to give nicer errors.
87 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, Ord, Hash,
88 RustcEncodable, RustcDecodable)]
89 pub struct Issue32330 {
90 /// fn where is region declared
93 /// name of region; duplicates the info in BrNamed but convenient
94 /// to have it here, and this code is only temporary
95 pub region_name: ast::Name,
98 /// NB: If you change this, you'll probably want to change the corresponding
99 /// AST structure in libsyntax/ast.rs as well.
100 #[derive(Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
101 pub enum TypeVariants<'tcx> {
102 /// The primitive boolean type. Written as `bool`.
105 /// The primitive character type; holds a Unicode scalar value
106 /// (a non-surrogate code point). Written as `char`.
109 /// A primitive signed integer type. For example, `i32`.
112 /// A primitive unsigned integer type. For example, `u32`.
115 /// A primitive floating-point type. For example, `f64`.
116 TyFloat(ast::FloatTy),
118 /// Structures, enumerations and unions.
120 /// Substs here, possibly against intuition, *may* contain `TyParam`s.
121 /// That is, even after substitution it is possible that there are type
122 /// variables. This happens when the `TyAdt` corresponds to an ADT
123 /// definition and not a concrete use of it.
124 TyAdt(&'tcx AdtDef, &'tcx Substs<'tcx>),
126 /// The pointee of a string slice. Written as `str`.
129 /// An array with the given length. Written as `[T; n]`.
130 TyArray(Ty<'tcx>, usize),
132 /// The pointee of an array slice. Written as `[T]`.
135 /// A raw pointer. Written as `*mut T` or `*const T`
136 TyRawPtr(TypeAndMut<'tcx>),
138 /// A reference; a pointer with an associated lifetime. Written as
139 /// `&'a mut T` or `&'a T`.
140 TyRef(Region<'tcx>, TypeAndMut<'tcx>),
142 /// The anonymous type of a function declaration/definition. Each
143 /// function has a unique type.
144 TyFnDef(DefId, &'tcx Substs<'tcx>, PolyFnSig<'tcx>),
146 /// A pointer to a function. Written as `fn() -> i32`.
147 /// FIXME: This is currently also used to represent the callee of a method;
148 /// see ty::MethodCallee etc.
149 TyFnPtr(PolyFnSig<'tcx>),
151 /// A trait, defined with `trait`.
152 TyDynamic(Binder<&'tcx Slice<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
154 /// The anonymous type of a closure. Used to represent the type of
156 TyClosure(DefId, ClosureSubsts<'tcx>),
158 /// The never type `!`
161 /// A tuple type. For example, `(i32, bool)`.
162 /// The bool indicates whether this is a unit tuple and was created by
163 /// defaulting a diverging type variable with feature(never_type) disabled.
164 /// It's only purpose is for raising future-compatibility warnings for when
165 /// diverging type variables start defaulting to ! instead of ().
166 TyTuple(&'tcx Slice<Ty<'tcx>>, bool),
168 /// The projection of an associated type. For example,
169 /// `<T as Trait<..>>::N`.
170 TyProjection(ProjectionTy<'tcx>),
172 /// Anonymized (`impl Trait`) type found in a return type.
173 /// The DefId comes from the `impl Trait` ast::Ty node, and the
174 /// substitutions are for the generics of the function in question.
175 /// After typeck, the concrete type can be found in the `types` map.
176 TyAnon(DefId, &'tcx Substs<'tcx>),
178 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
181 /// A type variable used during type-checking.
184 /// A placeholder for a type which could not be computed; this is
185 /// propagated to avoid useless error messages.
189 /// A closure can be modeled as a struct that looks like:
191 /// struct Closure<'l0...'li, T0...Tj, U0...Uk> {
197 /// where 'l0...'li and T0...Tj are the lifetime and type parameters
198 /// in scope on the function that defined the closure, and U0...Uk are
199 /// type parameters representing the types of its upvars (borrowed, if
202 /// So, for example, given this function:
204 /// fn foo<'a, T>(data: &'a mut T) {
205 /// do(|| data.count += 1)
208 /// the type of the closure would be something like:
210 /// struct Closure<'a, T, U0> {
214 /// Note that the type of the upvar is not specified in the struct.
215 /// You may wonder how the impl would then be able to use the upvar,
216 /// if it doesn't know it's type? The answer is that the impl is
217 /// (conceptually) not fully generic over Closure but rather tied to
218 /// instances with the expected upvar types:
220 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, &'b mut &'a mut T> {
224 /// You can see that the *impl* fully specified the type of the upvar
225 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
226 /// (Here, I am assuming that `data` is mut-borrowed.)
228 /// Now, the last question you may ask is: Why include the upvar types
229 /// as extra type parameters? The reason for this design is that the
230 /// upvar types can reference lifetimes that are internal to the
231 /// creating function. In my example above, for example, the lifetime
232 /// `'b` represents the extent of the closure itself; this is some
233 /// subset of `foo`, probably just the extent of the call to the to
234 /// `do()`. If we just had the lifetime/type parameters from the
235 /// enclosing function, we couldn't name this lifetime `'b`. Note that
236 /// there can also be lifetimes in the types of the upvars themselves,
237 /// if one of them happens to be a reference to something that the
238 /// creating fn owns.
240 /// OK, you say, so why not create a more minimal set of parameters
241 /// that just includes the extra lifetime parameters? The answer is
242 /// primarily that it would be hard --- we don't know at the time when
243 /// we create the closure type what the full types of the upvars are,
244 /// nor do we know which are borrowed and which are not. In this
245 /// design, we can just supply a fresh type parameter and figure that
248 /// All right, you say, but why include the type parameters from the
249 /// original function then? The answer is that trans may need them
250 /// when monomorphizing, and they may not appear in the upvars. A
251 /// closure could capture no variables but still make use of some
252 /// in-scope type parameter with a bound (e.g., if our example above
253 /// had an extra `U: Default`, and the closure called `U::default()`).
255 /// There is another reason. This design (implicitly) prohibits
256 /// closures from capturing themselves (except via a trait
257 /// object). This simplifies closure inference considerably, since it
258 /// means that when we infer the kind of a closure or its upvars, we
259 /// don't have to handle cycles where the decisions we make for
260 /// closure C wind up influencing the decisions we ought to make for
261 /// closure C (which would then require fixed point iteration to
262 /// handle). Plus it fixes an ICE. :P
263 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
264 pub struct ClosureSubsts<'tcx> {
265 /// Lifetime and type parameters from the enclosing function,
266 /// concatenated with the types of the upvars.
268 /// These are separated out because trans wants to pass them around
269 /// when monomorphizing.
270 pub substs: &'tcx Substs<'tcx>,
273 impl<'a, 'gcx, 'acx, 'tcx> ClosureSubsts<'tcx> {
275 pub fn upvar_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'acx>) ->
276 impl Iterator<Item=Ty<'tcx>> + 'tcx
278 let generics = tcx.generics_of(def_id);
279 self.substs[self.substs.len()-generics.own_count()..].iter().map(
280 |t| t.as_type().expect("unexpected region in upvars"))
284 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
285 pub enum ExistentialPredicate<'tcx> {
287 Trait(ExistentialTraitRef<'tcx>),
288 /// e.g. Iterator::Item = T
289 Projection(ExistentialProjection<'tcx>),
294 impl<'a, 'gcx, 'tcx> ExistentialPredicate<'tcx> {
295 pub fn cmp(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, other: &Self) -> Ordering {
296 use self::ExistentialPredicate::*;
297 match (*self, *other) {
298 (Trait(_), Trait(_)) => Ordering::Equal,
299 (Projection(ref a), Projection(ref b)) => a.sort_key(tcx).cmp(&b.sort_key(tcx)),
300 (AutoTrait(ref a), AutoTrait(ref b)) =>
301 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash),
302 (Trait(_), _) => Ordering::Less,
303 (Projection(_), Trait(_)) => Ordering::Greater,
304 (Projection(_), _) => Ordering::Less,
305 (AutoTrait(_), _) => Ordering::Greater,
311 impl<'a, 'gcx, 'tcx> Binder<ExistentialPredicate<'tcx>> {
312 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
313 -> ty::Predicate<'tcx> {
315 match *self.skip_binder() {
316 ExistentialPredicate::Trait(tr) => Binder(tr).with_self_ty(tcx, self_ty).to_predicate(),
317 ExistentialPredicate::Projection(p) =>
318 ty::Predicate::Projection(Binder(p.with_self_ty(tcx, self_ty))),
319 ExistentialPredicate::AutoTrait(did) => {
320 let trait_ref = Binder(ty::TraitRef {
322 substs: tcx.mk_substs_trait(self_ty, &[]),
324 trait_ref.to_predicate()
330 impl<'tcx> serialize::UseSpecializedDecodable for &'tcx Slice<ExistentialPredicate<'tcx>> {}
332 impl<'tcx> Slice<ExistentialPredicate<'tcx>> {
333 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
335 Some(&ExistentialPredicate::Trait(tr)) => Some(tr),
341 pub fn projection_bounds<'a>(&'a self) ->
342 impl Iterator<Item=ExistentialProjection<'tcx>> + 'a {
343 self.iter().filter_map(|predicate| {
345 ExistentialPredicate::Projection(p) => Some(p),
352 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
353 self.iter().filter_map(|predicate| {
355 ExistentialPredicate::AutoTrait(d) => Some(d),
362 impl<'tcx> Binder<&'tcx Slice<ExistentialPredicate<'tcx>>> {
363 pub fn principal(&self) -> Option<PolyExistentialTraitRef<'tcx>> {
364 self.skip_binder().principal().map(Binder)
368 pub fn projection_bounds<'a>(&'a self) ->
369 impl Iterator<Item=PolyExistentialProjection<'tcx>> + 'a {
370 self.skip_binder().projection_bounds().map(Binder)
374 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
375 self.skip_binder().auto_traits()
378 pub fn iter<'a>(&'a self)
379 -> impl DoubleEndedIterator<Item=Binder<ExistentialPredicate<'tcx>>> + 'tcx {
380 self.skip_binder().iter().cloned().map(Binder)
384 /// A complete reference to a trait. These take numerous guises in syntax,
385 /// but perhaps the most recognizable form is in a where clause:
389 /// This would be represented by a trait-reference where the def-id is the
390 /// def-id for the trait `Foo` and the substs define `T` as parameter 0,
391 /// and `U` as parameter 1.
393 /// Trait references also appear in object types like `Foo<U>`, but in
394 /// that case the `Self` parameter is absent from the substitutions.
396 /// Note that a `TraitRef` introduces a level of region binding, to
397 /// account for higher-ranked trait bounds like `T : for<'a> Foo<&'a
398 /// U>` or higher-ranked object types.
399 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
400 pub struct TraitRef<'tcx> {
402 pub substs: &'tcx Substs<'tcx>,
405 impl<'tcx> TraitRef<'tcx> {
406 pub fn new(def_id: DefId, substs: &'tcx Substs<'tcx>) -> TraitRef<'tcx> {
407 TraitRef { def_id: def_id, substs: substs }
410 pub fn self_ty(&self) -> Ty<'tcx> {
411 self.substs.type_at(0)
414 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
415 // Select only the "input types" from a trait-reference. For
416 // now this is all the types that appear in the
417 // trait-reference, but it should eventually exclude
423 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
425 impl<'tcx> PolyTraitRef<'tcx> {
426 pub fn self_ty(&self) -> Ty<'tcx> {
430 pub fn def_id(&self) -> DefId {
434 pub fn substs(&self) -> &'tcx Substs<'tcx> {
435 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
439 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
440 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
444 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
445 // Note that we preserve binding levels
446 Binder(ty::TraitPredicate { trait_ref: self.0.clone() })
450 /// An existential reference to a trait, where `Self` is erased.
451 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
453 /// exists T. T: Trait<'a, 'b, X, Y>
455 /// The substitutions don't include the erased `Self`, only trait
456 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
457 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
458 pub struct ExistentialTraitRef<'tcx> {
460 pub substs: &'tcx Substs<'tcx>,
463 impl<'a, 'gcx, 'tcx> ExistentialTraitRef<'tcx> {
464 pub fn input_types<'b>(&'b self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'b {
465 // Select only the "input types" from a trait-reference. For
466 // now this is all the types that appear in the
467 // trait-reference, but it should eventually exclude
472 /// Object types don't have a self-type specified. Therefore, when
473 /// we convert the principal trait-ref into a normal trait-ref,
474 /// you must give *some* self-type. A common choice is `mk_err()`
475 /// or some skolemized type.
476 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
477 -> ty::TraitRef<'tcx> {
478 // otherwise the escaping regions would be captured by the binder
479 assert!(!self_ty.has_escaping_regions());
483 substs: tcx.mk_substs(
484 iter::once(Kind::from(self_ty)).chain(self.substs.iter().cloned()))
489 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
491 impl<'tcx> PolyExistentialTraitRef<'tcx> {
492 pub fn def_id(&self) -> DefId {
496 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
497 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
502 /// Binder is a binder for higher-ranked lifetimes. It is part of the
503 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
504 /// (which would be represented by the type `PolyTraitRef ==
505 /// Binder<TraitRef>`). Note that when we skolemize, instantiate,
506 /// erase, or otherwise "discharge" these bound regions, we change the
507 /// type from `Binder<T>` to just `T` (see
508 /// e.g. `liberate_late_bound_regions`).
509 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
510 pub struct Binder<T>(pub T);
513 /// Skips the binder and returns the "bound" value. This is a
514 /// risky thing to do because it's easy to get confused about
515 /// debruijn indices and the like. It is usually better to
516 /// discharge the binder using `no_late_bound_regions` or
517 /// `replace_late_bound_regions` or something like
518 /// that. `skip_binder` is only valid when you are either
519 /// extracting data that has nothing to do with bound regions, you
520 /// are doing some sort of test that does not involve bound
521 /// regions, or you are being very careful about your depth
524 /// Some examples where `skip_binder` is reasonable:
525 /// - extracting the def-id from a PolyTraitRef;
526 /// - comparing the self type of a PolyTraitRef to see if it is equal to
527 /// a type parameter `X`, since the type `X` does not reference any regions
528 pub fn skip_binder(&self) -> &T {
532 pub fn as_ref(&self) -> Binder<&T> {
536 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
537 where F: FnOnce(&T) -> U
539 self.as_ref().map_bound(f)
542 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
543 where F: FnOnce(T) -> U
545 ty::Binder(f(self.0))
549 impl fmt::Debug for TypeFlags {
550 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
551 write!(f, "{:x}", self.bits)
555 /// Represents the projection of an associated type. In explicit UFCS
556 /// form this would be written `<T as Trait<..>>::N`.
557 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
558 pub struct ProjectionTy<'tcx> {
559 /// The trait reference `T as Trait<..>`.
560 pub trait_ref: ty::TraitRef<'tcx>,
562 /// The name `N` of the associated type.
565 /// Signature of a function type, which I have arbitrarily
566 /// decided to use to refer to the input/output types.
568 /// - `inputs` is the list of arguments and their modes.
569 /// - `output` is the return type.
570 /// - `variadic` indicates whether this is a variadic function. (only true for foreign fns)
571 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
572 pub struct FnSig<'tcx> {
573 pub inputs_and_output: &'tcx Slice<Ty<'tcx>>,
575 pub unsafety: hir::Unsafety,
579 impl<'tcx> FnSig<'tcx> {
580 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
581 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
584 pub fn output(&self) -> Ty<'tcx> {
585 self.inputs_and_output[self.inputs_and_output.len() - 1]
589 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
591 impl<'tcx> PolyFnSig<'tcx> {
592 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
593 Binder(self.skip_binder().inputs())
595 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
596 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
598 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
599 self.map_bound_ref(|fn_sig| fn_sig.output().clone())
601 pub fn variadic(&self) -> bool {
602 self.skip_binder().variadic
604 pub fn unsafety(&self) -> hir::Unsafety {
605 self.skip_binder().unsafety
607 pub fn abi(&self) -> abi::Abi {
608 self.skip_binder().abi
612 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
618 impl<'a, 'gcx, 'tcx> ParamTy {
619 pub fn new(index: u32, name: Name) -> ParamTy {
620 ParamTy { idx: index, name: name }
623 pub fn for_self() -> ParamTy {
624 ParamTy::new(0, keywords::SelfType.name())
627 pub fn for_def(def: &ty::TypeParameterDef) -> ParamTy {
628 ParamTy::new(def.index, def.name)
631 pub fn to_ty(self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
632 tcx.mk_param(self.idx, self.name)
635 pub fn is_self(&self) -> bool {
636 if self.name == keywords::SelfType.name() {
637 assert_eq!(self.idx, 0);
645 /// A [De Bruijn index][dbi] is a standard means of representing
646 /// regions (and perhaps later types) in a higher-ranked setting. In
647 /// particular, imagine a type like this:
649 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
652 /// | +------------+ 1 | |
654 /// +--------------------------------+ 2 |
656 /// +------------------------------------------+ 1
658 /// In this type, there are two binders (the outer fn and the inner
659 /// fn). We need to be able to determine, for any given region, which
660 /// fn type it is bound by, the inner or the outer one. There are
661 /// various ways you can do this, but a De Bruijn index is one of the
662 /// more convenient and has some nice properties. The basic idea is to
663 /// count the number of binders, inside out. Some examples should help
664 /// clarify what I mean.
666 /// Let's start with the reference type `&'b isize` that is the first
667 /// argument to the inner function. This region `'b` is assigned a De
668 /// Bruijn index of 1, meaning "the innermost binder" (in this case, a
669 /// fn). The region `'a` that appears in the second argument type (`&'a
670 /// isize`) would then be assigned a De Bruijn index of 2, meaning "the
671 /// second-innermost binder". (These indices are written on the arrays
674 /// What is interesting is that De Bruijn index attached to a particular
675 /// variable will vary depending on where it appears. For example,
676 /// the final type `&'a char` also refers to the region `'a` declared on
677 /// the outermost fn. But this time, this reference is not nested within
678 /// any other binders (i.e., it is not an argument to the inner fn, but
679 /// rather the outer one). Therefore, in this case, it is assigned a
680 /// De Bruijn index of 1, because the innermost binder in that location
683 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
684 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, Copy)]
685 pub struct DebruijnIndex {
686 /// We maintain the invariant that this is never 0. So 1 indicates
687 /// the innermost binder. To ensure this, create with `DebruijnIndex::new`.
691 pub type Region<'tcx> = &'tcx RegionKind<'tcx>;
693 /// Representation of regions.
695 /// Unlike types, most region variants are "fictitious", not concrete,
696 /// regions. Among these, `ReStatic`, `ReEmpty` and `ReScope` are the only
697 /// ones representing concrete regions.
701 /// These are regions that are stored behind a binder and must be substituted
702 /// with some concrete region before being used. There are 2 kind of
703 /// bound regions: early-bound, which are bound in an item's Generics,
704 /// and are substituted by a Substs, and late-bound, which are part of
705 /// higher-ranked types (e.g. `for<'a> fn(&'a ())`) and are substituted by
706 /// the likes of `liberate_late_bound_regions`. The distinction exists
707 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
709 /// Unlike TyParam-s, bound regions are not supposed to exist "in the wild"
710 /// outside their binder, e.g. in types passed to type inference, and
711 /// should first be substituted (by skolemized regions, free regions,
712 /// or region variables).
714 /// ## Skolemized and Free Regions
716 /// One often wants to work with bound regions without knowing their precise
717 /// identity. For example, when checking a function, the lifetime of a borrow
718 /// can end up being assigned to some region parameter. In these cases,
719 /// it must be ensured that bounds on the region can't be accidentally
720 /// assumed without being checked.
722 /// The process of doing that is called "skolemization". The bound regions
723 /// are replaced by skolemized markers, which don't satisfy any relation
724 /// not explicity provided.
726 /// There are 2 kinds of skolemized regions in rustc: `ReFree` and
727 /// `ReSkolemized`. When checking an item's body, `ReFree` is supposed
728 /// to be used. These also support explicit bounds: both the internally-stored
729 /// *scope*, which the region is assumed to outlive, as well as other
730 /// relations stored in the `FreeRegionMap`. Note that these relations
731 /// aren't checked when you `make_subregion` (or `eq_types`), only by
732 /// `resolve_regions_and_report_errors`.
734 /// When working with higher-ranked types, some region relations aren't
735 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
736 /// `ReSkolemized` is designed for this purpose. In these contexts,
737 /// there's also the risk that some inference variable laying around will
738 /// get unified with your skolemized region: if you want to check whether
739 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
740 /// with a skolemized region `'%a`, the variable `'_` would just be
741 /// instantiated to the skolemized region `'%a`, which is wrong because
742 /// the inference variable is supposed to satisfy the relation
743 /// *for every value of the skolemized region*. To ensure that doesn't
744 /// happen, you can use `leak_check`. This is more clearly explained
745 /// by infer/higher_ranked/README.md.
747 /// [1] http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
748 /// [2] http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
749 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable)]
750 pub enum RegionKind<'tcx> {
751 // Region bound in a type or fn declaration which will be
752 // substituted 'early' -- that is, at the same time when type
753 // parameters are substituted.
754 ReEarlyBound(EarlyBoundRegion),
756 // Region bound in a function scope, which will be substituted when the
757 // function is called.
758 ReLateBound(DebruijnIndex, BoundRegion),
760 /// When checking a function body, the types of all arguments and so forth
761 /// that refer to bound region parameters are modified to refer to free
762 /// region parameters.
763 ReFree(FreeRegion<'tcx>),
765 /// A concrete region naming some statically determined extent
766 /// (e.g. an expression or sequence of statements) within the
767 /// current function.
768 ReScope(region::CodeExtent<'tcx>),
770 /// Static data that has an "infinite" lifetime. Top in the region lattice.
773 /// A region variable. Should not exist after typeck.
776 /// A skolemized region - basically the higher-ranked version of ReFree.
777 /// Should not exist after typeck.
778 ReSkolemized(SkolemizedRegionVid, BoundRegion),
780 /// Empty lifetime is for data that is never accessed.
781 /// Bottom in the region lattice. We treat ReEmpty somewhat
782 /// specially; at least right now, we do not generate instances of
783 /// it during the GLB computations, but rather
784 /// generate an error instead. This is to improve error messages.
785 /// The only way to get an instance of ReEmpty is to have a region
786 /// variable with no constraints.
789 /// Erased region, used by trait selection, in MIR and during trans.
793 impl<'tcx> serialize::UseSpecializedDecodable for Region<'tcx> {}
795 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
796 pub struct EarlyBoundRegion {
801 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
806 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
811 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
812 pub struct FloatVid {
816 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
817 pub struct RegionVid {
821 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
822 pub struct SkolemizedRegionVid {
826 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
832 /// A `FreshTy` is one that is generated as a replacement for an
833 /// unbound type variable. This is convenient for caching etc. See
834 /// `infer::freshen` for more details.
840 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
841 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
842 pub struct ExistentialProjection<'tcx> {
843 pub trait_ref: ExistentialTraitRef<'tcx>,
848 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
850 impl<'a, 'tcx, 'gcx> ExistentialProjection<'tcx> {
851 pub fn item_name(&self) -> Name {
852 self.item_name // safe to skip the binder to access a name
855 pub fn sort_key(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> (u64, InternedString) {
856 // We want something here that is stable across crate boundaries.
857 // The DefId isn't but the `deterministic_hash` of the corresponding
859 let trait_def = tcx.trait_def(self.trait_ref.def_id);
860 let def_path_hash = trait_def.def_path_hash;
862 // An `ast::Name` is also not stable (it's just an index into an
863 // interning table), so map to the corresponding `InternedString`.
864 let item_name = self.item_name.as_str();
865 (def_path_hash, item_name)
868 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
870 -> ty::ProjectionPredicate<'tcx>
872 // otherwise the escaping regions would be captured by the binders
873 assert!(!self_ty.has_escaping_regions());
875 ty::ProjectionPredicate {
876 projection_ty: ty::ProjectionTy {
877 trait_ref: self.trait_ref.with_self_ty(tcx, self_ty),
878 item_name: self.item_name,
885 impl<'a, 'tcx, 'gcx> PolyExistentialProjection<'tcx> {
886 pub fn item_name(&self) -> Name {
887 self.skip_binder().item_name()
890 pub fn sort_key(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> (u64, InternedString) {
891 self.skip_binder().sort_key(tcx)
894 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
895 -> ty::PolyProjectionPredicate<'tcx> {
896 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
901 pub fn new(depth: u32) -> DebruijnIndex {
903 DebruijnIndex { depth: depth }
906 pub fn shifted(&self, amount: u32) -> DebruijnIndex {
907 DebruijnIndex { depth: self.depth + amount }
912 impl<'tcx> RegionKind<'tcx> {
913 pub fn is_bound(&self) -> bool {
915 ty::ReEarlyBound(..) => true,
916 ty::ReLateBound(..) => true,
921 pub fn needs_infer(&self) -> bool {
923 ty::ReVar(..) | ty::ReSkolemized(..) => true,
928 pub fn escapes_depth(&self, depth: u32) -> bool {
930 ty::ReLateBound(debruijn, _) => debruijn.depth > depth,
935 /// Returns the depth of `self` from the (1-based) binding level `depth`
936 pub fn from_depth(&self, depth: u32) -> RegionKind<'tcx> {
938 ty::ReLateBound(debruijn, r) => ty::ReLateBound(DebruijnIndex {
939 depth: debruijn.depth - (depth - 1)
945 pub fn type_flags(&self) -> TypeFlags {
946 let mut flags = TypeFlags::empty();
950 flags = flags | TypeFlags::HAS_RE_INFER;
951 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
953 ty::ReSkolemized(..) => {
954 flags = flags | TypeFlags::HAS_RE_INFER;
955 flags = flags | TypeFlags::HAS_RE_SKOL;
956 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
958 ty::ReLateBound(..) => { }
959 ty::ReEarlyBound(..) => { flags = flags | TypeFlags::HAS_RE_EARLY_BOUND; }
960 ty::ReStatic | ty::ReErased => { }
961 _ => { flags = flags | TypeFlags::HAS_FREE_REGIONS; }
965 ty::ReStatic | ty::ReEmpty | ty::ReErased => (),
966 _ => flags = flags | TypeFlags::HAS_LOCAL_NAMES,
969 debug!("type_flags({:?}) = {:?}", self, flags);
976 impl<'a, 'gcx, 'tcx> TyS<'tcx> {
977 pub fn as_opt_param_ty(&self) -> Option<ty::ParamTy> {
979 ty::TyParam(ref d) => Some(d.clone()),
984 pub fn is_nil(&self) -> bool {
986 TyTuple(ref tys, _) => tys.is_empty(),
991 pub fn is_never(&self) -> bool {
998 /// Test whether this is a `()` which was produced by defaulting a
999 /// diverging type variable with feature(never_type) disabled.
1000 pub fn is_defaulted_unit(&self) -> bool {
1002 TyTuple(_, true) => true,
1007 /// Checks whether a type is visibly uninhabited from a particular module.
1013 /// pub struct SecretlyUninhabited {
1020 /// pub struct AlsoSecretlyUninhabited {
1028 /// x: a::b::SecretlyUninhabited,
1029 /// y: c::AlsoSecretlyUninhabited,
1032 /// In this code, the type `Foo` will only be visibly uninhabited inside the
1033 /// modules b, c and d. This effects pattern-matching on `Foo` or types that
1038 /// let foo_result: Result<T, Foo> = ... ;
1039 /// let Ok(t) = foo_result;
1041 /// This code should only compile in modules where the uninhabitedness of Foo is
1043 pub fn is_uninhabited_from(&self, module: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
1044 let mut visited = FxHashMap::default();
1045 let forest = self.uninhabited_from(&mut visited, tcx);
1047 // To check whether this type is uninhabited at all (not just from the
1048 // given node) you could check whether the forest is empty.
1050 // forest.is_empty()
1052 forest.contains(tcx, module)
1055 pub fn is_primitive(&self) -> bool {
1057 TyBool | TyChar | TyInt(_) | TyUint(_) | TyFloat(_) => true,
1062 pub fn is_ty_var(&self) -> bool {
1064 TyInfer(TyVar(_)) => true,
1069 pub fn is_phantom_data(&self) -> bool {
1070 if let TyAdt(def, _) = self.sty {
1071 def.is_phantom_data()
1077 pub fn is_bool(&self) -> bool { self.sty == TyBool }
1079 pub fn is_param(&self, index: u32) -> bool {
1081 ty::TyParam(ref data) => data.idx == index,
1086 pub fn is_self(&self) -> bool {
1088 TyParam(ref p) => p.is_self(),
1093 pub fn is_slice(&self) -> bool {
1095 TyRawPtr(mt) | TyRef(_, mt) => match mt.ty.sty {
1096 TySlice(_) | TyStr => true,
1103 pub fn is_structural(&self) -> bool {
1105 TyAdt(..) | TyTuple(..) | TyArray(..) | TyClosure(..) => true,
1106 _ => self.is_slice() | self.is_trait(),
1111 pub fn is_simd(&self) -> bool {
1113 TyAdt(def, _) => def.repr.simd(),
1118 pub fn sequence_element_type(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
1120 TyArray(ty, _) | TySlice(ty) => ty,
1121 TyStr => tcx.mk_mach_uint(ast::UintTy::U8),
1122 _ => bug!("sequence_element_type called on non-sequence value: {}", self),
1126 pub fn simd_type(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
1128 TyAdt(def, substs) => {
1129 def.struct_variant().fields[0].ty(tcx, substs)
1131 _ => bug!("simd_type called on invalid type")
1135 pub fn simd_size(&self, _cx: TyCtxt) -> usize {
1137 TyAdt(def, _) => def.struct_variant().fields.len(),
1138 _ => bug!("simd_size called on invalid type")
1142 pub fn is_region_ptr(&self) -> bool {
1149 pub fn is_mutable_pointer(&self) -> bool {
1151 TyRawPtr(tnm) | TyRef(_, tnm) => if let hir::Mutability::MutMutable = tnm.mutbl {
1160 pub fn is_unsafe_ptr(&self) -> bool {
1162 TyRawPtr(_) => return true,
1167 pub fn is_box(&self) -> bool {
1169 TyAdt(def, _) => def.is_box(),
1174 /// panics if called on any type other than `Box<T>`
1175 pub fn boxed_ty(&self) -> Ty<'tcx> {
1177 TyAdt(def, substs) if def.is_box() => substs.type_at(0),
1178 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1182 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1183 /// (A TyRawPtr is scalar because it represents a non-managed pointer, so its
1184 /// contents are abstract to rustc.)
1185 pub fn is_scalar(&self) -> bool {
1187 TyBool | TyChar | TyInt(_) | TyFloat(_) | TyUint(_) |
1188 TyInfer(IntVar(_)) | TyInfer(FloatVar(_)) |
1189 TyFnDef(..) | TyFnPtr(_) | TyRawPtr(_) => true,
1194 /// Returns true if this type is a floating point type and false otherwise.
1195 pub fn is_floating_point(&self) -> bool {
1198 TyInfer(FloatVar(_)) => true,
1203 pub fn is_trait(&self) -> bool {
1205 TyDynamic(..) => true,
1210 pub fn is_closure(&self) -> bool {
1212 TyClosure(..) => true,
1217 pub fn is_integral(&self) -> bool {
1219 TyInfer(IntVar(_)) | TyInt(_) | TyUint(_) => true,
1224 pub fn is_fresh(&self) -> bool {
1226 TyInfer(FreshTy(_)) => true,
1227 TyInfer(FreshIntTy(_)) => true,
1228 TyInfer(FreshFloatTy(_)) => true,
1233 pub fn is_uint(&self) -> bool {
1235 TyInfer(IntVar(_)) | TyUint(ast::UintTy::Us) => true,
1240 pub fn is_char(&self) -> bool {
1247 pub fn is_fp(&self) -> bool {
1249 TyInfer(FloatVar(_)) | TyFloat(_) => true,
1254 pub fn is_numeric(&self) -> bool {
1255 self.is_integral() || self.is_fp()
1258 pub fn is_signed(&self) -> bool {
1265 pub fn is_machine(&self) -> bool {
1267 TyInt(ast::IntTy::Is) | TyUint(ast::UintTy::Us) => false,
1268 TyInt(..) | TyUint(..) | TyFloat(..) => true,
1273 pub fn has_concrete_skeleton(&self) -> bool {
1275 TyParam(_) | TyInfer(_) | TyError => false,
1280 /// Returns the type and mutability of *ty.
1282 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1283 /// Some types---notably unsafe ptrs---can only be dereferenced explicitly.
1284 pub fn builtin_deref(&self, explicit: bool, pref: ty::LvaluePreference)
1285 -> Option<TypeAndMut<'tcx>>
1288 TyAdt(def, _) if def.is_box() => {
1290 ty: self.boxed_ty(),
1291 mutbl: if pref == ty::PreferMutLvalue {
1298 TyRef(_, mt) => Some(mt),
1299 TyRawPtr(mt) if explicit => Some(mt),
1304 /// Returns the type of ty[i]
1305 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
1307 TyArray(ty, _) | TySlice(ty) => Some(ty),
1312 pub fn fn_sig(&self) -> PolyFnSig<'tcx> {
1314 TyFnDef(.., f) | TyFnPtr(f) => f,
1315 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self)
1319 /// Type accessors for substructures of types
1320 pub fn fn_args(&self) -> ty::Binder<&'tcx [Ty<'tcx>]> {
1321 self.fn_sig().inputs()
1324 pub fn fn_ret(&self) -> Binder<Ty<'tcx>> {
1325 self.fn_sig().output()
1328 pub fn is_fn(&self) -> bool {
1330 TyFnDef(..) | TyFnPtr(_) => true,
1335 pub fn ty_to_def_id(&self) -> Option<DefId> {
1337 TyDynamic(ref tt, ..) => tt.principal().map(|p| p.def_id()),
1338 TyAdt(def, _) => Some(def.did),
1339 TyClosure(id, _) => Some(id),
1344 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
1346 TyAdt(adt, _) => Some(adt),
1351 /// Returns the regions directly referenced from this type (but
1352 /// not types reachable from this type via `walk_tys`). This
1353 /// ignores late-bound regions binders.
1354 pub fn regions(&self) -> Vec<ty::Region<'tcx>> {
1356 TyRef(region, _) => {
1359 TyDynamic(ref obj, region) => {
1360 let mut v = vec![region];
1361 if let Some(p) = obj.principal() {
1362 v.extend(p.skip_binder().substs.regions());
1366 TyAdt(_, substs) | TyAnon(_, substs) => {
1367 substs.regions().collect()
1369 TyClosure(_, ref substs) => {
1370 substs.substs.regions().collect()
1372 TyProjection(ref data) => {
1373 data.trait_ref.substs.regions().collect()