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;
15 use middle::const_val::ConstVal;
17 use ty::subst::{Substs, Subst};
18 use ty::{self, AdtDef, TypeFlags, Ty, TyCtxt, TypeFoldable};
23 use std::cmp::Ordering;
25 use syntax::ast::{self, Name};
26 use syntax::symbol::keywords;
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 /// NB: If you change this, you'll probably want to change the corresponding
81 /// AST structure in libsyntax/ast.rs as well.
82 #[derive(Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
83 pub enum TypeVariants<'tcx> {
84 /// The primitive boolean type. Written as `bool`.
87 /// The primitive character type; holds a Unicode scalar value
88 /// (a non-surrogate code point). Written as `char`.
91 /// A primitive signed integer type. For example, `i32`.
94 /// A primitive unsigned integer type. For example, `u32`.
97 /// A primitive floating-point type. For example, `f64`.
98 TyFloat(ast::FloatTy),
100 /// Structures, enumerations and unions.
102 /// Substs here, possibly against intuition, *may* contain `TyParam`s.
103 /// That is, even after substitution it is possible that there are type
104 /// variables. This happens when the `TyAdt` corresponds to an ADT
105 /// definition and not a concrete use of it.
106 TyAdt(&'tcx AdtDef, &'tcx Substs<'tcx>),
108 /// The pointee of a string slice. Written as `str`.
111 /// An array with the given length. Written as `[T; n]`.
112 TyArray(Ty<'tcx>, &'tcx ty::Const<'tcx>),
114 /// The pointee of an array slice. Written as `[T]`.
117 /// A raw pointer. Written as `*mut T` or `*const T`
118 TyRawPtr(TypeAndMut<'tcx>),
120 /// A reference; a pointer with an associated lifetime. Written as
121 /// `&'a mut T` or `&'a T`.
122 TyRef(Region<'tcx>, TypeAndMut<'tcx>),
124 /// The anonymous type of a function declaration/definition. Each
125 /// function has a unique type.
126 TyFnDef(DefId, &'tcx Substs<'tcx>),
128 /// A pointer to a function. Written as `fn() -> i32`.
129 TyFnPtr(PolyFnSig<'tcx>),
131 /// A trait, defined with `trait`.
132 TyDynamic(Binder<&'tcx Slice<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
134 /// The anonymous type of a closure. Used to represent the type of
136 TyClosure(DefId, ClosureSubsts<'tcx>),
138 /// The anonymous type of a generator. Used to represent the type of
140 TyGenerator(DefId, ClosureSubsts<'tcx>, GeneratorInterior<'tcx>),
142 /// The never type `!`
145 /// A tuple type. For example, `(i32, bool)`.
146 /// The bool indicates whether this is a unit tuple and was created by
147 /// defaulting a diverging type variable with feature(never_type) disabled.
148 /// It's only purpose is for raising future-compatibility warnings for when
149 /// diverging type variables start defaulting to ! instead of ().
150 TyTuple(&'tcx Slice<Ty<'tcx>>, bool),
152 /// The projection of an associated type. For example,
153 /// `<T as Trait<..>>::N`.
154 TyProjection(ProjectionTy<'tcx>),
156 /// Anonymized (`impl Trait`) type found in a return type.
157 /// The DefId comes from the `impl Trait` ast::Ty node, and the
158 /// substitutions are for the generics of the function in question.
159 /// After typeck, the concrete type can be found in the `types` map.
160 TyAnon(DefId, &'tcx Substs<'tcx>),
162 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
165 /// A type variable used during type-checking.
168 /// A placeholder for a type which could not be computed; this is
169 /// propagated to avoid useless error messages.
173 /// A closure can be modeled as a struct that looks like:
175 /// struct Closure<'l0...'li, T0...Tj, U0...Uk> {
181 /// where 'l0...'li and T0...Tj are the lifetime and type parameters
182 /// in scope on the function that defined the closure, and U0...Uk are
183 /// type parameters representing the types of its upvars (borrowed, if
186 /// So, for example, given this function:
188 /// fn foo<'a, T>(data: &'a mut T) {
189 /// do(|| data.count += 1)
192 /// the type of the closure would be something like:
194 /// struct Closure<'a, T, U0> {
198 /// Note that the type of the upvar is not specified in the struct.
199 /// You may wonder how the impl would then be able to use the upvar,
200 /// if it doesn't know it's type? The answer is that the impl is
201 /// (conceptually) not fully generic over Closure but rather tied to
202 /// instances with the expected upvar types:
204 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, &'b mut &'a mut T> {
208 /// You can see that the *impl* fully specified the type of the upvar
209 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
210 /// (Here, I am assuming that `data` is mut-borrowed.)
212 /// Now, the last question you may ask is: Why include the upvar types
213 /// as extra type parameters? The reason for this design is that the
214 /// upvar types can reference lifetimes that are internal to the
215 /// creating function. In my example above, for example, the lifetime
216 /// `'b` represents the scope of the closure itself; this is some
217 /// subset of `foo`, probably just the scope of the call to the to
218 /// `do()`. If we just had the lifetime/type parameters from the
219 /// enclosing function, we couldn't name this lifetime `'b`. Note that
220 /// there can also be lifetimes in the types of the upvars themselves,
221 /// if one of them happens to be a reference to something that the
222 /// creating fn owns.
224 /// OK, you say, so why not create a more minimal set of parameters
225 /// that just includes the extra lifetime parameters? The answer is
226 /// primarily that it would be hard --- we don't know at the time when
227 /// we create the closure type what the full types of the upvars are,
228 /// nor do we know which are borrowed and which are not. In this
229 /// design, we can just supply a fresh type parameter and figure that
232 /// All right, you say, but why include the type parameters from the
233 /// original function then? The answer is that trans may need them
234 /// when monomorphizing, and they may not appear in the upvars. A
235 /// closure could capture no variables but still make use of some
236 /// in-scope type parameter with a bound (e.g., if our example above
237 /// had an extra `U: Default`, and the closure called `U::default()`).
239 /// There is another reason. This design (implicitly) prohibits
240 /// closures from capturing themselves (except via a trait
241 /// object). This simplifies closure inference considerably, since it
242 /// means that when we infer the kind of a closure or its upvars, we
243 /// don't have to handle cycles where the decisions we make for
244 /// closure C wind up influencing the decisions we ought to make for
245 /// closure C (which would then require fixed point iteration to
246 /// handle). Plus it fixes an ICE. :P
247 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
248 pub struct ClosureSubsts<'tcx> {
249 /// Lifetime and type parameters from the enclosing function,
250 /// concatenated with the types of the upvars.
252 /// These are separated out because trans wants to pass them around
253 /// when monomorphizing.
254 pub substs: &'tcx Substs<'tcx>,
257 impl<'a, 'gcx, 'acx, 'tcx> ClosureSubsts<'tcx> {
259 pub fn upvar_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'acx>) ->
260 impl Iterator<Item=Ty<'tcx>> + 'tcx
262 let generics = tcx.generics_of(def_id);
263 self.substs[self.substs.len()-generics.own_count()..].iter().map(
264 |t| t.as_type().expect("unexpected region in upvars"))
268 impl<'a, 'gcx, 'tcx> ClosureSubsts<'tcx> {
269 /// This returns the types of the MIR locals which had to be stored across suspension points.
270 /// It is calculated in rustc_mir::transform::generator::StateTransform.
271 /// All the types here must be in the tuple in GeneratorInterior.
272 pub fn state_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) ->
273 impl Iterator<Item=Ty<'tcx>> + 'a
275 let state = tcx.generator_layout(def_id).fields.iter();
276 state.map(move |d| d.ty.subst(tcx, self.substs))
279 /// This is the types of all the fields stored in a generator.
280 /// It includes the upvars, state types and the state discriminant which is u32.
281 pub fn field_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) ->
282 impl Iterator<Item=Ty<'tcx>> + 'a
284 let upvars = self.upvar_tys(def_id, tcx);
285 let state = self.state_tys(def_id, tcx);
286 upvars.chain(iter::once(tcx.types.u32)).chain(state)
290 /// This describes the types that can be contained in a generator.
291 /// It will be a type variable initially and unified in the last stages of typeck of a body.
292 /// It contains a tuple of all the types that could end up on a generator frame.
293 /// The state transformation MIR pass may only produce layouts which mention types in this tuple.
294 /// Upvars are not counted here.
295 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
296 pub struct GeneratorInterior<'tcx> {
297 pub witness: Ty<'tcx>,
300 impl<'tcx> GeneratorInterior<'tcx> {
301 pub fn new(witness: Ty<'tcx>) -> GeneratorInterior<'tcx> {
302 GeneratorInterior { witness }
305 pub fn as_slice(&self) -> &'tcx Slice<Ty<'tcx>> {
306 match self.witness.sty {
307 ty::TyTuple(s, _) => s,
313 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
314 pub enum ExistentialPredicate<'tcx> {
316 Trait(ExistentialTraitRef<'tcx>),
317 /// e.g. Iterator::Item = T
318 Projection(ExistentialProjection<'tcx>),
323 impl<'a, 'gcx, 'tcx> ExistentialPredicate<'tcx> {
324 pub fn cmp(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, other: &Self) -> Ordering {
325 use self::ExistentialPredicate::*;
326 match (*self, *other) {
327 (Trait(_), Trait(_)) => Ordering::Equal,
328 (Projection(ref a), Projection(ref b)) =>
329 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id)),
330 (AutoTrait(ref a), AutoTrait(ref b)) =>
331 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash),
332 (Trait(_), _) => Ordering::Less,
333 (Projection(_), Trait(_)) => Ordering::Greater,
334 (Projection(_), _) => Ordering::Less,
335 (AutoTrait(_), _) => Ordering::Greater,
341 impl<'a, 'gcx, 'tcx> Binder<ExistentialPredicate<'tcx>> {
342 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
343 -> ty::Predicate<'tcx> {
345 match *self.skip_binder() {
346 ExistentialPredicate::Trait(tr) => Binder(tr).with_self_ty(tcx, self_ty).to_predicate(),
347 ExistentialPredicate::Projection(p) =>
348 ty::Predicate::Projection(Binder(p.with_self_ty(tcx, self_ty))),
349 ExistentialPredicate::AutoTrait(did) => {
350 let trait_ref = Binder(ty::TraitRef {
352 substs: tcx.mk_substs_trait(self_ty, &[]),
354 trait_ref.to_predicate()
360 impl<'tcx> serialize::UseSpecializedDecodable for &'tcx Slice<ExistentialPredicate<'tcx>> {}
362 impl<'tcx> Slice<ExistentialPredicate<'tcx>> {
363 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
365 Some(&ExistentialPredicate::Trait(tr)) => Some(tr),
371 pub fn projection_bounds<'a>(&'a self) ->
372 impl Iterator<Item=ExistentialProjection<'tcx>> + 'a {
373 self.iter().filter_map(|predicate| {
375 ExistentialPredicate::Projection(p) => Some(p),
382 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
383 self.iter().filter_map(|predicate| {
385 ExistentialPredicate::AutoTrait(d) => Some(d),
392 impl<'tcx> Binder<&'tcx Slice<ExistentialPredicate<'tcx>>> {
393 pub fn principal(&self) -> Option<PolyExistentialTraitRef<'tcx>> {
394 self.skip_binder().principal().map(Binder)
398 pub fn projection_bounds<'a>(&'a self) ->
399 impl Iterator<Item=PolyExistentialProjection<'tcx>> + 'a {
400 self.skip_binder().projection_bounds().map(Binder)
404 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
405 self.skip_binder().auto_traits()
408 pub fn iter<'a>(&'a self)
409 -> impl DoubleEndedIterator<Item=Binder<ExistentialPredicate<'tcx>>> + 'tcx {
410 self.skip_binder().iter().cloned().map(Binder)
414 /// A complete reference to a trait. These take numerous guises in syntax,
415 /// but perhaps the most recognizable form is in a where clause:
419 /// This would be represented by a trait-reference where the def-id is the
420 /// def-id for the trait `Foo` and the substs define `T` as parameter 0,
421 /// and `U` as parameter 1.
423 /// Trait references also appear in object types like `Foo<U>`, but in
424 /// that case the `Self` parameter is absent from the substitutions.
426 /// Note that a `TraitRef` introduces a level of region binding, to
427 /// account for higher-ranked trait bounds like `T : for<'a> Foo<&'a
428 /// U>` or higher-ranked object types.
429 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
430 pub struct TraitRef<'tcx> {
432 pub substs: &'tcx Substs<'tcx>,
435 impl<'tcx> TraitRef<'tcx> {
436 pub fn new(def_id: DefId, substs: &'tcx Substs<'tcx>) -> TraitRef<'tcx> {
437 TraitRef { def_id: def_id, substs: substs }
440 pub fn self_ty(&self) -> Ty<'tcx> {
441 self.substs.type_at(0)
444 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
445 // Select only the "input types" from a trait-reference. For
446 // now this is all the types that appear in the
447 // trait-reference, but it should eventually exclude
453 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
455 impl<'tcx> PolyTraitRef<'tcx> {
456 pub fn self_ty(&self) -> Ty<'tcx> {
460 pub fn def_id(&self) -> DefId {
464 pub fn substs(&self) -> &'tcx Substs<'tcx> {
465 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
469 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
470 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
474 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
475 // Note that we preserve binding levels
476 Binder(ty::TraitPredicate { trait_ref: self.0.clone() })
480 /// An existential reference to a trait, where `Self` is erased.
481 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
483 /// exists T. T: Trait<'a, 'b, X, Y>
485 /// The substitutions don't include the erased `Self`, only trait
486 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
487 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
488 pub struct ExistentialTraitRef<'tcx> {
490 pub substs: &'tcx Substs<'tcx>,
493 impl<'a, 'gcx, 'tcx> ExistentialTraitRef<'tcx> {
494 pub fn input_types<'b>(&'b self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'b {
495 // Select only the "input types" from a trait-reference. For
496 // now this is all the types that appear in the
497 // trait-reference, but it should eventually exclude
502 /// Object types don't have a self-type specified. Therefore, when
503 /// we convert the principal trait-ref into a normal trait-ref,
504 /// you must give *some* self-type. A common choice is `mk_err()`
505 /// or some skolemized type.
506 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
507 -> ty::TraitRef<'tcx> {
508 // otherwise the escaping regions would be captured by the binder
509 assert!(!self_ty.has_escaping_regions());
513 substs: tcx.mk_substs(
514 iter::once(Kind::from(self_ty)).chain(self.substs.iter().cloned()))
519 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
521 impl<'tcx> PolyExistentialTraitRef<'tcx> {
522 pub fn def_id(&self) -> DefId {
526 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {
527 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
532 /// Binder is a binder for higher-ranked lifetimes. It is part of the
533 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
534 /// (which would be represented by the type `PolyTraitRef ==
535 /// Binder<TraitRef>`). Note that when we skolemize, instantiate,
536 /// erase, or otherwise "discharge" these bound regions, we change the
537 /// type from `Binder<T>` to just `T` (see
538 /// e.g. `liberate_late_bound_regions`).
539 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
540 pub struct Binder<T>(pub T);
543 /// Skips the binder and returns the "bound" value. This is a
544 /// risky thing to do because it's easy to get confused about
545 /// debruijn indices and the like. It is usually better to
546 /// discharge the binder using `no_late_bound_regions` or
547 /// `replace_late_bound_regions` or something like
548 /// that. `skip_binder` is only valid when you are either
549 /// extracting data that has nothing to do with bound regions, you
550 /// are doing some sort of test that does not involve bound
551 /// regions, or you are being very careful about your depth
554 /// Some examples where `skip_binder` is reasonable:
555 /// - extracting the def-id from a PolyTraitRef;
556 /// - comparing the self type of a PolyTraitRef to see if it is equal to
557 /// a type parameter `X`, since the type `X` does not reference any regions
558 pub fn skip_binder(&self) -> &T {
562 pub fn as_ref(&self) -> Binder<&T> {
566 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
567 where F: FnOnce(&T) -> U
569 self.as_ref().map_bound(f)
572 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
573 where F: FnOnce(T) -> U
575 ty::Binder(f(self.0))
579 /// Represents the projection of an associated type. In explicit UFCS
580 /// form this would be written `<T as Trait<..>>::N`.
581 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
582 pub struct ProjectionTy<'tcx> {
583 /// The parameters of the associated item.
584 pub substs: &'tcx Substs<'tcx>,
586 /// The DefId of the TraitItem for the associated type N.
588 /// Note that this is not the DefId of the TraitRef containing this
589 /// associated type, which is in tcx.associated_item(item_def_id).container.
590 pub item_def_id: DefId,
593 impl<'a, 'tcx> ProjectionTy<'tcx> {
594 /// Construct a ProjectionTy by searching the trait from trait_ref for the
595 /// associated item named item_name.
596 pub fn from_ref_and_name(
597 tcx: TyCtxt, trait_ref: ty::TraitRef<'tcx>, item_name: Name
598 ) -> ProjectionTy<'tcx> {
599 let item_def_id = tcx.associated_items(trait_ref.def_id).find(|item| {
600 item.kind == ty::AssociatedKind::Type &&
601 tcx.hygienic_eq(item_name, item.name, trait_ref.def_id)
605 substs: trait_ref.substs,
610 /// Extracts the underlying trait reference from this projection.
611 /// For example, if this is a projection of `<T as Iterator>::Item`,
612 /// then this function would return a `T: Iterator` trait reference.
613 pub fn trait_ref(&self, tcx: TyCtxt) -> ty::TraitRef<'tcx> {
614 let def_id = tcx.associated_item(self.item_def_id).container.id();
621 pub fn self_ty(&self) -> Ty<'tcx> {
622 self.substs.type_at(0)
626 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
627 pub struct GenSig<'tcx> {
628 pub yield_ty: Ty<'tcx>,
629 pub return_ty: Ty<'tcx>,
632 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
634 impl<'tcx> PolyGenSig<'tcx> {
635 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
636 self.map_bound_ref(|sig| sig.yield_ty)
638 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
639 self.map_bound_ref(|sig| sig.return_ty)
643 /// Signature of a function type, which I have arbitrarily
644 /// decided to use to refer to the input/output types.
646 /// - `inputs` is the list of arguments and their modes.
647 /// - `output` is the return type.
648 /// - `variadic` indicates whether this is a variadic function. (only true for foreign fns)
649 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
650 pub struct FnSig<'tcx> {
651 pub inputs_and_output: &'tcx Slice<Ty<'tcx>>,
653 pub unsafety: hir::Unsafety,
657 impl<'tcx> FnSig<'tcx> {
658 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
659 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
662 pub fn output(&self) -> Ty<'tcx> {
663 self.inputs_and_output[self.inputs_and_output.len() - 1]
667 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
669 impl<'tcx> PolyFnSig<'tcx> {
670 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
671 Binder(self.skip_binder().inputs())
673 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
674 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
676 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
677 self.map_bound_ref(|fn_sig| fn_sig.output().clone())
679 pub fn variadic(&self) -> bool {
680 self.skip_binder().variadic
682 pub fn unsafety(&self) -> hir::Unsafety {
683 self.skip_binder().unsafety
685 pub fn abi(&self) -> abi::Abi {
686 self.skip_binder().abi
690 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
696 impl<'a, 'gcx, 'tcx> ParamTy {
697 pub fn new(index: u32, name: Name) -> ParamTy {
698 ParamTy { idx: index, name: name }
701 pub fn for_self() -> ParamTy {
702 ParamTy::new(0, keywords::SelfType.name())
705 pub fn for_def(def: &ty::TypeParameterDef) -> ParamTy {
706 ParamTy::new(def.index, def.name)
709 pub fn to_ty(self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
710 tcx.mk_param(self.idx, self.name)
713 pub fn is_self(&self) -> bool {
714 if self.name == keywords::SelfType.name() {
715 assert_eq!(self.idx, 0);
723 /// A [De Bruijn index][dbi] is a standard means of representing
724 /// regions (and perhaps later types) in a higher-ranked setting. In
725 /// particular, imagine a type like this:
727 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
730 /// | +------------+ 1 | |
732 /// +--------------------------------+ 2 |
734 /// +------------------------------------------+ 1
736 /// In this type, there are two binders (the outer fn and the inner
737 /// fn). We need to be able to determine, for any given region, which
738 /// fn type it is bound by, the inner or the outer one. There are
739 /// various ways you can do this, but a De Bruijn index is one of the
740 /// more convenient and has some nice properties. The basic idea is to
741 /// count the number of binders, inside out. Some examples should help
742 /// clarify what I mean.
744 /// Let's start with the reference type `&'b isize` that is the first
745 /// argument to the inner function. This region `'b` is assigned a De
746 /// Bruijn index of 1, meaning "the innermost binder" (in this case, a
747 /// fn). The region `'a` that appears in the second argument type (`&'a
748 /// isize`) would then be assigned a De Bruijn index of 2, meaning "the
749 /// second-innermost binder". (These indices are written on the arrays
752 /// What is interesting is that De Bruijn index attached to a particular
753 /// variable will vary depending on where it appears. For example,
754 /// the final type `&'a char` also refers to the region `'a` declared on
755 /// the outermost fn. But this time, this reference is not nested within
756 /// any other binders (i.e., it is not an argument to the inner fn, but
757 /// rather the outer one). Therefore, in this case, it is assigned a
758 /// De Bruijn index of 1, because the innermost binder in that location
761 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
762 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, Copy)]
763 pub struct DebruijnIndex {
764 /// We maintain the invariant that this is never 0. So 1 indicates
765 /// the innermost binder. To ensure this, create with `DebruijnIndex::new`.
769 pub type Region<'tcx> = &'tcx RegionKind;
771 /// Representation of regions.
773 /// Unlike types, most region variants are "fictitious", not concrete,
774 /// regions. Among these, `ReStatic`, `ReEmpty` and `ReScope` are the only
775 /// ones representing concrete regions.
779 /// These are regions that are stored behind a binder and must be substituted
780 /// with some concrete region before being used. There are 2 kind of
781 /// bound regions: early-bound, which are bound in an item's Generics,
782 /// and are substituted by a Substs, and late-bound, which are part of
783 /// higher-ranked types (e.g. `for<'a> fn(&'a ())`) and are substituted by
784 /// the likes of `liberate_late_bound_regions`. The distinction exists
785 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
787 /// Unlike TyParam-s, bound regions are not supposed to exist "in the wild"
788 /// outside their binder, e.g. in types passed to type inference, and
789 /// should first be substituted (by skolemized regions, free regions,
790 /// or region variables).
792 /// ## Skolemized and Free Regions
794 /// One often wants to work with bound regions without knowing their precise
795 /// identity. For example, when checking a function, the lifetime of a borrow
796 /// can end up being assigned to some region parameter. In these cases,
797 /// it must be ensured that bounds on the region can't be accidentally
798 /// assumed without being checked.
800 /// The process of doing that is called "skolemization". The bound regions
801 /// are replaced by skolemized markers, which don't satisfy any relation
802 /// not explicitly provided.
804 /// There are 2 kinds of skolemized regions in rustc: `ReFree` and
805 /// `ReSkolemized`. When checking an item's body, `ReFree` is supposed
806 /// to be used. These also support explicit bounds: both the internally-stored
807 /// *scope*, which the region is assumed to outlive, as well as other
808 /// relations stored in the `FreeRegionMap`. Note that these relations
809 /// aren't checked when you `make_subregion` (or `eq_types`), only by
810 /// `resolve_regions_and_report_errors`.
812 /// When working with higher-ranked types, some region relations aren't
813 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
814 /// `ReSkolemized` is designed for this purpose. In these contexts,
815 /// there's also the risk that some inference variable laying around will
816 /// get unified with your skolemized region: if you want to check whether
817 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
818 /// with a skolemized region `'%a`, the variable `'_` would just be
819 /// instantiated to the skolemized region `'%a`, which is wrong because
820 /// the inference variable is supposed to satisfy the relation
821 /// *for every value of the skolemized region*. To ensure that doesn't
822 /// happen, you can use `leak_check`. This is more clearly explained
823 /// by infer/higher_ranked/README.md.
825 /// [1] http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
826 /// [2] http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
827 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable)]
828 pub enum RegionKind {
829 // Region bound in a type or fn declaration which will be
830 // substituted 'early' -- that is, at the same time when type
831 // parameters are substituted.
832 ReEarlyBound(EarlyBoundRegion),
834 // Region bound in a function scope, which will be substituted when the
835 // function is called.
836 ReLateBound(DebruijnIndex, BoundRegion),
838 /// When checking a function body, the types of all arguments and so forth
839 /// that refer to bound region parameters are modified to refer to free
840 /// region parameters.
843 /// A concrete region naming some statically determined scope
844 /// (e.g. an expression or sequence of statements) within the
845 /// current function.
846 ReScope(region::Scope),
848 /// Static data that has an "infinite" lifetime. Top in the region lattice.
851 /// A region variable. Should not exist after typeck.
854 /// A skolemized region - basically the higher-ranked version of ReFree.
855 /// Should not exist after typeck.
856 ReSkolemized(SkolemizedRegionVid, BoundRegion),
858 /// Empty lifetime is for data that is never accessed.
859 /// Bottom in the region lattice. We treat ReEmpty somewhat
860 /// specially; at least right now, we do not generate instances of
861 /// it during the GLB computations, but rather
862 /// generate an error instead. This is to improve error messages.
863 /// The only way to get an instance of ReEmpty is to have a region
864 /// variable with no constraints.
867 /// Erased region, used by trait selection, in MIR and during trans.
871 impl<'tcx> serialize::UseSpecializedDecodable for Region<'tcx> {}
873 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
874 pub struct EarlyBoundRegion {
880 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
885 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
890 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
891 pub struct FloatVid {
895 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
896 pub struct RegionVid {
900 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
901 pub struct SkolemizedRegionVid {
905 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
911 /// A `FreshTy` is one that is generated as a replacement for an
912 /// unbound type variable. This is convenient for caching etc. See
913 /// `infer::freshen` for more details.
919 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
920 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
921 pub struct ExistentialProjection<'tcx> {
922 pub item_def_id: DefId,
923 pub substs: &'tcx Substs<'tcx>,
927 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
929 impl<'a, 'tcx, 'gcx> ExistentialProjection<'tcx> {
930 /// Extracts the underlying existential trait reference from this projection.
931 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
932 /// then this function would return a `exists T. T: Iterator` existential trait
934 pub fn trait_ref(&self, tcx: TyCtxt) -> ty::ExistentialTraitRef<'tcx> {
935 let def_id = tcx.associated_item(self.item_def_id).container.id();
936 ty::ExistentialTraitRef{
942 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
944 -> ty::ProjectionPredicate<'tcx>
946 // otherwise the escaping regions would be captured by the binders
947 assert!(!self_ty.has_escaping_regions());
949 ty::ProjectionPredicate {
950 projection_ty: ty::ProjectionTy {
951 item_def_id: self.item_def_id,
952 substs: tcx.mk_substs(
953 iter::once(Kind::from(self_ty)).chain(self.substs.iter().cloned())),
960 impl<'a, 'tcx, 'gcx> PolyExistentialProjection<'tcx> {
961 pub fn with_self_ty(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, self_ty: Ty<'tcx>)
962 -> ty::PolyProjectionPredicate<'tcx> {
963 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
968 pub fn new(depth: u32) -> DebruijnIndex {
970 DebruijnIndex { depth: depth }
973 pub fn shifted(&self, amount: u32) -> DebruijnIndex {
974 DebruijnIndex { depth: self.depth + amount }
980 pub fn is_late_bound(&self) -> bool {
982 ty::ReLateBound(..) => true,
987 pub fn needs_infer(&self) -> bool {
989 ty::ReVar(..) | ty::ReSkolemized(..) => true,
994 pub fn escapes_depth(&self, depth: u32) -> bool {
996 ty::ReLateBound(debruijn, _) => debruijn.depth > depth,
1001 /// Returns the depth of `self` from the (1-based) binding level `depth`
1002 pub fn from_depth(&self, depth: u32) -> RegionKind {
1004 ty::ReLateBound(debruijn, r) => ty::ReLateBound(DebruijnIndex {
1005 depth: debruijn.depth - (depth - 1)
1011 pub fn type_flags(&self) -> TypeFlags {
1012 let mut flags = TypeFlags::empty();
1016 flags = flags | TypeFlags::HAS_RE_INFER;
1017 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
1019 ty::ReSkolemized(..) => {
1020 flags = flags | TypeFlags::HAS_RE_INFER;
1021 flags = flags | TypeFlags::HAS_RE_SKOL;
1022 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
1024 ty::ReLateBound(..) => { }
1025 ty::ReEarlyBound(..) => { flags = flags | TypeFlags::HAS_RE_EARLY_BOUND; }
1026 ty::ReStatic | ty::ReErased => { }
1027 _ => { flags = flags | TypeFlags::HAS_FREE_REGIONS; }
1031 ty::ReStatic | ty::ReEmpty | ty::ReErased => (),
1032 _ => flags = flags | TypeFlags::HAS_LOCAL_NAMES,
1035 debug!("type_flags({:?}) = {:?}", self, flags);
1042 impl<'a, 'gcx, 'tcx> TyS<'tcx> {
1043 pub fn as_opt_param_ty(&self) -> Option<ty::ParamTy> {
1045 ty::TyParam(ref d) => Some(d.clone()),
1050 pub fn is_nil(&self) -> bool {
1052 TyTuple(ref tys, _) => tys.is_empty(),
1057 pub fn is_never(&self) -> bool {
1064 /// Test whether this is a `()` which was produced by defaulting a
1065 /// diverging type variable with feature(never_type) disabled.
1066 pub fn is_defaulted_unit(&self) -> bool {
1068 TyTuple(_, true) => true,
1073 /// Checks whether a type is visibly uninhabited from a particular module.
1079 /// pub struct SecretlyUninhabited {
1086 /// pub struct AlsoSecretlyUninhabited {
1094 /// x: a::b::SecretlyUninhabited,
1095 /// y: c::AlsoSecretlyUninhabited,
1098 /// In this code, the type `Foo` will only be visibly uninhabited inside the
1099 /// modules b, c and d. This effects pattern-matching on `Foo` or types that
1104 /// let foo_result: Result<T, Foo> = ... ;
1105 /// let Ok(t) = foo_result;
1107 /// This code should only compile in modules where the uninhabitedness of Foo is
1109 pub fn is_uninhabited_from(&self, module: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> bool {
1110 let mut visited = FxHashMap::default();
1111 let forest = self.uninhabited_from(&mut visited, tcx);
1113 // To check whether this type is uninhabited at all (not just from the
1114 // given node) you could check whether the forest is empty.
1116 // forest.is_empty()
1118 forest.contains(tcx, module)
1121 pub fn is_primitive(&self) -> bool {
1123 TyBool | TyChar | TyInt(_) | TyUint(_) | TyFloat(_) => true,
1128 pub fn is_ty_var(&self) -> bool {
1130 TyInfer(TyVar(_)) => true,
1135 pub fn is_phantom_data(&self) -> bool {
1136 if let TyAdt(def, _) = self.sty {
1137 def.is_phantom_data()
1143 pub fn is_bool(&self) -> bool { self.sty == TyBool }
1145 pub fn is_param(&self, index: u32) -> bool {
1147 ty::TyParam(ref data) => data.idx == index,
1152 pub fn is_self(&self) -> bool {
1154 TyParam(ref p) => p.is_self(),
1159 pub fn is_slice(&self) -> bool {
1161 TyRawPtr(mt) | TyRef(_, mt) => match mt.ty.sty {
1162 TySlice(_) | TyStr => true,
1169 pub fn is_structural(&self) -> bool {
1171 TyAdt(..) | TyTuple(..) | TyArray(..) | TyClosure(..) => true,
1172 _ => self.is_slice() | self.is_trait(),
1177 pub fn is_simd(&self) -> bool {
1179 TyAdt(def, _) => def.repr.simd(),
1184 pub fn sequence_element_type(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
1186 TyArray(ty, _) | TySlice(ty) => ty,
1187 TyStr => tcx.mk_mach_uint(ast::UintTy::U8),
1188 _ => bug!("sequence_element_type called on non-sequence value: {}", self),
1192 pub fn simd_type(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
1194 TyAdt(def, substs) => {
1195 def.struct_variant().fields[0].ty(tcx, substs)
1197 _ => bug!("simd_type called on invalid type")
1201 pub fn simd_size(&self, _cx: TyCtxt) -> usize {
1203 TyAdt(def, _) => def.struct_variant().fields.len(),
1204 _ => bug!("simd_size called on invalid type")
1208 pub fn is_region_ptr(&self) -> bool {
1215 pub fn is_mutable_pointer(&self) -> bool {
1217 TyRawPtr(tnm) | TyRef(_, tnm) => if let hir::Mutability::MutMutable = tnm.mutbl {
1226 pub fn is_unsafe_ptr(&self) -> bool {
1228 TyRawPtr(_) => return true,
1233 pub fn is_box(&self) -> bool {
1235 TyAdt(def, _) => def.is_box(),
1240 /// panics if called on any type other than `Box<T>`
1241 pub fn boxed_ty(&self) -> Ty<'tcx> {
1243 TyAdt(def, substs) if def.is_box() => substs.type_at(0),
1244 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1248 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1249 /// (A TyRawPtr is scalar because it represents a non-managed pointer, so its
1250 /// contents are abstract to rustc.)
1251 pub fn is_scalar(&self) -> bool {
1253 TyBool | TyChar | TyInt(_) | TyFloat(_) | TyUint(_) |
1254 TyInfer(IntVar(_)) | TyInfer(FloatVar(_)) |
1255 TyFnDef(..) | TyFnPtr(_) | TyRawPtr(_) => true,
1260 /// Returns true if this type is a floating point type and false otherwise.
1261 pub fn is_floating_point(&self) -> bool {
1264 TyInfer(FloatVar(_)) => true,
1269 pub fn is_trait(&self) -> bool {
1271 TyDynamic(..) => true,
1276 pub fn is_closure(&self) -> bool {
1278 TyClosure(..) => true,
1283 pub fn is_integral(&self) -> bool {
1285 TyInfer(IntVar(_)) | TyInt(_) | TyUint(_) => true,
1290 pub fn is_fresh(&self) -> bool {
1292 TyInfer(FreshTy(_)) => true,
1293 TyInfer(FreshIntTy(_)) => true,
1294 TyInfer(FreshFloatTy(_)) => true,
1299 pub fn is_uint(&self) -> bool {
1301 TyInfer(IntVar(_)) | TyUint(ast::UintTy::Us) => true,
1306 pub fn is_char(&self) -> bool {
1313 pub fn is_fp(&self) -> bool {
1315 TyInfer(FloatVar(_)) | TyFloat(_) => true,
1320 pub fn is_numeric(&self) -> bool {
1321 self.is_integral() || self.is_fp()
1324 pub fn is_signed(&self) -> bool {
1331 pub fn is_machine(&self) -> bool {
1333 TyInt(ast::IntTy::Is) | TyUint(ast::UintTy::Us) => false,
1334 TyInt(..) | TyUint(..) | TyFloat(..) => true,
1339 pub fn has_concrete_skeleton(&self) -> bool {
1341 TyParam(_) | TyInfer(_) | TyError => false,
1346 /// Returns the type and mutability of *ty.
1348 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1349 /// Some types---notably unsafe ptrs---can only be dereferenced explicitly.
1350 pub fn builtin_deref(&self, explicit: bool, pref: ty::LvaluePreference)
1351 -> Option<TypeAndMut<'tcx>>
1354 TyAdt(def, _) if def.is_box() => {
1356 ty: self.boxed_ty(),
1357 mutbl: if pref == ty::PreferMutLvalue {
1364 TyRef(_, mt) => Some(mt),
1365 TyRawPtr(mt) if explicit => Some(mt),
1370 /// Returns the type of ty[i]
1371 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
1373 TyArray(ty, _) | TySlice(ty) => Some(ty),
1378 pub fn fn_sig(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> PolyFnSig<'tcx> {
1380 TyFnDef(def_id, substs) => {
1381 tcx.fn_sig(def_id).subst(tcx, substs)
1384 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self)
1388 pub fn is_fn(&self) -> bool {
1390 TyFnDef(..) | TyFnPtr(_) => true,
1395 pub fn ty_to_def_id(&self) -> Option<DefId> {
1397 TyDynamic(ref tt, ..) => tt.principal().map(|p| p.def_id()),
1398 TyAdt(def, _) => Some(def.did),
1399 TyClosure(id, _) => Some(id),
1404 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
1406 TyAdt(adt, _) => Some(adt),
1411 /// Returns the regions directly referenced from this type (but
1412 /// not types reachable from this type via `walk_tys`). This
1413 /// ignores late-bound regions binders.
1414 pub fn regions(&self) -> Vec<ty::Region<'tcx>> {
1416 TyRef(region, _) => {
1419 TyDynamic(ref obj, region) => {
1420 let mut v = vec![region];
1421 if let Some(p) = obj.principal() {
1422 v.extend(p.skip_binder().substs.regions());
1426 TyAdt(_, substs) | TyAnon(_, substs) => {
1427 substs.regions().collect()
1429 TyClosure(_, ref substs) | TyGenerator(_, ref substs, _) => {
1430 substs.substs.regions().collect()
1432 TyProjection(ref data) => {
1433 data.substs.regions().collect()
1457 /// Typed constant value.
1458 #[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq)]
1459 pub struct Const<'tcx> {
1462 // FIXME(eddyb) Replace this with a miri value.
1463 pub val: ConstVal<'tcx>,
1466 impl<'tcx> serialize::UseSpecializedDecodable for &'tcx Const<'tcx> {}