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, Subst}
;
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
;
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
>),
142 /// A pointer to a function. Written as `fn() -> i32`.
143 TyFnPtr(PolyFnSig
<'tcx
>),
145 /// A trait, defined with `trait`.
146 TyDynamic(Binder
<&'tcx Slice
<ExistentialPredicate
<'tcx
>>>, ty
::Region
<'tcx
>),
148 /// The anonymous type of a closure. Used to represent the type of
150 TyClosure(DefId
, ClosureSubsts
<'tcx
>),
152 /// The never type `!`
155 /// A tuple type. For example, `(i32, bool)`.
156 /// The bool indicates whether this is a unit tuple and was created by
157 /// defaulting a diverging type variable with feature(never_type) disabled.
158 /// It's only purpose is for raising future-compatibility warnings for when
159 /// diverging type variables start defaulting to ! instead of ().
160 TyTuple(&'tcx Slice
<Ty
<'tcx
>>, bool
),
162 /// The projection of an associated type. For example,
163 /// `<T as Trait<..>>::N`.
164 TyProjection(ProjectionTy
<'tcx
>),
166 /// Anonymized (`impl Trait`) type found in a return type.
167 /// The DefId comes from the `impl Trait` ast::Ty node, and the
168 /// substitutions are for the generics of the function in question.
169 /// After typeck, the concrete type can be found in the `types` map.
170 TyAnon(DefId
, &'tcx Substs
<'tcx
>),
172 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
175 /// A type variable used during type-checking.
178 /// A placeholder for a type which could not be computed; this is
179 /// propagated to avoid useless error messages.
183 /// A closure can be modeled as a struct that looks like:
185 /// struct Closure<'l0...'li, T0...Tj, U0...Uk> {
191 /// where 'l0...'li and T0...Tj are the lifetime and type parameters
192 /// in scope on the function that defined the closure, and U0...Uk are
193 /// type parameters representing the types of its upvars (borrowed, if
196 /// So, for example, given this function:
198 /// fn foo<'a, T>(data: &'a mut T) {
199 /// do(|| data.count += 1)
202 /// the type of the closure would be something like:
204 /// struct Closure<'a, T, U0> {
208 /// Note that the type of the upvar is not specified in the struct.
209 /// You may wonder how the impl would then be able to use the upvar,
210 /// if it doesn't know it's type? The answer is that the impl is
211 /// (conceptually) not fully generic over Closure but rather tied to
212 /// instances with the expected upvar types:
214 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, &'b mut &'a mut T> {
218 /// You can see that the *impl* fully specified the type of the upvar
219 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
220 /// (Here, I am assuming that `data` is mut-borrowed.)
222 /// Now, the last question you may ask is: Why include the upvar types
223 /// as extra type parameters? The reason for this design is that the
224 /// upvar types can reference lifetimes that are internal to the
225 /// creating function. In my example above, for example, the lifetime
226 /// `'b` represents the extent of the closure itself; this is some
227 /// subset of `foo`, probably just the extent of the call to the to
228 /// `do()`. If we just had the lifetime/type parameters from the
229 /// enclosing function, we couldn't name this lifetime `'b`. Note that
230 /// there can also be lifetimes in the types of the upvars themselves,
231 /// if one of them happens to be a reference to something that the
232 /// creating fn owns.
234 /// OK, you say, so why not create a more minimal set of parameters
235 /// that just includes the extra lifetime parameters? The answer is
236 /// primarily that it would be hard --- we don't know at the time when
237 /// we create the closure type what the full types of the upvars are,
238 /// nor do we know which are borrowed and which are not. In this
239 /// design, we can just supply a fresh type parameter and figure that
242 /// All right, you say, but why include the type parameters from the
243 /// original function then? The answer is that trans may need them
244 /// when monomorphizing, and they may not appear in the upvars. A
245 /// closure could capture no variables but still make use of some
246 /// in-scope type parameter with a bound (e.g., if our example above
247 /// had an extra `U: Default`, and the closure called `U::default()`).
249 /// There is another reason. This design (implicitly) prohibits
250 /// closures from capturing themselves (except via a trait
251 /// object). This simplifies closure inference considerably, since it
252 /// means that when we infer the kind of a closure or its upvars, we
253 /// don't have to handle cycles where the decisions we make for
254 /// closure C wind up influencing the decisions we ought to make for
255 /// closure C (which would then require fixed point iteration to
256 /// handle). Plus it fixes an ICE. :P
257 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
258 pub struct ClosureSubsts
<'tcx
> {
259 /// Lifetime and type parameters from the enclosing function,
260 /// concatenated with the types of the upvars.
262 /// These are separated out because trans wants to pass them around
263 /// when monomorphizing.
264 pub substs
: &'tcx Substs
<'tcx
>,
267 impl<'a
, 'gcx
, 'acx
, 'tcx
> ClosureSubsts
<'tcx
> {
269 pub fn upvar_tys(self, def_id
: DefId
, tcx
: TyCtxt
<'a
, 'gcx
, 'acx
>) ->
270 impl Iterator
<Item
=Ty
<'tcx
>> + 'tcx
272 let generics
= tcx
.generics_of(def_id
);
273 self.substs
[self.substs
.len()-generics
.own_count()..].iter().map(
274 |t
| t
.as_type().expect("unexpected region in upvars"))
278 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
279 pub enum ExistentialPredicate
<'tcx
> {
281 Trait(ExistentialTraitRef
<'tcx
>),
282 /// e.g. Iterator::Item = T
283 Projection(ExistentialProjection
<'tcx
>),
288 impl<'a
, 'gcx
, 'tcx
> ExistentialPredicate
<'tcx
> {
289 pub fn cmp(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>, other
: &Self) -> Ordering
{
290 use self::ExistentialPredicate
::*;
291 match (*self, *other
) {
292 (Trait(_
), Trait(_
)) => Ordering
::Equal
,
293 (Projection(ref a
), Projection(ref b
)) =>
294 tcx
.def_path_hash(a
.item_def_id
).cmp(&tcx
.def_path_hash(b
.item_def_id
)),
295 (AutoTrait(ref a
), AutoTrait(ref b
)) =>
296 tcx
.trait_def(*a
).def_path_hash
.cmp(&tcx
.trait_def(*b
).def_path_hash
),
297 (Trait(_
), _
) => Ordering
::Less
,
298 (Projection(_
), Trait(_
)) => Ordering
::Greater
,
299 (Projection(_
), _
) => Ordering
::Less
,
300 (AutoTrait(_
), _
) => Ordering
::Greater
,
306 impl<'a
, 'gcx
, 'tcx
> Binder
<ExistentialPredicate
<'tcx
>> {
307 pub fn with_self_ty(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>, self_ty
: Ty
<'tcx
>)
308 -> ty
::Predicate
<'tcx
> {
310 match *self.skip_binder() {
311 ExistentialPredicate
::Trait(tr
) => Binder(tr
).with_self_ty(tcx
, self_ty
).to_predicate(),
312 ExistentialPredicate
::Projection(p
) =>
313 ty
::Predicate
::Projection(Binder(p
.with_self_ty(tcx
, self_ty
))),
314 ExistentialPredicate
::AutoTrait(did
) => {
315 let trait_ref
= Binder(ty
::TraitRef
{
317 substs
: tcx
.mk_substs_trait(self_ty
, &[]),
319 trait_ref
.to_predicate()
325 impl<'tcx
> serialize
::UseSpecializedDecodable
for &'tcx Slice
<ExistentialPredicate
<'tcx
>> {}
327 impl<'tcx
> Slice
<ExistentialPredicate
<'tcx
>> {
328 pub fn principal(&self) -> Option
<ExistentialTraitRef
<'tcx
>> {
330 Some(&ExistentialPredicate
::Trait(tr
)) => Some(tr
),
336 pub fn projection_bounds
<'a
>(&'a
self) ->
337 impl Iterator
<Item
=ExistentialProjection
<'tcx
>> + 'a
{
338 self.iter().filter_map(|predicate
| {
340 ExistentialPredicate
::Projection(p
) => Some(p
),
347 pub fn auto_traits
<'a
>(&'a
self) -> impl Iterator
<Item
=DefId
> + 'a
{
348 self.iter().filter_map(|predicate
| {
350 ExistentialPredicate
::AutoTrait(d
) => Some(d
),
357 impl<'tcx
> Binder
<&'tcx Slice
<ExistentialPredicate
<'tcx
>>> {
358 pub fn principal(&self) -> Option
<PolyExistentialTraitRef
<'tcx
>> {
359 self.skip_binder().principal().map(Binder
)
363 pub fn projection_bounds
<'a
>(&'a
self) ->
364 impl Iterator
<Item
=PolyExistentialProjection
<'tcx
>> + 'a
{
365 self.skip_binder().projection_bounds().map(Binder
)
369 pub fn auto_traits
<'a
>(&'a
self) -> impl Iterator
<Item
=DefId
> + 'a
{
370 self.skip_binder().auto_traits()
373 pub fn iter
<'a
>(&'a
self)
374 -> impl DoubleEndedIterator
<Item
=Binder
<ExistentialPredicate
<'tcx
>>> + 'tcx
{
375 self.skip_binder().iter().cloned().map(Binder
)
379 /// A complete reference to a trait. These take numerous guises in syntax,
380 /// but perhaps the most recognizable form is in a where clause:
384 /// This would be represented by a trait-reference where the def-id is the
385 /// def-id for the trait `Foo` and the substs define `T` as parameter 0,
386 /// and `U` as parameter 1.
388 /// Trait references also appear in object types like `Foo<U>`, but in
389 /// that case the `Self` parameter is absent from the substitutions.
391 /// Note that a `TraitRef` introduces a level of region binding, to
392 /// account for higher-ranked trait bounds like `T : for<'a> Foo<&'a
393 /// U>` or higher-ranked object types.
394 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
395 pub struct TraitRef
<'tcx
> {
397 pub substs
: &'tcx Substs
<'tcx
>,
400 impl<'tcx
> TraitRef
<'tcx
> {
401 pub fn new(def_id
: DefId
, substs
: &'tcx Substs
<'tcx
>) -> TraitRef
<'tcx
> {
402 TraitRef { def_id: def_id, substs: substs }
405 pub fn self_ty(&self) -> Ty
<'tcx
> {
406 self.substs
.type_at(0)
409 pub fn input_types
<'a
>(&'a
self) -> impl DoubleEndedIterator
<Item
=Ty
<'tcx
>> + 'a
{
410 // Select only the "input types" from a trait-reference. For
411 // now this is all the types that appear in the
412 // trait-reference, but it should eventually exclude
418 pub type PolyTraitRef
<'tcx
> = Binder
<TraitRef
<'tcx
>>;
420 impl<'tcx
> PolyTraitRef
<'tcx
> {
421 pub fn self_ty(&self) -> Ty
<'tcx
> {
425 pub fn def_id(&self) -> DefId
{
429 pub fn substs(&self) -> &'tcx Substs
<'tcx
> {
430 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
434 pub fn input_types
<'a
>(&'a
self) -> impl DoubleEndedIterator
<Item
=Ty
<'tcx
>> + 'a
{
435 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
439 pub fn to_poly_trait_predicate(&self) -> ty
::PolyTraitPredicate
<'tcx
> {
440 // Note that we preserve binding levels
441 Binder(ty
::TraitPredicate { trait_ref: self.0.clone() }
)
445 /// An existential reference to a trait, where `Self` is erased.
446 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
448 /// exists T. T: Trait<'a, 'b, X, Y>
450 /// The substitutions don't include the erased `Self`, only trait
451 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
452 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
453 pub struct ExistentialTraitRef
<'tcx
> {
455 pub substs
: &'tcx Substs
<'tcx
>,
458 impl<'a
, 'gcx
, 'tcx
> ExistentialTraitRef
<'tcx
> {
459 pub fn input_types
<'b
>(&'b
self) -> impl DoubleEndedIterator
<Item
=Ty
<'tcx
>> + 'b
{
460 // Select only the "input types" from a trait-reference. For
461 // now this is all the types that appear in the
462 // trait-reference, but it should eventually exclude
467 /// Object types don't have a self-type specified. Therefore, when
468 /// we convert the principal trait-ref into a normal trait-ref,
469 /// you must give *some* self-type. A common choice is `mk_err()`
470 /// or some skolemized type.
471 pub fn with_self_ty(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>, self_ty
: Ty
<'tcx
>)
472 -> ty
::TraitRef
<'tcx
> {
473 // otherwise the escaping regions would be captured by the binder
474 assert
!(!self_ty
.has_escaping_regions());
478 substs
: tcx
.mk_substs(
479 iter
::once(Kind
::from(self_ty
)).chain(self.substs
.iter().cloned()))
484 pub type PolyExistentialTraitRef
<'tcx
> = Binder
<ExistentialTraitRef
<'tcx
>>;
486 impl<'tcx
> PolyExistentialTraitRef
<'tcx
> {
487 pub fn def_id(&self) -> DefId
{
491 pub fn input_types
<'a
>(&'a
self) -> impl DoubleEndedIterator
<Item
=Ty
<'tcx
>> + 'a
{
492 // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
497 /// Binder is a binder for higher-ranked lifetimes. It is part of the
498 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
499 /// (which would be represented by the type `PolyTraitRef ==
500 /// Binder<TraitRef>`). Note that when we skolemize, instantiate,
501 /// erase, or otherwise "discharge" these bound regions, we change the
502 /// type from `Binder<T>` to just `T` (see
503 /// e.g. `liberate_late_bound_regions`).
504 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
505 pub struct Binder
<T
>(pub T
);
508 /// Skips the binder and returns the "bound" value. This is a
509 /// risky thing to do because it's easy to get confused about
510 /// debruijn indices and the like. It is usually better to
511 /// discharge the binder using `no_late_bound_regions` or
512 /// `replace_late_bound_regions` or something like
513 /// that. `skip_binder` is only valid when you are either
514 /// extracting data that has nothing to do with bound regions, you
515 /// are doing some sort of test that does not involve bound
516 /// regions, or you are being very careful about your depth
519 /// Some examples where `skip_binder` is reasonable:
520 /// - extracting the def-id from a PolyTraitRef;
521 /// - comparing the self type of a PolyTraitRef to see if it is equal to
522 /// a type parameter `X`, since the type `X` does not reference any regions
523 pub fn skip_binder(&self) -> &T
{
527 pub fn as_ref(&self) -> Binder
<&T
> {
531 pub fn map_bound_ref
<F
, U
>(&self, f
: F
) -> Binder
<U
>
532 where F
: FnOnce(&T
) -> U
534 self.as_ref().map_bound(f
)
537 pub fn map_bound
<F
, U
>(self, f
: F
) -> Binder
<U
>
538 where F
: FnOnce(T
) -> U
540 ty
::Binder(f(self.0))
544 impl fmt
::Debug
for TypeFlags
{
545 fn fmt(&self, f
: &mut fmt
::Formatter
) -> fmt
::Result
{
546 write
!(f
, "{:x}", self.bits
)
550 /// Represents the projection of an associated type. In explicit UFCS
551 /// form this would be written `<T as Trait<..>>::N`.
552 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
553 pub struct ProjectionTy
<'tcx
> {
554 /// The parameters of the associated item.
555 pub substs
: &'tcx Substs
<'tcx
>,
557 /// The DefId of the TraitItem for the associated type N.
559 /// Note that this is not the DefId of the TraitRef containing this
560 /// associated type, which is in tcx.associated_item(item_def_id).container.
561 pub item_def_id
: DefId
,
564 impl<'a
, 'tcx
> ProjectionTy
<'tcx
> {
565 /// Construct a ProjectionTy by searching the trait from trait_ref for the
566 /// associated item named item_name.
567 pub fn from_ref_and_name(
568 tcx
: TyCtxt
, trait_ref
: ty
::TraitRef
<'tcx
>, item_name
: Name
569 ) -> ProjectionTy
<'tcx
> {
570 let item_def_id
= tcx
.associated_items(trait_ref
.def_id
).find(
571 |item
| item
.name
== item_name
&& item
.kind
== ty
::AssociatedKind
::Type
575 substs
: trait_ref
.substs
,
580 /// Extracts the underlying trait reference from this projection.
581 /// For example, if this is a projection of `<T as Iterator>::Item`,
582 /// then this function would return a `T: Iterator` trait reference.
583 pub fn trait_ref(&self, tcx
: TyCtxt
) -> ty
::TraitRef
<'tcx
> {
584 let def_id
= tcx
.associated_item(self.item_def_id
).container
.id();
591 pub fn self_ty(&self) -> Ty
<'tcx
> {
592 self.substs
.type_at(0)
597 /// Signature of a function type, which I have arbitrarily
598 /// decided to use to refer to the input/output types.
600 /// - `inputs` is the list of arguments and their modes.
601 /// - `output` is the return type.
602 /// - `variadic` indicates whether this is a variadic function. (only true for foreign fns)
603 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
604 pub struct FnSig
<'tcx
> {
605 pub inputs_and_output
: &'tcx Slice
<Ty
<'tcx
>>,
607 pub unsafety
: hir
::Unsafety
,
611 impl<'tcx
> FnSig
<'tcx
> {
612 pub fn inputs(&self) -> &'tcx
[Ty
<'tcx
>] {
613 &self.inputs_and_output
[..self.inputs_and_output
.len() - 1]
616 pub fn output(&self) -> Ty
<'tcx
> {
617 self.inputs_and_output
[self.inputs_and_output
.len() - 1]
621 pub type PolyFnSig
<'tcx
> = Binder
<FnSig
<'tcx
>>;
623 impl<'tcx
> PolyFnSig
<'tcx
> {
624 pub fn inputs(&self) -> Binder
<&'tcx
[Ty
<'tcx
>]> {
625 Binder(self.skip_binder().inputs())
627 pub fn input(&self, index
: usize) -> ty
::Binder
<Ty
<'tcx
>> {
628 self.map_bound_ref(|fn_sig
| fn_sig
.inputs()[index
])
630 pub fn output(&self) -> ty
::Binder
<Ty
<'tcx
>> {
631 self.map_bound_ref(|fn_sig
| fn_sig
.output().clone())
633 pub fn variadic(&self) -> bool
{
634 self.skip_binder().variadic
636 pub fn unsafety(&self) -> hir
::Unsafety
{
637 self.skip_binder().unsafety
639 pub fn abi(&self) -> abi
::Abi
{
640 self.skip_binder().abi
644 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
650 impl<'a
, 'gcx
, 'tcx
> ParamTy
{
651 pub fn new(index
: u32, name
: Name
) -> ParamTy
{
652 ParamTy { idx: index, name: name }
655 pub fn for_self() -> ParamTy
{
656 ParamTy
::new(0, keywords
::SelfType
.name())
659 pub fn for_def(def
: &ty
::TypeParameterDef
) -> ParamTy
{
660 ParamTy
::new(def
.index
, def
.name
)
663 pub fn to_ty(self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>) -> Ty
<'tcx
> {
664 tcx
.mk_param(self.idx
, self.name
)
667 pub fn is_self(&self) -> bool
{
668 if self.name
== keywords
::SelfType
.name() {
669 assert_eq
!(self.idx
, 0);
677 /// A [De Bruijn index][dbi] is a standard means of representing
678 /// regions (and perhaps later types) in a higher-ranked setting. In
679 /// particular, imagine a type like this:
681 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
684 /// | +------------+ 1 | |
686 /// +--------------------------------+ 2 |
688 /// +------------------------------------------+ 1
690 /// In this type, there are two binders (the outer fn and the inner
691 /// fn). We need to be able to determine, for any given region, which
692 /// fn type it is bound by, the inner or the outer one. There are
693 /// various ways you can do this, but a De Bruijn index is one of the
694 /// more convenient and has some nice properties. The basic idea is to
695 /// count the number of binders, inside out. Some examples should help
696 /// clarify what I mean.
698 /// Let's start with the reference type `&'b isize` that is the first
699 /// argument to the inner function. This region `'b` is assigned a De
700 /// Bruijn index of 1, meaning "the innermost binder" (in this case, a
701 /// fn). The region `'a` that appears in the second argument type (`&'a
702 /// isize`) would then be assigned a De Bruijn index of 2, meaning "the
703 /// second-innermost binder". (These indices are written on the arrays
706 /// What is interesting is that De Bruijn index attached to a particular
707 /// variable will vary depending on where it appears. For example,
708 /// the final type `&'a char` also refers to the region `'a` declared on
709 /// the outermost fn. But this time, this reference is not nested within
710 /// any other binders (i.e., it is not an argument to the inner fn, but
711 /// rather the outer one). Therefore, in this case, it is assigned a
712 /// De Bruijn index of 1, because the innermost binder in that location
715 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
716 #[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, Copy)]
717 pub struct DebruijnIndex
{
718 /// We maintain the invariant that this is never 0. So 1 indicates
719 /// the innermost binder. To ensure this, create with `DebruijnIndex::new`.
723 pub type Region
<'tcx
> = &'tcx RegionKind
;
725 /// Representation of regions.
727 /// Unlike types, most region variants are "fictitious", not concrete,
728 /// regions. Among these, `ReStatic`, `ReEmpty` and `ReScope` are the only
729 /// ones representing concrete regions.
733 /// These are regions that are stored behind a binder and must be substituted
734 /// with some concrete region before being used. There are 2 kind of
735 /// bound regions: early-bound, which are bound in an item's Generics,
736 /// and are substituted by a Substs, and late-bound, which are part of
737 /// higher-ranked types (e.g. `for<'a> fn(&'a ())`) and are substituted by
738 /// the likes of `liberate_late_bound_regions`. The distinction exists
739 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
741 /// Unlike TyParam-s, bound regions are not supposed to exist "in the wild"
742 /// outside their binder, e.g. in types passed to type inference, and
743 /// should first be substituted (by skolemized regions, free regions,
744 /// or region variables).
746 /// ## Skolemized and Free Regions
748 /// One often wants to work with bound regions without knowing their precise
749 /// identity. For example, when checking a function, the lifetime of a borrow
750 /// can end up being assigned to some region parameter. In these cases,
751 /// it must be ensured that bounds on the region can't be accidentally
752 /// assumed without being checked.
754 /// The process of doing that is called "skolemization". The bound regions
755 /// are replaced by skolemized markers, which don't satisfy any relation
756 /// not explicitly provided.
758 /// There are 2 kinds of skolemized regions in rustc: `ReFree` and
759 /// `ReSkolemized`. When checking an item's body, `ReFree` is supposed
760 /// to be used. These also support explicit bounds: both the internally-stored
761 /// *scope*, which the region is assumed to outlive, as well as other
762 /// relations stored in the `FreeRegionMap`. Note that these relations
763 /// aren't checked when you `make_subregion` (or `eq_types`), only by
764 /// `resolve_regions_and_report_errors`.
766 /// When working with higher-ranked types, some region relations aren't
767 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
768 /// `ReSkolemized` is designed for this purpose. In these contexts,
769 /// there's also the risk that some inference variable laying around will
770 /// get unified with your skolemized region: if you want to check whether
771 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
772 /// with a skolemized region `'%a`, the variable `'_` would just be
773 /// instantiated to the skolemized region `'%a`, which is wrong because
774 /// the inference variable is supposed to satisfy the relation
775 /// *for every value of the skolemized region*. To ensure that doesn't
776 /// happen, you can use `leak_check`. This is more clearly explained
777 /// by infer/higher_ranked/README.md.
779 /// [1] http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
780 /// [2] http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
781 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable)]
782 pub enum RegionKind
{
783 // Region bound in a type or fn declaration which will be
784 // substituted 'early' -- that is, at the same time when type
785 // parameters are substituted.
786 ReEarlyBound(EarlyBoundRegion
),
788 // Region bound in a function scope, which will be substituted when the
789 // function is called.
790 ReLateBound(DebruijnIndex
, BoundRegion
),
792 /// When checking a function body, the types of all arguments and so forth
793 /// that refer to bound region parameters are modified to refer to free
794 /// region parameters.
797 /// A concrete region naming some statically determined extent
798 /// (e.g. an expression or sequence of statements) within the
799 /// current function.
800 ReScope(region
::CodeExtent
),
802 /// Static data that has an "infinite" lifetime. Top in the region lattice.
805 /// A region variable. Should not exist after typeck.
808 /// A skolemized region - basically the higher-ranked version of ReFree.
809 /// Should not exist after typeck.
810 ReSkolemized(SkolemizedRegionVid
, BoundRegion
),
812 /// Empty lifetime is for data that is never accessed.
813 /// Bottom in the region lattice. We treat ReEmpty somewhat
814 /// specially; at least right now, we do not generate instances of
815 /// it during the GLB computations, but rather
816 /// generate an error instead. This is to improve error messages.
817 /// The only way to get an instance of ReEmpty is to have a region
818 /// variable with no constraints.
821 /// Erased region, used by trait selection, in MIR and during trans.
825 impl<'tcx
> serialize
::UseSpecializedDecodable
for Region
<'tcx
> {}
827 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
828 pub struct EarlyBoundRegion
{
834 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
839 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
844 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
845 pub struct FloatVid
{
849 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
850 pub struct RegionVid
{
854 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
855 pub struct SkolemizedRegionVid
{
859 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
865 /// A `FreshTy` is one that is generated as a replacement for an
866 /// unbound type variable. This is convenient for caching etc. See
867 /// `infer::freshen` for more details.
873 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
874 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
875 pub struct ExistentialProjection
<'tcx
> {
876 pub item_def_id
: DefId
,
877 pub substs
: &'tcx Substs
<'tcx
>,
881 pub type PolyExistentialProjection
<'tcx
> = Binder
<ExistentialProjection
<'tcx
>>;
883 impl<'a
, 'tcx
, 'gcx
> ExistentialProjection
<'tcx
> {
884 /// Extracts the underlying existential trait reference from this projection.
885 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
886 /// then this function would return a `exists T. T: Iterator` existential trait
888 pub fn trait_ref(&self, tcx
: TyCtxt
) -> ty
::ExistentialTraitRef
<'tcx
> {
889 let def_id
= tcx
.associated_item(self.item_def_id
).container
.id();
890 ty
::ExistentialTraitRef
{
896 pub fn with_self_ty(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>,
898 -> ty
::ProjectionPredicate
<'tcx
>
900 // otherwise the escaping regions would be captured by the binders
901 assert
!(!self_ty
.has_escaping_regions());
903 ty
::ProjectionPredicate
{
904 projection_ty
: ty
::ProjectionTy
{
905 item_def_id
: self.item_def_id
,
906 substs
: tcx
.mk_substs(
907 iter
::once(Kind
::from(self_ty
)).chain(self.substs
.iter().cloned())),
914 impl<'a
, 'tcx
, 'gcx
> PolyExistentialProjection
<'tcx
> {
915 pub fn with_self_ty(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>, self_ty
: Ty
<'tcx
>)
916 -> ty
::PolyProjectionPredicate
<'tcx
> {
917 self.map_bound(|p
| p
.with_self_ty(tcx
, self_ty
))
922 pub fn new(depth
: u32) -> DebruijnIndex
{
924 DebruijnIndex { depth: depth }
927 pub fn shifted(&self, amount
: u32) -> DebruijnIndex
{
928 DebruijnIndex { depth: self.depth + amount }
934 pub fn is_late_bound(&self) -> bool
{
936 ty
::ReLateBound(..) => true,
941 pub fn needs_infer(&self) -> bool
{
943 ty
::ReVar(..) | ty
::ReSkolemized(..) => true,
948 pub fn escapes_depth(&self, depth
: u32) -> bool
{
950 ty
::ReLateBound(debruijn
, _
) => debruijn
.depth
> depth
,
955 /// Returns the depth of `self` from the (1-based) binding level `depth`
956 pub fn from_depth(&self, depth
: u32) -> RegionKind
{
958 ty
::ReLateBound(debruijn
, r
) => ty
::ReLateBound(DebruijnIndex
{
959 depth
: debruijn
.depth
- (depth
- 1)
965 pub fn type_flags(&self) -> TypeFlags
{
966 let mut flags
= TypeFlags
::empty();
970 flags
= flags
| TypeFlags
::HAS_RE_INFER
;
971 flags
= flags
| TypeFlags
::KEEP_IN_LOCAL_TCX
;
973 ty
::ReSkolemized(..) => {
974 flags
= flags
| TypeFlags
::HAS_RE_INFER
;
975 flags
= flags
| TypeFlags
::HAS_RE_SKOL
;
976 flags
= flags
| TypeFlags
::KEEP_IN_LOCAL_TCX
;
978 ty
::ReLateBound(..) => { }
979 ty
::ReEarlyBound(..) => { flags = flags | TypeFlags::HAS_RE_EARLY_BOUND; }
980 ty
::ReStatic
| ty
::ReErased
=> { }
981 _
=> { flags = flags | TypeFlags::HAS_FREE_REGIONS; }
985 ty
::ReStatic
| ty
::ReEmpty
| ty
::ReErased
=> (),
986 _
=> flags
= flags
| TypeFlags
::HAS_LOCAL_NAMES
,
989 debug
!("type_flags({:?}) = {:?}", self, flags
);
994 // This method returns whether the given Region is Named
995 pub fn is_named_region(&self) -> bool
{
997 ty
::ReFree(ref free_region
) => {
998 match free_region
.bound_region
{
999 ty
::BrNamed(..) => true,
1009 impl<'a
, 'gcx
, 'tcx
> TyS
<'tcx
> {
1010 pub fn as_opt_param_ty(&self) -> Option
<ty
::ParamTy
> {
1012 ty
::TyParam(ref d
) => Some(d
.clone()),
1017 pub fn is_nil(&self) -> bool
{
1019 TyTuple(ref tys
, _
) => tys
.is_empty(),
1024 pub fn is_never(&self) -> bool
{
1031 /// Test whether this is a `()` which was produced by defaulting a
1032 /// diverging type variable with feature(never_type) disabled.
1033 pub fn is_defaulted_unit(&self) -> bool
{
1035 TyTuple(_
, true) => true,
1040 /// Checks whether a type is visibly uninhabited from a particular module.
1046 /// pub struct SecretlyUninhabited {
1053 /// pub struct AlsoSecretlyUninhabited {
1061 /// x: a::b::SecretlyUninhabited,
1062 /// y: c::AlsoSecretlyUninhabited,
1065 /// In this code, the type `Foo` will only be visibly uninhabited inside the
1066 /// modules b, c and d. This effects pattern-matching on `Foo` or types that
1071 /// let foo_result: Result<T, Foo> = ... ;
1072 /// let Ok(t) = foo_result;
1074 /// This code should only compile in modules where the uninhabitedness of Foo is
1076 pub fn is_uninhabited_from(&self, module
: DefId
, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>) -> bool
{
1077 let mut visited
= FxHashMap
::default();
1078 let forest
= self.uninhabited_from(&mut visited
, tcx
);
1080 // To check whether this type is uninhabited at all (not just from the
1081 // given node) you could check whether the forest is empty.
1083 // forest.is_empty()
1085 forest
.contains(tcx
, module
)
1088 pub fn is_primitive(&self) -> bool
{
1090 TyBool
| TyChar
| TyInt(_
) | TyUint(_
) | TyFloat(_
) => true,
1095 pub fn is_ty_var(&self) -> bool
{
1097 TyInfer(TyVar(_
)) => true,
1102 pub fn is_phantom_data(&self) -> bool
{
1103 if let TyAdt(def
, _
) = self.sty
{
1104 def
.is_phantom_data()
1110 pub fn is_bool(&self) -> bool { self.sty == TyBool }
1112 pub fn is_param(&self, index
: u32) -> bool
{
1114 ty
::TyParam(ref data
) => data
.idx
== index
,
1119 pub fn is_self(&self) -> bool
{
1121 TyParam(ref p
) => p
.is_self(),
1126 pub fn is_slice(&self) -> bool
{
1128 TyRawPtr(mt
) | TyRef(_
, mt
) => match mt
.ty
.sty
{
1129 TySlice(_
) | TyStr
=> true,
1136 pub fn is_structural(&self) -> bool
{
1138 TyAdt(..) | TyTuple(..) | TyArray(..) | TyClosure(..) => true,
1139 _
=> self.is_slice() | self.is_trait(),
1144 pub fn is_simd(&self) -> bool
{
1146 TyAdt(def
, _
) => def
.repr
.simd(),
1151 pub fn sequence_element_type(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>) -> Ty
<'tcx
> {
1153 TyArray(ty
, _
) | TySlice(ty
) => ty
,
1154 TyStr
=> tcx
.mk_mach_uint(ast
::UintTy
::U8
),
1155 _
=> bug
!("sequence_element_type called on non-sequence value: {}", self),
1159 pub fn simd_type(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>) -> Ty
<'tcx
> {
1161 TyAdt(def
, substs
) => {
1162 def
.struct_variant().fields
[0].ty(tcx
, substs
)
1164 _
=> bug
!("simd_type called on invalid type")
1168 pub fn simd_size(&self, _cx
: TyCtxt
) -> usize {
1170 TyAdt(def
, _
) => def
.struct_variant().fields
.len(),
1171 _
=> bug
!("simd_size called on invalid type")
1175 pub fn is_region_ptr(&self) -> bool
{
1182 pub fn is_mutable_pointer(&self) -> bool
{
1184 TyRawPtr(tnm
) | TyRef(_
, tnm
) => if let hir
::Mutability
::MutMutable
= tnm
.mutbl
{
1193 pub fn is_unsafe_ptr(&self) -> bool
{
1195 TyRawPtr(_
) => return true,
1200 pub fn is_box(&self) -> bool
{
1202 TyAdt(def
, _
) => def
.is_box(),
1207 /// panics if called on any type other than `Box<T>`
1208 pub fn boxed_ty(&self) -> Ty
<'tcx
> {
1210 TyAdt(def
, substs
) if def
.is_box() => substs
.type_at(0),
1211 _
=> bug
!("`boxed_ty` is called on non-box type {:?}", self),
1215 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1216 /// (A TyRawPtr is scalar because it represents a non-managed pointer, so its
1217 /// contents are abstract to rustc.)
1218 pub fn is_scalar(&self) -> bool
{
1220 TyBool
| TyChar
| TyInt(_
) | TyFloat(_
) | TyUint(_
) |
1221 TyInfer(IntVar(_
)) | TyInfer(FloatVar(_
)) |
1222 TyFnDef(..) | TyFnPtr(_
) | TyRawPtr(_
) => true,
1227 /// Returns true if this type is a floating point type and false otherwise.
1228 pub fn is_floating_point(&self) -> bool
{
1231 TyInfer(FloatVar(_
)) => true,
1236 pub fn is_trait(&self) -> bool
{
1238 TyDynamic(..) => true,
1243 pub fn is_closure(&self) -> bool
{
1245 TyClosure(..) => true,
1250 pub fn is_integral(&self) -> bool
{
1252 TyInfer(IntVar(_
)) | TyInt(_
) | TyUint(_
) => true,
1257 pub fn is_fresh(&self) -> bool
{
1259 TyInfer(FreshTy(_
)) => true,
1260 TyInfer(FreshIntTy(_
)) => true,
1261 TyInfer(FreshFloatTy(_
)) => true,
1266 pub fn is_uint(&self) -> bool
{
1268 TyInfer(IntVar(_
)) | TyUint(ast
::UintTy
::Us
) => true,
1273 pub fn is_char(&self) -> bool
{
1280 pub fn is_fp(&self) -> bool
{
1282 TyInfer(FloatVar(_
)) | TyFloat(_
) => true,
1287 pub fn is_numeric(&self) -> bool
{
1288 self.is_integral() || self.is_fp()
1291 pub fn is_signed(&self) -> bool
{
1298 pub fn is_machine(&self) -> bool
{
1300 TyInt(ast
::IntTy
::Is
) | TyUint(ast
::UintTy
::Us
) => false,
1301 TyInt(..) | TyUint(..) | TyFloat(..) => true,
1306 pub fn has_concrete_skeleton(&self) -> bool
{
1308 TyParam(_
) | TyInfer(_
) | TyError
=> false,
1313 /// Returns the type and mutability of *ty.
1315 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1316 /// Some types---notably unsafe ptrs---can only be dereferenced explicitly.
1317 pub fn builtin_deref(&self, explicit
: bool
, pref
: ty
::LvaluePreference
)
1318 -> Option
<TypeAndMut
<'tcx
>>
1321 TyAdt(def
, _
) if def
.is_box() => {
1323 ty
: self.boxed_ty(),
1324 mutbl
: if pref
== ty
::PreferMutLvalue
{
1331 TyRef(_
, mt
) => Some(mt
),
1332 TyRawPtr(mt
) if explicit
=> Some(mt
),
1337 /// Returns the type of ty[i]
1338 pub fn builtin_index(&self) -> Option
<Ty
<'tcx
>> {
1340 TyArray(ty
, _
) | TySlice(ty
) => Some(ty
),
1345 pub fn fn_sig(&self, tcx
: TyCtxt
<'a
, 'gcx
, 'tcx
>) -> PolyFnSig
<'tcx
> {
1347 TyFnDef(def_id
, substs
) => {
1348 tcx
.fn_sig(def_id
).subst(tcx
, substs
)
1351 _
=> bug
!("Ty::fn_sig() called on non-fn type: {:?}", self)
1355 pub fn is_fn(&self) -> bool
{
1357 TyFnDef(..) | TyFnPtr(_
) => true,
1362 pub fn ty_to_def_id(&self) -> Option
<DefId
> {
1364 TyDynamic(ref tt
, ..) => tt
.principal().map(|p
| p
.def_id()),
1365 TyAdt(def
, _
) => Some(def
.did
),
1366 TyClosure(id
, _
) => Some(id
),
1371 pub fn ty_adt_def(&self) -> Option
<&'tcx AdtDef
> {
1373 TyAdt(adt
, _
) => Some(adt
),
1378 /// Returns the regions directly referenced from this type (but
1379 /// not types reachable from this type via `walk_tys`). This
1380 /// ignores late-bound regions binders.
1381 pub fn regions(&self) -> Vec
<ty
::Region
<'tcx
>> {
1383 TyRef(region
, _
) => {
1386 TyDynamic(ref obj
, region
) => {
1387 let mut v
= vec
![region
];
1388 if let Some(p
) = obj
.principal() {
1389 v
.extend(p
.skip_binder().substs
.regions());
1393 TyAdt(_
, substs
) | TyAnon(_
, substs
) => {
1394 substs
.regions().collect()
1396 TyClosure(_
, ref substs
) => {
1397 substs
.substs
.regions().collect()
1399 TyProjection(ref data
) => {
1400 data
.substs
.regions().collect()