1 //! This module contains `TyKind` and its major components.
3 #![allow(rustc::usage_of_ty_tykind)]
8 use crate::infer::canonical::Canonical;
9 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
11 self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness,
13 use crate::ty::{DelaySpanBugEmitted, List, ParamEnv, TyS};
14 use polonius_engine::Atom;
16 use rustc_data_structures::captures::Captures;
18 use rustc_hir::def_id::DefId;
19 use rustc_index::vec::Idx;
20 use rustc_macros::HashStable;
21 use rustc_span::symbol::{kw, Ident, Symbol};
22 use rustc_target::abi::VariantIdx;
23 use rustc_target::spec::abi;
25 use std::cmp::Ordering;
26 use std::marker::PhantomData;
28 use ty::util::IntTypeExt;
30 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
31 #[derive(HashStable, TypeFoldable, Lift)]
32 pub struct TypeAndMut<'tcx> {
34 pub mutbl: hir::Mutability,
37 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
39 /// A "free" region `fr` can be interpreted as "some region
40 /// at least as big as the scope `fr.scope`".
41 pub struct FreeRegion {
43 pub bound_region: BoundRegion,
46 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
48 pub enum BoundRegion {
49 /// An anonymous region parameter for a given fn (&T)
52 /// Named region parameters for functions (a in &'a T)
54 /// The `DefId` is needed to distinguish free regions in
55 /// the event of shadowing.
56 BrNamed(DefId, Symbol),
58 /// Anonymous region for the implicit env pointer parameter
64 pub fn is_named(&self) -> bool {
66 BoundRegion::BrNamed(_, name) => name != kw::UnderscoreLifetime,
71 /// When canonicalizing, we replace unbound inference variables and free
72 /// regions with anonymous late bound regions. This method asserts that
73 /// we have an anonymous late bound region, which hence may refer to
74 /// a canonical variable.
75 pub fn assert_bound_var(&self) -> BoundVar {
77 BoundRegion::BrAnon(var) => BoundVar::from_u32(var),
78 _ => bug!("bound region is not anonymous"),
83 /// N.B., if you change this, you'll probably want to change the corresponding
84 /// AST structure in `librustc_ast/ast.rs` as well.
85 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
87 #[rustc_diagnostic_item = "TyKind"]
88 pub enum TyKind<'tcx> {
89 /// The primitive boolean type. Written as `bool`.
92 /// The primitive character type; holds a Unicode scalar value
93 /// (a non-surrogate code point). Written as `char`.
96 /// A primitive signed integer type. For example, `i32`.
99 /// A primitive unsigned integer type. For example, `u32`.
102 /// A primitive floating-point type. For example, `f64`.
105 /// Structures, enumerations and unions.
107 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
108 /// That is, even after substitution it is possible that there are type
109 /// variables. This happens when the `Adt` corresponds to an ADT
110 /// definition and not a concrete use of it.
111 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
113 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
116 /// The pointee of a string slice. Written as `str`.
119 /// An array with the given length. Written as `[T; n]`.
120 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
122 /// The pointee of an array slice. Written as `[T]`.
125 /// A raw pointer. Written as `*mut T` or `*const T`
126 RawPtr(TypeAndMut<'tcx>),
128 /// A reference; a pointer with an associated lifetime. Written as
129 /// `&'a mut T` or `&'a T`.
130 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
132 /// The anonymous type of a function declaration/definition. Each
133 /// function has a unique type, which is output (for a function
134 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
136 /// For example the type of `bar` here:
139 /// fn foo() -> i32 { 1 }
140 /// let bar = foo; // bar: fn() -> i32 {foo}
142 FnDef(DefId, SubstsRef<'tcx>),
144 /// A pointer to a function. Written as `fn() -> i32`.
146 /// For example the type of `bar` here:
149 /// fn foo() -> i32 { 1 }
150 /// let bar: fn() -> i32 = foo;
152 FnPtr(PolyFnSig<'tcx>),
154 /// A trait, defined with `trait`.
155 Dynamic(Binder<&'tcx List<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
157 /// The anonymous type of a closure. Used to represent the type of
159 Closure(DefId, SubstsRef<'tcx>),
161 /// The anonymous type of a generator. Used to represent the type of
163 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
165 /// A type representin the types stored inside a generator.
166 /// This should only appear in GeneratorInteriors.
167 GeneratorWitness(Binder<&'tcx List<Ty<'tcx>>>),
169 /// The never type `!`
172 /// A tuple type. For example, `(i32, bool)`.
173 /// Use `TyS::tuple_fields` to iterate over the field types.
174 Tuple(SubstsRef<'tcx>),
176 /// The projection of an associated type. For example,
177 /// `<T as Trait<..>>::N`.
178 Projection(ProjectionTy<'tcx>),
180 /// Opaque (`impl Trait`) type found in a return type.
181 /// The `DefId` comes either from
182 /// * the `impl Trait` ast::Ty node,
183 /// * or the `type Foo = impl Trait` declaration
184 /// The substitutions are for the generics of the function in question.
185 /// After typeck, the concrete type can be found in the `types` map.
186 Opaque(DefId, SubstsRef<'tcx>),
188 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
191 /// Bound type variable, used only when preparing a trait query.
192 Bound(ty::DebruijnIndex, BoundTy),
194 /// A placeholder type - universally quantified higher-ranked type.
195 Placeholder(ty::PlaceholderType),
197 /// A type variable used during type checking.
200 /// A placeholder for a type which could not be computed; this is
201 /// propagated to avoid useless error messages.
202 Error(DelaySpanBugEmitted),
207 pub fn is_primitive(&self) -> bool {
209 Bool | Char | Int(_) | Uint(_) | Float(_) => true,
215 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
216 #[cfg(target_arch = "x86_64")]
217 static_assert_size!(TyKind<'_>, 24);
219 /// A closure can be modeled as a struct that looks like:
221 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
225 /// - 'l0...'li and T0...Tj are the generic parameters
226 /// in scope on the function that defined the closure,
227 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
228 /// is rather hackily encoded via a scalar type. See
229 /// `TyS::to_opt_closure_kind` for details.
230 /// - CS represents the *closure signature*, representing as a `fn()`
231 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
232 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
234 /// - U is a type parameter representing the types of its upvars, tupled up
235 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
236 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
238 /// So, for example, given this function:
240 /// fn foo<'a, T>(data: &'a mut T) {
241 /// do(|| data.count += 1)
244 /// the type of the closure would be something like:
246 /// struct Closure<'a, T, U>(...U);
248 /// Note that the type of the upvar is not specified in the struct.
249 /// You may wonder how the impl would then be able to use the upvar,
250 /// if it doesn't know it's type? The answer is that the impl is
251 /// (conceptually) not fully generic over Closure but rather tied to
252 /// instances with the expected upvar types:
254 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
258 /// You can see that the *impl* fully specified the type of the upvar
259 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
260 /// (Here, I am assuming that `data` is mut-borrowed.)
262 /// Now, the last question you may ask is: Why include the upvar types
263 /// in an extra type parameter? The reason for this design is that the
264 /// upvar types can reference lifetimes that are internal to the
265 /// creating function. In my example above, for example, the lifetime
266 /// `'b` represents the scope of the closure itself; this is some
267 /// subset of `foo`, probably just the scope of the call to the to
268 /// `do()`. If we just had the lifetime/type parameters from the
269 /// enclosing function, we couldn't name this lifetime `'b`. Note that
270 /// there can also be lifetimes in the types of the upvars themselves,
271 /// if one of them happens to be a reference to something that the
272 /// creating fn owns.
274 /// OK, you say, so why not create a more minimal set of parameters
275 /// that just includes the extra lifetime parameters? The answer is
276 /// primarily that it would be hard --- we don't know at the time when
277 /// we create the closure type what the full types of the upvars are,
278 /// nor do we know which are borrowed and which are not. In this
279 /// design, we can just supply a fresh type parameter and figure that
282 /// All right, you say, but why include the type parameters from the
283 /// original function then? The answer is that codegen may need them
284 /// when monomorphizing, and they may not appear in the upvars. A
285 /// closure could capture no variables but still make use of some
286 /// in-scope type parameter with a bound (e.g., if our example above
287 /// had an extra `U: Default`, and the closure called `U::default()`).
289 /// There is another reason. This design (implicitly) prohibits
290 /// closures from capturing themselves (except via a trait
291 /// object). This simplifies closure inference considerably, since it
292 /// means that when we infer the kind of a closure or its upvars, we
293 /// don't have to handle cycles where the decisions we make for
294 /// closure C wind up influencing the decisions we ought to make for
295 /// closure C (which would then require fixed point iteration to
296 /// handle). Plus it fixes an ICE. :P
300 /// Generators are handled similarly in `GeneratorSubsts`. The set of
301 /// type parameters is similar, but `CK` and `CS` are replaced by the
302 /// following type parameters:
304 /// * `GS`: The generator's "resume type", which is the type of the
305 /// argument passed to `resume`, and the type of `yield` expressions
306 /// inside the generator.
307 /// * `GY`: The "yield type", which is the type of values passed to
308 /// `yield` inside the generator.
309 /// * `GR`: The "return type", which is the type of value returned upon
310 /// completion of the generator.
311 /// * `GW`: The "generator witness".
312 #[derive(Copy, Clone, Debug, TypeFoldable)]
313 pub struct ClosureSubsts<'tcx> {
314 /// Lifetime and type parameters from the enclosing function,
315 /// concatenated with a tuple containing the types of the upvars.
317 /// These are separated out because codegen wants to pass them around
318 /// when monomorphizing.
319 pub substs: SubstsRef<'tcx>,
322 /// Struct returned by `split()`.
323 pub struct ClosureSubstsParts<'tcx, T> {
324 pub parent_substs: &'tcx [GenericArg<'tcx>],
325 pub closure_kind_ty: T,
326 pub closure_sig_as_fn_ptr_ty: T,
327 pub tupled_upvars_ty: T,
330 impl<'tcx> ClosureSubsts<'tcx> {
331 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
332 /// for the closure parent, alongside additional closure-specific components.
335 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
336 ) -> ClosureSubsts<'tcx> {
338 substs: tcx.mk_substs(
339 parts.parent_substs.iter().copied().chain(
340 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
342 .map(|&ty| ty.into()),
348 /// Divides the closure substs into their respective components.
349 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
350 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
351 match self.substs[..] {
352 [ref parent_substs @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
356 closure_sig_as_fn_ptr_ty,
360 _ => bug!("closure substs missing synthetics"),
364 /// Returns `true` only if enough of the synthetic types are known to
365 /// allow using all of the methods on `ClosureSubsts` without panicking.
367 /// Used primarily by `ty::print::pretty` to be able to handle closure
368 /// types that haven't had their synthetic types substituted in.
369 pub fn is_valid(self) -> bool {
370 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
373 /// Returns the substitutions of the closure's parent.
374 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
375 self.split().parent_substs
379 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
380 self.tupled_upvars_ty().tuple_fields()
383 /// Returns the tuple type representing the upvars for this closure.
385 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
386 self.split().tupled_upvars_ty.expect_ty()
389 /// Returns the closure kind for this closure; may return a type
390 /// variable during inference. To get the closure kind during
391 /// inference, use `infcx.closure_kind(substs)`.
392 pub fn kind_ty(self) -> Ty<'tcx> {
393 self.split().closure_kind_ty.expect_ty()
396 /// Returns the `fn` pointer type representing the closure signature for this
398 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
399 // type is known at the time of the creation of `ClosureSubsts`,
400 // see `rustc_typeck::check::closure`.
401 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
402 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
405 /// Returns the closure kind for this closure; only usable outside
406 /// of an inference context, because in that context we know that
407 /// there are no type variables.
409 /// If you have an inference context, use `infcx.closure_kind()`.
410 pub fn kind(self) -> ty::ClosureKind {
411 self.kind_ty().to_opt_closure_kind().unwrap()
414 /// Extracts the signature from the closure.
415 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
416 let ty = self.sig_as_fn_ptr_ty();
418 ty::FnPtr(sig) => sig,
419 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
424 /// Similar to `ClosureSubsts`; see the above documentation for more.
425 #[derive(Copy, Clone, Debug, TypeFoldable)]
426 pub struct GeneratorSubsts<'tcx> {
427 pub substs: SubstsRef<'tcx>,
430 pub struct GeneratorSubstsParts<'tcx, T> {
431 pub parent_substs: &'tcx [GenericArg<'tcx>],
436 pub tupled_upvars_ty: T,
439 impl<'tcx> GeneratorSubsts<'tcx> {
440 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
441 /// for the generator parent, alongside additional generator-specific components.
444 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
445 ) -> GeneratorSubsts<'tcx> {
447 substs: tcx.mk_substs(
448 parts.parent_substs.iter().copied().chain(
454 parts.tupled_upvars_ty,
457 .map(|&ty| ty.into()),
463 /// Divides the generator substs into their respective components.
464 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
465 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
466 match self.substs[..] {
467 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
468 GeneratorSubstsParts {
477 _ => bug!("generator substs missing synthetics"),
481 /// Returns `true` only if enough of the synthetic types are known to
482 /// allow using all of the methods on `GeneratorSubsts` without panicking.
484 /// Used primarily by `ty::print::pretty` to be able to handle generator
485 /// types that haven't had their synthetic types substituted in.
486 pub fn is_valid(self) -> bool {
487 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
490 /// Returns the substitutions of the generator's parent.
491 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
492 self.split().parent_substs
495 /// This describes the types that can be contained in a generator.
496 /// It will be a type variable initially and unified in the last stages of typeck of a body.
497 /// It contains a tuple of all the types that could end up on a generator frame.
498 /// The state transformation MIR pass may only produce layouts which mention types
499 /// in this tuple. Upvars are not counted here.
500 pub fn witness(self) -> Ty<'tcx> {
501 self.split().witness.expect_ty()
505 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
506 self.tupled_upvars_ty().tuple_fields()
509 /// Returns the tuple type representing the upvars for this generator.
511 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
512 self.split().tupled_upvars_ty.expect_ty()
515 /// Returns the type representing the resume type of the generator.
516 pub fn resume_ty(self) -> Ty<'tcx> {
517 self.split().resume_ty.expect_ty()
520 /// Returns the type representing the yield type of the generator.
521 pub fn yield_ty(self) -> Ty<'tcx> {
522 self.split().yield_ty.expect_ty()
525 /// Returns the type representing the return type of the generator.
526 pub fn return_ty(self) -> Ty<'tcx> {
527 self.split().return_ty.expect_ty()
530 /// Returns the "generator signature", which consists of its yield
531 /// and return types.
533 /// N.B., some bits of the code prefers to see this wrapped in a
534 /// binder, but it never contains bound regions. Probably this
535 /// function should be removed.
536 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
537 ty::Binder::dummy(self.sig())
540 /// Returns the "generator signature", which consists of its resume, yield
541 /// and return types.
542 pub fn sig(self) -> GenSig<'tcx> {
544 resume_ty: self.resume_ty(),
545 yield_ty: self.yield_ty(),
546 return_ty: self.return_ty(),
551 impl<'tcx> GeneratorSubsts<'tcx> {
552 /// Generator has not been resumed yet.
553 pub const UNRESUMED: usize = 0;
554 /// Generator has returned or is completed.
555 pub const RETURNED: usize = 1;
556 /// Generator has been poisoned.
557 pub const POISONED: usize = 2;
559 const UNRESUMED_NAME: &'static str = "Unresumed";
560 const RETURNED_NAME: &'static str = "Returned";
561 const POISONED_NAME: &'static str = "Panicked";
563 /// The valid variant indices of this generator.
565 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
566 // FIXME requires optimized MIR
567 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
568 VariantIdx::new(0)..VariantIdx::new(num_variants)
571 /// The discriminant for the given variant. Panics if the `variant_index` is
574 pub fn discriminant_for_variant(
578 variant_index: VariantIdx,
580 // Generators don't support explicit discriminant values, so they are
581 // the same as the variant index.
582 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
583 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
586 /// The set of all discriminants for the generator, enumerated with their
589 pub fn discriminants(
593 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
594 self.variant_range(def_id, tcx).map(move |index| {
595 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
599 /// Calls `f` with a reference to the name of the enumerator for the given
601 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
603 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
604 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
605 Self::POISONED => Cow::from(Self::POISONED_NAME),
606 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
610 /// The type of the state discriminant used in the generator type.
612 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
616 /// This returns the types of the MIR locals which had to be stored across suspension points.
617 /// It is calculated in rustc_mir::transform::generator::StateTransform.
618 /// All the types here must be in the tuple in GeneratorInterior.
620 /// The locals are grouped by their variant number. Note that some locals may
621 /// be repeated in multiple variants.
627 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
628 let layout = tcx.generator_layout(def_id);
629 layout.variant_fields.iter().map(move |variant| {
630 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
634 /// This is the types of the fields of a generator which are not stored in a
637 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
642 #[derive(Debug, Copy, Clone)]
643 pub enum UpvarSubsts<'tcx> {
644 Closure(SubstsRef<'tcx>),
645 Generator(SubstsRef<'tcx>),
648 impl<'tcx> UpvarSubsts<'tcx> {
650 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
651 let tupled_upvars_ty = match self {
652 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
653 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
655 tupled_upvars_ty.expect_ty().tuple_fields()
659 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
660 #[derive(HashStable, TypeFoldable)]
661 pub enum ExistentialPredicate<'tcx> {
662 /// E.g., `Iterator`.
663 Trait(ExistentialTraitRef<'tcx>),
664 /// E.g., `Iterator::Item = T`.
665 Projection(ExistentialProjection<'tcx>),
670 impl<'tcx> ExistentialPredicate<'tcx> {
671 /// Compares via an ordering that will not change if modules are reordered or other changes are
672 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
673 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
674 use self::ExistentialPredicate::*;
675 match (*self, *other) {
676 (Trait(_), Trait(_)) => Ordering::Equal,
677 (Projection(ref a), Projection(ref b)) => {
678 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
680 (AutoTrait(ref a), AutoTrait(ref b)) => {
681 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
683 (Trait(_), _) => Ordering::Less,
684 (Projection(_), Trait(_)) => Ordering::Greater,
685 (Projection(_), _) => Ordering::Less,
686 (AutoTrait(_), _) => Ordering::Greater,
691 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
692 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
693 use crate::ty::ToPredicate;
694 match self.skip_binder() {
695 ExistentialPredicate::Trait(tr) => {
696 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
698 ExistentialPredicate::Projection(p) => {
699 Binder(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
701 ExistentialPredicate::AutoTrait(did) => {
703 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
704 trait_ref.without_const().to_predicate(tcx)
710 impl<'tcx> List<ExistentialPredicate<'tcx>> {
711 /// Returns the "principal `DefId`" of this set of existential predicates.
713 /// A Rust trait object type consists (in addition to a lifetime bound)
714 /// of a set of trait bounds, which are separated into any number
715 /// of auto-trait bounds, and at most one non-auto-trait bound. The
716 /// non-auto-trait bound is called the "principal" of the trait
719 /// Only the principal can have methods or type parameters (because
720 /// auto traits can have neither of them). This is important, because
721 /// it means the auto traits can be treated as an unordered set (methods
722 /// would force an order for the vtable, while relating traits with
723 /// type parameters without knowing the order to relate them in is
724 /// a rather non-trivial task).
726 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
727 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
728 /// are the set `{Sync}`.
730 /// It is also possible to have a "trivial" trait object that
731 /// consists only of auto traits, with no principal - for example,
732 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
733 /// is `{Send, Sync}`, while there is no principal. These trait objects
734 /// have a "trivial" vtable consisting of just the size, alignment,
736 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
738 ExistentialPredicate::Trait(tr) => Some(tr),
743 pub fn principal_def_id(&self) -> Option<DefId> {
744 self.principal().map(|trait_ref| trait_ref.def_id)
748 pub fn projection_bounds<'a>(
750 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
751 self.iter().filter_map(|predicate| match predicate {
752 ExistentialPredicate::Projection(projection) => Some(projection),
758 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
759 self.iter().filter_map(|predicate| match predicate {
760 ExistentialPredicate::AutoTrait(did) => Some(did),
766 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
767 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
768 self.skip_binder().principal().map(Binder::bind)
771 pub fn principal_def_id(&self) -> Option<DefId> {
772 self.skip_binder().principal_def_id()
776 pub fn projection_bounds<'a>(
778 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
779 self.skip_binder().projection_bounds().map(Binder::bind)
783 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
784 self.skip_binder().auto_traits()
789 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
790 self.skip_binder().iter().map(Binder::bind)
794 /// A complete reference to a trait. These take numerous guises in syntax,
795 /// but perhaps the most recognizable form is in a where-clause:
799 /// This would be represented by a trait-reference where the `DefId` is the
800 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
801 /// and `U` as parameter 1.
803 /// Trait references also appear in object types like `Foo<U>`, but in
804 /// that case the `Self` parameter is absent from the substitutions.
805 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
806 #[derive(HashStable, TypeFoldable)]
807 pub struct TraitRef<'tcx> {
809 pub substs: SubstsRef<'tcx>,
812 impl<'tcx> TraitRef<'tcx> {
813 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
814 TraitRef { def_id, substs }
817 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
818 /// are the parameters defined on trait.
819 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
820 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
824 pub fn self_ty(&self) -> Ty<'tcx> {
825 self.substs.type_at(0)
831 substs: SubstsRef<'tcx>,
832 ) -> ty::TraitRef<'tcx> {
833 let defs = tcx.generics_of(trait_id);
835 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
839 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
841 impl<'tcx> PolyTraitRef<'tcx> {
842 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
843 self.map_bound_ref(|tr| tr.self_ty())
846 pub fn def_id(&self) -> DefId {
847 self.skip_binder().def_id
850 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
851 // Note that we preserve binding levels
852 Binder(ty::TraitPredicate { trait_ref: self.skip_binder() })
856 /// An existential reference to a trait, where `Self` is erased.
857 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
859 /// exists T. T: Trait<'a, 'b, X, Y>
861 /// The substitutions don't include the erased `Self`, only trait
862 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
863 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
864 #[derive(HashStable, TypeFoldable)]
865 pub struct ExistentialTraitRef<'tcx> {
867 pub substs: SubstsRef<'tcx>,
870 impl<'tcx> ExistentialTraitRef<'tcx> {
871 pub fn erase_self_ty(
873 trait_ref: ty::TraitRef<'tcx>,
874 ) -> ty::ExistentialTraitRef<'tcx> {
875 // Assert there is a Self.
876 trait_ref.substs.type_at(0);
878 ty::ExistentialTraitRef {
879 def_id: trait_ref.def_id,
880 substs: tcx.intern_substs(&trait_ref.substs[1..]),
884 /// Object types don't have a self type specified. Therefore, when
885 /// we convert the principal trait-ref into a normal trait-ref,
886 /// you must give *some* self type. A common choice is `mk_err()`
887 /// or some placeholder type.
888 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
889 // otherwise the escaping vars would be captured by the binder
890 // debug_assert!(!self_ty.has_escaping_bound_vars());
892 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
896 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
898 impl<'tcx> PolyExistentialTraitRef<'tcx> {
899 pub fn def_id(&self) -> DefId {
900 self.skip_binder().def_id
903 /// Object types don't have a self type specified. Therefore, when
904 /// we convert the principal trait-ref into a normal trait-ref,
905 /// you must give *some* self type. A common choice is `mk_err()`
906 /// or some placeholder type.
907 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
908 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
912 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
913 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
914 /// (which would be represented by the type `PolyTraitRef ==
915 /// Binder<TraitRef>`). Note that when we instantiate,
916 /// erase, or otherwise "discharge" these bound vars, we change the
917 /// type from `Binder<T>` to just `T` (see
918 /// e.g., `liberate_late_bound_regions`).
919 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
920 pub struct Binder<T>(T);
923 /// Wraps `value` in a binder, asserting that `value` does not
924 /// contain any bound vars that would be bound by the
925 /// binder. This is commonly used to 'inject' a value T into a
926 /// different binding level.
927 pub fn dummy<'tcx>(value: T) -> Binder<T>
929 T: TypeFoldable<'tcx>,
931 debug_assert!(!value.has_escaping_bound_vars());
935 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
936 pub fn bind(value: T) -> Binder<T> {
940 /// Wraps `value` in a binder without actually binding any currently
941 /// unbound variables.
943 /// Note that this will shift all debrujin indices of escaping bound variables
944 /// by 1 to avoid accidential captures.
945 pub fn wrap_nonbinding(tcx: TyCtxt<'tcx>, value: T) -> Binder<T>
947 T: TypeFoldable<'tcx>,
949 if value.has_escaping_bound_vars() {
950 Binder::bind(super::fold::shift_vars(tcx, &value, 1))
956 /// Skips the binder and returns the "bound" value. This is a
957 /// risky thing to do because it's easy to get confused about
958 /// De Bruijn indices and the like. It is usually better to
959 /// discharge the binder using `no_bound_vars` or
960 /// `replace_late_bound_regions` or something like
961 /// that. `skip_binder` is only valid when you are either
962 /// extracting data that has nothing to do with bound vars, you
963 /// are doing some sort of test that does not involve bound
964 /// regions, or you are being very careful about your depth
967 /// Some examples where `skip_binder` is reasonable:
969 /// - extracting the `DefId` from a PolyTraitRef;
970 /// - comparing the self type of a PolyTraitRef to see if it is equal to
971 /// a type parameter `X`, since the type `X` does not reference any regions
972 pub fn skip_binder(self) -> T {
976 pub fn as_ref(&self) -> Binder<&T> {
980 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
984 self.as_ref().map_bound(f)
987 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
994 /// Unwraps and returns the value within, but only if it contains
995 /// no bound vars at all. (In other words, if this binder --
996 /// and indeed any enclosing binder -- doesn't bind anything at
997 /// all.) Otherwise, returns `None`.
999 /// (One could imagine having a method that just unwraps a single
1000 /// binder, but permits late-bound vars bound by enclosing
1001 /// binders, but that would require adjusting the debruijn
1002 /// indices, and given the shallow binding structure we often use,
1003 /// would not be that useful.)
1004 pub fn no_bound_vars<'tcx>(self) -> Option<T>
1006 T: TypeFoldable<'tcx>,
1008 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1011 /// Given two things that have the same binder level,
1012 /// and an operation that wraps on their contents, executes the operation
1013 /// and then wraps its result.
1015 /// `f` should consider bound regions at depth 1 to be free, and
1016 /// anything it produces with bound regions at depth 1 will be
1017 /// bound in the resulting return value.
1018 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
1020 F: FnOnce(T, U) -> R,
1022 Binder(f(self.0, u.0))
1025 /// Splits the contents into two things that share the same binder
1026 /// level as the original, returning two distinct binders.
1028 /// `f` should consider bound regions at depth 1 to be free, and
1029 /// anything it produces with bound regions at depth 1 will be
1030 /// bound in the resulting return values.
1031 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
1033 F: FnOnce(T) -> (U, V),
1035 let (u, v) = f(self.0);
1036 (Binder(u), Binder(v))
1040 impl<T> Binder<Option<T>> {
1041 pub fn transpose(self) -> Option<Binder<T>> {
1043 Some(v) => Some(Binder(v)),
1049 /// Represents the projection of an associated type. In explicit UFCS
1050 /// form this would be written `<T as Trait<..>>::N`.
1051 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1052 #[derive(HashStable, TypeFoldable)]
1053 pub struct ProjectionTy<'tcx> {
1054 /// The parameters of the associated item.
1055 pub substs: SubstsRef<'tcx>,
1057 /// The `DefId` of the `TraitItem` for the associated type `N`.
1059 /// Note that this is not the `DefId` of the `TraitRef` containing this
1060 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1061 pub item_def_id: DefId,
1064 impl<'tcx> ProjectionTy<'tcx> {
1065 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
1066 /// associated item named `item_name`.
1067 pub fn from_ref_and_name(
1069 trait_ref: ty::TraitRef<'tcx>,
1071 ) -> ProjectionTy<'tcx> {
1072 let item_def_id = tcx
1073 .associated_items(trait_ref.def_id)
1074 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1078 ProjectionTy { substs: trait_ref.substs, item_def_id }
1081 /// Extracts the underlying trait reference from this projection.
1082 /// For example, if this is a projection of `<T as Iterator>::Item`,
1083 /// then this function would return a `T: Iterator` trait reference.
1084 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1085 let def_id = tcx.associated_item(self.item_def_id).container.id();
1086 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1089 pub fn self_ty(&self) -> Ty<'tcx> {
1090 self.substs.type_at(0)
1094 #[derive(Copy, Clone, Debug, TypeFoldable)]
1095 pub struct GenSig<'tcx> {
1096 pub resume_ty: Ty<'tcx>,
1097 pub yield_ty: Ty<'tcx>,
1098 pub return_ty: Ty<'tcx>,
1101 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1103 impl<'tcx> PolyGenSig<'tcx> {
1104 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1105 self.map_bound_ref(|sig| sig.resume_ty)
1107 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1108 self.map_bound_ref(|sig| sig.yield_ty)
1110 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1111 self.map_bound_ref(|sig| sig.return_ty)
1115 /// Signature of a function type, which we have arbitrarily
1116 /// decided to use to refer to the input/output types.
1118 /// - `inputs`: is the list of arguments and their modes.
1119 /// - `output`: is the return type.
1120 /// - `c_variadic`: indicates whether this is a C-variadic function.
1121 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1122 #[derive(HashStable, TypeFoldable)]
1123 pub struct FnSig<'tcx> {
1124 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1125 pub c_variadic: bool,
1126 pub unsafety: hir::Unsafety,
1130 impl<'tcx> FnSig<'tcx> {
1131 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1132 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1135 pub fn output(&self) -> Ty<'tcx> {
1136 self.inputs_and_output[self.inputs_and_output.len() - 1]
1139 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1141 fn fake() -> FnSig<'tcx> {
1143 inputs_and_output: List::empty(),
1145 unsafety: hir::Unsafety::Normal,
1146 abi: abi::Abi::Rust,
1151 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1153 impl<'tcx> PolyFnSig<'tcx> {
1155 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1156 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1159 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1160 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1162 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1163 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1166 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1167 self.map_bound_ref(|fn_sig| fn_sig.output())
1169 pub fn c_variadic(&self) -> bool {
1170 self.skip_binder().c_variadic
1172 pub fn unsafety(&self) -> hir::Unsafety {
1173 self.skip_binder().unsafety
1175 pub fn abi(&self) -> abi::Abi {
1176 self.skip_binder().abi
1180 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1182 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1183 #[derive(HashStable)]
1184 pub struct ParamTy {
1189 impl<'tcx> ParamTy {
1190 pub fn new(index: u32, name: Symbol) -> ParamTy {
1191 ParamTy { index, name }
1194 pub fn for_self() -> ParamTy {
1195 ParamTy::new(0, kw::SelfUpper)
1198 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1199 ParamTy::new(def.index, def.name)
1202 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1203 tcx.mk_ty_param(self.index, self.name)
1207 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1208 #[derive(HashStable)]
1209 pub struct ParamConst {
1214 impl<'tcx> ParamConst {
1215 pub fn new(index: u32, name: Symbol) -> ParamConst {
1216 ParamConst { index, name }
1219 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1220 ParamConst::new(def.index, def.name)
1223 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
1224 tcx.mk_const_param(self.index, self.name, ty)
1228 rustc_index::newtype_index! {
1229 /// A [De Bruijn index][dbi] is a standard means of representing
1230 /// regions (and perhaps later types) in a higher-ranked setting. In
1231 /// particular, imagine a type like this:
1233 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1236 /// | +------------+ 0 | |
1238 /// +--------------------------------+ 1 |
1240 /// +------------------------------------------+ 0
1242 /// In this type, there are two binders (the outer fn and the inner
1243 /// fn). We need to be able to determine, for any given region, which
1244 /// fn type it is bound by, the inner or the outer one. There are
1245 /// various ways you can do this, but a De Bruijn index is one of the
1246 /// more convenient and has some nice properties. The basic idea is to
1247 /// count the number of binders, inside out. Some examples should help
1248 /// clarify what I mean.
1250 /// Let's start with the reference type `&'b isize` that is the first
1251 /// argument to the inner function. This region `'b` is assigned a De
1252 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1253 /// fn). The region `'a` that appears in the second argument type (`&'a
1254 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1255 /// second-innermost binder". (These indices are written on the arrays
1256 /// in the diagram).
1258 /// What is interesting is that De Bruijn index attached to a particular
1259 /// variable will vary depending on where it appears. For example,
1260 /// the final type `&'a char` also refers to the region `'a` declared on
1261 /// the outermost fn. But this time, this reference is not nested within
1262 /// any other binders (i.e., it is not an argument to the inner fn, but
1263 /// rather the outer one). Therefore, in this case, it is assigned a
1264 /// De Bruijn index of 0, because the innermost binder in that location
1265 /// is the outer fn.
1267 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1268 #[derive(HashStable)]
1269 pub struct DebruijnIndex {
1270 DEBUG_FORMAT = "DebruijnIndex({})",
1271 const INNERMOST = 0,
1275 pub type Region<'tcx> = &'tcx RegionKind;
1277 /// Representation of regions. Note that the NLL checker uses a distinct
1278 /// representation of regions. For this reason, it internally replaces all the
1279 /// regions with inference variables -- the index of the variable is then used
1280 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1281 /// module for more information.
1283 /// ## The Region lattice within a given function
1285 /// In general, the region lattice looks like
1288 /// static ----------+-----...------+ (greatest)
1290 /// early-bound and | |
1291 /// free regions | |
1294 /// empty(root) placeholder(U1) |
1296 /// | / placeholder(Un)
1301 /// empty(Un) -------- (smallest)
1304 /// Early-bound/free regions are the named lifetimes in scope from the
1305 /// function declaration. They have relationships to one another
1306 /// determined based on the declared relationships from the
1309 /// Note that inference variables and bound regions are not included
1310 /// in this diagram. In the case of inference variables, they should
1311 /// be inferred to some other region from the diagram. In the case of
1312 /// bound regions, they are excluded because they don't make sense to
1313 /// include -- the diagram indicates the relationship between free
1316 /// ## Inference variables
1318 /// During region inference, we sometimes create inference variables,
1319 /// represented as `ReVar`. These will be inferred by the code in
1320 /// `infer::lexical_region_resolve` to some free region from the
1321 /// lattice above (the minimal region that meets the
1324 /// During NLL checking, where regions are defined differently, we
1325 /// also use `ReVar` -- in that case, the index is used to index into
1326 /// the NLL region checker's data structures. The variable may in fact
1327 /// represent either a free region or an inference variable, in that
1330 /// ## Bound Regions
1332 /// These are regions that are stored behind a binder and must be substituted
1333 /// with some concrete region before being used. There are two kind of
1334 /// bound regions: early-bound, which are bound in an item's `Generics`,
1335 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1336 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1337 /// the likes of `liberate_late_bound_regions`. The distinction exists
1338 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1340 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1341 /// outside their binder, e.g., in types passed to type inference, and
1342 /// should first be substituted (by placeholder regions, free regions,
1343 /// or region variables).
1345 /// ## Placeholder and Free Regions
1347 /// One often wants to work with bound regions without knowing their precise
1348 /// identity. For example, when checking a function, the lifetime of a borrow
1349 /// can end up being assigned to some region parameter. In these cases,
1350 /// it must be ensured that bounds on the region can't be accidentally
1351 /// assumed without being checked.
1353 /// To do this, we replace the bound regions with placeholder markers,
1354 /// which don't satisfy any relation not explicitly provided.
1356 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1357 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1358 /// to be used. These also support explicit bounds: both the internally-stored
1359 /// *scope*, which the region is assumed to outlive, as well as other
1360 /// relations stored in the `FreeRegionMap`. Note that these relations
1361 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1362 /// `resolve_regions_and_report_errors`.
1364 /// When working with higher-ranked types, some region relations aren't
1365 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1366 /// `RePlaceholder` is designed for this purpose. In these contexts,
1367 /// there's also the risk that some inference variable laying around will
1368 /// get unified with your placeholder region: if you want to check whether
1369 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1370 /// with a placeholder region `'%a`, the variable `'_` would just be
1371 /// instantiated to the placeholder region `'%a`, which is wrong because
1372 /// the inference variable is supposed to satisfy the relation
1373 /// *for every value of the placeholder region*. To ensure that doesn't
1374 /// happen, you can use `leak_check`. This is more clearly explained
1375 /// by the [rustc dev guide].
1377 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1378 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1379 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1380 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1381 pub enum RegionKind {
1382 /// Region bound in a type or fn declaration which will be
1383 /// substituted 'early' -- that is, at the same time when type
1384 /// parameters are substituted.
1385 ReEarlyBound(EarlyBoundRegion),
1387 /// Region bound in a function scope, which will be substituted when the
1388 /// function is called.
1389 ReLateBound(DebruijnIndex, BoundRegion),
1391 /// When checking a function body, the types of all arguments and so forth
1392 /// that refer to bound region parameters are modified to refer to free
1393 /// region parameters.
1396 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1399 /// A region variable. Should not exist after typeck.
1402 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1403 /// Should not exist after typeck.
1404 RePlaceholder(ty::PlaceholderRegion),
1406 /// Empty lifetime is for data that is never accessed. We tag the
1407 /// empty lifetime with a universe -- the idea is that we don't
1408 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1409 /// Therefore, the `'empty` in a universe `U` is less than all
1410 /// regions visible from `U`, but not less than regions not visible
1412 ReEmpty(ty::UniverseIndex),
1414 /// Erased region, used by trait selection, in MIR and during codegen.
1418 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1419 pub struct EarlyBoundRegion {
1425 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1430 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1431 pub struct ConstVid<'tcx> {
1433 pub phantom: PhantomData<&'tcx ()>,
1436 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1441 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1442 pub struct FloatVid {
1446 rustc_index::newtype_index! {
1447 pub struct RegionVid {
1448 DEBUG_FORMAT = custom,
1452 impl Atom for RegionVid {
1453 fn index(self) -> usize {
1458 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1459 #[derive(HashStable)]
1465 /// A `FreshTy` is one that is generated as a replacement for an
1466 /// unbound type variable. This is convenient for caching etc. See
1467 /// `infer::freshen` for more details.
1473 rustc_index::newtype_index! {
1474 pub struct BoundVar { .. }
1477 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1478 #[derive(HashStable)]
1479 pub struct BoundTy {
1481 pub kind: BoundTyKind,
1484 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1485 #[derive(HashStable)]
1486 pub enum BoundTyKind {
1491 impl From<BoundVar> for BoundTy {
1492 fn from(var: BoundVar) -> Self {
1493 BoundTy { var, kind: BoundTyKind::Anon }
1497 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1498 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1499 #[derive(HashStable, TypeFoldable)]
1500 pub struct ExistentialProjection<'tcx> {
1501 pub item_def_id: DefId,
1502 pub substs: SubstsRef<'tcx>,
1506 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1508 impl<'tcx> ExistentialProjection<'tcx> {
1509 /// Extracts the underlying existential trait reference from this projection.
1510 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1511 /// then this function would return a `exists T. T: Iterator` existential trait
1513 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1514 let def_id = tcx.associated_item(self.item_def_id).container.id();
1515 ty::ExistentialTraitRef { def_id, substs: self.substs }
1518 pub fn with_self_ty(
1522 ) -> ty::ProjectionPredicate<'tcx> {
1523 // otherwise the escaping regions would be captured by the binders
1524 debug_assert!(!self_ty.has_escaping_bound_vars());
1526 ty::ProjectionPredicate {
1527 projection_ty: ty::ProjectionTy {
1528 item_def_id: self.item_def_id,
1529 substs: tcx.mk_substs_trait(self_ty, self.substs),
1536 impl<'tcx> PolyExistentialProjection<'tcx> {
1537 pub fn with_self_ty(
1541 ) -> ty::PolyProjectionPredicate<'tcx> {
1542 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1545 pub fn item_def_id(&self) -> DefId {
1546 self.skip_binder().item_def_id
1550 impl DebruijnIndex {
1551 /// Returns the resulting index when this value is moved into
1552 /// `amount` number of new binders. So, e.g., if you had
1554 /// for<'a> fn(&'a x)
1556 /// and you wanted to change it to
1558 /// for<'a> fn(for<'b> fn(&'a x))
1560 /// you would need to shift the index for `'a` into a new binder.
1562 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1563 DebruijnIndex::from_u32(self.as_u32() + amount)
1566 /// Update this index in place by shifting it "in" through
1567 /// `amount` number of binders.
1568 pub fn shift_in(&mut self, amount: u32) {
1569 *self = self.shifted_in(amount);
1572 /// Returns the resulting index when this value is moved out from
1573 /// `amount` number of new binders.
1575 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1576 DebruijnIndex::from_u32(self.as_u32() - amount)
1579 /// Update in place by shifting out from `amount` binders.
1580 pub fn shift_out(&mut self, amount: u32) {
1581 *self = self.shifted_out(amount);
1584 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1585 /// innermost binder. That is, if we have something bound at `to_binder`,
1586 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1587 /// when moving a region out from inside binders:
1590 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1591 /// // Binder: D3 D2 D1 ^^
1594 /// Here, the region `'a` would have the De Bruijn index D3,
1595 /// because it is the bound 3 binders out. However, if we wanted
1596 /// to refer to that region `'a` in the second argument (the `_`),
1597 /// those two binders would not be in scope. In that case, we
1598 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1599 /// De Bruijn index of `'a` to D1 (the innermost binder).
1601 /// If we invoke `shift_out_to_binder` and the region is in fact
1602 /// bound by one of the binders we are shifting out of, that is an
1603 /// error (and should fail an assertion failure).
1604 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1605 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1609 /// Region utilities
1611 /// Is this region named by the user?
1612 pub fn has_name(&self) -> bool {
1614 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1615 RegionKind::ReLateBound(_, br) => br.is_named(),
1616 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1617 RegionKind::ReStatic => true,
1618 RegionKind::ReVar(..) => false,
1619 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1620 RegionKind::ReEmpty(_) => false,
1621 RegionKind::ReErased => false,
1625 pub fn is_late_bound(&self) -> bool {
1627 ty::ReLateBound(..) => true,
1632 pub fn is_placeholder(&self) -> bool {
1634 ty::RePlaceholder(..) => true,
1639 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1641 ty::ReLateBound(debruijn, _) => debruijn >= index,
1646 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1647 /// innermost binder. That is, if we have something bound at `to_binder`,
1648 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1649 /// when moving a region out from inside binders:
1652 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1653 /// // Binder: D3 D2 D1 ^^
1656 /// Here, the region `'a` would have the De Bruijn index D3,
1657 /// because it is the bound 3 binders out. However, if we wanted
1658 /// to refer to that region `'a` in the second argument (the `_`),
1659 /// those two binders would not be in scope. In that case, we
1660 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1661 /// De Bruijn index of `'a` to D1 (the innermost binder).
1663 /// If we invoke `shift_out_to_binder` and the region is in fact
1664 /// bound by one of the binders we are shifting out of, that is an
1665 /// error (and should fail an assertion failure).
1666 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1668 ty::ReLateBound(debruijn, r) => {
1669 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1675 pub fn type_flags(&self) -> TypeFlags {
1676 let mut flags = TypeFlags::empty();
1680 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1681 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1682 flags = flags | TypeFlags::HAS_RE_INFER;
1684 ty::RePlaceholder(..) => {
1685 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1686 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1687 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1689 ty::ReEarlyBound(..) => {
1690 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1691 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1692 flags = flags | TypeFlags::HAS_RE_PARAM;
1694 ty::ReFree { .. } => {
1695 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1696 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1698 ty::ReEmpty(_) | ty::ReStatic => {
1699 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1701 ty::ReLateBound(..) => {
1702 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1705 flags = flags | TypeFlags::HAS_RE_ERASED;
1709 debug!("type_flags({:?}) = {:?}", self, flags);
1714 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1715 /// For example, consider the regions in this snippet of code:
1719 /// ^^ -- early bound, declared on an impl
1721 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1722 /// ^^ ^^ ^ anonymous, late-bound
1723 /// | early-bound, appears in where-clauses
1724 /// late-bound, appears only in fn args
1729 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1730 /// of the impl, and for all the other highlighted regions, it
1731 /// would return the `DefId` of the function. In other cases (not shown), this
1732 /// function might return the `DefId` of a closure.
1733 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1735 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1736 ty::ReFree(fr) => fr.scope,
1737 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1743 impl<'tcx> TyS<'tcx> {
1745 pub fn is_unit(&self) -> bool {
1747 Tuple(ref tys) => tys.is_empty(),
1753 pub fn is_never(&self) -> bool {
1760 /// Checks whether a type is definitely uninhabited. This is
1761 /// conservative: for some types that are uninhabited we return `false`,
1762 /// but we only return `true` for types that are definitely uninhabited.
1763 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1764 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1765 /// size, to account for partial initialisation. See #49298 for details.)
1766 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1767 // FIXME(varkor): we can make this less conversative by substituting concrete
1771 ty::Adt(def, _) if def.is_union() => {
1772 // For now, `union`s are never considered uninhabited.
1775 ty::Adt(def, _) => {
1776 // Any ADT is uninhabited if either:
1777 // (a) It has no variants (i.e. an empty `enum`);
1778 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1779 // one uninhabited field.
1780 def.variants.iter().all(|var| {
1781 var.fields.iter().any(|field| {
1782 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1787 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1789 ty::Array(ty, len) => {
1790 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1791 // If the array is definitely non-empty, it's uninhabited if
1792 // the type of its elements is uninhabited.
1793 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1798 // References to uninitialised memory is valid for any type, including
1799 // uninhabited types, in unsafe code, so we treat all references as
1808 pub fn is_primitive(&self) -> bool {
1809 self.kind.is_primitive()
1813 pub fn is_ty_var(&self) -> bool {
1815 Infer(TyVar(_)) => true,
1821 pub fn is_ty_infer(&self) -> bool {
1829 pub fn is_phantom_data(&self) -> bool {
1830 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1834 pub fn is_bool(&self) -> bool {
1838 /// Returns `true` if this type is a `str`.
1840 pub fn is_str(&self) -> bool {
1845 pub fn is_param(&self, index: u32) -> bool {
1847 ty::Param(ref data) => data.index == index,
1853 pub fn is_slice(&self) -> bool {
1855 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1856 Slice(_) | Str => true,
1864 pub fn is_simd(&self) -> bool {
1866 Adt(def, _) => def.repr.simd(),
1871 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1873 Array(ty, _) | Slice(ty) => ty,
1874 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1875 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1879 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1881 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1882 _ => bug!("`simd_type` called on invalid type"),
1886 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1887 // Parameter currently unused, but probably needed in the future to
1888 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1890 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1891 _ => bug!("`simd_size` called on invalid type"),
1895 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1897 Adt(def, substs) => {
1898 let variant = def.non_enum_variant();
1899 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1901 _ => bug!("`simd_size_and_type` called on invalid type"),
1906 pub fn is_region_ptr(&self) -> bool {
1914 pub fn is_mutable_ptr(&self) -> bool {
1916 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1917 | Ref(_, _, hir::Mutability::Mut) => true,
1923 pub fn is_unsafe_ptr(&self) -> bool {
1930 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1932 pub fn is_any_ptr(&self) -> bool {
1933 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1937 pub fn is_box(&self) -> bool {
1939 Adt(def, _) => def.is_box(),
1944 /// Panics if called on any type other than `Box<T>`.
1945 pub fn boxed_ty(&self) -> Ty<'tcx> {
1947 Adt(def, substs) if def.is_box() => substs.type_at(0),
1948 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1952 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1953 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1954 /// contents are abstract to rustc.)
1956 pub fn is_scalar(&self) -> bool {
1963 | Infer(IntVar(_) | FloatVar(_))
1966 | RawPtr(_) => true,
1971 /// Returns `true` if this type is a floating point type.
1973 pub fn is_floating_point(&self) -> bool {
1975 Float(_) | Infer(FloatVar(_)) => true,
1981 pub fn is_trait(&self) -> bool {
1983 Dynamic(..) => true,
1989 pub fn is_enum(&self) -> bool {
1991 Adt(adt_def, _) => adt_def.is_enum(),
1997 pub fn is_closure(&self) -> bool {
1999 Closure(..) => true,
2005 pub fn is_generator(&self) -> bool {
2007 Generator(..) => true,
2013 pub fn is_integral(&self) -> bool {
2015 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
2021 pub fn is_fresh_ty(&self) -> bool {
2023 Infer(FreshTy(_)) => true,
2029 pub fn is_fresh(&self) -> bool {
2031 Infer(FreshTy(_)) => true,
2032 Infer(FreshIntTy(_)) => true,
2033 Infer(FreshFloatTy(_)) => true,
2039 pub fn is_char(&self) -> bool {
2047 pub fn is_numeric(&self) -> bool {
2048 self.is_integral() || self.is_floating_point()
2052 pub fn is_signed(&self) -> bool {
2060 pub fn is_ptr_sized_integral(&self) -> bool {
2062 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
2068 pub fn is_machine(&self) -> bool {
2070 Int(..) | Uint(..) | Float(..) => true,
2076 pub fn has_concrete_skeleton(&self) -> bool {
2078 Param(_) | Infer(_) | Error(_) => false,
2083 /// Returns the type and mutability of `*ty`.
2085 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2086 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2087 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2089 Adt(def, _) if def.is_box() => {
2090 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2092 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2093 RawPtr(mt) if explicit => Some(mt),
2098 /// Returns the type of `ty[i]`.
2099 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2101 Array(ty, _) | Slice(ty) => Some(ty),
2106 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2108 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2111 // ignore errors (#54954)
2112 ty::Binder::dummy(FnSig::fake())
2114 Closure(..) => bug!(
2115 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2117 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2122 pub fn is_fn(&self) -> bool {
2124 FnDef(..) | FnPtr(_) => true,
2130 pub fn is_fn_ptr(&self) -> bool {
2138 pub fn is_impl_trait(&self) -> bool {
2146 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2148 Adt(adt, _) => Some(adt),
2153 /// Iterates over tuple fields.
2154 /// Panics when called on anything but a tuple.
2155 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2157 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2158 _ => bug!("tuple_fields called on non-tuple"),
2162 /// If the type contains variants, returns the valid range of variant indices.
2164 // FIXME: This requires the optimized MIR in the case of generators.
2166 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2168 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2169 TyKind::Generator(def_id, substs, _) => {
2170 Some(substs.as_generator().variant_range(def_id, tcx))
2176 /// If the type contains variants, returns the variant for `variant_index`.
2177 /// Panics if `variant_index` is out of range.
2179 // FIXME: This requires the optimized MIR in the case of generators.
2181 pub fn discriminant_for_variant(
2184 variant_index: VariantIdx,
2185 ) -> Option<Discr<'tcx>> {
2187 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2188 bug!("discriminant_for_variant called on zero variant enum");
2190 TyKind::Adt(adt, _) if adt.is_enum() => {
2191 Some(adt.discriminant_for_variant(tcx, variant_index))
2193 TyKind::Generator(def_id, substs, _) => {
2194 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2200 /// Returns the type of the discriminant of this type.
2201 pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2203 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2204 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2206 // This can only be `0`, for now, so `u8` will suffice.
2212 /// When we create a closure, we record its kind (i.e., what trait
2213 /// it implements) into its `ClosureSubsts` using a type
2214 /// parameter. This is kind of a phantom type, except that the
2215 /// most convenient thing for us to are the integral types. This
2216 /// function converts such a special type into the closure
2217 /// kind. To go the other way, use
2218 /// `tcx.closure_kind_ty(closure_kind)`.
2220 /// Note that during type checking, we use an inference variable
2221 /// to represent the closure kind, because it has not yet been
2222 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2223 /// is complete, that type variable will be unified.
2224 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2226 Int(int_ty) => match int_ty {
2227 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2228 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2229 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2230 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2233 // "Bound" types appear in canonical queries when the
2234 // closure type is not yet known
2235 Bound(..) | Infer(_) => None,
2237 Error(_) => Some(ty::ClosureKind::Fn),
2239 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2243 /// Fast path helper for testing if a type is `Sized`.
2245 /// Returning true means the type is known to be sized. Returning
2246 /// `false` means nothing -- could be sized, might not be.
2247 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2249 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2260 | ty::GeneratorWitness(..)
2264 | ty::Error(_) => true,
2266 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2268 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2270 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2272 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2274 ty::Infer(ty::TyVar(_)) => false,
2277 | ty::Placeholder(..)
2278 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2279 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2284 /// Is this a zero-sized type?
2285 pub fn is_zst(&'tcx self, tcx: TyCtxt<'tcx>, did: DefId) -> bool {
2286 tcx.layout_of(tcx.param_env(did).and(self)).map(|layout| layout.is_zst()).unwrap_or(false)