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::{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, RustcEncodable, RustcDecodable)]
31 #[derive(HashStable, TypeFoldable, Lift)]
32 pub struct TypeAndMut<'tcx> {
34 pub mutbl: hir::Mutability,
37 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable, RustcDecodable, 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, RustcEncodable, RustcDecodable, 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, RustcEncodable, RustcDecodable, 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 /// A type that is not publicly constructable. This prevents people from making `TyKind::Error`
216 /// except through `tcx.err*()`.
217 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
218 #[derive(RustcEncodable, RustcDecodable, HashStable)]
219 pub struct DelaySpanBugEmitted(pub(super) ());
221 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
222 #[cfg(target_arch = "x86_64")]
223 static_assert_size!(TyKind<'_>, 24);
225 /// A closure can be modeled as a struct that looks like:
227 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
231 /// - 'l0...'li and T0...Tj are the generic parameters
232 /// in scope on the function that defined the closure,
233 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
234 /// is rather hackily encoded via a scalar type. See
235 /// `TyS::to_opt_closure_kind` for details.
236 /// - CS represents the *closure signature*, representing as a `fn()`
237 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
238 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
240 /// - U is a type parameter representing the types of its upvars, tupled up
241 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
242 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
244 /// So, for example, given this function:
246 /// fn foo<'a, T>(data: &'a mut T) {
247 /// do(|| data.count += 1)
250 /// the type of the closure would be something like:
252 /// struct Closure<'a, T, U>(...U);
254 /// Note that the type of the upvar is not specified in the struct.
255 /// You may wonder how the impl would then be able to use the upvar,
256 /// if it doesn't know it's type? The answer is that the impl is
257 /// (conceptually) not fully generic over Closure but rather tied to
258 /// instances with the expected upvar types:
260 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
264 /// You can see that the *impl* fully specified the type of the upvar
265 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
266 /// (Here, I am assuming that `data` is mut-borrowed.)
268 /// Now, the last question you may ask is: Why include the upvar types
269 /// in an extra type parameter? The reason for this design is that the
270 /// upvar types can reference lifetimes that are internal to the
271 /// creating function. In my example above, for example, the lifetime
272 /// `'b` represents the scope of the closure itself; this is some
273 /// subset of `foo`, probably just the scope of the call to the to
274 /// `do()`. If we just had the lifetime/type parameters from the
275 /// enclosing function, we couldn't name this lifetime `'b`. Note that
276 /// there can also be lifetimes in the types of the upvars themselves,
277 /// if one of them happens to be a reference to something that the
278 /// creating fn owns.
280 /// OK, you say, so why not create a more minimal set of parameters
281 /// that just includes the extra lifetime parameters? The answer is
282 /// primarily that it would be hard --- we don't know at the time when
283 /// we create the closure type what the full types of the upvars are,
284 /// nor do we know which are borrowed and which are not. In this
285 /// design, we can just supply a fresh type parameter and figure that
288 /// All right, you say, but why include the type parameters from the
289 /// original function then? The answer is that codegen may need them
290 /// when monomorphizing, and they may not appear in the upvars. A
291 /// closure could capture no variables but still make use of some
292 /// in-scope type parameter with a bound (e.g., if our example above
293 /// had an extra `U: Default`, and the closure called `U::default()`).
295 /// There is another reason. This design (implicitly) prohibits
296 /// closures from capturing themselves (except via a trait
297 /// object). This simplifies closure inference considerably, since it
298 /// means that when we infer the kind of a closure or its upvars, we
299 /// don't have to handle cycles where the decisions we make for
300 /// closure C wind up influencing the decisions we ought to make for
301 /// closure C (which would then require fixed point iteration to
302 /// handle). Plus it fixes an ICE. :P
306 /// Generators are handled similarly in `GeneratorSubsts`. The set of
307 /// type parameters is similar, but `CK` and `CS` are replaced by the
308 /// following type parameters:
310 /// * `GS`: The generator's "resume type", which is the type of the
311 /// argument passed to `resume`, and the type of `yield` expressions
312 /// inside the generator.
313 /// * `GY`: The "yield type", which is the type of values passed to
314 /// `yield` inside the generator.
315 /// * `GR`: The "return type", which is the type of value returned upon
316 /// completion of the generator.
317 /// * `GW`: The "generator witness".
318 #[derive(Copy, Clone, Debug, TypeFoldable)]
319 pub struct ClosureSubsts<'tcx> {
320 /// Lifetime and type parameters from the enclosing function,
321 /// concatenated with a tuple containing the types of the upvars.
323 /// These are separated out because codegen wants to pass them around
324 /// when monomorphizing.
325 pub substs: SubstsRef<'tcx>,
328 /// Struct returned by `split()`. Note that these are subslices of the
329 /// parent slice and not canonical substs themselves.
330 struct SplitClosureSubsts<'tcx> {
331 parent: &'tcx [GenericArg<'tcx>],
332 closure_kind_ty: GenericArg<'tcx>,
333 closure_sig_as_fn_ptr_ty: GenericArg<'tcx>,
334 tupled_upvars_ty: GenericArg<'tcx>,
337 impl<'tcx> ClosureSubsts<'tcx> {
338 /// Divides the closure substs into their respective
339 /// components. Single source of truth with respect to the
341 fn split(self) -> SplitClosureSubsts<'tcx> {
342 match self.substs[..] {
343 [ref parent @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
347 closure_sig_as_fn_ptr_ty,
351 _ => bug!("closure substs missing synthetics"),
355 /// Returns `true` only if enough of the synthetic types are known to
356 /// allow using all of the methods on `ClosureSubsts` without panicking.
358 /// Used primarily by `ty::print::pretty` to be able to handle closure
359 /// types that haven't had their synthetic types substituted in.
360 pub fn is_valid(self) -> bool {
361 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
364 /// Returns the substitutions of the closure's parent.
365 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
370 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
371 self.tupled_upvars_ty().tuple_fields()
374 /// Returns the tuple type representing the upvars for this closure.
376 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
377 self.split().tupled_upvars_ty.expect_ty()
380 /// Returns the closure kind for this closure; may return a type
381 /// variable during inference. To get the closure kind during
382 /// inference, use `infcx.closure_kind(substs)`.
383 pub fn kind_ty(self) -> Ty<'tcx> {
384 self.split().closure_kind_ty.expect_ty()
387 /// Returns the `fn` pointer type representing the closure signature for this
389 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
390 // type is known at the time of the creation of `ClosureSubsts`,
391 // see `rustc_typeck::check::closure`.
392 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
393 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
396 /// Returns the closure kind for this closure; only usable outside
397 /// of an inference context, because in that context we know that
398 /// there are no type variables.
400 /// If you have an inference context, use `infcx.closure_kind()`.
401 pub fn kind(self) -> ty::ClosureKind {
402 self.kind_ty().to_opt_closure_kind().unwrap()
405 /// Extracts the signature from the closure.
406 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
407 let ty = self.sig_as_fn_ptr_ty();
409 ty::FnPtr(sig) => sig,
410 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
415 /// Similar to `ClosureSubsts`; see the above documentation for more.
416 #[derive(Copy, Clone, Debug, TypeFoldable)]
417 pub struct GeneratorSubsts<'tcx> {
418 pub substs: SubstsRef<'tcx>,
421 struct SplitGeneratorSubsts<'tcx> {
422 parent: &'tcx [GenericArg<'tcx>],
423 resume_ty: GenericArg<'tcx>,
424 yield_ty: GenericArg<'tcx>,
425 return_ty: GenericArg<'tcx>,
426 witness: GenericArg<'tcx>,
427 tupled_upvars_ty: GenericArg<'tcx>,
430 impl<'tcx> GeneratorSubsts<'tcx> {
431 fn split(self) -> SplitGeneratorSubsts<'tcx> {
432 match self.substs[..] {
433 [ref parent @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
434 SplitGeneratorSubsts {
443 _ => bug!("generator substs missing synthetics"),
447 /// Returns `true` only if enough of the synthetic types are known to
448 /// allow using all of the methods on `GeneratorSubsts` without panicking.
450 /// Used primarily by `ty::print::pretty` to be able to handle generator
451 /// types that haven't had their synthetic types substituted in.
452 pub fn is_valid(self) -> bool {
453 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
456 /// Returns the substitutions of the generator's parent.
457 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
461 /// This describes the types that can be contained in a generator.
462 /// It will be a type variable initially and unified in the last stages of typeck of a body.
463 /// It contains a tuple of all the types that could end up on a generator frame.
464 /// The state transformation MIR pass may only produce layouts which mention types
465 /// in this tuple. Upvars are not counted here.
466 pub fn witness(self) -> Ty<'tcx> {
467 self.split().witness.expect_ty()
471 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
472 self.tupled_upvars_ty().tuple_fields()
475 /// Returns the tuple type representing the upvars for this generator.
477 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
478 self.split().tupled_upvars_ty.expect_ty()
481 /// Returns the type representing the resume type of the generator.
482 pub fn resume_ty(self) -> Ty<'tcx> {
483 self.split().resume_ty.expect_ty()
486 /// Returns the type representing the yield type of the generator.
487 pub fn yield_ty(self) -> Ty<'tcx> {
488 self.split().yield_ty.expect_ty()
491 /// Returns the type representing the return type of the generator.
492 pub fn return_ty(self) -> Ty<'tcx> {
493 self.split().return_ty.expect_ty()
496 /// Returns the "generator signature", which consists of its yield
497 /// and return types.
499 /// N.B., some bits of the code prefers to see this wrapped in a
500 /// binder, but it never contains bound regions. Probably this
501 /// function should be removed.
502 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
503 ty::Binder::dummy(self.sig())
506 /// Returns the "generator signature", which consists of its resume, yield
507 /// and return types.
508 pub fn sig(self) -> GenSig<'tcx> {
510 resume_ty: self.resume_ty(),
511 yield_ty: self.yield_ty(),
512 return_ty: self.return_ty(),
517 impl<'tcx> GeneratorSubsts<'tcx> {
518 /// Generator has not been resumed yet.
519 pub const UNRESUMED: usize = 0;
520 /// Generator has returned or is completed.
521 pub const RETURNED: usize = 1;
522 /// Generator has been poisoned.
523 pub const POISONED: usize = 2;
525 const UNRESUMED_NAME: &'static str = "Unresumed";
526 const RETURNED_NAME: &'static str = "Returned";
527 const POISONED_NAME: &'static str = "Panicked";
529 /// The valid variant indices of this generator.
531 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
532 // FIXME requires optimized MIR
533 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
534 VariantIdx::new(0)..VariantIdx::new(num_variants)
537 /// The discriminant for the given variant. Panics if the `variant_index` is
540 pub fn discriminant_for_variant(
544 variant_index: VariantIdx,
546 // Generators don't support explicit discriminant values, so they are
547 // the same as the variant index.
548 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
549 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
552 /// The set of all discriminants for the generator, enumerated with their
555 pub fn discriminants(
559 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
560 self.variant_range(def_id, tcx).map(move |index| {
561 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
565 /// Calls `f` with a reference to the name of the enumerator for the given
567 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
569 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
570 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
571 Self::POISONED => Cow::from(Self::POISONED_NAME),
572 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
576 /// The type of the state discriminant used in the generator type.
578 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
582 /// This returns the types of the MIR locals which had to be stored across suspension points.
583 /// It is calculated in rustc_mir::transform::generator::StateTransform.
584 /// All the types here must be in the tuple in GeneratorInterior.
586 /// The locals are grouped by their variant number. Note that some locals may
587 /// be repeated in multiple variants.
593 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
594 let layout = tcx.generator_layout(def_id);
595 layout.variant_fields.iter().map(move |variant| {
596 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
600 /// This is the types of the fields of a generator which are not stored in a
603 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
608 #[derive(Debug, Copy, Clone)]
609 pub enum UpvarSubsts<'tcx> {
610 Closure(SubstsRef<'tcx>),
611 Generator(SubstsRef<'tcx>),
614 impl<'tcx> UpvarSubsts<'tcx> {
616 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
617 let tupled_upvars_ty = match self {
618 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
619 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
621 tupled_upvars_ty.expect_ty().tuple_fields()
625 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, RustcEncodable, RustcDecodable)]
626 #[derive(HashStable, TypeFoldable)]
627 pub enum ExistentialPredicate<'tcx> {
628 /// E.g., `Iterator`.
629 Trait(ExistentialTraitRef<'tcx>),
630 /// E.g., `Iterator::Item = T`.
631 Projection(ExistentialProjection<'tcx>),
636 impl<'tcx> ExistentialPredicate<'tcx> {
637 /// Compares via an ordering that will not change if modules are reordered or other changes are
638 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
639 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
640 use self::ExistentialPredicate::*;
641 match (*self, *other) {
642 (Trait(_), Trait(_)) => Ordering::Equal,
643 (Projection(ref a), Projection(ref b)) => {
644 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
646 (AutoTrait(ref a), AutoTrait(ref b)) => {
647 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
649 (Trait(_), _) => Ordering::Less,
650 (Projection(_), Trait(_)) => Ordering::Greater,
651 (Projection(_), _) => Ordering::Less,
652 (AutoTrait(_), _) => Ordering::Greater,
657 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
658 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
659 use crate::ty::ToPredicate;
660 match self.skip_binder() {
661 ExistentialPredicate::Trait(tr) => {
662 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
664 ExistentialPredicate::Projection(p) => {
665 Binder(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
667 ExistentialPredicate::AutoTrait(did) => {
669 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
670 trait_ref.without_const().to_predicate(tcx)
676 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx List<ExistentialPredicate<'tcx>> {}
678 impl<'tcx> List<ExistentialPredicate<'tcx>> {
679 /// Returns the "principal `DefId`" of this set of existential predicates.
681 /// A Rust trait object type consists (in addition to a lifetime bound)
682 /// of a set of trait bounds, which are separated into any number
683 /// of auto-trait bounds, and at most one non-auto-trait bound. The
684 /// non-auto-trait bound is called the "principal" of the trait
687 /// Only the principal can have methods or type parameters (because
688 /// auto traits can have neither of them). This is important, because
689 /// it means the auto traits can be treated as an unordered set (methods
690 /// would force an order for the vtable, while relating traits with
691 /// type parameters without knowing the order to relate them in is
692 /// a rather non-trivial task).
694 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
695 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
696 /// are the set `{Sync}`.
698 /// It is also possible to have a "trivial" trait object that
699 /// consists only of auto traits, with no principal - for example,
700 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
701 /// is `{Send, Sync}`, while there is no principal. These trait objects
702 /// have a "trivial" vtable consisting of just the size, alignment,
704 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
706 ExistentialPredicate::Trait(tr) => Some(tr),
711 pub fn principal_def_id(&self) -> Option<DefId> {
712 self.principal().map(|trait_ref| trait_ref.def_id)
716 pub fn projection_bounds<'a>(
718 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
719 self.iter().filter_map(|predicate| match predicate {
720 ExistentialPredicate::Projection(projection) => Some(projection),
726 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
727 self.iter().filter_map(|predicate| match predicate {
728 ExistentialPredicate::AutoTrait(did) => Some(did),
734 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
735 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
736 self.skip_binder().principal().map(Binder::bind)
739 pub fn principal_def_id(&self) -> Option<DefId> {
740 self.skip_binder().principal_def_id()
744 pub fn projection_bounds<'a>(
746 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
747 self.skip_binder().projection_bounds().map(Binder::bind)
751 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
752 self.skip_binder().auto_traits()
757 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
758 self.skip_binder().iter().map(Binder::bind)
762 /// A complete reference to a trait. These take numerous guises in syntax,
763 /// but perhaps the most recognizable form is in a where-clause:
767 /// This would be represented by a trait-reference where the `DefId` is the
768 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
769 /// and `U` as parameter 1.
771 /// Trait references also appear in object types like `Foo<U>`, but in
772 /// that case the `Self` parameter is absent from the substitutions.
773 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
774 #[derive(HashStable, TypeFoldable)]
775 pub struct TraitRef<'tcx> {
777 pub substs: SubstsRef<'tcx>,
780 impl<'tcx> TraitRef<'tcx> {
781 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
782 TraitRef { def_id, substs }
785 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
786 /// are the parameters defined on trait.
787 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
788 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
792 pub fn self_ty(&self) -> Ty<'tcx> {
793 self.substs.type_at(0)
799 substs: SubstsRef<'tcx>,
800 ) -> ty::TraitRef<'tcx> {
801 let defs = tcx.generics_of(trait_id);
803 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
807 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
809 impl<'tcx> PolyTraitRef<'tcx> {
810 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
811 self.map_bound_ref(|tr| tr.self_ty())
814 pub fn def_id(&self) -> DefId {
815 self.skip_binder().def_id
818 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
819 // Note that we preserve binding levels
820 Binder(ty::TraitPredicate { trait_ref: self.skip_binder() })
824 /// An existential reference to a trait, where `Self` is erased.
825 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
827 /// exists T. T: Trait<'a, 'b, X, Y>
829 /// The substitutions don't include the erased `Self`, only trait
830 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
831 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
832 #[derive(HashStable, TypeFoldable)]
833 pub struct ExistentialTraitRef<'tcx> {
835 pub substs: SubstsRef<'tcx>,
838 impl<'tcx> ExistentialTraitRef<'tcx> {
839 pub fn erase_self_ty(
841 trait_ref: ty::TraitRef<'tcx>,
842 ) -> ty::ExistentialTraitRef<'tcx> {
843 // Assert there is a Self.
844 trait_ref.substs.type_at(0);
846 ty::ExistentialTraitRef {
847 def_id: trait_ref.def_id,
848 substs: tcx.intern_substs(&trait_ref.substs[1..]),
852 /// Object types don't have a self type specified. Therefore, when
853 /// we convert the principal trait-ref into a normal trait-ref,
854 /// you must give *some* self type. A common choice is `mk_err()`
855 /// or some placeholder type.
856 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
857 // otherwise the escaping vars would be captured by the binder
858 // debug_assert!(!self_ty.has_escaping_bound_vars());
860 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
864 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
866 impl<'tcx> PolyExistentialTraitRef<'tcx> {
867 pub fn def_id(&self) -> DefId {
868 self.skip_binder().def_id
871 /// Object types don't have a self type specified. Therefore, when
872 /// we convert the principal trait-ref into a normal trait-ref,
873 /// you must give *some* self type. A common choice is `mk_err()`
874 /// or some placeholder type.
875 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
876 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
880 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
881 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
882 /// (which would be represented by the type `PolyTraitRef ==
883 /// Binder<TraitRef>`). Note that when we instantiate,
884 /// erase, or otherwise "discharge" these bound vars, we change the
885 /// type from `Binder<T>` to just `T` (see
886 /// e.g., `liberate_late_bound_regions`).
887 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
888 pub struct Binder<T>(T);
891 /// Wraps `value` in a binder, asserting that `value` does not
892 /// contain any bound vars that would be bound by the
893 /// binder. This is commonly used to 'inject' a value T into a
894 /// different binding level.
895 pub fn dummy<'tcx>(value: T) -> Binder<T>
897 T: TypeFoldable<'tcx>,
899 debug_assert!(!value.has_escaping_bound_vars());
903 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
904 pub fn bind(value: T) -> Binder<T> {
908 /// Wraps `value` in a binder without actually binding any currently
909 /// unbound variables.
911 /// Note that this will shift all debrujin indices of escaping bound variables
912 /// by 1 to avoid accidential captures.
913 pub fn wrap_nonbinding(tcx: TyCtxt<'tcx>, value: T) -> Binder<T>
915 T: TypeFoldable<'tcx>,
917 if value.has_escaping_bound_vars() {
918 Binder::bind(super::fold::shift_vars(tcx, &value, 1))
924 /// Skips the binder and returns the "bound" value. This is a
925 /// risky thing to do because it's easy to get confused about
926 /// De Bruijn indices and the like. It is usually better to
927 /// discharge the binder using `no_bound_vars` or
928 /// `replace_late_bound_regions` or something like
929 /// that. `skip_binder` is only valid when you are either
930 /// extracting data that has nothing to do with bound vars, you
931 /// are doing some sort of test that does not involve bound
932 /// regions, or you are being very careful about your depth
935 /// Some examples where `skip_binder` is reasonable:
937 /// - extracting the `DefId` from a PolyTraitRef;
938 /// - comparing the self type of a PolyTraitRef to see if it is equal to
939 /// a type parameter `X`, since the type `X` does not reference any regions
940 pub fn skip_binder(self) -> T {
944 pub fn as_ref(&self) -> Binder<&T> {
948 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
952 self.as_ref().map_bound(f)
955 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
962 /// Unwraps and returns the value within, but only if it contains
963 /// no bound vars at all. (In other words, if this binder --
964 /// and indeed any enclosing binder -- doesn't bind anything at
965 /// all.) Otherwise, returns `None`.
967 /// (One could imagine having a method that just unwraps a single
968 /// binder, but permits late-bound vars bound by enclosing
969 /// binders, but that would require adjusting the debruijn
970 /// indices, and given the shallow binding structure we often use,
971 /// would not be that useful.)
972 pub fn no_bound_vars<'tcx>(self) -> Option<T>
974 T: TypeFoldable<'tcx>,
976 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
979 /// Given two things that have the same binder level,
980 /// and an operation that wraps on their contents, executes the operation
981 /// and then wraps its result.
983 /// `f` should consider bound regions at depth 1 to be free, and
984 /// anything it produces with bound regions at depth 1 will be
985 /// bound in the resulting return value.
986 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
988 F: FnOnce(T, U) -> R,
990 Binder(f(self.0, u.0))
993 /// Splits the contents into two things that share the same binder
994 /// level as the original, returning two distinct binders.
996 /// `f` should consider bound regions at depth 1 to be free, and
997 /// anything it produces with bound regions at depth 1 will be
998 /// bound in the resulting return values.
999 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
1001 F: FnOnce(T) -> (U, V),
1003 let (u, v) = f(self.0);
1004 (Binder(u), Binder(v))
1008 impl<T> Binder<Option<T>> {
1009 pub fn transpose(self) -> Option<Binder<T>> {
1011 Some(v) => Some(Binder(v)),
1017 /// Represents the projection of an associated type. In explicit UFCS
1018 /// form this would be written `<T as Trait<..>>::N`.
1019 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1020 #[derive(HashStable, TypeFoldable)]
1021 pub struct ProjectionTy<'tcx> {
1022 /// The parameters of the associated item.
1023 pub substs: SubstsRef<'tcx>,
1025 /// The `DefId` of the `TraitItem` for the associated type `N`.
1027 /// Note that this is not the `DefId` of the `TraitRef` containing this
1028 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1029 pub item_def_id: DefId,
1032 impl<'tcx> ProjectionTy<'tcx> {
1033 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
1034 /// associated item named `item_name`.
1035 pub fn from_ref_and_name(
1037 trait_ref: ty::TraitRef<'tcx>,
1039 ) -> ProjectionTy<'tcx> {
1040 let item_def_id = tcx
1041 .associated_items(trait_ref.def_id)
1042 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1046 ProjectionTy { substs: trait_ref.substs, item_def_id }
1049 /// Extracts the underlying trait reference from this projection.
1050 /// For example, if this is a projection of `<T as Iterator>::Item`,
1051 /// then this function would return a `T: Iterator` trait reference.
1052 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1053 let def_id = tcx.associated_item(self.item_def_id).container.id();
1054 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1057 pub fn self_ty(&self) -> Ty<'tcx> {
1058 self.substs.type_at(0)
1062 #[derive(Copy, Clone, Debug, TypeFoldable)]
1063 pub struct GenSig<'tcx> {
1064 pub resume_ty: Ty<'tcx>,
1065 pub yield_ty: Ty<'tcx>,
1066 pub return_ty: Ty<'tcx>,
1069 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1071 impl<'tcx> PolyGenSig<'tcx> {
1072 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1073 self.map_bound_ref(|sig| sig.resume_ty)
1075 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1076 self.map_bound_ref(|sig| sig.yield_ty)
1078 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1079 self.map_bound_ref(|sig| sig.return_ty)
1083 /// Signature of a function type, which we have arbitrarily
1084 /// decided to use to refer to the input/output types.
1086 /// - `inputs`: is the list of arguments and their modes.
1087 /// - `output`: is the return type.
1088 /// - `c_variadic`: indicates whether this is a C-variadic function.
1089 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1090 #[derive(HashStable, TypeFoldable)]
1091 pub struct FnSig<'tcx> {
1092 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1093 pub c_variadic: bool,
1094 pub unsafety: hir::Unsafety,
1098 impl<'tcx> FnSig<'tcx> {
1099 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1100 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1103 pub fn output(&self) -> Ty<'tcx> {
1104 self.inputs_and_output[self.inputs_and_output.len() - 1]
1107 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1109 fn fake() -> FnSig<'tcx> {
1111 inputs_and_output: List::empty(),
1113 unsafety: hir::Unsafety::Normal,
1114 abi: abi::Abi::Rust,
1119 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1121 impl<'tcx> PolyFnSig<'tcx> {
1123 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1124 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1127 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1128 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1130 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1131 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1134 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1135 self.map_bound_ref(|fn_sig| fn_sig.output())
1137 pub fn c_variadic(&self) -> bool {
1138 self.skip_binder().c_variadic
1140 pub fn unsafety(&self) -> hir::Unsafety {
1141 self.skip_binder().unsafety
1143 pub fn abi(&self) -> abi::Abi {
1144 self.skip_binder().abi
1148 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1150 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1151 #[derive(HashStable)]
1152 pub struct ParamTy {
1157 impl<'tcx> ParamTy {
1158 pub fn new(index: u32, name: Symbol) -> ParamTy {
1159 ParamTy { index, name }
1162 pub fn for_self() -> ParamTy {
1163 ParamTy::new(0, kw::SelfUpper)
1166 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1167 ParamTy::new(def.index, def.name)
1170 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1171 tcx.mk_ty_param(self.index, self.name)
1175 #[derive(Copy, Clone, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
1176 #[derive(HashStable)]
1177 pub struct ParamConst {
1182 impl<'tcx> ParamConst {
1183 pub fn new(index: u32, name: Symbol) -> ParamConst {
1184 ParamConst { index, name }
1187 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1188 ParamConst::new(def.index, def.name)
1191 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
1192 tcx.mk_const_param(self.index, self.name, ty)
1196 rustc_index::newtype_index! {
1197 /// A [De Bruijn index][dbi] is a standard means of representing
1198 /// regions (and perhaps later types) in a higher-ranked setting. In
1199 /// particular, imagine a type like this:
1201 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1204 /// | +------------+ 0 | |
1206 /// +--------------------------------+ 1 |
1208 /// +------------------------------------------+ 0
1210 /// In this type, there are two binders (the outer fn and the inner
1211 /// fn). We need to be able to determine, for any given region, which
1212 /// fn type it is bound by, the inner or the outer one. There are
1213 /// various ways you can do this, but a De Bruijn index is one of the
1214 /// more convenient and has some nice properties. The basic idea is to
1215 /// count the number of binders, inside out. Some examples should help
1216 /// clarify what I mean.
1218 /// Let's start with the reference type `&'b isize` that is the first
1219 /// argument to the inner function. This region `'b` is assigned a De
1220 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1221 /// fn). The region `'a` that appears in the second argument type (`&'a
1222 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1223 /// second-innermost binder". (These indices are written on the arrays
1224 /// in the diagram).
1226 /// What is interesting is that De Bruijn index attached to a particular
1227 /// variable will vary depending on where it appears. For example,
1228 /// the final type `&'a char` also refers to the region `'a` declared on
1229 /// the outermost fn. But this time, this reference is not nested within
1230 /// any other binders (i.e., it is not an argument to the inner fn, but
1231 /// rather the outer one). Therefore, in this case, it is assigned a
1232 /// De Bruijn index of 0, because the innermost binder in that location
1233 /// is the outer fn.
1235 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1236 #[derive(HashStable)]
1237 pub struct DebruijnIndex {
1238 DEBUG_FORMAT = "DebruijnIndex({})",
1239 const INNERMOST = 0,
1243 pub type Region<'tcx> = &'tcx RegionKind;
1245 /// Representation of regions. Note that the NLL checker uses a distinct
1246 /// representation of regions. For this reason, it internally replaces all the
1247 /// regions with inference variables -- the index of the variable is then used
1248 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1249 /// module for more information.
1251 /// ## The Region lattice within a given function
1253 /// In general, the region lattice looks like
1256 /// static ----------+-----...------+ (greatest)
1258 /// early-bound and | |
1259 /// free regions | |
1262 /// empty(root) placeholder(U1) |
1264 /// | / placeholder(Un)
1269 /// empty(Un) -------- (smallest)
1272 /// Early-bound/free regions are the named lifetimes in scope from the
1273 /// function declaration. They have relationships to one another
1274 /// determined based on the declared relationships from the
1277 /// Note that inference variables and bound regions are not included
1278 /// in this diagram. In the case of inference variables, they should
1279 /// be inferred to some other region from the diagram. In the case of
1280 /// bound regions, they are excluded because they don't make sense to
1281 /// include -- the diagram indicates the relationship between free
1284 /// ## Inference variables
1286 /// During region inference, we sometimes create inference variables,
1287 /// represented as `ReVar`. These will be inferred by the code in
1288 /// `infer::lexical_region_resolve` to some free region from the
1289 /// lattice above (the minimal region that meets the
1292 /// During NLL checking, where regions are defined differently, we
1293 /// also use `ReVar` -- in that case, the index is used to index into
1294 /// the NLL region checker's data structures. The variable may in fact
1295 /// represent either a free region or an inference variable, in that
1298 /// ## Bound Regions
1300 /// These are regions that are stored behind a binder and must be substituted
1301 /// with some concrete region before being used. There are two kind of
1302 /// bound regions: early-bound, which are bound in an item's `Generics`,
1303 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1304 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1305 /// the likes of `liberate_late_bound_regions`. The distinction exists
1306 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1308 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1309 /// outside their binder, e.g., in types passed to type inference, and
1310 /// should first be substituted (by placeholder regions, free regions,
1311 /// or region variables).
1313 /// ## Placeholder and Free Regions
1315 /// One often wants to work with bound regions without knowing their precise
1316 /// identity. For example, when checking a function, the lifetime of a borrow
1317 /// can end up being assigned to some region parameter. In these cases,
1318 /// it must be ensured that bounds on the region can't be accidentally
1319 /// assumed without being checked.
1321 /// To do this, we replace the bound regions with placeholder markers,
1322 /// which don't satisfy any relation not explicitly provided.
1324 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1325 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1326 /// to be used. These also support explicit bounds: both the internally-stored
1327 /// *scope*, which the region is assumed to outlive, as well as other
1328 /// relations stored in the `FreeRegionMap`. Note that these relations
1329 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1330 /// `resolve_regions_and_report_errors`.
1332 /// When working with higher-ranked types, some region relations aren't
1333 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1334 /// `RePlaceholder` is designed for this purpose. In these contexts,
1335 /// there's also the risk that some inference variable laying around will
1336 /// get unified with your placeholder region: if you want to check whether
1337 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1338 /// with a placeholder region `'%a`, the variable `'_` would just be
1339 /// instantiated to the placeholder region `'%a`, which is wrong because
1340 /// the inference variable is supposed to satisfy the relation
1341 /// *for every value of the placeholder region*. To ensure that doesn't
1342 /// happen, you can use `leak_check`. This is more clearly explained
1343 /// by the [rustc dev guide].
1345 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1346 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1347 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1348 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable, PartialOrd, Ord)]
1349 pub enum RegionKind {
1350 /// Region bound in a type or fn declaration which will be
1351 /// substituted 'early' -- that is, at the same time when type
1352 /// parameters are substituted.
1353 ReEarlyBound(EarlyBoundRegion),
1355 /// Region bound in a function scope, which will be substituted when the
1356 /// function is called.
1357 ReLateBound(DebruijnIndex, BoundRegion),
1359 /// When checking a function body, the types of all arguments and so forth
1360 /// that refer to bound region parameters are modified to refer to free
1361 /// region parameters.
1364 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1367 /// A region variable. Should not exist after typeck.
1370 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1371 /// Should not exist after typeck.
1372 RePlaceholder(ty::PlaceholderRegion),
1374 /// Empty lifetime is for data that is never accessed. We tag the
1375 /// empty lifetime with a universe -- the idea is that we don't
1376 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1377 /// Therefore, the `'empty` in a universe `U` is less than all
1378 /// regions visible from `U`, but not less than regions not visible
1380 ReEmpty(ty::UniverseIndex),
1382 /// Erased region, used by trait selection, in MIR and during codegen.
1386 impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
1388 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, PartialOrd, Ord)]
1389 pub struct EarlyBoundRegion {
1395 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1400 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1401 pub struct ConstVid<'tcx> {
1403 pub phantom: PhantomData<&'tcx ()>,
1406 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1411 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1412 pub struct FloatVid {
1416 rustc_index::newtype_index! {
1417 pub struct RegionVid {
1418 DEBUG_FORMAT = custom,
1422 impl Atom for RegionVid {
1423 fn index(self) -> usize {
1428 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1429 #[derive(HashStable)]
1435 /// A `FreshTy` is one that is generated as a replacement for an
1436 /// unbound type variable. This is convenient for caching etc. See
1437 /// `infer::freshen` for more details.
1443 rustc_index::newtype_index! {
1444 pub struct BoundVar { .. }
1447 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1448 #[derive(HashStable)]
1449 pub struct BoundTy {
1451 pub kind: BoundTyKind,
1454 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1455 #[derive(HashStable)]
1456 pub enum BoundTyKind {
1461 impl From<BoundVar> for BoundTy {
1462 fn from(var: BoundVar) -> Self {
1463 BoundTy { var, kind: BoundTyKind::Anon }
1467 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1468 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1469 #[derive(HashStable, TypeFoldable)]
1470 pub struct ExistentialProjection<'tcx> {
1471 pub item_def_id: DefId,
1472 pub substs: SubstsRef<'tcx>,
1476 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1478 impl<'tcx> ExistentialProjection<'tcx> {
1479 /// Extracts the underlying existential trait reference from this projection.
1480 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1481 /// then this function would return a `exists T. T: Iterator` existential trait
1483 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1484 let def_id = tcx.associated_item(self.item_def_id).container.id();
1485 ty::ExistentialTraitRef { def_id, substs: self.substs }
1488 pub fn with_self_ty(
1492 ) -> ty::ProjectionPredicate<'tcx> {
1493 // otherwise the escaping regions would be captured by the binders
1494 debug_assert!(!self_ty.has_escaping_bound_vars());
1496 ty::ProjectionPredicate {
1497 projection_ty: ty::ProjectionTy {
1498 item_def_id: self.item_def_id,
1499 substs: tcx.mk_substs_trait(self_ty, self.substs),
1506 impl<'tcx> PolyExistentialProjection<'tcx> {
1507 pub fn with_self_ty(
1511 ) -> ty::PolyProjectionPredicate<'tcx> {
1512 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1515 pub fn item_def_id(&self) -> DefId {
1516 self.skip_binder().item_def_id
1520 impl DebruijnIndex {
1521 /// Returns the resulting index when this value is moved into
1522 /// `amount` number of new binders. So, e.g., if you had
1524 /// for<'a> fn(&'a x)
1526 /// and you wanted to change it to
1528 /// for<'a> fn(for<'b> fn(&'a x))
1530 /// you would need to shift the index for `'a` into a new binder.
1532 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1533 DebruijnIndex::from_u32(self.as_u32() + amount)
1536 /// Update this index in place by shifting it "in" through
1537 /// `amount` number of binders.
1538 pub fn shift_in(&mut self, amount: u32) {
1539 *self = self.shifted_in(amount);
1542 /// Returns the resulting index when this value is moved out from
1543 /// `amount` number of new binders.
1545 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1546 DebruijnIndex::from_u32(self.as_u32() - amount)
1549 /// Update in place by shifting out from `amount` binders.
1550 pub fn shift_out(&mut self, amount: u32) {
1551 *self = self.shifted_out(amount);
1554 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1555 /// innermost binder. That is, if we have something bound at `to_binder`,
1556 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1557 /// when moving a region out from inside binders:
1560 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1561 /// // Binder: D3 D2 D1 ^^
1564 /// Here, the region `'a` would have the De Bruijn index D3,
1565 /// because it is the bound 3 binders out. However, if we wanted
1566 /// to refer to that region `'a` in the second argument (the `_`),
1567 /// those two binders would not be in scope. In that case, we
1568 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1569 /// De Bruijn index of `'a` to D1 (the innermost binder).
1571 /// If we invoke `shift_out_to_binder` and the region is in fact
1572 /// bound by one of the binders we are shifting out of, that is an
1573 /// error (and should fail an assertion failure).
1574 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1575 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1579 /// Region utilities
1581 /// Is this region named by the user?
1582 pub fn has_name(&self) -> bool {
1584 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1585 RegionKind::ReLateBound(_, br) => br.is_named(),
1586 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1587 RegionKind::ReStatic => true,
1588 RegionKind::ReVar(..) => false,
1589 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1590 RegionKind::ReEmpty(_) => false,
1591 RegionKind::ReErased => false,
1595 pub fn is_late_bound(&self) -> bool {
1597 ty::ReLateBound(..) => true,
1602 pub fn is_placeholder(&self) -> bool {
1604 ty::RePlaceholder(..) => true,
1609 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1611 ty::ReLateBound(debruijn, _) => debruijn >= index,
1616 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1617 /// innermost binder. That is, if we have something bound at `to_binder`,
1618 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1619 /// when moving a region out from inside binders:
1622 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1623 /// // Binder: D3 D2 D1 ^^
1626 /// Here, the region `'a` would have the De Bruijn index D3,
1627 /// because it is the bound 3 binders out. However, if we wanted
1628 /// to refer to that region `'a` in the second argument (the `_`),
1629 /// those two binders would not be in scope. In that case, we
1630 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1631 /// De Bruijn index of `'a` to D1 (the innermost binder).
1633 /// If we invoke `shift_out_to_binder` and the region is in fact
1634 /// bound by one of the binders we are shifting out of, that is an
1635 /// error (and should fail an assertion failure).
1636 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1638 ty::ReLateBound(debruijn, r) => {
1639 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1645 pub fn type_flags(&self) -> TypeFlags {
1646 let mut flags = TypeFlags::empty();
1650 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1651 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1652 flags = flags | TypeFlags::HAS_RE_INFER;
1654 ty::RePlaceholder(..) => {
1655 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1656 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1657 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1659 ty::ReEarlyBound(..) => {
1660 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1661 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1662 flags = flags | TypeFlags::HAS_RE_PARAM;
1664 ty::ReFree { .. } => {
1665 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1666 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1668 ty::ReEmpty(_) | ty::ReStatic => {
1669 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1671 ty::ReLateBound(..) => {
1672 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1675 flags = flags | TypeFlags::HAS_RE_ERASED;
1679 debug!("type_flags({:?}) = {:?}", self, flags);
1684 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1685 /// For example, consider the regions in this snippet of code:
1689 /// ^^ -- early bound, declared on an impl
1691 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1692 /// ^^ ^^ ^ anonymous, late-bound
1693 /// | early-bound, appears in where-clauses
1694 /// late-bound, appears only in fn args
1699 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1700 /// of the impl, and for all the other highlighted regions, it
1701 /// would return the `DefId` of the function. In other cases (not shown), this
1702 /// function might return the `DefId` of a closure.
1703 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1705 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1706 ty::ReFree(fr) => fr.scope,
1707 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1713 impl<'tcx> TyS<'tcx> {
1715 pub fn is_unit(&self) -> bool {
1717 Tuple(ref tys) => tys.is_empty(),
1723 pub fn is_never(&self) -> bool {
1730 /// Checks whether a type is definitely uninhabited. This is
1731 /// conservative: for some types that are uninhabited we return `false`,
1732 /// but we only return `true` for types that are definitely uninhabited.
1733 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1734 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1735 /// size, to account for partial initialisation. See #49298 for details.)
1736 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1737 // FIXME(varkor): we can make this less conversative by substituting concrete
1741 ty::Adt(def, _) if def.is_union() => {
1742 // For now, `union`s are never considered uninhabited.
1745 ty::Adt(def, _) => {
1746 // Any ADT is uninhabited if either:
1747 // (a) It has no variants (i.e. an empty `enum`);
1748 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1749 // one uninhabited field.
1750 def.variants.iter().all(|var| {
1751 var.fields.iter().any(|field| {
1752 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1757 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1759 ty::Array(ty, len) => {
1760 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1761 // If the array is definitely non-empty, it's uninhabited if
1762 // the type of its elements is uninhabited.
1763 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1768 // References to uninitialised memory is valid for any type, including
1769 // uninhabited types, in unsafe code, so we treat all references as
1778 pub fn is_primitive(&self) -> bool {
1779 self.kind.is_primitive()
1783 pub fn is_ty_var(&self) -> bool {
1785 Infer(TyVar(_)) => true,
1791 pub fn is_ty_infer(&self) -> bool {
1799 pub fn is_phantom_data(&self) -> bool {
1800 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1804 pub fn is_bool(&self) -> bool {
1808 /// Returns `true` if this type is a `str`.
1810 pub fn is_str(&self) -> bool {
1815 pub fn is_param(&self, index: u32) -> bool {
1817 ty::Param(ref data) => data.index == index,
1823 pub fn is_slice(&self) -> bool {
1825 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1826 Slice(_) | Str => true,
1834 pub fn is_simd(&self) -> bool {
1836 Adt(def, _) => def.repr.simd(),
1841 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1843 Array(ty, _) | Slice(ty) => ty,
1844 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1845 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1849 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1851 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1852 _ => bug!("`simd_type` called on invalid type"),
1856 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1857 // Parameter currently unused, but probably needed in the future to
1858 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1860 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1861 _ => bug!("`simd_size` called on invalid type"),
1865 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1867 Adt(def, substs) => {
1868 let variant = def.non_enum_variant();
1869 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1871 _ => bug!("`simd_size_and_type` called on invalid type"),
1876 pub fn is_region_ptr(&self) -> bool {
1884 pub fn is_mutable_ptr(&self) -> bool {
1886 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1887 | Ref(_, _, hir::Mutability::Mut) => true,
1893 pub fn is_unsafe_ptr(&self) -> bool {
1900 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1902 pub fn is_any_ptr(&self) -> bool {
1903 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1907 pub fn is_box(&self) -> bool {
1909 Adt(def, _) => def.is_box(),
1914 /// Panics if called on any type other than `Box<T>`.
1915 pub fn boxed_ty(&self) -> Ty<'tcx> {
1917 Adt(def, substs) if def.is_box() => substs.type_at(0),
1918 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1922 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1923 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1924 /// contents are abstract to rustc.)
1926 pub fn is_scalar(&self) -> bool {
1933 | Infer(IntVar(_) | FloatVar(_))
1936 | RawPtr(_) => true,
1941 /// Returns `true` if this type is a floating point type.
1943 pub fn is_floating_point(&self) -> bool {
1945 Float(_) | Infer(FloatVar(_)) => true,
1951 pub fn is_trait(&self) -> bool {
1953 Dynamic(..) => true,
1959 pub fn is_enum(&self) -> bool {
1961 Adt(adt_def, _) => adt_def.is_enum(),
1967 pub fn is_closure(&self) -> bool {
1969 Closure(..) => true,
1975 pub fn is_generator(&self) -> bool {
1977 Generator(..) => true,
1983 pub fn is_integral(&self) -> bool {
1985 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
1991 pub fn is_fresh_ty(&self) -> bool {
1993 Infer(FreshTy(_)) => true,
1999 pub fn is_fresh(&self) -> bool {
2001 Infer(FreshTy(_)) => true,
2002 Infer(FreshIntTy(_)) => true,
2003 Infer(FreshFloatTy(_)) => true,
2009 pub fn is_char(&self) -> bool {
2017 pub fn is_numeric(&self) -> bool {
2018 self.is_integral() || self.is_floating_point()
2022 pub fn is_signed(&self) -> bool {
2030 pub fn is_ptr_sized_integral(&self) -> bool {
2032 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
2038 pub fn is_machine(&self) -> bool {
2040 Int(..) | Uint(..) | Float(..) => true,
2046 pub fn has_concrete_skeleton(&self) -> bool {
2048 Param(_) | Infer(_) | Error(_) => false,
2053 /// Returns the type and mutability of `*ty`.
2055 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2056 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2057 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2059 Adt(def, _) if def.is_box() => {
2060 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2062 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2063 RawPtr(mt) if explicit => Some(mt),
2068 /// Returns the type of `ty[i]`.
2069 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2071 Array(ty, _) | Slice(ty) => Some(ty),
2076 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2078 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2081 // ignore errors (#54954)
2082 ty::Binder::dummy(FnSig::fake())
2084 Closure(..) => bug!(
2085 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2087 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2092 pub fn is_fn(&self) -> bool {
2094 FnDef(..) | FnPtr(_) => true,
2100 pub fn is_fn_ptr(&self) -> bool {
2108 pub fn is_impl_trait(&self) -> bool {
2116 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2118 Adt(adt, _) => Some(adt),
2123 /// Iterates over tuple fields.
2124 /// Panics when called on anything but a tuple.
2125 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2127 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2128 _ => bug!("tuple_fields called on non-tuple"),
2132 /// If the type contains variants, returns the valid range of variant indices.
2134 // FIXME: This requires the optimized MIR in the case of generators.
2136 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2138 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2139 TyKind::Generator(def_id, substs, _) => {
2140 Some(substs.as_generator().variant_range(def_id, tcx))
2146 /// If the type contains variants, returns the variant for `variant_index`.
2147 /// Panics if `variant_index` is out of range.
2149 // FIXME: This requires the optimized MIR in the case of generators.
2151 pub fn discriminant_for_variant(
2154 variant_index: VariantIdx,
2155 ) -> Option<Discr<'tcx>> {
2157 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2158 bug!("discriminant_for_variant called on zero variant enum");
2160 TyKind::Adt(adt, _) if adt.is_enum() => {
2161 Some(adt.discriminant_for_variant(tcx, variant_index))
2163 TyKind::Generator(def_id, substs, _) => {
2164 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2170 /// Returns the type of the discriminant of this type.
2171 pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2173 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2174 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2176 // This can only be `0`, for now, so `u8` will suffice.
2182 /// When we create a closure, we record its kind (i.e., what trait
2183 /// it implements) into its `ClosureSubsts` using a type
2184 /// parameter. This is kind of a phantom type, except that the
2185 /// most convenient thing for us to are the integral types. This
2186 /// function converts such a special type into the closure
2187 /// kind. To go the other way, use
2188 /// `tcx.closure_kind_ty(closure_kind)`.
2190 /// Note that during type checking, we use an inference variable
2191 /// to represent the closure kind, because it has not yet been
2192 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2193 /// is complete, that type variable will be unified.
2194 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2196 Int(int_ty) => match int_ty {
2197 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2198 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2199 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2200 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2203 // "Bound" types appear in canonical queries when the
2204 // closure type is not yet known
2205 Bound(..) | Infer(_) => None,
2207 Error(_) => Some(ty::ClosureKind::Fn),
2209 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2213 /// Fast path helper for testing if a type is `Sized`.
2215 /// Returning true means the type is known to be sized. Returning
2216 /// `false` means nothing -- could be sized, might not be.
2217 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2219 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2230 | ty::GeneratorWitness(..)
2234 | ty::Error(_) => true,
2236 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2238 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2240 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2242 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2244 ty::Infer(ty::TyVar(_)) => false,
2247 | ty::Placeholder(..)
2248 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2249 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2254 /// Is this a zero-sized type?
2255 pub fn is_zst(&'tcx self, tcx: TyCtxt<'tcx>, did: DefId) -> bool {
2256 tcx.layout_of(tcx.param_env(did).and(self)).map(|layout| layout.is_zst()).unwrap_or(false)