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),
205 /// A type that is not publicly constructable. This prevents people from making `TyKind::Error`
206 /// except through `tcx.err*()`.
207 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
208 #[derive(RustcEncodable, RustcDecodable, HashStable)]
209 pub struct DelaySpanBugEmitted(pub(super) ());
211 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
212 #[cfg(target_arch = "x86_64")]
213 static_assert_size!(TyKind<'_>, 24);
215 /// A closure can be modeled as a struct that looks like:
217 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
221 /// - 'l0...'li and T0...Tj are the generic parameters
222 /// in scope on the function that defined the closure,
223 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
224 /// is rather hackily encoded via a scalar type. See
225 /// `TyS::to_opt_closure_kind` for details.
226 /// - CS represents the *closure signature*, representing as a `fn()`
227 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
228 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
230 /// - U is a type parameter representing the types of its upvars, tupled up
231 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
232 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
234 /// So, for example, given this function:
236 /// fn foo<'a, T>(data: &'a mut T) {
237 /// do(|| data.count += 1)
240 /// the type of the closure would be something like:
242 /// struct Closure<'a, T, U>(...U);
244 /// Note that the type of the upvar is not specified in the struct.
245 /// You may wonder how the impl would then be able to use the upvar,
246 /// if it doesn't know it's type? The answer is that the impl is
247 /// (conceptually) not fully generic over Closure but rather tied to
248 /// instances with the expected upvar types:
250 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
254 /// You can see that the *impl* fully specified the type of the upvar
255 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
256 /// (Here, I am assuming that `data` is mut-borrowed.)
258 /// Now, the last question you may ask is: Why include the upvar types
259 /// in an extra type parameter? The reason for this design is that the
260 /// upvar types can reference lifetimes that are internal to the
261 /// creating function. In my example above, for example, the lifetime
262 /// `'b` represents the scope of the closure itself; this is some
263 /// subset of `foo`, probably just the scope of the call to the to
264 /// `do()`. If we just had the lifetime/type parameters from the
265 /// enclosing function, we couldn't name this lifetime `'b`. Note that
266 /// there can also be lifetimes in the types of the upvars themselves,
267 /// if one of them happens to be a reference to something that the
268 /// creating fn owns.
270 /// OK, you say, so why not create a more minimal set of parameters
271 /// that just includes the extra lifetime parameters? The answer is
272 /// primarily that it would be hard --- we don't know at the time when
273 /// we create the closure type what the full types of the upvars are,
274 /// nor do we know which are borrowed and which are not. In this
275 /// design, we can just supply a fresh type parameter and figure that
278 /// All right, you say, but why include the type parameters from the
279 /// original function then? The answer is that codegen may need them
280 /// when monomorphizing, and they may not appear in the upvars. A
281 /// closure could capture no variables but still make use of some
282 /// in-scope type parameter with a bound (e.g., if our example above
283 /// had an extra `U: Default`, and the closure called `U::default()`).
285 /// There is another reason. This design (implicitly) prohibits
286 /// closures from capturing themselves (except via a trait
287 /// object). This simplifies closure inference considerably, since it
288 /// means that when we infer the kind of a closure or its upvars, we
289 /// don't have to handle cycles where the decisions we make for
290 /// closure C wind up influencing the decisions we ought to make for
291 /// closure C (which would then require fixed point iteration to
292 /// handle). Plus it fixes an ICE. :P
296 /// Generators are handled similarly in `GeneratorSubsts`. The set of
297 /// type parameters is similar, but `CK` and `CS` are replaced by the
298 /// following type parameters:
300 /// * `GS`: The generator's "resume type", which is the type of the
301 /// argument passed to `resume`, and the type of `yield` expressions
302 /// inside the generator.
303 /// * `GY`: The "yield type", which is the type of values passed to
304 /// `yield` inside the generator.
305 /// * `GR`: The "return type", which is the type of value returned upon
306 /// completion of the generator.
307 /// * `GW`: The "generator witness".
308 #[derive(Copy, Clone, Debug, TypeFoldable)]
309 pub struct ClosureSubsts<'tcx> {
310 /// Lifetime and type parameters from the enclosing function,
311 /// concatenated with a tuple containing the types of the upvars.
313 /// These are separated out because codegen wants to pass them around
314 /// when monomorphizing.
315 pub substs: SubstsRef<'tcx>,
318 /// Struct returned by `split()`. Note that these are subslices of the
319 /// parent slice and not canonical substs themselves.
320 struct SplitClosureSubsts<'tcx> {
321 parent: &'tcx [GenericArg<'tcx>],
322 closure_kind_ty: GenericArg<'tcx>,
323 closure_sig_as_fn_ptr_ty: GenericArg<'tcx>,
324 tupled_upvars_ty: GenericArg<'tcx>,
327 impl<'tcx> ClosureSubsts<'tcx> {
328 /// Divides the closure substs into their respective
329 /// components. Single source of truth with respect to the
331 fn split(self) -> SplitClosureSubsts<'tcx> {
332 match self.substs[..] {
333 [ref parent @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
337 closure_sig_as_fn_ptr_ty,
341 _ => bug!("closure substs missing synthetics"),
345 /// Returns `true` only if enough of the synthetic types are known to
346 /// allow using all of the methods on `ClosureSubsts` without panicking.
348 /// Used primarily by `ty::print::pretty` to be able to handle closure
349 /// types that haven't had their synthetic types substituted in.
350 pub fn is_valid(self) -> bool {
351 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
354 /// Returns the substitutions of the closure's parent.
355 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
360 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
361 self.tupled_upvars_ty().tuple_fields()
364 /// Returns the tuple type representing the upvars for this closure.
366 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
367 self.split().tupled_upvars_ty.expect_ty()
370 /// Returns the closure kind for this closure; may return a type
371 /// variable during inference. To get the closure kind during
372 /// inference, use `infcx.closure_kind(substs)`.
373 pub fn kind_ty(self) -> Ty<'tcx> {
374 self.split().closure_kind_ty.expect_ty()
377 /// Returns the `fn` pointer type representing the closure signature for this
379 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
380 // type is known at the time of the creation of `ClosureSubsts`,
381 // see `rustc_typeck::check::closure`.
382 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
383 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
386 /// Returns the closure kind for this closure; only usable outside
387 /// of an inference context, because in that context we know that
388 /// there are no type variables.
390 /// If you have an inference context, use `infcx.closure_kind()`.
391 pub fn kind(self) -> ty::ClosureKind {
392 self.kind_ty().to_opt_closure_kind().unwrap()
395 /// Extracts the signature from the closure.
396 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
397 let ty = self.sig_as_fn_ptr_ty();
399 ty::FnPtr(sig) => sig,
400 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
405 /// Similar to `ClosureSubsts`; see the above documentation for more.
406 #[derive(Copy, Clone, Debug, TypeFoldable)]
407 pub struct GeneratorSubsts<'tcx> {
408 pub substs: SubstsRef<'tcx>,
411 struct SplitGeneratorSubsts<'tcx> {
412 parent: &'tcx [GenericArg<'tcx>],
413 resume_ty: GenericArg<'tcx>,
414 yield_ty: GenericArg<'tcx>,
415 return_ty: GenericArg<'tcx>,
416 witness: GenericArg<'tcx>,
417 tupled_upvars_ty: GenericArg<'tcx>,
420 impl<'tcx> GeneratorSubsts<'tcx> {
421 fn split(self) -> SplitGeneratorSubsts<'tcx> {
422 match self.substs[..] {
423 [ref parent @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
424 SplitGeneratorSubsts {
433 _ => bug!("generator substs missing synthetics"),
437 /// Returns `true` only if enough of the synthetic types are known to
438 /// allow using all of the methods on `GeneratorSubsts` without panicking.
440 /// Used primarily by `ty::print::pretty` to be able to handle generator
441 /// types that haven't had their synthetic types substituted in.
442 pub fn is_valid(self) -> bool {
443 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
446 /// Returns the substitutions of the generator's parent.
447 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
451 /// This describes the types that can be contained in a generator.
452 /// It will be a type variable initially and unified in the last stages of typeck of a body.
453 /// It contains a tuple of all the types that could end up on a generator frame.
454 /// The state transformation MIR pass may only produce layouts which mention types
455 /// in this tuple. Upvars are not counted here.
456 pub fn witness(self) -> Ty<'tcx> {
457 self.split().witness.expect_ty()
461 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
462 self.tupled_upvars_ty().tuple_fields()
465 /// Returns the tuple type representing the upvars for this generator.
467 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
468 self.split().tupled_upvars_ty.expect_ty()
471 /// Returns the type representing the resume type of the generator.
472 pub fn resume_ty(self) -> Ty<'tcx> {
473 self.split().resume_ty.expect_ty()
476 /// Returns the type representing the yield type of the generator.
477 pub fn yield_ty(self) -> Ty<'tcx> {
478 self.split().yield_ty.expect_ty()
481 /// Returns the type representing the return type of the generator.
482 pub fn return_ty(self) -> Ty<'tcx> {
483 self.split().return_ty.expect_ty()
486 /// Returns the "generator signature", which consists of its yield
487 /// and return types.
489 /// N.B., some bits of the code prefers to see this wrapped in a
490 /// binder, but it never contains bound regions. Probably this
491 /// function should be removed.
492 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
493 ty::Binder::dummy(self.sig())
496 /// Returns the "generator signature", which consists of its resume, yield
497 /// and return types.
498 pub fn sig(self) -> GenSig<'tcx> {
500 resume_ty: self.resume_ty(),
501 yield_ty: self.yield_ty(),
502 return_ty: self.return_ty(),
507 impl<'tcx> GeneratorSubsts<'tcx> {
508 /// Generator has not been resumed yet.
509 pub const UNRESUMED: usize = 0;
510 /// Generator has returned or is completed.
511 pub const RETURNED: usize = 1;
512 /// Generator has been poisoned.
513 pub const POISONED: usize = 2;
515 const UNRESUMED_NAME: &'static str = "Unresumed";
516 const RETURNED_NAME: &'static str = "Returned";
517 const POISONED_NAME: &'static str = "Panicked";
519 /// The valid variant indices of this generator.
521 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
522 // FIXME requires optimized MIR
523 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
524 VariantIdx::new(0)..VariantIdx::new(num_variants)
527 /// The discriminant for the given variant. Panics if the `variant_index` is
530 pub fn discriminant_for_variant(
534 variant_index: VariantIdx,
536 // Generators don't support explicit discriminant values, so they are
537 // the same as the variant index.
538 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
539 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
542 /// The set of all discriminants for the generator, enumerated with their
545 pub fn discriminants(
549 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
550 self.variant_range(def_id, tcx).map(move |index| {
551 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
555 /// Calls `f` with a reference to the name of the enumerator for the given
557 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
559 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
560 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
561 Self::POISONED => Cow::from(Self::POISONED_NAME),
562 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
566 /// The type of the state discriminant used in the generator type.
568 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
572 /// This returns the types of the MIR locals which had to be stored across suspension points.
573 /// It is calculated in rustc_mir::transform::generator::StateTransform.
574 /// All the types here must be in the tuple in GeneratorInterior.
576 /// The locals are grouped by their variant number. Note that some locals may
577 /// be repeated in multiple variants.
583 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
584 let layout = tcx.generator_layout(def_id);
585 layout.variant_fields.iter().map(move |variant| {
586 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
590 /// This is the types of the fields of a generator which are not stored in a
593 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
598 #[derive(Debug, Copy, Clone)]
599 pub enum UpvarSubsts<'tcx> {
600 Closure(SubstsRef<'tcx>),
601 Generator(SubstsRef<'tcx>),
604 impl<'tcx> UpvarSubsts<'tcx> {
606 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
607 let tupled_upvars_ty = match self {
608 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
609 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
611 tupled_upvars_ty.expect_ty().tuple_fields()
615 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, RustcEncodable, RustcDecodable)]
616 #[derive(HashStable, TypeFoldable)]
617 pub enum ExistentialPredicate<'tcx> {
618 /// E.g., `Iterator`.
619 Trait(ExistentialTraitRef<'tcx>),
620 /// E.g., `Iterator::Item = T`.
621 Projection(ExistentialProjection<'tcx>),
626 impl<'tcx> ExistentialPredicate<'tcx> {
627 /// Compares via an ordering that will not change if modules are reordered or other changes are
628 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
629 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
630 use self::ExistentialPredicate::*;
631 match (*self, *other) {
632 (Trait(_), Trait(_)) => Ordering::Equal,
633 (Projection(ref a), Projection(ref b)) => {
634 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
636 (AutoTrait(ref a), AutoTrait(ref b)) => {
637 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
639 (Trait(_), _) => Ordering::Less,
640 (Projection(_), Trait(_)) => Ordering::Greater,
641 (Projection(_), _) => Ordering::Less,
642 (AutoTrait(_), _) => Ordering::Greater,
647 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
648 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
649 use crate::ty::ToPredicate;
650 match self.skip_binder() {
651 ExistentialPredicate::Trait(tr) => {
652 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
654 ExistentialPredicate::Projection(p) => {
655 ty::PredicateKind::Projection(Binder(p.with_self_ty(tcx, self_ty)))
658 ExistentialPredicate::AutoTrait(did) => {
660 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
661 trait_ref.without_const().to_predicate(tcx)
667 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx List<ExistentialPredicate<'tcx>> {}
669 impl<'tcx> List<ExistentialPredicate<'tcx>> {
670 /// Returns the "principal `DefId`" of this set of existential predicates.
672 /// A Rust trait object type consists (in addition to a lifetime bound)
673 /// of a set of trait bounds, which are separated into any number
674 /// of auto-trait bounds, and at most one non-auto-trait bound. The
675 /// non-auto-trait bound is called the "principal" of the trait
678 /// Only the principal can have methods or type parameters (because
679 /// auto traits can have neither of them). This is important, because
680 /// it means the auto traits can be treated as an unordered set (methods
681 /// would force an order for the vtable, while relating traits with
682 /// type parameters without knowing the order to relate them in is
683 /// a rather non-trivial task).
685 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
686 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
687 /// are the set `{Sync}`.
689 /// It is also possible to have a "trivial" trait object that
690 /// consists only of auto traits, with no principal - for example,
691 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
692 /// is `{Send, Sync}`, while there is no principal. These trait objects
693 /// have a "trivial" vtable consisting of just the size, alignment,
695 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
697 ExistentialPredicate::Trait(tr) => Some(tr),
702 pub fn principal_def_id(&self) -> Option<DefId> {
703 self.principal().map(|trait_ref| trait_ref.def_id)
707 pub fn projection_bounds<'a>(
709 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
710 self.iter().filter_map(|predicate| match predicate {
711 ExistentialPredicate::Projection(projection) => Some(projection),
717 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
718 self.iter().filter_map(|predicate| match predicate {
719 ExistentialPredicate::AutoTrait(did) => Some(did),
725 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
726 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
727 self.skip_binder().principal().map(Binder::bind)
730 pub fn principal_def_id(&self) -> Option<DefId> {
731 self.skip_binder().principal_def_id()
735 pub fn projection_bounds<'a>(
737 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
738 self.skip_binder().projection_bounds().map(Binder::bind)
742 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
743 self.skip_binder().auto_traits()
748 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
749 self.skip_binder().iter().map(Binder::bind)
753 /// A complete reference to a trait. These take numerous guises in syntax,
754 /// but perhaps the most recognizable form is in a where-clause:
758 /// This would be represented by a trait-reference where the `DefId` is the
759 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
760 /// and `U` as parameter 1.
762 /// Trait references also appear in object types like `Foo<U>`, but in
763 /// that case the `Self` parameter is absent from the substitutions.
764 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
765 #[derive(HashStable, TypeFoldable)]
766 pub struct TraitRef<'tcx> {
768 pub substs: SubstsRef<'tcx>,
771 impl<'tcx> TraitRef<'tcx> {
772 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
773 TraitRef { def_id, substs }
776 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
777 /// are the parameters defined on trait.
778 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
779 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
783 pub fn self_ty(&self) -> Ty<'tcx> {
784 self.substs.type_at(0)
790 substs: SubstsRef<'tcx>,
791 ) -> ty::TraitRef<'tcx> {
792 let defs = tcx.generics_of(trait_id);
794 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
798 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
800 impl<'tcx> PolyTraitRef<'tcx> {
801 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
802 self.map_bound_ref(|tr| tr.self_ty())
805 pub fn def_id(&self) -> DefId {
806 self.skip_binder().def_id
809 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
810 // Note that we preserve binding levels
811 Binder(ty::TraitPredicate { trait_ref: self.skip_binder() })
815 /// An existential reference to a trait, where `Self` is erased.
816 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
818 /// exists T. T: Trait<'a, 'b, X, Y>
820 /// The substitutions don't include the erased `Self`, only trait
821 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
822 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
823 #[derive(HashStable, TypeFoldable)]
824 pub struct ExistentialTraitRef<'tcx> {
826 pub substs: SubstsRef<'tcx>,
829 impl<'tcx> ExistentialTraitRef<'tcx> {
830 pub fn erase_self_ty(
832 trait_ref: ty::TraitRef<'tcx>,
833 ) -> ty::ExistentialTraitRef<'tcx> {
834 // Assert there is a Self.
835 trait_ref.substs.type_at(0);
837 ty::ExistentialTraitRef {
838 def_id: trait_ref.def_id,
839 substs: tcx.intern_substs(&trait_ref.substs[1..]),
843 /// Object types don't have a self type specified. Therefore, when
844 /// we convert the principal trait-ref into a normal trait-ref,
845 /// you must give *some* self type. A common choice is `mk_err()`
846 /// or some placeholder type.
847 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
848 // otherwise the escaping vars would be captured by the binder
849 // debug_assert!(!self_ty.has_escaping_bound_vars());
851 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
855 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
857 impl<'tcx> PolyExistentialTraitRef<'tcx> {
858 pub fn def_id(&self) -> DefId {
859 self.skip_binder().def_id
862 /// Object types don't have a self type specified. Therefore, when
863 /// we convert the principal trait-ref into a normal trait-ref,
864 /// you must give *some* self type. A common choice is `mk_err()`
865 /// or some placeholder type.
866 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
867 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
871 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
872 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
873 /// (which would be represented by the type `PolyTraitRef ==
874 /// Binder<TraitRef>`). Note that when we instantiate,
875 /// erase, or otherwise "discharge" these bound vars, we change the
876 /// type from `Binder<T>` to just `T` (see
877 /// e.g., `liberate_late_bound_regions`).
878 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
879 pub struct Binder<T>(T);
882 /// Wraps `value` in a binder, asserting that `value` does not
883 /// contain any bound vars that would be bound by the
884 /// binder. This is commonly used to 'inject' a value T into a
885 /// different binding level.
886 pub fn dummy<'tcx>(value: T) -> Binder<T>
888 T: TypeFoldable<'tcx>,
890 debug_assert!(!value.has_escaping_bound_vars());
894 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
895 pub fn bind(value: T) -> Binder<T> {
899 /// Skips the binder and returns the "bound" value. This is a
900 /// risky thing to do because it's easy to get confused about
901 /// De Bruijn indices and the like. It is usually better to
902 /// discharge the binder using `no_bound_vars` or
903 /// `replace_late_bound_regions` or something like
904 /// that. `skip_binder` is only valid when you are either
905 /// extracting data that has nothing to do with bound vars, you
906 /// are doing some sort of test that does not involve bound
907 /// regions, or you are being very careful about your depth
910 /// Some examples where `skip_binder` is reasonable:
912 /// - extracting the `DefId` from a PolyTraitRef;
913 /// - comparing the self type of a PolyTraitRef to see if it is equal to
914 /// a type parameter `X`, since the type `X` does not reference any regions
915 pub fn skip_binder(self) -> T {
919 pub fn as_ref(&self) -> Binder<&T> {
923 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
927 self.as_ref().map_bound(f)
930 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
937 /// Unwraps and returns the value within, but only if it contains
938 /// no bound vars at all. (In other words, if this binder --
939 /// and indeed any enclosing binder -- doesn't bind anything at
940 /// all.) Otherwise, returns `None`.
942 /// (One could imagine having a method that just unwraps a single
943 /// binder, but permits late-bound vars bound by enclosing
944 /// binders, but that would require adjusting the debruijn
945 /// indices, and given the shallow binding structure we often use,
946 /// would not be that useful.)
947 pub fn no_bound_vars<'tcx>(self) -> Option<T>
949 T: TypeFoldable<'tcx>,
951 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
954 /// Given two things that have the same binder level,
955 /// and an operation that wraps on their contents, executes the operation
956 /// and then wraps its result.
958 /// `f` should consider bound regions at depth 1 to be free, and
959 /// anything it produces with bound regions at depth 1 will be
960 /// bound in the resulting return value.
961 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
963 F: FnOnce(T, U) -> R,
965 Binder(f(self.0, u.0))
968 /// Splits the contents into two things that share the same binder
969 /// level as the original, returning two distinct binders.
971 /// `f` should consider bound regions at depth 1 to be free, and
972 /// anything it produces with bound regions at depth 1 will be
973 /// bound in the resulting return values.
974 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
976 F: FnOnce(T) -> (U, V),
978 let (u, v) = f(self.0);
979 (Binder(u), Binder(v))
983 /// Represents the projection of an associated type. In explicit UFCS
984 /// form this would be written `<T as Trait<..>>::N`.
985 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
986 #[derive(HashStable, TypeFoldable)]
987 pub struct ProjectionTy<'tcx> {
988 /// The parameters of the associated item.
989 pub substs: SubstsRef<'tcx>,
991 /// The `DefId` of the `TraitItem` for the associated type `N`.
993 /// Note that this is not the `DefId` of the `TraitRef` containing this
994 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
995 pub item_def_id: DefId,
998 impl<'tcx> ProjectionTy<'tcx> {
999 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
1000 /// associated item named `item_name`.
1001 pub fn from_ref_and_name(
1003 trait_ref: ty::TraitRef<'tcx>,
1005 ) -> ProjectionTy<'tcx> {
1006 let item_def_id = tcx
1007 .associated_items(trait_ref.def_id)
1008 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1012 ProjectionTy { substs: trait_ref.substs, item_def_id }
1015 /// Extracts the underlying trait reference from this projection.
1016 /// For example, if this is a projection of `<T as Iterator>::Item`,
1017 /// then this function would return a `T: Iterator` trait reference.
1018 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1019 let def_id = tcx.associated_item(self.item_def_id).container.id();
1020 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1023 pub fn self_ty(&self) -> Ty<'tcx> {
1024 self.substs.type_at(0)
1028 #[derive(Copy, Clone, Debug, TypeFoldable)]
1029 pub struct GenSig<'tcx> {
1030 pub resume_ty: Ty<'tcx>,
1031 pub yield_ty: Ty<'tcx>,
1032 pub return_ty: Ty<'tcx>,
1035 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1037 impl<'tcx> PolyGenSig<'tcx> {
1038 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1039 self.map_bound_ref(|sig| sig.resume_ty)
1041 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1042 self.map_bound_ref(|sig| sig.yield_ty)
1044 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1045 self.map_bound_ref(|sig| sig.return_ty)
1049 /// Signature of a function type, which we have arbitrarily
1050 /// decided to use to refer to the input/output types.
1052 /// - `inputs`: is the list of arguments and their modes.
1053 /// - `output`: is the return type.
1054 /// - `c_variadic`: indicates whether this is a C-variadic function.
1055 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1056 #[derive(HashStable, TypeFoldable)]
1057 pub struct FnSig<'tcx> {
1058 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1059 pub c_variadic: bool,
1060 pub unsafety: hir::Unsafety,
1064 impl<'tcx> FnSig<'tcx> {
1065 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1066 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1069 pub fn output(&self) -> Ty<'tcx> {
1070 self.inputs_and_output[self.inputs_and_output.len() - 1]
1073 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1075 fn fake() -> FnSig<'tcx> {
1077 inputs_and_output: List::empty(),
1079 unsafety: hir::Unsafety::Normal,
1080 abi: abi::Abi::Rust,
1085 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1087 impl<'tcx> PolyFnSig<'tcx> {
1089 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1090 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1093 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1094 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1096 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1097 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1100 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1101 self.map_bound_ref(|fn_sig| fn_sig.output())
1103 pub fn c_variadic(&self) -> bool {
1104 self.skip_binder().c_variadic
1106 pub fn unsafety(&self) -> hir::Unsafety {
1107 self.skip_binder().unsafety
1109 pub fn abi(&self) -> abi::Abi {
1110 self.skip_binder().abi
1114 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1116 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1117 #[derive(HashStable)]
1118 pub struct ParamTy {
1123 impl<'tcx> ParamTy {
1124 pub fn new(index: u32, name: Symbol) -> ParamTy {
1125 ParamTy { index, name }
1128 pub fn for_self() -> ParamTy {
1129 ParamTy::new(0, kw::SelfUpper)
1132 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1133 ParamTy::new(def.index, def.name)
1136 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1137 tcx.mk_ty_param(self.index, self.name)
1141 #[derive(Copy, Clone, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
1142 #[derive(HashStable)]
1143 pub struct ParamConst {
1148 impl<'tcx> ParamConst {
1149 pub fn new(index: u32, name: Symbol) -> ParamConst {
1150 ParamConst { index, name }
1153 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1154 ParamConst::new(def.index, def.name)
1157 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
1158 tcx.mk_const_param(self.index, self.name, ty)
1162 rustc_index::newtype_index! {
1163 /// A [De Bruijn index][dbi] is a standard means of representing
1164 /// regions (and perhaps later types) in a higher-ranked setting. In
1165 /// particular, imagine a type like this:
1167 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1170 /// | +------------+ 0 | |
1172 /// +--------------------------------+ 1 |
1174 /// +------------------------------------------+ 0
1176 /// In this type, there are two binders (the outer fn and the inner
1177 /// fn). We need to be able to determine, for any given region, which
1178 /// fn type it is bound by, the inner or the outer one. There are
1179 /// various ways you can do this, but a De Bruijn index is one of the
1180 /// more convenient and has some nice properties. The basic idea is to
1181 /// count the number of binders, inside out. Some examples should help
1182 /// clarify what I mean.
1184 /// Let's start with the reference type `&'b isize` that is the first
1185 /// argument to the inner function. This region `'b` is assigned a De
1186 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1187 /// fn). The region `'a` that appears in the second argument type (`&'a
1188 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1189 /// second-innermost binder". (These indices are written on the arrays
1190 /// in the diagram).
1192 /// What is interesting is that De Bruijn index attached to a particular
1193 /// variable will vary depending on where it appears. For example,
1194 /// the final type `&'a char` also refers to the region `'a` declared on
1195 /// the outermost fn. But this time, this reference is not nested within
1196 /// any other binders (i.e., it is not an argument to the inner fn, but
1197 /// rather the outer one). Therefore, in this case, it is assigned a
1198 /// De Bruijn index of 0, because the innermost binder in that location
1199 /// is the outer fn.
1201 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1202 #[derive(HashStable)]
1203 pub struct DebruijnIndex {
1204 DEBUG_FORMAT = "DebruijnIndex({})",
1205 const INNERMOST = 0,
1209 pub type Region<'tcx> = &'tcx RegionKind;
1211 /// Representation of regions. Note that the NLL checker uses a distinct
1212 /// representation of regions. For this reason, it internally replaces all the
1213 /// regions with inference variables -- the index of the variable is then used
1214 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1215 /// module for more information.
1217 /// ## The Region lattice within a given function
1219 /// In general, the region lattice looks like
1222 /// static ----------+-----...------+ (greatest)
1224 /// early-bound and | |
1225 /// free regions | |
1228 /// empty(root) placeholder(U1) |
1230 /// | / placeholder(Un)
1235 /// empty(Un) -------- (smallest)
1238 /// Early-bound/free regions are the named lifetimes in scope from the
1239 /// function declaration. They have relationships to one another
1240 /// determined based on the declared relationships from the
1243 /// Note that inference variables and bound regions are not included
1244 /// in this diagram. In the case of inference variables, they should
1245 /// be inferred to some other region from the diagram. In the case of
1246 /// bound regions, they are excluded because they don't make sense to
1247 /// include -- the diagram indicates the relationship between free
1250 /// ## Inference variables
1252 /// During region inference, we sometimes create inference variables,
1253 /// represented as `ReVar`. These will be inferred by the code in
1254 /// `infer::lexical_region_resolve` to some free region from the
1255 /// lattice above (the minimal region that meets the
1258 /// During NLL checking, where regions are defined differently, we
1259 /// also use `ReVar` -- in that case, the index is used to index into
1260 /// the NLL region checker's data structures. The variable may in fact
1261 /// represent either a free region or an inference variable, in that
1264 /// ## Bound Regions
1266 /// These are regions that are stored behind a binder and must be substituted
1267 /// with some concrete region before being used. There are two kind of
1268 /// bound regions: early-bound, which are bound in an item's `Generics`,
1269 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1270 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1271 /// the likes of `liberate_late_bound_regions`. The distinction exists
1272 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1274 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1275 /// outside their binder, e.g., in types passed to type inference, and
1276 /// should first be substituted (by placeholder regions, free regions,
1277 /// or region variables).
1279 /// ## Placeholder and Free Regions
1281 /// One often wants to work with bound regions without knowing their precise
1282 /// identity. For example, when checking a function, the lifetime of a borrow
1283 /// can end up being assigned to some region parameter. In these cases,
1284 /// it must be ensured that bounds on the region can't be accidentally
1285 /// assumed without being checked.
1287 /// To do this, we replace the bound regions with placeholder markers,
1288 /// which don't satisfy any relation not explicitly provided.
1290 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1291 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1292 /// to be used. These also support explicit bounds: both the internally-stored
1293 /// *scope*, which the region is assumed to outlive, as well as other
1294 /// relations stored in the `FreeRegionMap`. Note that these relations
1295 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1296 /// `resolve_regions_and_report_errors`.
1298 /// When working with higher-ranked types, some region relations aren't
1299 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1300 /// `RePlaceholder` is designed for this purpose. In these contexts,
1301 /// there's also the risk that some inference variable laying around will
1302 /// get unified with your placeholder region: if you want to check whether
1303 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1304 /// with a placeholder region `'%a`, the variable `'_` would just be
1305 /// instantiated to the placeholder region `'%a`, which is wrong because
1306 /// the inference variable is supposed to satisfy the relation
1307 /// *for every value of the placeholder region*. To ensure that doesn't
1308 /// happen, you can use `leak_check`. This is more clearly explained
1309 /// by the [rustc dev guide].
1311 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1312 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1313 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1314 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable, PartialOrd, Ord)]
1315 pub enum RegionKind {
1316 /// Region bound in a type or fn declaration which will be
1317 /// substituted 'early' -- that is, at the same time when type
1318 /// parameters are substituted.
1319 ReEarlyBound(EarlyBoundRegion),
1321 /// Region bound in a function scope, which will be substituted when the
1322 /// function is called.
1323 ReLateBound(DebruijnIndex, BoundRegion),
1325 /// When checking a function body, the types of all arguments and so forth
1326 /// that refer to bound region parameters are modified to refer to free
1327 /// region parameters.
1330 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1333 /// A region variable. Should not exist after typeck.
1336 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1337 /// Should not exist after typeck.
1338 RePlaceholder(ty::PlaceholderRegion),
1340 /// Empty lifetime is for data that is never accessed. We tag the
1341 /// empty lifetime with a universe -- the idea is that we don't
1342 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1343 /// Therefore, the `'empty` in a universe `U` is less than all
1344 /// regions visible from `U`, but not less than regions not visible
1346 ReEmpty(ty::UniverseIndex),
1348 /// Erased region, used by trait selection, in MIR and during codegen.
1352 impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
1354 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, PartialOrd, Ord)]
1355 pub struct EarlyBoundRegion {
1361 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1366 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1367 pub struct ConstVid<'tcx> {
1369 pub phantom: PhantomData<&'tcx ()>,
1372 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1377 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1378 pub struct FloatVid {
1382 rustc_index::newtype_index! {
1383 pub struct RegionVid {
1384 DEBUG_FORMAT = custom,
1388 impl Atom for RegionVid {
1389 fn index(self) -> usize {
1394 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1395 #[derive(HashStable)]
1401 /// A `FreshTy` is one that is generated as a replacement for an
1402 /// unbound type variable. This is convenient for caching etc. See
1403 /// `infer::freshen` for more details.
1409 rustc_index::newtype_index! {
1410 pub struct BoundVar { .. }
1413 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1414 #[derive(HashStable)]
1415 pub struct BoundTy {
1417 pub kind: BoundTyKind,
1420 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1421 #[derive(HashStable)]
1422 pub enum BoundTyKind {
1427 impl From<BoundVar> for BoundTy {
1428 fn from(var: BoundVar) -> Self {
1429 BoundTy { var, kind: BoundTyKind::Anon }
1433 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1434 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1435 #[derive(HashStable, TypeFoldable)]
1436 pub struct ExistentialProjection<'tcx> {
1437 pub item_def_id: DefId,
1438 pub substs: SubstsRef<'tcx>,
1442 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1444 impl<'tcx> ExistentialProjection<'tcx> {
1445 /// Extracts the underlying existential trait reference from this projection.
1446 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1447 /// then this function would return a `exists T. T: Iterator` existential trait
1449 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1450 let def_id = tcx.associated_item(self.item_def_id).container.id();
1451 ty::ExistentialTraitRef { def_id, substs: self.substs }
1454 pub fn with_self_ty(
1458 ) -> ty::ProjectionPredicate<'tcx> {
1459 // otherwise the escaping regions would be captured by the binders
1460 debug_assert!(!self_ty.has_escaping_bound_vars());
1462 ty::ProjectionPredicate {
1463 projection_ty: ty::ProjectionTy {
1464 item_def_id: self.item_def_id,
1465 substs: tcx.mk_substs_trait(self_ty, self.substs),
1472 impl<'tcx> PolyExistentialProjection<'tcx> {
1473 pub fn with_self_ty(
1477 ) -> ty::PolyProjectionPredicate<'tcx> {
1478 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1481 pub fn item_def_id(&self) -> DefId {
1482 self.skip_binder().item_def_id
1486 impl DebruijnIndex {
1487 /// Returns the resulting index when this value is moved into
1488 /// `amount` number of new binders. So, e.g., if you had
1490 /// for<'a> fn(&'a x)
1492 /// and you wanted to change it to
1494 /// for<'a> fn(for<'b> fn(&'a x))
1496 /// you would need to shift the index for `'a` into a new binder.
1498 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1499 DebruijnIndex::from_u32(self.as_u32() + amount)
1502 /// Update this index in place by shifting it "in" through
1503 /// `amount` number of binders.
1504 pub fn shift_in(&mut self, amount: u32) {
1505 *self = self.shifted_in(amount);
1508 /// Returns the resulting index when this value is moved out from
1509 /// `amount` number of new binders.
1511 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1512 DebruijnIndex::from_u32(self.as_u32() - amount)
1515 /// Update in place by shifting out from `amount` binders.
1516 pub fn shift_out(&mut self, amount: u32) {
1517 *self = self.shifted_out(amount);
1520 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1521 /// innermost binder. That is, if we have something bound at `to_binder`,
1522 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1523 /// when moving a region out from inside binders:
1526 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1527 /// // Binder: D3 D2 D1 ^^
1530 /// Here, the region `'a` would have the De Bruijn index D3,
1531 /// because it is the bound 3 binders out. However, if we wanted
1532 /// to refer to that region `'a` in the second argument (the `_`),
1533 /// those two binders would not be in scope. In that case, we
1534 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1535 /// De Bruijn index of `'a` to D1 (the innermost binder).
1537 /// If we invoke `shift_out_to_binder` and the region is in fact
1538 /// bound by one of the binders we are shifting out of, that is an
1539 /// error (and should fail an assertion failure).
1540 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1541 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1545 /// Region utilities
1547 /// Is this region named by the user?
1548 pub fn has_name(&self) -> bool {
1550 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1551 RegionKind::ReLateBound(_, br) => br.is_named(),
1552 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1553 RegionKind::ReStatic => true,
1554 RegionKind::ReVar(..) => false,
1555 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1556 RegionKind::ReEmpty(_) => false,
1557 RegionKind::ReErased => false,
1561 pub fn is_late_bound(&self) -> bool {
1563 ty::ReLateBound(..) => true,
1568 pub fn is_placeholder(&self) -> bool {
1570 ty::RePlaceholder(..) => true,
1575 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1577 ty::ReLateBound(debruijn, _) => debruijn >= index,
1582 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1583 /// innermost binder. That is, if we have something bound at `to_binder`,
1584 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1585 /// when moving a region out from inside binders:
1588 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1589 /// // Binder: D3 D2 D1 ^^
1592 /// Here, the region `'a` would have the De Bruijn index D3,
1593 /// because it is the bound 3 binders out. However, if we wanted
1594 /// to refer to that region `'a` in the second argument (the `_`),
1595 /// those two binders would not be in scope. In that case, we
1596 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1597 /// De Bruijn index of `'a` to D1 (the innermost binder).
1599 /// If we invoke `shift_out_to_binder` and the region is in fact
1600 /// bound by one of the binders we are shifting out of, that is an
1601 /// error (and should fail an assertion failure).
1602 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1604 ty::ReLateBound(debruijn, r) => {
1605 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1611 pub fn type_flags(&self) -> TypeFlags {
1612 let mut flags = TypeFlags::empty();
1616 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1617 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1618 flags = flags | TypeFlags::HAS_RE_INFER;
1620 ty::RePlaceholder(..) => {
1621 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1622 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1623 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1625 ty::ReEarlyBound(..) => {
1626 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1627 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1628 flags = flags | TypeFlags::HAS_RE_PARAM;
1630 ty::ReFree { .. } => {
1631 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1632 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1634 ty::ReEmpty(_) | ty::ReStatic => {
1635 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1637 ty::ReLateBound(..) => {
1638 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1641 flags = flags | TypeFlags::HAS_RE_ERASED;
1645 debug!("type_flags({:?}) = {:?}", self, flags);
1650 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1651 /// For example, consider the regions in this snippet of code:
1655 /// ^^ -- early bound, declared on an impl
1657 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1658 /// ^^ ^^ ^ anonymous, late-bound
1659 /// | early-bound, appears in where-clauses
1660 /// late-bound, appears only in fn args
1665 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1666 /// of the impl, and for all the other highlighted regions, it
1667 /// would return the `DefId` of the function. In other cases (not shown), this
1668 /// function might return the `DefId` of a closure.
1669 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1671 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1672 ty::ReFree(fr) => fr.scope,
1673 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1679 impl<'tcx> TyS<'tcx> {
1681 pub fn is_unit(&self) -> bool {
1683 Tuple(ref tys) => tys.is_empty(),
1689 pub fn is_never(&self) -> bool {
1696 /// Checks whether a type is definitely uninhabited. This is
1697 /// conservative: for some types that are uninhabited we return `false`,
1698 /// but we only return `true` for types that are definitely uninhabited.
1699 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1700 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1701 /// size, to account for partial initialisation. See #49298 for details.)
1702 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1703 // FIXME(varkor): we can make this less conversative by substituting concrete
1707 ty::Adt(def, _) if def.is_union() => {
1708 // For now, `union`s are never considered uninhabited.
1711 ty::Adt(def, _) => {
1712 // Any ADT is uninhabited if either:
1713 // (a) It has no variants (i.e. an empty `enum`);
1714 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1715 // one uninhabited field.
1716 def.variants.iter().all(|var| {
1717 var.fields.iter().any(|field| {
1718 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1723 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1725 ty::Array(ty, len) => {
1726 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1727 // If the array is definitely non-empty, it's uninhabited if
1728 // the type of its elements is uninhabited.
1729 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1734 // References to uninitialised memory is valid for any type, including
1735 // uninhabited types, in unsafe code, so we treat all references as
1744 pub fn is_primitive(&self) -> bool {
1746 Bool | Char | Int(_) | Uint(_) | Float(_) => true,
1752 pub fn is_ty_var(&self) -> bool {
1754 Infer(TyVar(_)) => true,
1760 pub fn is_ty_infer(&self) -> bool {
1768 pub fn is_phantom_data(&self) -> bool {
1769 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1773 pub fn is_bool(&self) -> bool {
1777 /// Returns `true` if this type is a `str`.
1779 pub fn is_str(&self) -> bool {
1784 pub fn is_param(&self, index: u32) -> bool {
1786 ty::Param(ref data) => data.index == index,
1792 pub fn is_slice(&self) -> bool {
1794 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1795 Slice(_) | Str => true,
1803 pub fn is_simd(&self) -> bool {
1805 Adt(def, _) => def.repr.simd(),
1810 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1812 Array(ty, _) | Slice(ty) => ty,
1813 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1814 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1818 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1820 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1821 _ => bug!("`simd_type` called on invalid type"),
1825 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1826 // Parameter currently unused, but probably needed in the future to
1827 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1829 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1830 _ => bug!("`simd_size` called on invalid type"),
1834 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1836 Adt(def, substs) => {
1837 let variant = def.non_enum_variant();
1838 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1840 _ => bug!("`simd_size_and_type` called on invalid type"),
1845 pub fn is_region_ptr(&self) -> bool {
1853 pub fn is_mutable_ptr(&self) -> bool {
1855 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1856 | Ref(_, _, hir::Mutability::Mut) => true,
1862 pub fn is_unsafe_ptr(&self) -> bool {
1869 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1871 pub fn is_any_ptr(&self) -> bool {
1872 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1876 pub fn is_box(&self) -> bool {
1878 Adt(def, _) => def.is_box(),
1883 /// Panics if called on any type other than `Box<T>`.
1884 pub fn boxed_ty(&self) -> Ty<'tcx> {
1886 Adt(def, substs) if def.is_box() => substs.type_at(0),
1887 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1891 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1892 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1893 /// contents are abstract to rustc.)
1895 pub fn is_scalar(&self) -> bool {
1902 | Infer(IntVar(_) | FloatVar(_))
1905 | RawPtr(_) => true,
1910 /// Returns `true` if this type is a floating point type.
1912 pub fn is_floating_point(&self) -> bool {
1914 Float(_) | Infer(FloatVar(_)) => true,
1920 pub fn is_trait(&self) -> bool {
1922 Dynamic(..) => true,
1928 pub fn is_enum(&self) -> bool {
1930 Adt(adt_def, _) => adt_def.is_enum(),
1936 pub fn is_closure(&self) -> bool {
1938 Closure(..) => true,
1944 pub fn is_generator(&self) -> bool {
1946 Generator(..) => true,
1952 pub fn is_integral(&self) -> bool {
1954 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
1960 pub fn is_fresh_ty(&self) -> bool {
1962 Infer(FreshTy(_)) => true,
1968 pub fn is_fresh(&self) -> bool {
1970 Infer(FreshTy(_)) => true,
1971 Infer(FreshIntTy(_)) => true,
1972 Infer(FreshFloatTy(_)) => true,
1978 pub fn is_char(&self) -> bool {
1986 pub fn is_numeric(&self) -> bool {
1987 self.is_integral() || self.is_floating_point()
1991 pub fn is_signed(&self) -> bool {
1999 pub fn is_ptr_sized_integral(&self) -> bool {
2001 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
2007 pub fn is_machine(&self) -> bool {
2009 Int(..) | Uint(..) | Float(..) => true,
2015 pub fn has_concrete_skeleton(&self) -> bool {
2017 Param(_) | Infer(_) | Error(_) => false,
2022 /// Returns the type and mutability of `*ty`.
2024 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2025 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2026 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2028 Adt(def, _) if def.is_box() => {
2029 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2031 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2032 RawPtr(mt) if explicit => Some(mt),
2037 /// Returns the type of `ty[i]`.
2038 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2040 Array(ty, _) | Slice(ty) => Some(ty),
2045 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2047 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2050 // ignore errors (#54954)
2051 ty::Binder::dummy(FnSig::fake())
2053 Closure(..) => bug!(
2054 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2056 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2061 pub fn is_fn(&self) -> bool {
2063 FnDef(..) | FnPtr(_) => true,
2069 pub fn is_fn_ptr(&self) -> bool {
2077 pub fn is_impl_trait(&self) -> bool {
2085 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2087 Adt(adt, _) => Some(adt),
2092 /// Iterates over tuple fields.
2093 /// Panics when called on anything but a tuple.
2094 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2096 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2097 _ => bug!("tuple_fields called on non-tuple"),
2101 /// If the type contains variants, returns the valid range of variant indices.
2103 // FIXME: This requires the optimized MIR in the case of generators.
2105 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2107 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2108 TyKind::Generator(def_id, substs, _) => {
2109 Some(substs.as_generator().variant_range(def_id, tcx))
2115 /// If the type contains variants, returns the variant for `variant_index`.
2116 /// Panics if `variant_index` is out of range.
2118 // FIXME: This requires the optimized MIR in the case of generators.
2120 pub fn discriminant_for_variant(
2123 variant_index: VariantIdx,
2124 ) -> Option<Discr<'tcx>> {
2126 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2127 bug!("discriminant_for_variant called on zero variant enum");
2129 TyKind::Adt(adt, _) if adt.is_enum() => {
2130 Some(adt.discriminant_for_variant(tcx, variant_index))
2132 TyKind::Generator(def_id, substs, _) => {
2133 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2139 /// Returns the type of the discriminant of this type.
2140 pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2142 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2143 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2145 // This can only be `0`, for now, so `u8` will suffice.
2151 /// When we create a closure, we record its kind (i.e., what trait
2152 /// it implements) into its `ClosureSubsts` using a type
2153 /// parameter. This is kind of a phantom type, except that the
2154 /// most convenient thing for us to are the integral types. This
2155 /// function converts such a special type into the closure
2156 /// kind. To go the other way, use
2157 /// `tcx.closure_kind_ty(closure_kind)`.
2159 /// Note that during type checking, we use an inference variable
2160 /// to represent the closure kind, because it has not yet been
2161 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2162 /// is complete, that type variable will be unified.
2163 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2165 Int(int_ty) => match int_ty {
2166 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2167 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2168 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2169 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2172 // "Bound" types appear in canonical queries when the
2173 // closure type is not yet known
2174 Bound(..) | Infer(_) => None,
2176 Error(_) => Some(ty::ClosureKind::Fn),
2178 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2182 /// Fast path helper for testing if a type is `Sized`.
2184 /// Returning true means the type is known to be sized. Returning
2185 /// `false` means nothing -- could be sized, might not be.
2186 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2188 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2199 | ty::GeneratorWitness(..)
2203 | ty::Error(_) => true,
2205 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2207 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2209 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2211 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2213 ty::Infer(ty::TyVar(_)) => false,
2216 | ty::Placeholder(..)
2217 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2218 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2223 /// Is this a zero-sized type?
2224 pub fn is_zst(&'tcx self, tcx: TyCtxt<'tcx>, did: DefId) -> bool {
2225 tcx.layout_of(tcx.param_env(did).and(self)).map(|layout| layout.is_zst()).unwrap_or(false)