1 //! This module contains `TyKind` and its major components.
3 #![allow(rustc::usage_of_ty_tykind)]
8 use crate::infer::canonical::Canonical;
9 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
11 self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness,
13 use crate::ty::{DelaySpanBugEmitted, List, ParamEnv, TyS};
14 use polonius_engine::Atom;
16 use rustc_data_structures::captures::Captures;
18 use rustc_hir::def_id::DefId;
19 use rustc_index::vec::Idx;
20 use rustc_macros::HashStable;
21 use rustc_span::symbol::{kw, Ident, Symbol};
22 use rustc_target::abi::VariantIdx;
23 use rustc_target::spec::abi;
25 use std::cmp::Ordering;
26 use std::marker::PhantomData;
28 use ty::util::IntTypeExt;
30 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
31 #[derive(HashStable, TypeFoldable, Lift)]
32 pub struct TypeAndMut<'tcx> {
34 pub mutbl: hir::Mutability,
37 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
39 /// A "free" region `fr` can be interpreted as "some region
40 /// at least as big as the scope `fr.scope`".
41 pub struct FreeRegion {
43 pub bound_region: BoundRegion,
46 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
48 pub enum BoundRegion {
49 /// An anonymous region parameter for a given fn (&T)
52 /// Named region parameters for functions (a in &'a T)
54 /// The `DefId` is needed to distinguish free regions in
55 /// the event of shadowing.
56 BrNamed(DefId, Symbol),
58 /// Anonymous region for the implicit env pointer parameter
64 pub fn is_named(&self) -> bool {
66 BoundRegion::BrNamed(_, name) => name != kw::UnderscoreLifetime,
71 /// When canonicalizing, we replace unbound inference variables and free
72 /// regions with anonymous late bound regions. This method asserts that
73 /// we have an anonymous late bound region, which hence may refer to
74 /// a canonical variable.
75 pub fn assert_bound_var(&self) -> BoundVar {
77 BoundRegion::BrAnon(var) => BoundVar::from_u32(var),
78 _ => bug!("bound region is not anonymous"),
83 /// N.B., if you change this, you'll probably want to change the corresponding
84 /// AST structure in `librustc_ast/ast.rs` as well.
85 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
87 #[rustc_diagnostic_item = "TyKind"]
88 pub enum TyKind<'tcx> {
89 /// The primitive boolean type. Written as `bool`.
92 /// The primitive character type; holds a Unicode scalar value
93 /// (a non-surrogate code point). Written as `char`.
96 /// A primitive signed integer type. For example, `i32`.
99 /// A primitive unsigned integer type. For example, `u32`.
102 /// A primitive floating-point type. For example, `f64`.
105 /// Structures, enumerations and unions.
107 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
108 /// That is, even after substitution it is possible that there are type
109 /// variables. This happens when the `Adt` corresponds to an ADT
110 /// definition and not a concrete use of it.
111 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
113 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
116 /// The pointee of a string slice. Written as `str`.
119 /// An array with the given length. Written as `[T; n]`.
120 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
122 /// The pointee of an array slice. Written as `[T]`.
125 /// A raw pointer. Written as `*mut T` or `*const T`
126 RawPtr(TypeAndMut<'tcx>),
128 /// A reference; a pointer with an associated lifetime. Written as
129 /// `&'a mut T` or `&'a T`.
130 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
132 /// The anonymous type of a function declaration/definition. Each
133 /// function has a unique type, which is output (for a function
134 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
136 /// For example the type of `bar` here:
139 /// fn foo() -> i32 { 1 }
140 /// let bar = foo; // bar: fn() -> i32 {foo}
142 FnDef(DefId, SubstsRef<'tcx>),
144 /// A pointer to a function. Written as `fn() -> i32`.
146 /// For example the type of `bar` here:
149 /// fn foo() -> i32 { 1 }
150 /// let bar: fn() -> i32 = foo;
152 FnPtr(PolyFnSig<'tcx>),
154 /// A trait, defined with `trait`.
155 Dynamic(Binder<&'tcx List<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
157 /// The anonymous type of a closure. Used to represent the type of
159 Closure(DefId, SubstsRef<'tcx>),
161 /// The anonymous type of a generator. Used to represent the type of
163 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
165 /// A type representin the types stored inside a generator.
166 /// This should only appear in GeneratorInteriors.
167 GeneratorWitness(Binder<&'tcx List<Ty<'tcx>>>),
169 /// The never type `!`
172 /// A tuple type. For example, `(i32, bool)`.
173 /// Use `TyS::tuple_fields` to iterate over the field types.
174 Tuple(SubstsRef<'tcx>),
176 /// The projection of an associated type. For example,
177 /// `<T as Trait<..>>::N`.
178 Projection(ProjectionTy<'tcx>),
180 /// Opaque (`impl Trait`) type found in a return type.
181 /// The `DefId` comes either from
182 /// * the `impl Trait` ast::Ty node,
183 /// * or the `type Foo = impl Trait` declaration
184 /// The substitutions are for the generics of the function in question.
185 /// After typeck, the concrete type can be found in the `types` map.
186 Opaque(DefId, SubstsRef<'tcx>),
188 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
191 /// Bound type variable, used only when preparing a trait query.
192 Bound(ty::DebruijnIndex, BoundTy),
194 /// A placeholder type - universally quantified higher-ranked type.
195 Placeholder(ty::PlaceholderType),
197 /// A type variable used during type checking.
200 /// A placeholder for a type which could not be computed; this is
201 /// propagated to avoid useless error messages.
202 Error(DelaySpanBugEmitted),
207 pub fn is_primitive(&self) -> bool {
209 Bool | Char | Int(_) | Uint(_) | Float(_) => true,
215 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
216 #[cfg(target_arch = "x86_64")]
217 static_assert_size!(TyKind<'_>, 24);
219 /// A closure can be modeled as a struct that looks like:
221 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
225 /// - 'l0...'li and T0...Tj are the generic parameters
226 /// in scope on the function that defined the closure,
227 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
228 /// is rather hackily encoded via a scalar type. See
229 /// `TyS::to_opt_closure_kind` for details.
230 /// - CS represents the *closure signature*, representing as a `fn()`
231 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
232 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
234 /// - U is a type parameter representing the types of its upvars, tupled up
235 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
236 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
238 /// So, for example, given this function:
240 /// fn foo<'a, T>(data: &'a mut T) {
241 /// do(|| data.count += 1)
244 /// the type of the closure would be something like:
246 /// struct Closure<'a, T, U>(...U);
248 /// Note that the type of the upvar is not specified in the struct.
249 /// You may wonder how the impl would then be able to use the upvar,
250 /// if it doesn't know it's type? The answer is that the impl is
251 /// (conceptually) not fully generic over Closure but rather tied to
252 /// instances with the expected upvar types:
254 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
258 /// You can see that the *impl* fully specified the type of the upvar
259 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
260 /// (Here, I am assuming that `data` is mut-borrowed.)
262 /// Now, the last question you may ask is: Why include the upvar types
263 /// in an extra type parameter? The reason for this design is that the
264 /// upvar types can reference lifetimes that are internal to the
265 /// creating function. In my example above, for example, the lifetime
266 /// `'b` represents the scope of the closure itself; this is some
267 /// subset of `foo`, probably just the scope of the call to the to
268 /// `do()`. If we just had the lifetime/type parameters from the
269 /// enclosing function, we couldn't name this lifetime `'b`. Note that
270 /// there can also be lifetimes in the types of the upvars themselves,
271 /// if one of them happens to be a reference to something that the
272 /// creating fn owns.
274 /// OK, you say, so why not create a more minimal set of parameters
275 /// that just includes the extra lifetime parameters? The answer is
276 /// primarily that it would be hard --- we don't know at the time when
277 /// we create the closure type what the full types of the upvars are,
278 /// nor do we know which are borrowed and which are not. In this
279 /// design, we can just supply a fresh type parameter and figure that
282 /// All right, you say, but why include the type parameters from the
283 /// original function then? The answer is that codegen may need them
284 /// when monomorphizing, and they may not appear in the upvars. A
285 /// closure could capture no variables but still make use of some
286 /// in-scope type parameter with a bound (e.g., if our example above
287 /// had an extra `U: Default`, and the closure called `U::default()`).
289 /// There is another reason. This design (implicitly) prohibits
290 /// closures from capturing themselves (except via a trait
291 /// object). This simplifies closure inference considerably, since it
292 /// means that when we infer the kind of a closure or its upvars, we
293 /// don't have to handle cycles where the decisions we make for
294 /// closure C wind up influencing the decisions we ought to make for
295 /// closure C (which would then require fixed point iteration to
296 /// handle). Plus it fixes an ICE. :P
300 /// Generators are handled similarly in `GeneratorSubsts`. The set of
301 /// type parameters is similar, but `CK` and `CS` are replaced by the
302 /// following type parameters:
304 /// * `GS`: The generator's "resume type", which is the type of the
305 /// argument passed to `resume`, and the type of `yield` expressions
306 /// inside the generator.
307 /// * `GY`: The "yield type", which is the type of values passed to
308 /// `yield` inside the generator.
309 /// * `GR`: The "return type", which is the type of value returned upon
310 /// completion of the generator.
311 /// * `GW`: The "generator witness".
312 #[derive(Copy, Clone, Debug, TypeFoldable)]
313 pub struct ClosureSubsts<'tcx> {
314 /// Lifetime and type parameters from the enclosing function,
315 /// concatenated with a tuple containing the types of the upvars.
317 /// These are separated out because codegen wants to pass them around
318 /// when monomorphizing.
319 pub substs: SubstsRef<'tcx>,
322 /// Struct returned by `split()`. Note that these are subslices of the
323 /// parent slice and not canonical substs themselves.
324 struct SplitClosureSubsts<'tcx> {
325 parent: &'tcx [GenericArg<'tcx>],
326 closure_kind_ty: GenericArg<'tcx>,
327 closure_sig_as_fn_ptr_ty: GenericArg<'tcx>,
328 tupled_upvars_ty: GenericArg<'tcx>,
331 impl<'tcx> ClosureSubsts<'tcx> {
332 /// Divides the closure substs into their respective
333 /// components. Single source of truth with respect to the
335 fn split(self) -> SplitClosureSubsts<'tcx> {
336 match self.substs[..] {
337 [ref parent @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
341 closure_sig_as_fn_ptr_ty,
345 _ => bug!("closure substs missing synthetics"),
349 /// Returns `true` only if enough of the synthetic types are known to
350 /// allow using all of the methods on `ClosureSubsts` without panicking.
352 /// Used primarily by `ty::print::pretty` to be able to handle closure
353 /// types that haven't had their synthetic types substituted in.
354 pub fn is_valid(self) -> bool {
355 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
358 /// Returns the substitutions of the closure's parent.
359 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
364 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
365 self.tupled_upvars_ty().tuple_fields()
368 /// Returns the tuple type representing the upvars for this closure.
370 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
371 self.split().tupled_upvars_ty.expect_ty()
374 /// Returns the closure kind for this closure; may return a type
375 /// variable during inference. To get the closure kind during
376 /// inference, use `infcx.closure_kind(substs)`.
377 pub fn kind_ty(self) -> Ty<'tcx> {
378 self.split().closure_kind_ty.expect_ty()
381 /// Returns the `fn` pointer type representing the closure signature for this
383 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
384 // type is known at the time of the creation of `ClosureSubsts`,
385 // see `rustc_typeck::check::closure`.
386 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
387 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
390 /// Returns the closure kind for this closure; only usable outside
391 /// of an inference context, because in that context we know that
392 /// there are no type variables.
394 /// If you have an inference context, use `infcx.closure_kind()`.
395 pub fn kind(self) -> ty::ClosureKind {
396 self.kind_ty().to_opt_closure_kind().unwrap()
399 /// Extracts the signature from the closure.
400 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
401 let ty = self.sig_as_fn_ptr_ty();
403 ty::FnPtr(sig) => sig,
404 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
409 /// Similar to `ClosureSubsts`; see the above documentation for more.
410 #[derive(Copy, Clone, Debug, TypeFoldable)]
411 pub struct GeneratorSubsts<'tcx> {
412 pub substs: SubstsRef<'tcx>,
415 struct SplitGeneratorSubsts<'tcx> {
416 parent: &'tcx [GenericArg<'tcx>],
417 resume_ty: GenericArg<'tcx>,
418 yield_ty: GenericArg<'tcx>,
419 return_ty: GenericArg<'tcx>,
420 witness: GenericArg<'tcx>,
421 tupled_upvars_ty: GenericArg<'tcx>,
424 impl<'tcx> GeneratorSubsts<'tcx> {
425 fn split(self) -> SplitGeneratorSubsts<'tcx> {
426 match self.substs[..] {
427 [ref parent @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
428 SplitGeneratorSubsts {
437 _ => bug!("generator substs missing synthetics"),
441 /// Returns `true` only if enough of the synthetic types are known to
442 /// allow using all of the methods on `GeneratorSubsts` without panicking.
444 /// Used primarily by `ty::print::pretty` to be able to handle generator
445 /// types that haven't had their synthetic types substituted in.
446 pub fn is_valid(self) -> bool {
447 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
450 /// Returns the substitutions of the generator's parent.
451 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
455 /// This describes the types that can be contained in a generator.
456 /// It will be a type variable initially and unified in the last stages of typeck of a body.
457 /// It contains a tuple of all the types that could end up on a generator frame.
458 /// The state transformation MIR pass may only produce layouts which mention types
459 /// in this tuple. Upvars are not counted here.
460 pub fn witness(self) -> Ty<'tcx> {
461 self.split().witness.expect_ty()
465 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
466 self.tupled_upvars_ty().tuple_fields()
469 /// Returns the tuple type representing the upvars for this generator.
471 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
472 self.split().tupled_upvars_ty.expect_ty()
475 /// Returns the type representing the resume type of the generator.
476 pub fn resume_ty(self) -> Ty<'tcx> {
477 self.split().resume_ty.expect_ty()
480 /// Returns the type representing the yield type of the generator.
481 pub fn yield_ty(self) -> Ty<'tcx> {
482 self.split().yield_ty.expect_ty()
485 /// Returns the type representing the return type of the generator.
486 pub fn return_ty(self) -> Ty<'tcx> {
487 self.split().return_ty.expect_ty()
490 /// Returns the "generator signature", which consists of its yield
491 /// and return types.
493 /// N.B., some bits of the code prefers to see this wrapped in a
494 /// binder, but it never contains bound regions. Probably this
495 /// function should be removed.
496 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
497 ty::Binder::dummy(self.sig())
500 /// Returns the "generator signature", which consists of its resume, yield
501 /// and return types.
502 pub fn sig(self) -> GenSig<'tcx> {
504 resume_ty: self.resume_ty(),
505 yield_ty: self.yield_ty(),
506 return_ty: self.return_ty(),
511 impl<'tcx> GeneratorSubsts<'tcx> {
512 /// Generator has not been resumed yet.
513 pub const UNRESUMED: usize = 0;
514 /// Generator has returned or is completed.
515 pub const RETURNED: usize = 1;
516 /// Generator has been poisoned.
517 pub const POISONED: usize = 2;
519 const UNRESUMED_NAME: &'static str = "Unresumed";
520 const RETURNED_NAME: &'static str = "Returned";
521 const POISONED_NAME: &'static str = "Panicked";
523 /// The valid variant indices of this generator.
525 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
526 // FIXME requires optimized MIR
527 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
528 VariantIdx::new(0)..VariantIdx::new(num_variants)
531 /// The discriminant for the given variant. Panics if the `variant_index` is
534 pub fn discriminant_for_variant(
538 variant_index: VariantIdx,
540 // Generators don't support explicit discriminant values, so they are
541 // the same as the variant index.
542 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
543 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
546 /// The set of all discriminants for the generator, enumerated with their
549 pub fn discriminants(
553 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
554 self.variant_range(def_id, tcx).map(move |index| {
555 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
559 /// Calls `f` with a reference to the name of the enumerator for the given
561 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
563 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
564 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
565 Self::POISONED => Cow::from(Self::POISONED_NAME),
566 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
570 /// The type of the state discriminant used in the generator type.
572 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
576 /// This returns the types of the MIR locals which had to be stored across suspension points.
577 /// It is calculated in rustc_mir::transform::generator::StateTransform.
578 /// All the types here must be in the tuple in GeneratorInterior.
580 /// The locals are grouped by their variant number. Note that some locals may
581 /// be repeated in multiple variants.
587 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
588 let layout = tcx.generator_layout(def_id);
589 layout.variant_fields.iter().map(move |variant| {
590 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
594 /// This is the types of the fields of a generator which are not stored in a
597 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
602 #[derive(Debug, Copy, Clone)]
603 pub enum UpvarSubsts<'tcx> {
604 Closure(SubstsRef<'tcx>),
605 Generator(SubstsRef<'tcx>),
608 impl<'tcx> UpvarSubsts<'tcx> {
610 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
611 let tupled_upvars_ty = match self {
612 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
613 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
615 tupled_upvars_ty.expect_ty().tuple_fields()
619 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
620 #[derive(HashStable, TypeFoldable)]
621 pub enum ExistentialPredicate<'tcx> {
622 /// E.g., `Iterator`.
623 Trait(ExistentialTraitRef<'tcx>),
624 /// E.g., `Iterator::Item = T`.
625 Projection(ExistentialProjection<'tcx>),
630 impl<'tcx> ExistentialPredicate<'tcx> {
631 /// Compares via an ordering that will not change if modules are reordered or other changes are
632 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
633 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
634 use self::ExistentialPredicate::*;
635 match (*self, *other) {
636 (Trait(_), Trait(_)) => Ordering::Equal,
637 (Projection(ref a), Projection(ref b)) => {
638 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
640 (AutoTrait(ref a), AutoTrait(ref b)) => {
641 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
643 (Trait(_), _) => Ordering::Less,
644 (Projection(_), Trait(_)) => Ordering::Greater,
645 (Projection(_), _) => Ordering::Less,
646 (AutoTrait(_), _) => Ordering::Greater,
651 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
652 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
653 use crate::ty::ToPredicate;
654 match self.skip_binder() {
655 ExistentialPredicate::Trait(tr) => {
656 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
658 ExistentialPredicate::Projection(p) => {
659 Binder(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
661 ExistentialPredicate::AutoTrait(did) => {
663 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
664 trait_ref.without_const().to_predicate(tcx)
670 impl<'tcx> List<ExistentialPredicate<'tcx>> {
671 /// Returns the "principal `DefId`" of this set of existential predicates.
673 /// A Rust trait object type consists (in addition to a lifetime bound)
674 /// of a set of trait bounds, which are separated into any number
675 /// of auto-trait bounds, and at most one non-auto-trait bound. The
676 /// non-auto-trait bound is called the "principal" of the trait
679 /// Only the principal can have methods or type parameters (because
680 /// auto traits can have neither of them). This is important, because
681 /// it means the auto traits can be treated as an unordered set (methods
682 /// would force an order for the vtable, while relating traits with
683 /// type parameters without knowing the order to relate them in is
684 /// a rather non-trivial task).
686 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
687 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
688 /// are the set `{Sync}`.
690 /// It is also possible to have a "trivial" trait object that
691 /// consists only of auto traits, with no principal - for example,
692 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
693 /// is `{Send, Sync}`, while there is no principal. These trait objects
694 /// have a "trivial" vtable consisting of just the size, alignment,
696 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
698 ExistentialPredicate::Trait(tr) => Some(tr),
703 pub fn principal_def_id(&self) -> Option<DefId> {
704 self.principal().map(|trait_ref| trait_ref.def_id)
708 pub fn projection_bounds<'a>(
710 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
711 self.iter().filter_map(|predicate| match predicate {
712 ExistentialPredicate::Projection(projection) => Some(projection),
718 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
719 self.iter().filter_map(|predicate| match predicate {
720 ExistentialPredicate::AutoTrait(did) => Some(did),
726 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
727 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
728 self.skip_binder().principal().map(Binder::bind)
731 pub fn principal_def_id(&self) -> Option<DefId> {
732 self.skip_binder().principal_def_id()
736 pub fn projection_bounds<'a>(
738 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
739 self.skip_binder().projection_bounds().map(Binder::bind)
743 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
744 self.skip_binder().auto_traits()
749 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
750 self.skip_binder().iter().map(Binder::bind)
754 /// A complete reference to a trait. These take numerous guises in syntax,
755 /// but perhaps the most recognizable form is in a where-clause:
759 /// This would be represented by a trait-reference where the `DefId` is the
760 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
761 /// and `U` as parameter 1.
763 /// Trait references also appear in object types like `Foo<U>`, but in
764 /// that case the `Self` parameter is absent from the substitutions.
765 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
766 #[derive(HashStable, TypeFoldable)]
767 pub struct TraitRef<'tcx> {
769 pub substs: SubstsRef<'tcx>,
772 impl<'tcx> TraitRef<'tcx> {
773 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
774 TraitRef { def_id, substs }
777 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
778 /// are the parameters defined on trait.
779 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
780 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
784 pub fn self_ty(&self) -> Ty<'tcx> {
785 self.substs.type_at(0)
791 substs: SubstsRef<'tcx>,
792 ) -> ty::TraitRef<'tcx> {
793 let defs = tcx.generics_of(trait_id);
795 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
799 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
801 impl<'tcx> PolyTraitRef<'tcx> {
802 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
803 self.map_bound_ref(|tr| tr.self_ty())
806 pub fn def_id(&self) -> DefId {
807 self.skip_binder().def_id
810 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
811 // Note that we preserve binding levels
812 Binder(ty::TraitPredicate { trait_ref: self.skip_binder() })
816 /// An existential reference to a trait, where `Self` is erased.
817 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
819 /// exists T. T: Trait<'a, 'b, X, Y>
821 /// The substitutions don't include the erased `Self`, only trait
822 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
823 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
824 #[derive(HashStable, TypeFoldable)]
825 pub struct ExistentialTraitRef<'tcx> {
827 pub substs: SubstsRef<'tcx>,
830 impl<'tcx> ExistentialTraitRef<'tcx> {
831 pub fn erase_self_ty(
833 trait_ref: ty::TraitRef<'tcx>,
834 ) -> ty::ExistentialTraitRef<'tcx> {
835 // Assert there is a Self.
836 trait_ref.substs.type_at(0);
838 ty::ExistentialTraitRef {
839 def_id: trait_ref.def_id,
840 substs: tcx.intern_substs(&trait_ref.substs[1..]),
844 /// Object types don't have a self type specified. Therefore, when
845 /// we convert the principal trait-ref into a normal trait-ref,
846 /// you must give *some* self type. A common choice is `mk_err()`
847 /// or some placeholder type.
848 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
849 // otherwise the escaping vars would be captured by the binder
850 // debug_assert!(!self_ty.has_escaping_bound_vars());
852 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
856 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
858 impl<'tcx> PolyExistentialTraitRef<'tcx> {
859 pub fn def_id(&self) -> DefId {
860 self.skip_binder().def_id
863 /// Object types don't have a self type specified. Therefore, when
864 /// we convert the principal trait-ref into a normal trait-ref,
865 /// you must give *some* self type. A common choice is `mk_err()`
866 /// or some placeholder type.
867 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
868 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
872 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
873 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
874 /// (which would be represented by the type `PolyTraitRef ==
875 /// Binder<TraitRef>`). Note that when we instantiate,
876 /// erase, or otherwise "discharge" these bound vars, we change the
877 /// type from `Binder<T>` to just `T` (see
878 /// e.g., `liberate_late_bound_regions`).
879 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
880 pub struct Binder<T>(T);
883 /// Wraps `value` in a binder, asserting that `value` does not
884 /// contain any bound vars that would be bound by the
885 /// binder. This is commonly used to 'inject' a value T into a
886 /// different binding level.
887 pub fn dummy<'tcx>(value: T) -> Binder<T>
889 T: TypeFoldable<'tcx>,
891 debug_assert!(!value.has_escaping_bound_vars());
895 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
896 pub fn bind(value: T) -> Binder<T> {
900 /// Wraps `value` in a binder without actually binding any currently
901 /// unbound variables.
903 /// Note that this will shift all debrujin indices of escaping bound variables
904 /// by 1 to avoid accidential captures.
905 pub fn wrap_nonbinding(tcx: TyCtxt<'tcx>, value: T) -> Binder<T>
907 T: TypeFoldable<'tcx>,
909 if value.has_escaping_bound_vars() {
910 Binder::bind(super::fold::shift_vars(tcx, &value, 1))
916 /// Skips the binder and returns the "bound" value. This is a
917 /// risky thing to do because it's easy to get confused about
918 /// De Bruijn indices and the like. It is usually better to
919 /// discharge the binder using `no_bound_vars` or
920 /// `replace_late_bound_regions` or something like
921 /// that. `skip_binder` is only valid when you are either
922 /// extracting data that has nothing to do with bound vars, you
923 /// are doing some sort of test that does not involve bound
924 /// regions, or you are being very careful about your depth
927 /// Some examples where `skip_binder` is reasonable:
929 /// - extracting the `DefId` from a PolyTraitRef;
930 /// - comparing the self type of a PolyTraitRef to see if it is equal to
931 /// a type parameter `X`, since the type `X` does not reference any regions
932 pub fn skip_binder(self) -> T {
936 pub fn as_ref(&self) -> Binder<&T> {
940 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
944 self.as_ref().map_bound(f)
947 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
954 /// Unwraps and returns the value within, but only if it contains
955 /// no bound vars at all. (In other words, if this binder --
956 /// and indeed any enclosing binder -- doesn't bind anything at
957 /// all.) Otherwise, returns `None`.
959 /// (One could imagine having a method that just unwraps a single
960 /// binder, but permits late-bound vars bound by enclosing
961 /// binders, but that would require adjusting the debruijn
962 /// indices, and given the shallow binding structure we often use,
963 /// would not be that useful.)
964 pub fn no_bound_vars<'tcx>(self) -> Option<T>
966 T: TypeFoldable<'tcx>,
968 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
971 /// Given two things that have the same binder level,
972 /// and an operation that wraps on their contents, executes the operation
973 /// and then wraps its result.
975 /// `f` should consider bound regions at depth 1 to be free, and
976 /// anything it produces with bound regions at depth 1 will be
977 /// bound in the resulting return value.
978 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
980 F: FnOnce(T, U) -> R,
982 Binder(f(self.0, u.0))
985 /// Splits the contents into two things that share the same binder
986 /// level as the original, returning two distinct binders.
988 /// `f` should consider bound regions at depth 1 to be free, and
989 /// anything it produces with bound regions at depth 1 will be
990 /// bound in the resulting return values.
991 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
993 F: FnOnce(T) -> (U, V),
995 let (u, v) = f(self.0);
996 (Binder(u), Binder(v))
1000 impl<T> Binder<Option<T>> {
1001 pub fn transpose(self) -> Option<Binder<T>> {
1003 Some(v) => Some(Binder(v)),
1009 /// Represents the projection of an associated type. In explicit UFCS
1010 /// form this would be written `<T as Trait<..>>::N`.
1011 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1012 #[derive(HashStable, TypeFoldable)]
1013 pub struct ProjectionTy<'tcx> {
1014 /// The parameters of the associated item.
1015 pub substs: SubstsRef<'tcx>,
1017 /// The `DefId` of the `TraitItem` for the associated type `N`.
1019 /// Note that this is not the `DefId` of the `TraitRef` containing this
1020 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1021 pub item_def_id: DefId,
1024 impl<'tcx> ProjectionTy<'tcx> {
1025 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
1026 /// associated item named `item_name`.
1027 pub fn from_ref_and_name(
1029 trait_ref: ty::TraitRef<'tcx>,
1031 ) -> ProjectionTy<'tcx> {
1032 let item_def_id = tcx
1033 .associated_items(trait_ref.def_id)
1034 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1038 ProjectionTy { substs: trait_ref.substs, item_def_id }
1041 /// Extracts the underlying trait reference from this projection.
1042 /// For example, if this is a projection of `<T as Iterator>::Item`,
1043 /// then this function would return a `T: Iterator` trait reference.
1044 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1045 let def_id = tcx.associated_item(self.item_def_id).container.id();
1046 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1049 pub fn self_ty(&self) -> Ty<'tcx> {
1050 self.substs.type_at(0)
1054 #[derive(Copy, Clone, Debug, TypeFoldable)]
1055 pub struct GenSig<'tcx> {
1056 pub resume_ty: Ty<'tcx>,
1057 pub yield_ty: Ty<'tcx>,
1058 pub return_ty: Ty<'tcx>,
1061 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1063 impl<'tcx> PolyGenSig<'tcx> {
1064 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1065 self.map_bound_ref(|sig| sig.resume_ty)
1067 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1068 self.map_bound_ref(|sig| sig.yield_ty)
1070 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1071 self.map_bound_ref(|sig| sig.return_ty)
1075 /// Signature of a function type, which we have arbitrarily
1076 /// decided to use to refer to the input/output types.
1078 /// - `inputs`: is the list of arguments and their modes.
1079 /// - `output`: is the return type.
1080 /// - `c_variadic`: indicates whether this is a C-variadic function.
1081 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1082 #[derive(HashStable, TypeFoldable)]
1083 pub struct FnSig<'tcx> {
1084 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1085 pub c_variadic: bool,
1086 pub unsafety: hir::Unsafety,
1090 impl<'tcx> FnSig<'tcx> {
1091 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1092 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1095 pub fn output(&self) -> Ty<'tcx> {
1096 self.inputs_and_output[self.inputs_and_output.len() - 1]
1099 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1101 fn fake() -> FnSig<'tcx> {
1103 inputs_and_output: List::empty(),
1105 unsafety: hir::Unsafety::Normal,
1106 abi: abi::Abi::Rust,
1111 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1113 impl<'tcx> PolyFnSig<'tcx> {
1115 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1116 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1119 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1120 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1122 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1123 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1126 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1127 self.map_bound_ref(|fn_sig| fn_sig.output())
1129 pub fn c_variadic(&self) -> bool {
1130 self.skip_binder().c_variadic
1132 pub fn unsafety(&self) -> hir::Unsafety {
1133 self.skip_binder().unsafety
1135 pub fn abi(&self) -> abi::Abi {
1136 self.skip_binder().abi
1140 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1142 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1143 #[derive(HashStable)]
1144 pub struct ParamTy {
1149 impl<'tcx> ParamTy {
1150 pub fn new(index: u32, name: Symbol) -> ParamTy {
1151 ParamTy { index, name }
1154 pub fn for_self() -> ParamTy {
1155 ParamTy::new(0, kw::SelfUpper)
1158 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1159 ParamTy::new(def.index, def.name)
1162 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1163 tcx.mk_ty_param(self.index, self.name)
1167 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1168 #[derive(HashStable)]
1169 pub struct ParamConst {
1174 impl<'tcx> ParamConst {
1175 pub fn new(index: u32, name: Symbol) -> ParamConst {
1176 ParamConst { index, name }
1179 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1180 ParamConst::new(def.index, def.name)
1183 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
1184 tcx.mk_const_param(self.index, self.name, ty)
1188 rustc_index::newtype_index! {
1189 /// A [De Bruijn index][dbi] is a standard means of representing
1190 /// regions (and perhaps later types) in a higher-ranked setting. In
1191 /// particular, imagine a type like this:
1193 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1196 /// | +------------+ 0 | |
1198 /// +--------------------------------+ 1 |
1200 /// +------------------------------------------+ 0
1202 /// In this type, there are two binders (the outer fn and the inner
1203 /// fn). We need to be able to determine, for any given region, which
1204 /// fn type it is bound by, the inner or the outer one. There are
1205 /// various ways you can do this, but a De Bruijn index is one of the
1206 /// more convenient and has some nice properties. The basic idea is to
1207 /// count the number of binders, inside out. Some examples should help
1208 /// clarify what I mean.
1210 /// Let's start with the reference type `&'b isize` that is the first
1211 /// argument to the inner function. This region `'b` is assigned a De
1212 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1213 /// fn). The region `'a` that appears in the second argument type (`&'a
1214 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1215 /// second-innermost binder". (These indices are written on the arrays
1216 /// in the diagram).
1218 /// What is interesting is that De Bruijn index attached to a particular
1219 /// variable will vary depending on where it appears. For example,
1220 /// the final type `&'a char` also refers to the region `'a` declared on
1221 /// the outermost fn. But this time, this reference is not nested within
1222 /// any other binders (i.e., it is not an argument to the inner fn, but
1223 /// rather the outer one). Therefore, in this case, it is assigned a
1224 /// De Bruijn index of 0, because the innermost binder in that location
1225 /// is the outer fn.
1227 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1228 #[derive(HashStable)]
1229 pub struct DebruijnIndex {
1230 DEBUG_FORMAT = "DebruijnIndex({})",
1231 const INNERMOST = 0,
1235 pub type Region<'tcx> = &'tcx RegionKind;
1237 /// Representation of regions. Note that the NLL checker uses a distinct
1238 /// representation of regions. For this reason, it internally replaces all the
1239 /// regions with inference variables -- the index of the variable is then used
1240 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1241 /// module for more information.
1243 /// ## The Region lattice within a given function
1245 /// In general, the region lattice looks like
1248 /// static ----------+-----...------+ (greatest)
1250 /// early-bound and | |
1251 /// free regions | |
1254 /// empty(root) placeholder(U1) |
1256 /// | / placeholder(Un)
1261 /// empty(Un) -------- (smallest)
1264 /// Early-bound/free regions are the named lifetimes in scope from the
1265 /// function declaration. They have relationships to one another
1266 /// determined based on the declared relationships from the
1269 /// Note that inference variables and bound regions are not included
1270 /// in this diagram. In the case of inference variables, they should
1271 /// be inferred to some other region from the diagram. In the case of
1272 /// bound regions, they are excluded because they don't make sense to
1273 /// include -- the diagram indicates the relationship between free
1276 /// ## Inference variables
1278 /// During region inference, we sometimes create inference variables,
1279 /// represented as `ReVar`. These will be inferred by the code in
1280 /// `infer::lexical_region_resolve` to some free region from the
1281 /// lattice above (the minimal region that meets the
1284 /// During NLL checking, where regions are defined differently, we
1285 /// also use `ReVar` -- in that case, the index is used to index into
1286 /// the NLL region checker's data structures. The variable may in fact
1287 /// represent either a free region or an inference variable, in that
1290 /// ## Bound Regions
1292 /// These are regions that are stored behind a binder and must be substituted
1293 /// with some concrete region before being used. There are two kind of
1294 /// bound regions: early-bound, which are bound in an item's `Generics`,
1295 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1296 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1297 /// the likes of `liberate_late_bound_regions`. The distinction exists
1298 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1300 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1301 /// outside their binder, e.g., in types passed to type inference, and
1302 /// should first be substituted (by placeholder regions, free regions,
1303 /// or region variables).
1305 /// ## Placeholder and Free Regions
1307 /// One often wants to work with bound regions without knowing their precise
1308 /// identity. For example, when checking a function, the lifetime of a borrow
1309 /// can end up being assigned to some region parameter. In these cases,
1310 /// it must be ensured that bounds on the region can't be accidentally
1311 /// assumed without being checked.
1313 /// To do this, we replace the bound regions with placeholder markers,
1314 /// which don't satisfy any relation not explicitly provided.
1316 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1317 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1318 /// to be used. These also support explicit bounds: both the internally-stored
1319 /// *scope*, which the region is assumed to outlive, as well as other
1320 /// relations stored in the `FreeRegionMap`. Note that these relations
1321 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1322 /// `resolve_regions_and_report_errors`.
1324 /// When working with higher-ranked types, some region relations aren't
1325 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1326 /// `RePlaceholder` is designed for this purpose. In these contexts,
1327 /// there's also the risk that some inference variable laying around will
1328 /// get unified with your placeholder region: if you want to check whether
1329 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1330 /// with a placeholder region `'%a`, the variable `'_` would just be
1331 /// instantiated to the placeholder region `'%a`, which is wrong because
1332 /// the inference variable is supposed to satisfy the relation
1333 /// *for every value of the placeholder region*. To ensure that doesn't
1334 /// happen, you can use `leak_check`. This is more clearly explained
1335 /// by the [rustc dev guide].
1337 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1338 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1339 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1340 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1341 pub enum RegionKind {
1342 /// Region bound in a type or fn declaration which will be
1343 /// substituted 'early' -- that is, at the same time when type
1344 /// parameters are substituted.
1345 ReEarlyBound(EarlyBoundRegion),
1347 /// Region bound in a function scope, which will be substituted when the
1348 /// function is called.
1349 ReLateBound(DebruijnIndex, BoundRegion),
1351 /// When checking a function body, the types of all arguments and so forth
1352 /// that refer to bound region parameters are modified to refer to free
1353 /// region parameters.
1356 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1359 /// A region variable. Should not exist after typeck.
1362 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1363 /// Should not exist after typeck.
1364 RePlaceholder(ty::PlaceholderRegion),
1366 /// Empty lifetime is for data that is never accessed. We tag the
1367 /// empty lifetime with a universe -- the idea is that we don't
1368 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1369 /// Therefore, the `'empty` in a universe `U` is less than all
1370 /// regions visible from `U`, but not less than regions not visible
1372 ReEmpty(ty::UniverseIndex),
1374 /// Erased region, used by trait selection, in MIR and during codegen.
1378 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1379 pub struct EarlyBoundRegion {
1385 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1390 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1391 pub struct ConstVid<'tcx> {
1393 pub phantom: PhantomData<&'tcx ()>,
1396 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1401 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1402 pub struct FloatVid {
1406 rustc_index::newtype_index! {
1407 pub struct RegionVid {
1408 DEBUG_FORMAT = custom,
1412 impl Atom for RegionVid {
1413 fn index(self) -> usize {
1418 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1419 #[derive(HashStable)]
1425 /// A `FreshTy` is one that is generated as a replacement for an
1426 /// unbound type variable. This is convenient for caching etc. See
1427 /// `infer::freshen` for more details.
1433 rustc_index::newtype_index! {
1434 pub struct BoundVar { .. }
1437 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1438 #[derive(HashStable)]
1439 pub struct BoundTy {
1441 pub kind: BoundTyKind,
1444 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1445 #[derive(HashStable)]
1446 pub enum BoundTyKind {
1451 impl From<BoundVar> for BoundTy {
1452 fn from(var: BoundVar) -> Self {
1453 BoundTy { var, kind: BoundTyKind::Anon }
1457 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1458 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1459 #[derive(HashStable, TypeFoldable)]
1460 pub struct ExistentialProjection<'tcx> {
1461 pub item_def_id: DefId,
1462 pub substs: SubstsRef<'tcx>,
1466 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1468 impl<'tcx> ExistentialProjection<'tcx> {
1469 /// Extracts the underlying existential trait reference from this projection.
1470 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1471 /// then this function would return a `exists T. T: Iterator` existential trait
1473 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1474 let def_id = tcx.associated_item(self.item_def_id).container.id();
1475 ty::ExistentialTraitRef { def_id, substs: self.substs }
1478 pub fn with_self_ty(
1482 ) -> ty::ProjectionPredicate<'tcx> {
1483 // otherwise the escaping regions would be captured by the binders
1484 debug_assert!(!self_ty.has_escaping_bound_vars());
1486 ty::ProjectionPredicate {
1487 projection_ty: ty::ProjectionTy {
1488 item_def_id: self.item_def_id,
1489 substs: tcx.mk_substs_trait(self_ty, self.substs),
1496 impl<'tcx> PolyExistentialProjection<'tcx> {
1497 pub fn with_self_ty(
1501 ) -> ty::PolyProjectionPredicate<'tcx> {
1502 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1505 pub fn item_def_id(&self) -> DefId {
1506 self.skip_binder().item_def_id
1510 impl DebruijnIndex {
1511 /// Returns the resulting index when this value is moved into
1512 /// `amount` number of new binders. So, e.g., if you had
1514 /// for<'a> fn(&'a x)
1516 /// and you wanted to change it to
1518 /// for<'a> fn(for<'b> fn(&'a x))
1520 /// you would need to shift the index for `'a` into a new binder.
1522 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1523 DebruijnIndex::from_u32(self.as_u32() + amount)
1526 /// Update this index in place by shifting it "in" through
1527 /// `amount` number of binders.
1528 pub fn shift_in(&mut self, amount: u32) {
1529 *self = self.shifted_in(amount);
1532 /// Returns the resulting index when this value is moved out from
1533 /// `amount` number of new binders.
1535 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1536 DebruijnIndex::from_u32(self.as_u32() - amount)
1539 /// Update in place by shifting out from `amount` binders.
1540 pub fn shift_out(&mut self, amount: u32) {
1541 *self = self.shifted_out(amount);
1544 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1545 /// innermost binder. That is, if we have something bound at `to_binder`,
1546 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1547 /// when moving a region out from inside binders:
1550 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1551 /// // Binder: D3 D2 D1 ^^
1554 /// Here, the region `'a` would have the De Bruijn index D3,
1555 /// because it is the bound 3 binders out. However, if we wanted
1556 /// to refer to that region `'a` in the second argument (the `_`),
1557 /// those two binders would not be in scope. In that case, we
1558 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1559 /// De Bruijn index of `'a` to D1 (the innermost binder).
1561 /// If we invoke `shift_out_to_binder` and the region is in fact
1562 /// bound by one of the binders we are shifting out of, that is an
1563 /// error (and should fail an assertion failure).
1564 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1565 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1569 /// Region utilities
1571 /// Is this region named by the user?
1572 pub fn has_name(&self) -> bool {
1574 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1575 RegionKind::ReLateBound(_, br) => br.is_named(),
1576 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1577 RegionKind::ReStatic => true,
1578 RegionKind::ReVar(..) => false,
1579 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1580 RegionKind::ReEmpty(_) => false,
1581 RegionKind::ReErased => false,
1585 pub fn is_late_bound(&self) -> bool {
1587 ty::ReLateBound(..) => true,
1592 pub fn is_placeholder(&self) -> bool {
1594 ty::RePlaceholder(..) => true,
1599 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1601 ty::ReLateBound(debruijn, _) => debruijn >= index,
1606 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1607 /// innermost binder. That is, if we have something bound at `to_binder`,
1608 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1609 /// when moving a region out from inside binders:
1612 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1613 /// // Binder: D3 D2 D1 ^^
1616 /// Here, the region `'a` would have the De Bruijn index D3,
1617 /// because it is the bound 3 binders out. However, if we wanted
1618 /// to refer to that region `'a` in the second argument (the `_`),
1619 /// those two binders would not be in scope. In that case, we
1620 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1621 /// De Bruijn index of `'a` to D1 (the innermost binder).
1623 /// If we invoke `shift_out_to_binder` and the region is in fact
1624 /// bound by one of the binders we are shifting out of, that is an
1625 /// error (and should fail an assertion failure).
1626 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1628 ty::ReLateBound(debruijn, r) => {
1629 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1635 pub fn type_flags(&self) -> TypeFlags {
1636 let mut flags = TypeFlags::empty();
1640 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1641 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1642 flags = flags | TypeFlags::HAS_RE_INFER;
1644 ty::RePlaceholder(..) => {
1645 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1646 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1647 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1649 ty::ReEarlyBound(..) => {
1650 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1651 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1652 flags = flags | TypeFlags::HAS_RE_PARAM;
1654 ty::ReFree { .. } => {
1655 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1656 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1658 ty::ReEmpty(_) | ty::ReStatic => {
1659 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1661 ty::ReLateBound(..) => {
1662 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1665 flags = flags | TypeFlags::HAS_RE_ERASED;
1669 debug!("type_flags({:?}) = {:?}", self, flags);
1674 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1675 /// For example, consider the regions in this snippet of code:
1679 /// ^^ -- early bound, declared on an impl
1681 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1682 /// ^^ ^^ ^ anonymous, late-bound
1683 /// | early-bound, appears in where-clauses
1684 /// late-bound, appears only in fn args
1689 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1690 /// of the impl, and for all the other highlighted regions, it
1691 /// would return the `DefId` of the function. In other cases (not shown), this
1692 /// function might return the `DefId` of a closure.
1693 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1695 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1696 ty::ReFree(fr) => fr.scope,
1697 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1703 impl<'tcx> TyS<'tcx> {
1705 pub fn is_unit(&self) -> bool {
1707 Tuple(ref tys) => tys.is_empty(),
1713 pub fn is_never(&self) -> bool {
1720 /// Checks whether a type is definitely uninhabited. This is
1721 /// conservative: for some types that are uninhabited we return `false`,
1722 /// but we only return `true` for types that are definitely uninhabited.
1723 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1724 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1725 /// size, to account for partial initialisation. See #49298 for details.)
1726 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1727 // FIXME(varkor): we can make this less conversative by substituting concrete
1731 ty::Adt(def, _) if def.is_union() => {
1732 // For now, `union`s are never considered uninhabited.
1735 ty::Adt(def, _) => {
1736 // Any ADT is uninhabited if either:
1737 // (a) It has no variants (i.e. an empty `enum`);
1738 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1739 // one uninhabited field.
1740 def.variants.iter().all(|var| {
1741 var.fields.iter().any(|field| {
1742 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1747 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1749 ty::Array(ty, len) => {
1750 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1751 // If the array is definitely non-empty, it's uninhabited if
1752 // the type of its elements is uninhabited.
1753 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1758 // References to uninitialised memory is valid for any type, including
1759 // uninhabited types, in unsafe code, so we treat all references as
1768 pub fn is_primitive(&self) -> bool {
1769 self.kind.is_primitive()
1773 pub fn is_ty_var(&self) -> bool {
1775 Infer(TyVar(_)) => true,
1781 pub fn is_ty_infer(&self) -> bool {
1789 pub fn is_phantom_data(&self) -> bool {
1790 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1794 pub fn is_bool(&self) -> bool {
1798 /// Returns `true` if this type is a `str`.
1800 pub fn is_str(&self) -> bool {
1805 pub fn is_param(&self, index: u32) -> bool {
1807 ty::Param(ref data) => data.index == index,
1813 pub fn is_slice(&self) -> bool {
1815 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1816 Slice(_) | Str => true,
1824 pub fn is_simd(&self) -> bool {
1826 Adt(def, _) => def.repr.simd(),
1831 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1833 Array(ty, _) | Slice(ty) => ty,
1834 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1835 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1839 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1841 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1842 _ => bug!("`simd_type` called on invalid type"),
1846 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1847 // Parameter currently unused, but probably needed in the future to
1848 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1850 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1851 _ => bug!("`simd_size` called on invalid type"),
1855 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1857 Adt(def, substs) => {
1858 let variant = def.non_enum_variant();
1859 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1861 _ => bug!("`simd_size_and_type` called on invalid type"),
1866 pub fn is_region_ptr(&self) -> bool {
1874 pub fn is_mutable_ptr(&self) -> bool {
1876 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1877 | Ref(_, _, hir::Mutability::Mut) => true,
1883 pub fn is_unsafe_ptr(&self) -> bool {
1890 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1892 pub fn is_any_ptr(&self) -> bool {
1893 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1897 pub fn is_box(&self) -> bool {
1899 Adt(def, _) => def.is_box(),
1904 /// Panics if called on any type other than `Box<T>`.
1905 pub fn boxed_ty(&self) -> Ty<'tcx> {
1907 Adt(def, substs) if def.is_box() => substs.type_at(0),
1908 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1912 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1913 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1914 /// contents are abstract to rustc.)
1916 pub fn is_scalar(&self) -> bool {
1923 | Infer(IntVar(_) | FloatVar(_))
1926 | RawPtr(_) => true,
1931 /// Returns `true` if this type is a floating point type.
1933 pub fn is_floating_point(&self) -> bool {
1935 Float(_) | Infer(FloatVar(_)) => true,
1941 pub fn is_trait(&self) -> bool {
1943 Dynamic(..) => true,
1949 pub fn is_enum(&self) -> bool {
1951 Adt(adt_def, _) => adt_def.is_enum(),
1957 pub fn is_closure(&self) -> bool {
1959 Closure(..) => true,
1965 pub fn is_generator(&self) -> bool {
1967 Generator(..) => true,
1973 pub fn is_integral(&self) -> bool {
1975 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
1981 pub fn is_fresh_ty(&self) -> bool {
1983 Infer(FreshTy(_)) => true,
1989 pub fn is_fresh(&self) -> bool {
1991 Infer(FreshTy(_)) => true,
1992 Infer(FreshIntTy(_)) => true,
1993 Infer(FreshFloatTy(_)) => true,
1999 pub fn is_char(&self) -> bool {
2007 pub fn is_numeric(&self) -> bool {
2008 self.is_integral() || self.is_floating_point()
2012 pub fn is_signed(&self) -> bool {
2020 pub fn is_ptr_sized_integral(&self) -> bool {
2022 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
2028 pub fn is_machine(&self) -> bool {
2030 Int(..) | Uint(..) | Float(..) => true,
2036 pub fn has_concrete_skeleton(&self) -> bool {
2038 Param(_) | Infer(_) | Error(_) => false,
2043 /// Returns the type and mutability of `*ty`.
2045 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2046 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2047 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2049 Adt(def, _) if def.is_box() => {
2050 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2052 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2053 RawPtr(mt) if explicit => Some(mt),
2058 /// Returns the type of `ty[i]`.
2059 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2061 Array(ty, _) | Slice(ty) => Some(ty),
2066 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2068 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2071 // ignore errors (#54954)
2072 ty::Binder::dummy(FnSig::fake())
2074 Closure(..) => bug!(
2075 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2077 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2082 pub fn is_fn(&self) -> bool {
2084 FnDef(..) | FnPtr(_) => true,
2090 pub fn is_fn_ptr(&self) -> bool {
2098 pub fn is_impl_trait(&self) -> bool {
2106 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2108 Adt(adt, _) => Some(adt),
2113 /// Iterates over tuple fields.
2114 /// Panics when called on anything but a tuple.
2115 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2117 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2118 _ => bug!("tuple_fields called on non-tuple"),
2122 /// If the type contains variants, returns the valid range of variant indices.
2124 // FIXME: This requires the optimized MIR in the case of generators.
2126 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2128 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2129 TyKind::Generator(def_id, substs, _) => {
2130 Some(substs.as_generator().variant_range(def_id, tcx))
2136 /// If the type contains variants, returns the variant for `variant_index`.
2137 /// Panics if `variant_index` is out of range.
2139 // FIXME: This requires the optimized MIR in the case of generators.
2141 pub fn discriminant_for_variant(
2144 variant_index: VariantIdx,
2145 ) -> Option<Discr<'tcx>> {
2147 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2148 bug!("discriminant_for_variant called on zero variant enum");
2150 TyKind::Adt(adt, _) if adt.is_enum() => {
2151 Some(adt.discriminant_for_variant(tcx, variant_index))
2153 TyKind::Generator(def_id, substs, _) => {
2154 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2160 /// Returns the type of the discriminant of this type.
2161 pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2163 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2164 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2166 // This can only be `0`, for now, so `u8` will suffice.
2172 /// When we create a closure, we record its kind (i.e., what trait
2173 /// it implements) into its `ClosureSubsts` using a type
2174 /// parameter. This is kind of a phantom type, except that the
2175 /// most convenient thing for us to are the integral types. This
2176 /// function converts such a special type into the closure
2177 /// kind. To go the other way, use
2178 /// `tcx.closure_kind_ty(closure_kind)`.
2180 /// Note that during type checking, we use an inference variable
2181 /// to represent the closure kind, because it has not yet been
2182 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2183 /// is complete, that type variable will be unified.
2184 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2186 Int(int_ty) => match int_ty {
2187 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2188 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2189 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2190 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2193 // "Bound" types appear in canonical queries when the
2194 // closure type is not yet known
2195 Bound(..) | Infer(_) => None,
2197 Error(_) => Some(ty::ClosureKind::Fn),
2199 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2203 /// Fast path helper for testing if a type is `Sized`.
2205 /// Returning true means the type is known to be sized. Returning
2206 /// `false` means nothing -- could be sized, might not be.
2207 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2209 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2220 | ty::GeneratorWitness(..)
2224 | ty::Error(_) => true,
2226 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2228 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2230 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2232 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2234 ty::Infer(ty::TyVar(_)) => false,
2237 | ty::Placeholder(..)
2238 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2239 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2244 /// Is this a zero-sized type?
2245 pub fn is_zst(&'tcx self, tcx: TyCtxt<'tcx>, did: DefId) -> bool {
2246 tcx.layout_of(tcx.param_env(did).and(self)).map(|layout| layout.is_zst()).unwrap_or(false)