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(&'tcx List<Binder<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,
214 /// Get the article ("a" or "an") to use with this type.
215 pub fn article(&self) -> &'static str {
217 Int(_) | Float(_) | Array(_, _) => "an",
218 Adt(def, _) if def.is_enum() => "an",
219 // This should never happen, but ICEing and causing the user's code
220 // to not compile felt too harsh.
227 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
228 #[cfg(target_arch = "x86_64")]
229 static_assert_size!(TyKind<'_>, 24);
231 /// A closure can be modeled as a struct that looks like:
233 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
237 /// - 'l0...'li and T0...Tj are the generic parameters
238 /// in scope on the function that defined the closure,
239 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
240 /// is rather hackily encoded via a scalar type. See
241 /// `TyS::to_opt_closure_kind` for details.
242 /// - CS represents the *closure signature*, representing as a `fn()`
243 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
244 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
246 /// - U is a type parameter representing the types of its upvars, tupled up
247 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
248 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
250 /// So, for example, given this function:
252 /// fn foo<'a, T>(data: &'a mut T) {
253 /// do(|| data.count += 1)
256 /// the type of the closure would be something like:
258 /// struct Closure<'a, T, U>(...U);
260 /// Note that the type of the upvar is not specified in the struct.
261 /// You may wonder how the impl would then be able to use the upvar,
262 /// if it doesn't know it's type? The answer is that the impl is
263 /// (conceptually) not fully generic over Closure but rather tied to
264 /// instances with the expected upvar types:
266 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
270 /// You can see that the *impl* fully specified the type of the upvar
271 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
272 /// (Here, I am assuming that `data` is mut-borrowed.)
274 /// Now, the last question you may ask is: Why include the upvar types
275 /// in an extra type parameter? The reason for this design is that the
276 /// upvar types can reference lifetimes that are internal to the
277 /// creating function. In my example above, for example, the lifetime
278 /// `'b` represents the scope of the closure itself; this is some
279 /// subset of `foo`, probably just the scope of the call to the to
280 /// `do()`. If we just had the lifetime/type parameters from the
281 /// enclosing function, we couldn't name this lifetime `'b`. Note that
282 /// there can also be lifetimes in the types of the upvars themselves,
283 /// if one of them happens to be a reference to something that the
284 /// creating fn owns.
286 /// OK, you say, so why not create a more minimal set of parameters
287 /// that just includes the extra lifetime parameters? The answer is
288 /// primarily that it would be hard --- we don't know at the time when
289 /// we create the closure type what the full types of the upvars are,
290 /// nor do we know which are borrowed and which are not. In this
291 /// design, we can just supply a fresh type parameter and figure that
294 /// All right, you say, but why include the type parameters from the
295 /// original function then? The answer is that codegen may need them
296 /// when monomorphizing, and they may not appear in the upvars. A
297 /// closure could capture no variables but still make use of some
298 /// in-scope type parameter with a bound (e.g., if our example above
299 /// had an extra `U: Default`, and the closure called `U::default()`).
301 /// There is another reason. This design (implicitly) prohibits
302 /// closures from capturing themselves (except via a trait
303 /// object). This simplifies closure inference considerably, since it
304 /// means that when we infer the kind of a closure or its upvars, we
305 /// don't have to handle cycles where the decisions we make for
306 /// closure C wind up influencing the decisions we ought to make for
307 /// closure C (which would then require fixed point iteration to
308 /// handle). Plus it fixes an ICE. :P
312 /// Generators are handled similarly in `GeneratorSubsts`. The set of
313 /// type parameters is similar, but `CK` and `CS` are replaced by the
314 /// following type parameters:
316 /// * `GS`: The generator's "resume type", which is the type of the
317 /// argument passed to `resume`, and the type of `yield` expressions
318 /// inside the generator.
319 /// * `GY`: The "yield type", which is the type of values passed to
320 /// `yield` inside the generator.
321 /// * `GR`: The "return type", which is the type of value returned upon
322 /// completion of the generator.
323 /// * `GW`: The "generator witness".
324 #[derive(Copy, Clone, Debug, TypeFoldable)]
325 pub struct ClosureSubsts<'tcx> {
326 /// Lifetime and type parameters from the enclosing function,
327 /// concatenated with a tuple containing the types of the upvars.
329 /// These are separated out because codegen wants to pass them around
330 /// when monomorphizing.
331 pub substs: SubstsRef<'tcx>,
334 /// Struct returned by `split()`.
335 pub struct ClosureSubstsParts<'tcx, T> {
336 pub parent_substs: &'tcx [GenericArg<'tcx>],
337 pub closure_kind_ty: T,
338 pub closure_sig_as_fn_ptr_ty: T,
339 pub tupled_upvars_ty: T,
342 impl<'tcx> ClosureSubsts<'tcx> {
343 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
344 /// for the closure parent, alongside additional closure-specific components.
347 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
348 ) -> ClosureSubsts<'tcx> {
350 substs: tcx.mk_substs(
351 parts.parent_substs.iter().copied().chain(
352 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
354 .map(|&ty| ty.into()),
360 /// Divides the closure substs into their respective components.
361 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
362 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
363 match self.substs[..] {
364 [ref parent_substs @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
368 closure_sig_as_fn_ptr_ty,
372 _ => bug!("closure substs missing synthetics"),
376 /// Returns `true` only if enough of the synthetic types are known to
377 /// allow using all of the methods on `ClosureSubsts` without panicking.
379 /// Used primarily by `ty::print::pretty` to be able to handle closure
380 /// types that haven't had their synthetic types substituted in.
381 pub fn is_valid(self) -> bool {
382 self.substs.len() >= 3
383 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
386 /// Returns the substitutions of the closure's parent.
387 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
388 self.split().parent_substs
391 /// Returns an iterator over the list of types of captured paths by the closure.
392 /// In case there was a type error in figuring out the types of the captured path, an
393 /// empty iterator is returned.
395 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
396 match self.tupled_upvars_ty().kind() {
397 TyKind::Error(_) => None,
398 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
399 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
400 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
406 /// Returns the tuple type representing the upvars for this closure.
408 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
409 self.split().tupled_upvars_ty.expect_ty()
412 /// Returns the closure kind for this closure; may return a type
413 /// variable during inference. To get the closure kind during
414 /// inference, use `infcx.closure_kind(substs)`.
415 pub fn kind_ty(self) -> Ty<'tcx> {
416 self.split().closure_kind_ty.expect_ty()
419 /// Returns the `fn` pointer type representing the closure signature for this
421 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
422 // type is known at the time of the creation of `ClosureSubsts`,
423 // see `rustc_typeck::check::closure`.
424 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
425 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
428 /// Returns the closure kind for this closure; only usable outside
429 /// of an inference context, because in that context we know that
430 /// there are no type variables.
432 /// If you have an inference context, use `infcx.closure_kind()`.
433 pub fn kind(self) -> ty::ClosureKind {
434 self.kind_ty().to_opt_closure_kind().unwrap()
437 /// Extracts the signature from the closure.
438 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
439 let ty = self.sig_as_fn_ptr_ty();
441 ty::FnPtr(sig) => *sig,
442 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind()),
447 /// Similar to `ClosureSubsts`; see the above documentation for more.
448 #[derive(Copy, Clone, Debug, TypeFoldable)]
449 pub struct GeneratorSubsts<'tcx> {
450 pub substs: SubstsRef<'tcx>,
453 pub struct GeneratorSubstsParts<'tcx, T> {
454 pub parent_substs: &'tcx [GenericArg<'tcx>],
459 pub tupled_upvars_ty: T,
462 impl<'tcx> GeneratorSubsts<'tcx> {
463 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
464 /// for the generator parent, alongside additional generator-specific components.
467 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
468 ) -> GeneratorSubsts<'tcx> {
470 substs: tcx.mk_substs(
471 parts.parent_substs.iter().copied().chain(
477 parts.tupled_upvars_ty,
480 .map(|&ty| ty.into()),
486 /// Divides the generator substs into their respective components.
487 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
488 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
489 match self.substs[..] {
490 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
491 GeneratorSubstsParts {
500 _ => bug!("generator substs missing synthetics"),
504 /// Returns `true` only if enough of the synthetic types are known to
505 /// allow using all of the methods on `GeneratorSubsts` without panicking.
507 /// Used primarily by `ty::print::pretty` to be able to handle generator
508 /// types that haven't had their synthetic types substituted in.
509 pub fn is_valid(self) -> bool {
510 self.substs.len() >= 5
511 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
514 /// Returns the substitutions of the generator's parent.
515 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
516 self.split().parent_substs
519 /// This describes the types that can be contained in a generator.
520 /// It will be a type variable initially and unified in the last stages of typeck of a body.
521 /// It contains a tuple of all the types that could end up on a generator frame.
522 /// The state transformation MIR pass may only produce layouts which mention types
523 /// in this tuple. Upvars are not counted here.
524 pub fn witness(self) -> Ty<'tcx> {
525 self.split().witness.expect_ty()
528 /// Returns an iterator over the list of types of captured paths by the generator.
529 /// In case there was a type error in figuring out the types of the captured path, an
530 /// empty iterator is returned.
532 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
533 match self.tupled_upvars_ty().kind() {
534 TyKind::Error(_) => None,
535 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
536 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
537 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
543 /// Returns the tuple type representing the upvars for this generator.
545 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
546 self.split().tupled_upvars_ty.expect_ty()
549 /// Returns the type representing the resume type of the generator.
550 pub fn resume_ty(self) -> Ty<'tcx> {
551 self.split().resume_ty.expect_ty()
554 /// Returns the type representing the yield type of the generator.
555 pub fn yield_ty(self) -> Ty<'tcx> {
556 self.split().yield_ty.expect_ty()
559 /// Returns the type representing the return type of the generator.
560 pub fn return_ty(self) -> Ty<'tcx> {
561 self.split().return_ty.expect_ty()
564 /// Returns the "generator signature", which consists of its yield
565 /// and return types.
567 /// N.B., some bits of the code prefers to see this wrapped in a
568 /// binder, but it never contains bound regions. Probably this
569 /// function should be removed.
570 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
571 ty::Binder::dummy(self.sig())
574 /// Returns the "generator signature", which consists of its resume, yield
575 /// and return types.
576 pub fn sig(self) -> GenSig<'tcx> {
578 resume_ty: self.resume_ty(),
579 yield_ty: self.yield_ty(),
580 return_ty: self.return_ty(),
585 impl<'tcx> GeneratorSubsts<'tcx> {
586 /// Generator has not been resumed yet.
587 pub const UNRESUMED: usize = 0;
588 /// Generator has returned or is completed.
589 pub const RETURNED: usize = 1;
590 /// Generator has been poisoned.
591 pub const POISONED: usize = 2;
593 const UNRESUMED_NAME: &'static str = "Unresumed";
594 const RETURNED_NAME: &'static str = "Returned";
595 const POISONED_NAME: &'static str = "Panicked";
597 /// The valid variant indices of this generator.
599 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
600 // FIXME requires optimized MIR
601 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
602 VariantIdx::new(0)..VariantIdx::new(num_variants)
605 /// The discriminant for the given variant. Panics if the `variant_index` is
608 pub fn discriminant_for_variant(
612 variant_index: VariantIdx,
614 // Generators don't support explicit discriminant values, so they are
615 // the same as the variant index.
616 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
617 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
620 /// The set of all discriminants for the generator, enumerated with their
623 pub fn discriminants(
627 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
628 self.variant_range(def_id, tcx).map(move |index| {
629 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
633 /// Calls `f` with a reference to the name of the enumerator for the given
635 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
637 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
638 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
639 Self::POISONED => Cow::from(Self::POISONED_NAME),
640 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
644 /// The type of the state discriminant used in the generator type.
646 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
650 /// This returns the types of the MIR locals which had to be stored across suspension points.
651 /// It is calculated in rustc_mir::transform::generator::StateTransform.
652 /// All the types here must be in the tuple in GeneratorInterior.
654 /// The locals are grouped by their variant number. Note that some locals may
655 /// be repeated in multiple variants.
661 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
662 let layout = tcx.generator_layout(def_id);
663 layout.variant_fields.iter().map(move |variant| {
664 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
668 /// This is the types of the fields of a generator which are not stored in a
671 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
676 #[derive(Debug, Copy, Clone)]
677 pub enum UpvarSubsts<'tcx> {
678 Closure(SubstsRef<'tcx>),
679 Generator(SubstsRef<'tcx>),
682 impl<'tcx> UpvarSubsts<'tcx> {
683 /// Returns an iterator over the list of types of captured paths by the closure/generator.
684 /// In case there was a type error in figuring out the types of the captured path, an
685 /// empty iterator is returned.
687 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
688 let tupled_tys = match self {
689 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
690 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
693 match tupled_tys.kind() {
694 TyKind::Error(_) => None,
695 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
696 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
697 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
704 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
706 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
707 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
712 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
713 #[derive(HashStable, TypeFoldable)]
714 pub enum ExistentialPredicate<'tcx> {
715 /// E.g., `Iterator`.
716 Trait(ExistentialTraitRef<'tcx>),
717 /// E.g., `Iterator::Item = T`.
718 Projection(ExistentialProjection<'tcx>),
723 impl<'tcx> ExistentialPredicate<'tcx> {
724 /// Compares via an ordering that will not change if modules are reordered or other changes are
725 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
726 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
727 use self::ExistentialPredicate::*;
728 match (*self, *other) {
729 (Trait(_), Trait(_)) => Ordering::Equal,
730 (Projection(ref a), Projection(ref b)) => {
731 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
733 (AutoTrait(ref a), AutoTrait(ref b)) => {
734 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
736 (Trait(_), _) => Ordering::Less,
737 (Projection(_), Trait(_)) => Ordering::Greater,
738 (Projection(_), _) => Ordering::Less,
739 (AutoTrait(_), _) => Ordering::Greater,
744 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
745 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
746 use crate::ty::ToPredicate;
747 match self.skip_binder() {
748 ExistentialPredicate::Trait(tr) => {
749 self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
751 ExistentialPredicate::Projection(p) => {
752 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
754 ExistentialPredicate::AutoTrait(did) => {
755 let trait_ref = self.rebind(ty::TraitRef {
757 substs: tcx.mk_substs_trait(self_ty, &[]),
759 trait_ref.without_const().to_predicate(tcx)
765 impl<'tcx> List<ty::Binder<ExistentialPredicate<'tcx>>> {
766 /// Returns the "principal `DefId`" of this set of existential predicates.
768 /// A Rust trait object type consists (in addition to a lifetime bound)
769 /// of a set of trait bounds, which are separated into any number
770 /// of auto-trait bounds, and at most one non-auto-trait bound. The
771 /// non-auto-trait bound is called the "principal" of the trait
774 /// Only the principal can have methods or type parameters (because
775 /// auto traits can have neither of them). This is important, because
776 /// it means the auto traits can be treated as an unordered set (methods
777 /// would force an order for the vtable, while relating traits with
778 /// type parameters without knowing the order to relate them in is
779 /// a rather non-trivial task).
781 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
782 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
783 /// are the set `{Sync}`.
785 /// It is also possible to have a "trivial" trait object that
786 /// consists only of auto traits, with no principal - for example,
787 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
788 /// is `{Send, Sync}`, while there is no principal. These trait objects
789 /// have a "trivial" vtable consisting of just the size, alignment,
791 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
793 .map_bound(|this| match this {
794 ExistentialPredicate::Trait(tr) => Some(tr),
800 pub fn principal_def_id(&self) -> Option<DefId> {
801 self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
805 pub fn projection_bounds<'a>(
807 ) -> impl Iterator<Item = ty::Binder<ExistentialProjection<'tcx>>> + 'a {
808 self.iter().filter_map(|predicate| {
810 .map_bound(|pred| match pred {
811 ExistentialPredicate::Projection(projection) => Some(projection),
819 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
820 self.iter().filter_map(|predicate| match predicate.skip_binder() {
821 ExistentialPredicate::AutoTrait(did) => Some(did),
827 /// A complete reference to a trait. These take numerous guises in syntax,
828 /// but perhaps the most recognizable form is in a where-clause:
832 /// This would be represented by a trait-reference where the `DefId` is the
833 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
834 /// and `U` as parameter 1.
836 /// Trait references also appear in object types like `Foo<U>`, but in
837 /// that case the `Self` parameter is absent from the substitutions.
838 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
839 #[derive(HashStable, TypeFoldable)]
840 pub struct TraitRef<'tcx> {
842 pub substs: SubstsRef<'tcx>,
845 impl<'tcx> TraitRef<'tcx> {
846 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
847 TraitRef { def_id, substs }
850 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
851 /// are the parameters defined on trait.
852 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
853 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
857 pub fn self_ty(&self) -> Ty<'tcx> {
858 self.substs.type_at(0)
864 substs: SubstsRef<'tcx>,
865 ) -> ty::TraitRef<'tcx> {
866 let defs = tcx.generics_of(trait_id);
868 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
872 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
874 impl<'tcx> PolyTraitRef<'tcx> {
875 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
876 self.map_bound_ref(|tr| tr.self_ty())
879 pub fn def_id(&self) -> DefId {
880 self.skip_binder().def_id
883 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
884 self.map_bound(|trait_ref| ty::TraitPredicate { trait_ref })
888 /// An existential reference to a trait, where `Self` is erased.
889 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
891 /// exists T. T: Trait<'a, 'b, X, Y>
893 /// The substitutions don't include the erased `Self`, only trait
894 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
895 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
896 #[derive(HashStable, TypeFoldable)]
897 pub struct ExistentialTraitRef<'tcx> {
899 pub substs: SubstsRef<'tcx>,
902 impl<'tcx> ExistentialTraitRef<'tcx> {
903 pub fn erase_self_ty(
905 trait_ref: ty::TraitRef<'tcx>,
906 ) -> ty::ExistentialTraitRef<'tcx> {
907 // Assert there is a Self.
908 trait_ref.substs.type_at(0);
910 ty::ExistentialTraitRef {
911 def_id: trait_ref.def_id,
912 substs: tcx.intern_substs(&trait_ref.substs[1..]),
916 /// Object types don't have a self type specified. Therefore, when
917 /// we convert the principal trait-ref into a normal trait-ref,
918 /// you must give *some* self type. A common choice is `mk_err()`
919 /// or some placeholder type.
920 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
921 // otherwise the escaping vars would be captured by the binder
922 // debug_assert!(!self_ty.has_escaping_bound_vars());
924 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
928 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
930 impl<'tcx> PolyExistentialTraitRef<'tcx> {
931 pub fn def_id(&self) -> DefId {
932 self.skip_binder().def_id
935 /// Object types don't have a self type specified. Therefore, when
936 /// we convert the principal trait-ref into a normal trait-ref,
937 /// you must give *some* self type. A common choice is `mk_err()`
938 /// or some placeholder type.
939 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
940 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
944 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
945 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
946 /// (which would be represented by the type `PolyTraitRef ==
947 /// Binder<TraitRef>`). Note that when we instantiate,
948 /// erase, or otherwise "discharge" these bound vars, we change the
949 /// type from `Binder<T>` to just `T` (see
950 /// e.g., `liberate_late_bound_regions`).
951 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
952 pub struct Binder<T>(T);
955 /// Wraps `value` in a binder, asserting that `value` does not
956 /// contain any bound vars that would be bound by the
957 /// binder. This is commonly used to 'inject' a value T into a
958 /// different binding level.
959 pub fn dummy<'tcx>(value: T) -> Binder<T>
961 T: TypeFoldable<'tcx>,
963 debug_assert!(!value.has_escaping_bound_vars());
967 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
968 pub fn bind(value: T) -> Binder<T> {
972 /// Wraps `value` in a binder without actually binding any currently
973 /// unbound variables.
975 /// Note that this will shift all debrujin indices of escaping bound variables
976 /// by 1 to avoid accidential captures.
977 pub fn wrap_nonbinding(tcx: TyCtxt<'tcx>, value: T) -> Binder<T>
979 T: TypeFoldable<'tcx>,
981 if value.has_escaping_bound_vars() {
982 Binder::bind(super::fold::shift_vars(tcx, value, 1))
988 /// Skips the binder and returns the "bound" value. This is a
989 /// risky thing to do because it's easy to get confused about
990 /// De Bruijn indices and the like. It is usually better to
991 /// discharge the binder using `no_bound_vars` or
992 /// `replace_late_bound_regions` or something like
993 /// that. `skip_binder` is only valid when you are either
994 /// extracting data that has nothing to do with bound vars, you
995 /// are doing some sort of test that does not involve bound
996 /// regions, or you are being very careful about your depth
999 /// Some examples where `skip_binder` is reasonable:
1001 /// - extracting the `DefId` from a PolyTraitRef;
1002 /// - comparing the self type of a PolyTraitRef to see if it is equal to
1003 /// a type parameter `X`, since the type `X` does not reference any regions
1004 pub fn skip_binder(self) -> T {
1008 pub fn as_ref(&self) -> Binder<&T> {
1012 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
1016 self.as_ref().map_bound(f)
1019 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
1026 /// Wraps a `value` in a binder, using the same bound variables as the
1027 /// current `Binder`. This should not be used if the new value *changes*
1028 /// the bound variables. Note: the (old or new) value itself does not
1029 /// necessarily need to *name* all the bound variables.
1031 /// This currently doesn't do anything different than `bind`, because we
1032 /// don't actually track bound vars. However, semantically, it is different
1033 /// because bound vars aren't allowed to change here, whereas they are
1034 /// in `bind`. This may be (debug) asserted in the future.
1035 pub fn rebind<U>(&self, value: U) -> Binder<U> {
1039 /// Unwraps and returns the value within, but only if it contains
1040 /// no bound vars at all. (In other words, if this binder --
1041 /// and indeed any enclosing binder -- doesn't bind anything at
1042 /// all.) Otherwise, returns `None`.
1044 /// (One could imagine having a method that just unwraps a single
1045 /// binder, but permits late-bound vars bound by enclosing
1046 /// binders, but that would require adjusting the debruijn
1047 /// indices, and given the shallow binding structure we often use,
1048 /// would not be that useful.)
1049 pub fn no_bound_vars<'tcx>(self) -> Option<T>
1051 T: TypeFoldable<'tcx>,
1053 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1056 /// Given two things that have the same binder level,
1057 /// and an operation that wraps on their contents, executes the operation
1058 /// and then wraps its result.
1060 /// `f` should consider bound regions at depth 1 to be free, and
1061 /// anything it produces with bound regions at depth 1 will be
1062 /// bound in the resulting return value.
1063 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
1065 F: FnOnce(T, U) -> R,
1067 Binder(f(self.0, u.0))
1070 /// Splits the contents into two things that share the same binder
1071 /// level as the original, returning two distinct binders.
1073 /// `f` should consider bound regions at depth 1 to be free, and
1074 /// anything it produces with bound regions at depth 1 will be
1075 /// bound in the resulting return values.
1076 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
1078 F: FnOnce(T) -> (U, V),
1080 let (u, v) = f(self.0);
1081 (Binder(u), Binder(v))
1085 impl<T> Binder<Option<T>> {
1086 pub fn transpose(self) -> Option<Binder<T>> {
1091 /// Represents the projection of an associated type. In explicit UFCS
1092 /// form this would be written `<T as Trait<..>>::N`.
1093 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1094 #[derive(HashStable, TypeFoldable)]
1095 pub struct ProjectionTy<'tcx> {
1096 /// The parameters of the associated item.
1097 pub substs: SubstsRef<'tcx>,
1099 /// The `DefId` of the `TraitItem` for the associated type `N`.
1101 /// Note that this is not the `DefId` of the `TraitRef` containing this
1102 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1103 pub item_def_id: DefId,
1106 impl<'tcx> ProjectionTy<'tcx> {
1107 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
1108 /// associated item named `item_name`.
1109 pub fn from_ref_and_name(
1111 trait_ref: ty::TraitRef<'tcx>,
1113 ) -> ProjectionTy<'tcx> {
1114 let item_def_id = tcx
1115 .associated_items(trait_ref.def_id)
1116 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1120 ProjectionTy { substs: trait_ref.substs, item_def_id }
1123 /// Extracts the underlying trait reference from this projection.
1124 /// For example, if this is a projection of `<T as Iterator>::Item`,
1125 /// then this function would return a `T: Iterator` trait reference.
1126 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1127 let def_id = tcx.associated_item(self.item_def_id).container.id();
1128 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1131 pub fn self_ty(&self) -> Ty<'tcx> {
1132 self.substs.type_at(0)
1136 #[derive(Copy, Clone, Debug, TypeFoldable)]
1137 pub struct GenSig<'tcx> {
1138 pub resume_ty: Ty<'tcx>,
1139 pub yield_ty: Ty<'tcx>,
1140 pub return_ty: Ty<'tcx>,
1143 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1145 impl<'tcx> PolyGenSig<'tcx> {
1146 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1147 self.map_bound_ref(|sig| sig.resume_ty)
1149 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1150 self.map_bound_ref(|sig| sig.yield_ty)
1152 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1153 self.map_bound_ref(|sig| sig.return_ty)
1157 /// Signature of a function type, which we have arbitrarily
1158 /// decided to use to refer to the input/output types.
1160 /// - `inputs`: is the list of arguments and their modes.
1161 /// - `output`: is the return type.
1162 /// - `c_variadic`: indicates whether this is a C-variadic function.
1163 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1164 #[derive(HashStable, TypeFoldable)]
1165 pub struct FnSig<'tcx> {
1166 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1167 pub c_variadic: bool,
1168 pub unsafety: hir::Unsafety,
1172 impl<'tcx> FnSig<'tcx> {
1173 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1174 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1177 pub fn output(&self) -> Ty<'tcx> {
1178 self.inputs_and_output[self.inputs_and_output.len() - 1]
1181 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1183 fn fake() -> FnSig<'tcx> {
1185 inputs_and_output: List::empty(),
1187 unsafety: hir::Unsafety::Normal,
1188 abi: abi::Abi::Rust,
1193 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1195 impl<'tcx> PolyFnSig<'tcx> {
1197 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1198 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1201 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1202 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1204 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1205 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1208 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1209 self.map_bound_ref(|fn_sig| fn_sig.output())
1211 pub fn c_variadic(&self) -> bool {
1212 self.skip_binder().c_variadic
1214 pub fn unsafety(&self) -> hir::Unsafety {
1215 self.skip_binder().unsafety
1217 pub fn abi(&self) -> abi::Abi {
1218 self.skip_binder().abi
1222 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1224 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1225 #[derive(HashStable)]
1226 pub struct ParamTy {
1231 impl<'tcx> ParamTy {
1232 pub fn new(index: u32, name: Symbol) -> ParamTy {
1233 ParamTy { index, name }
1236 pub fn for_self() -> ParamTy {
1237 ParamTy::new(0, kw::SelfUpper)
1240 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1241 ParamTy::new(def.index, def.name)
1244 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1245 tcx.mk_ty_param(self.index, self.name)
1249 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1250 #[derive(HashStable)]
1251 pub struct ParamConst {
1256 impl<'tcx> ParamConst {
1257 pub fn new(index: u32, name: Symbol) -> ParamConst {
1258 ParamConst { index, name }
1261 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1262 ParamConst::new(def.index, def.name)
1265 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
1266 tcx.mk_const_param(self.index, self.name, ty)
1270 rustc_index::newtype_index! {
1271 /// A [De Bruijn index][dbi] is a standard means of representing
1272 /// regions (and perhaps later types) in a higher-ranked setting. In
1273 /// particular, imagine a type like this:
1275 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1278 /// | +------------+ 0 | |
1280 /// +----------------------------------+ 1 |
1282 /// +----------------------------------------------+ 0
1284 /// In this type, there are two binders (the outer fn and the inner
1285 /// fn). We need to be able to determine, for any given region, which
1286 /// fn type it is bound by, the inner or the outer one. There are
1287 /// various ways you can do this, but a De Bruijn index is one of the
1288 /// more convenient and has some nice properties. The basic idea is to
1289 /// count the number of binders, inside out. Some examples should help
1290 /// clarify what I mean.
1292 /// Let's start with the reference type `&'b isize` that is the first
1293 /// argument to the inner function. This region `'b` is assigned a De
1294 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1295 /// fn). The region `'a` that appears in the second argument type (`&'a
1296 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1297 /// second-innermost binder". (These indices are written on the arrays
1298 /// in the diagram).
1300 /// What is interesting is that De Bruijn index attached to a particular
1301 /// variable will vary depending on where it appears. For example,
1302 /// the final type `&'a char` also refers to the region `'a` declared on
1303 /// the outermost fn. But this time, this reference is not nested within
1304 /// any other binders (i.e., it is not an argument to the inner fn, but
1305 /// rather the outer one). Therefore, in this case, it is assigned a
1306 /// De Bruijn index of 0, because the innermost binder in that location
1307 /// is the outer fn.
1309 /// [dbi]: https://en.wikipedia.org/wiki/De_Bruijn_index
1310 #[derive(HashStable)]
1311 pub struct DebruijnIndex {
1312 DEBUG_FORMAT = "DebruijnIndex({})",
1313 const INNERMOST = 0,
1317 pub type Region<'tcx> = &'tcx RegionKind;
1319 /// Representation of regions. Note that the NLL checker uses a distinct
1320 /// representation of regions. For this reason, it internally replaces all the
1321 /// regions with inference variables -- the index of the variable is then used
1322 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1323 /// module for more information.
1325 /// ## The Region lattice within a given function
1327 /// In general, the region lattice looks like
1330 /// static ----------+-----...------+ (greatest)
1332 /// early-bound and | |
1333 /// free regions | |
1336 /// empty(root) placeholder(U1) |
1338 /// | / placeholder(Un)
1343 /// empty(Un) -------- (smallest)
1346 /// Early-bound/free regions are the named lifetimes in scope from the
1347 /// function declaration. They have relationships to one another
1348 /// determined based on the declared relationships from the
1351 /// Note that inference variables and bound regions are not included
1352 /// in this diagram. In the case of inference variables, they should
1353 /// be inferred to some other region from the diagram. In the case of
1354 /// bound regions, they are excluded because they don't make sense to
1355 /// include -- the diagram indicates the relationship between free
1358 /// ## Inference variables
1360 /// During region inference, we sometimes create inference variables,
1361 /// represented as `ReVar`. These will be inferred by the code in
1362 /// `infer::lexical_region_resolve` to some free region from the
1363 /// lattice above (the minimal region that meets the
1366 /// During NLL checking, where regions are defined differently, we
1367 /// also use `ReVar` -- in that case, the index is used to index into
1368 /// the NLL region checker's data structures. The variable may in fact
1369 /// represent either a free region or an inference variable, in that
1372 /// ## Bound Regions
1374 /// These are regions that are stored behind a binder and must be substituted
1375 /// with some concrete region before being used. There are two kind of
1376 /// bound regions: early-bound, which are bound in an item's `Generics`,
1377 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1378 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1379 /// the likes of `liberate_late_bound_regions`. The distinction exists
1380 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1382 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1383 /// outside their binder, e.g., in types passed to type inference, and
1384 /// should first be substituted (by placeholder regions, free regions,
1385 /// or region variables).
1387 /// ## Placeholder and Free Regions
1389 /// One often wants to work with bound regions without knowing their precise
1390 /// identity. For example, when checking a function, the lifetime of a borrow
1391 /// can end up being assigned to some region parameter. In these cases,
1392 /// it must be ensured that bounds on the region can't be accidentally
1393 /// assumed without being checked.
1395 /// To do this, we replace the bound regions with placeholder markers,
1396 /// which don't satisfy any relation not explicitly provided.
1398 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1399 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1400 /// to be used. These also support explicit bounds: both the internally-stored
1401 /// *scope*, which the region is assumed to outlive, as well as other
1402 /// relations stored in the `FreeRegionMap`. Note that these relations
1403 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1404 /// `resolve_regions_and_report_errors`.
1406 /// When working with higher-ranked types, some region relations aren't
1407 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1408 /// `RePlaceholder` is designed for this purpose. In these contexts,
1409 /// there's also the risk that some inference variable laying around will
1410 /// get unified with your placeholder region: if you want to check whether
1411 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1412 /// with a placeholder region `'%a`, the variable `'_` would just be
1413 /// instantiated to the placeholder region `'%a`, which is wrong because
1414 /// the inference variable is supposed to satisfy the relation
1415 /// *for every value of the placeholder region*. To ensure that doesn't
1416 /// happen, you can use `leak_check`. This is more clearly explained
1417 /// by the [rustc dev guide].
1419 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1420 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1421 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1422 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1423 pub enum RegionKind {
1424 /// Region bound in a type or fn declaration which will be
1425 /// substituted 'early' -- that is, at the same time when type
1426 /// parameters are substituted.
1427 ReEarlyBound(EarlyBoundRegion),
1429 /// Region bound in a function scope, which will be substituted when the
1430 /// function is called.
1431 ReLateBound(DebruijnIndex, BoundRegion),
1433 /// When checking a function body, the types of all arguments and so forth
1434 /// that refer to bound region parameters are modified to refer to free
1435 /// region parameters.
1438 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1441 /// A region variable. Should not exist after typeck.
1444 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1445 /// Should not exist after typeck.
1446 RePlaceholder(ty::PlaceholderRegion),
1448 /// Empty lifetime is for data that is never accessed. We tag the
1449 /// empty lifetime with a universe -- the idea is that we don't
1450 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1451 /// Therefore, the `'empty` in a universe `U` is less than all
1452 /// regions visible from `U`, but not less than regions not visible
1454 ReEmpty(ty::UniverseIndex),
1456 /// Erased region, used by trait selection, in MIR and during codegen.
1460 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1461 pub struct EarlyBoundRegion {
1467 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1472 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1473 pub struct ConstVid<'tcx> {
1475 pub phantom: PhantomData<&'tcx ()>,
1478 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1483 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1484 pub struct FloatVid {
1488 rustc_index::newtype_index! {
1489 pub struct RegionVid {
1490 DEBUG_FORMAT = custom,
1494 impl Atom for RegionVid {
1495 fn index(self) -> usize {
1500 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1501 #[derive(HashStable)]
1507 /// A `FreshTy` is one that is generated as a replacement for an
1508 /// unbound type variable. This is convenient for caching etc. See
1509 /// `infer::freshen` for more details.
1515 rustc_index::newtype_index! {
1516 pub struct BoundVar { .. }
1519 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1520 #[derive(HashStable)]
1521 pub struct BoundTy {
1523 pub kind: BoundTyKind,
1526 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1527 #[derive(HashStable)]
1528 pub enum BoundTyKind {
1533 impl From<BoundVar> for BoundTy {
1534 fn from(var: BoundVar) -> Self {
1535 BoundTy { var, kind: BoundTyKind::Anon }
1539 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1540 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1541 #[derive(HashStable, TypeFoldable)]
1542 pub struct ExistentialProjection<'tcx> {
1543 pub item_def_id: DefId,
1544 pub substs: SubstsRef<'tcx>,
1548 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1550 impl<'tcx> ExistentialProjection<'tcx> {
1551 /// Extracts the underlying existential trait reference from this projection.
1552 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1553 /// then this function would return a `exists T. T: Iterator` existential trait
1555 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1556 // FIXME(generic_associated_types): substs is the substs of the
1557 // associated type, which should be truncated to get the correct substs
1559 let def_id = tcx.associated_item(self.item_def_id).container.id();
1560 ty::ExistentialTraitRef { def_id, substs: self.substs }
1563 pub fn with_self_ty(
1567 ) -> ty::ProjectionPredicate<'tcx> {
1568 // otherwise the escaping regions would be captured by the binders
1569 debug_assert!(!self_ty.has_escaping_bound_vars());
1571 ty::ProjectionPredicate {
1572 projection_ty: ty::ProjectionTy {
1573 item_def_id: self.item_def_id,
1574 substs: tcx.mk_substs_trait(self_ty, self.substs),
1581 impl<'tcx> PolyExistentialProjection<'tcx> {
1582 pub fn with_self_ty(
1586 ) -> ty::PolyProjectionPredicate<'tcx> {
1587 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1590 pub fn item_def_id(&self) -> DefId {
1591 self.skip_binder().item_def_id
1595 impl DebruijnIndex {
1596 /// Returns the resulting index when this value is moved into
1597 /// `amount` number of new binders. So, e.g., if you had
1599 /// for<'a> fn(&'a x)
1601 /// and you wanted to change it to
1603 /// for<'a> fn(for<'b> fn(&'a x))
1605 /// you would need to shift the index for `'a` into a new binder.
1607 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1608 DebruijnIndex::from_u32(self.as_u32() + amount)
1611 /// Update this index in place by shifting it "in" through
1612 /// `amount` number of binders.
1613 pub fn shift_in(&mut self, amount: u32) {
1614 *self = self.shifted_in(amount);
1617 /// Returns the resulting index when this value is moved out from
1618 /// `amount` number of new binders.
1620 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1621 DebruijnIndex::from_u32(self.as_u32() - amount)
1624 /// Update in place by shifting out from `amount` binders.
1625 pub fn shift_out(&mut self, amount: u32) {
1626 *self = self.shifted_out(amount);
1629 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1630 /// innermost binder. That is, if we have something bound at `to_binder`,
1631 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1632 /// when moving a region out from inside binders:
1635 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1636 /// // Binder: D3 D2 D1 ^^
1639 /// Here, the region `'a` would have the De Bruijn index D3,
1640 /// because it is the bound 3 binders out. However, if we wanted
1641 /// to refer to that region `'a` in the second argument (the `_`),
1642 /// those two binders would not be in scope. In that case, we
1643 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1644 /// De Bruijn index of `'a` to D1 (the innermost binder).
1646 /// If we invoke `shift_out_to_binder` and the region is in fact
1647 /// bound by one of the binders we are shifting out of, that is an
1648 /// error (and should fail an assertion failure).
1649 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1650 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1654 /// Region utilities
1656 /// Is this region named by the user?
1657 pub fn has_name(&self) -> bool {
1659 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1660 RegionKind::ReLateBound(_, br) => br.is_named(),
1661 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1662 RegionKind::ReStatic => true,
1663 RegionKind::ReVar(..) => false,
1664 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1665 RegionKind::ReEmpty(_) => false,
1666 RegionKind::ReErased => false,
1670 pub fn is_late_bound(&self) -> bool {
1672 ty::ReLateBound(..) => true,
1677 pub fn is_placeholder(&self) -> bool {
1679 ty::RePlaceholder(..) => true,
1684 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1686 ty::ReLateBound(debruijn, _) => debruijn >= index,
1691 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1692 /// innermost binder. That is, if we have something bound at `to_binder`,
1693 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1694 /// when moving a region out from inside binders:
1697 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1698 /// // Binder: D3 D2 D1 ^^
1701 /// Here, the region `'a` would have the De Bruijn index D3,
1702 /// because it is the bound 3 binders out. However, if we wanted
1703 /// to refer to that region `'a` in the second argument (the `_`),
1704 /// those two binders would not be in scope. In that case, we
1705 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1706 /// De Bruijn index of `'a` to D1 (the innermost binder).
1708 /// If we invoke `shift_out_to_binder` and the region is in fact
1709 /// bound by one of the binders we are shifting out of, that is an
1710 /// error (and should fail an assertion failure).
1711 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1713 ty::ReLateBound(debruijn, r) => {
1714 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1720 pub fn type_flags(&self) -> TypeFlags {
1721 let mut flags = TypeFlags::empty();
1725 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1726 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1727 flags = flags | TypeFlags::HAS_RE_INFER;
1729 ty::RePlaceholder(..) => {
1730 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1731 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1732 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1734 ty::ReEarlyBound(..) => {
1735 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1736 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1737 flags = flags | TypeFlags::HAS_RE_PARAM;
1739 ty::ReFree { .. } => {
1740 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1741 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1743 ty::ReEmpty(_) | ty::ReStatic => {
1744 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1746 ty::ReLateBound(..) => {
1747 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1750 flags = flags | TypeFlags::HAS_RE_ERASED;
1754 debug!("type_flags({:?}) = {:?}", self, flags);
1759 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1760 /// For example, consider the regions in this snippet of code:
1764 /// ^^ -- early bound, declared on an impl
1766 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1767 /// ^^ ^^ ^ anonymous, late-bound
1768 /// | early-bound, appears in where-clauses
1769 /// late-bound, appears only in fn args
1774 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1775 /// of the impl, and for all the other highlighted regions, it
1776 /// would return the `DefId` of the function. In other cases (not shown), this
1777 /// function might return the `DefId` of a closure.
1778 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1780 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1781 ty::ReFree(fr) => fr.scope,
1782 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1788 impl<'tcx> TyS<'tcx> {
1790 pub fn kind(&self) -> &TyKind<'tcx> {
1795 pub fn flags(&self) -> TypeFlags {
1800 pub fn is_unit(&self) -> bool {
1802 Tuple(ref tys) => tys.is_empty(),
1808 pub fn is_never(&self) -> bool {
1809 matches!(self.kind(), Never)
1812 /// Checks whether a type is definitely uninhabited. This is
1813 /// conservative: for some types that are uninhabited we return `false`,
1814 /// but we only return `true` for types that are definitely uninhabited.
1815 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1816 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1817 /// size, to account for partial initialisation. See #49298 for details.)
1818 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1819 // FIXME(varkor): we can make this less conversative by substituting concrete
1823 ty::Adt(def, _) if def.is_union() => {
1824 // For now, `union`s are never considered uninhabited.
1827 ty::Adt(def, _) => {
1828 // Any ADT is uninhabited if either:
1829 // (a) It has no variants (i.e. an empty `enum`);
1830 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1831 // one uninhabited field.
1832 def.variants.iter().all(|var| {
1833 var.fields.iter().any(|field| {
1834 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1839 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1841 ty::Array(ty, len) => {
1842 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1843 Some(0) | None => false,
1844 // If the array is definitely non-empty, it's uninhabited if
1845 // the type of its elements is uninhabited.
1846 Some(1..) => ty.conservative_is_privately_uninhabited(tcx),
1850 // References to uninitialised memory is valid for any type, including
1851 // uninhabited types, in unsafe code, so we treat all references as
1860 pub fn is_primitive(&self) -> bool {
1861 self.kind().is_primitive()
1865 pub fn is_adt(&self) -> bool {
1866 matches!(self.kind(), Adt(..))
1870 pub fn is_ref(&self) -> bool {
1871 matches!(self.kind(), Ref(..))
1875 pub fn is_ty_var(&self) -> bool {
1876 matches!(self.kind(), Infer(TyVar(_)))
1880 pub fn is_ty_infer(&self) -> bool {
1881 matches!(self.kind(), Infer(_))
1885 pub fn is_phantom_data(&self) -> bool {
1886 if let Adt(def, _) = self.kind() { def.is_phantom_data() } else { false }
1890 pub fn is_bool(&self) -> bool {
1891 *self.kind() == Bool
1894 /// Returns `true` if this type is a `str`.
1896 pub fn is_str(&self) -> bool {
1901 pub fn is_param(&self, index: u32) -> bool {
1903 ty::Param(ref data) => data.index == index,
1909 pub fn is_slice(&self) -> bool {
1911 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_) | Str),
1917 pub fn is_array(&self) -> bool {
1918 matches!(self.kind(), Array(..))
1922 pub fn is_simd(&self) -> bool {
1924 Adt(def, _) => def.repr.simd(),
1929 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1931 Array(ty, _) | Slice(ty) => ty,
1932 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1933 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1937 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1939 Adt(def, substs) => {
1940 let variant = def.non_enum_variant();
1941 let f0_ty = variant.fields[0].ty(tcx, substs);
1943 match f0_ty.kind() {
1944 Array(f0_elem_ty, f0_len) => {
1945 // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112
1946 // The way we evaluate the `N` in `[T; N]` here only works since we use
1947 // `simd_size_and_type` post-monomorphization. It will probably start to ICE
1948 // if we use it in generic code. See the `simd-array-trait` ui test.
1949 (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, f0_elem_ty)
1951 _ => (variant.fields.len() as u64, f0_ty),
1954 _ => bug!("`simd_size_and_type` called on invalid type"),
1959 pub fn is_region_ptr(&self) -> bool {
1960 matches!(self.kind(), Ref(..))
1964 pub fn is_mutable_ptr(&self) -> bool {
1967 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1968 | Ref(_, _, hir::Mutability::Mut)
1973 pub fn is_unsafe_ptr(&self) -> bool {
1974 matches!(self.kind(), RawPtr(_))
1977 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1979 pub fn is_any_ptr(&self) -> bool {
1980 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1984 pub fn is_box(&self) -> bool {
1986 Adt(def, _) => def.is_box(),
1991 /// Panics if called on any type other than `Box<T>`.
1992 pub fn boxed_ty(&self) -> Ty<'tcx> {
1994 Adt(def, substs) if def.is_box() => substs.type_at(0),
1995 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1999 /// A scalar type is one that denotes an atomic datum, with no sub-components.
2000 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
2001 /// contents are abstract to rustc.)
2003 pub fn is_scalar(&self) -> bool {
2006 Bool | Char | Int(_) | Float(_) | Uint(_) | FnDef(..) | FnPtr(_) | RawPtr(_)
2007 | Infer(IntVar(_) | FloatVar(_))
2011 /// Returns `true` if this type is a floating point type.
2013 pub fn is_floating_point(&self) -> bool {
2014 matches!(self.kind(), Float(_) | Infer(FloatVar(_)))
2018 pub fn is_trait(&self) -> bool {
2019 matches!(self.kind(), Dynamic(..))
2023 pub fn is_enum(&self) -> bool {
2025 Adt(adt_def, _) => adt_def.is_enum(),
2031 pub fn is_closure(&self) -> bool {
2032 matches!(self.kind(), Closure(..))
2036 pub fn is_generator(&self) -> bool {
2037 matches!(self.kind(), Generator(..))
2041 pub fn is_integral(&self) -> bool {
2042 matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_))
2046 pub fn is_fresh_ty(&self) -> bool {
2047 matches!(self.kind(), Infer(FreshTy(_)))
2051 pub fn is_fresh(&self) -> bool {
2052 matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_)))
2056 pub fn is_char(&self) -> bool {
2057 matches!(self.kind(), Char)
2061 pub fn is_numeric(&self) -> bool {
2062 self.is_integral() || self.is_floating_point()
2066 pub fn is_signed(&self) -> bool {
2067 matches!(self.kind(), Int(_))
2071 pub fn is_ptr_sized_integral(&self) -> bool {
2072 matches!(self.kind(), Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize))
2076 pub fn is_machine(&self) -> bool {
2077 matches!(self.kind(), Int(..) | Uint(..) | Float(..))
2081 pub fn has_concrete_skeleton(&self) -> bool {
2082 !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
2085 /// Returns the type and mutability of `*ty`.
2087 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2088 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2089 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2091 Adt(def, _) if def.is_box() => {
2092 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2094 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl: *mutbl }),
2095 RawPtr(mt) if explicit => Some(*mt),
2100 /// Returns the type of `ty[i]`.
2101 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2103 Array(ty, _) | Slice(ty) => Some(ty),
2108 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2110 FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
2113 // ignore errors (#54954)
2114 ty::Binder::dummy(FnSig::fake())
2116 Closure(..) => bug!(
2117 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2119 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2124 pub fn is_fn(&self) -> bool {
2125 matches!(self.kind(), FnDef(..) | FnPtr(_))
2129 pub fn is_fn_ptr(&self) -> bool {
2130 matches!(self.kind(), FnPtr(_))
2134 pub fn is_impl_trait(&self) -> bool {
2135 matches!(self.kind(), Opaque(..))
2139 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2141 Adt(adt, _) => Some(adt),
2146 /// Iterates over tuple fields.
2147 /// Panics when called on anything but a tuple.
2148 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2150 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2151 _ => bug!("tuple_fields called on non-tuple"),
2155 /// If the type contains variants, returns the valid range of variant indices.
2157 // FIXME: This requires the optimized MIR in the case of generators.
2159 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2161 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2162 TyKind::Generator(def_id, substs, _) => {
2163 Some(substs.as_generator().variant_range(*def_id, tcx))
2169 /// If the type contains variants, returns the variant for `variant_index`.
2170 /// Panics if `variant_index` is out of range.
2172 // FIXME: This requires the optimized MIR in the case of generators.
2174 pub fn discriminant_for_variant(
2177 variant_index: VariantIdx,
2178 ) -> Option<Discr<'tcx>> {
2180 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2181 bug!("discriminant_for_variant called on zero variant enum");
2183 TyKind::Adt(adt, _) if adt.is_enum() => {
2184 Some(adt.discriminant_for_variant(tcx, variant_index))
2186 TyKind::Generator(def_id, substs, _) => {
2187 Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
2193 /// Returns the type of the discriminant of this type.
2194 pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2196 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2197 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2199 // This can only be `0`, for now, so `u8` will suffice.
2205 /// When we create a closure, we record its kind (i.e., what trait
2206 /// it implements) into its `ClosureSubsts` using a type
2207 /// parameter. This is kind of a phantom type, except that the
2208 /// most convenient thing for us to are the integral types. This
2209 /// function converts such a special type into the closure
2210 /// kind. To go the other way, use
2211 /// `tcx.closure_kind_ty(closure_kind)`.
2213 /// Note that during type checking, we use an inference variable
2214 /// to represent the closure kind, because it has not yet been
2215 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2216 /// is complete, that type variable will be unified.
2217 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2219 Int(int_ty) => match int_ty {
2220 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2221 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2222 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2223 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2226 // "Bound" types appear in canonical queries when the
2227 // closure type is not yet known
2228 Bound(..) | Infer(_) => None,
2230 Error(_) => Some(ty::ClosureKind::Fn),
2232 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2236 /// Fast path helper for testing if a type is `Sized`.
2238 /// Returning true means the type is known to be sized. Returning
2239 /// `false` means nothing -- could be sized, might not be.
2241 /// Note that we could never rely on the fact that a type such as `[_]` is
2242 /// trivially `!Sized` because we could be in a type environment with a
2243 /// bound such as `[_]: Copy`. A function with such a bound obviously never
2244 /// can be called, but that doesn't mean it shouldn't typecheck. This is why
2245 /// this method doesn't return `Option<bool>`.
2246 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2248 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2259 | ty::GeneratorWitness(..)
2263 | ty::Error(_) => true,
2265 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2267 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2269 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2271 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2273 ty::Infer(ty::TyVar(_)) => false,
2276 | ty::Placeholder(..)
2277 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2278 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)