1 //! This module contains `TyKind` and its major components.
3 #![allow(rustc::usage_of_ty_tykind)]
7 use crate::infer::canonical::Canonical;
8 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
9 use crate::ty::InferTy::{self, *};
11 self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness,
13 use crate::ty::{DelaySpanBugEmitted, List, ParamEnv, TyS};
14 use polonius_engine::Atom;
15 use rustc_data_structures::captures::Captures;
17 use rustc_hir::def_id::DefId;
18 use rustc_index::vec::Idx;
19 use rustc_macros::HashStable;
20 use rustc_span::symbol::{kw, Ident, Symbol};
21 use rustc_target::abi::VariantIdx;
22 use rustc_target::spec::abi;
24 use std::cmp::Ordering;
25 use std::marker::PhantomData;
27 use ty::util::IntTypeExt;
29 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
30 #[derive(HashStable, TypeFoldable, Lift)]
31 pub struct TypeAndMut<'tcx> {
33 pub mutbl: hir::Mutability,
36 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
38 /// A "free" region `fr` can be interpreted as "some region
39 /// at least as big as the scope `fr.scope`".
40 pub struct FreeRegion {
42 pub bound_region: BoundRegionKind,
45 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
47 pub enum BoundRegionKind {
48 /// An anonymous region parameter for a given fn (&T)
51 /// Named region parameters for functions (a in &'a T)
53 /// The `DefId` is needed to distinguish free regions in
54 /// the event of shadowing.
55 BrNamed(DefId, Symbol),
57 /// Anonymous region for the implicit env pointer parameter
62 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
64 pub struct BoundRegion {
65 pub kind: BoundRegionKind,
69 /// When canonicalizing, we replace unbound inference variables and free
70 /// regions with anonymous late bound regions. This method asserts that
71 /// we have an anonymous late bound region, which hence may refer to
72 /// a canonical variable.
73 pub fn assert_bound_var(&self) -> BoundVar {
75 BoundRegionKind::BrAnon(var) => BoundVar::from_u32(var),
76 _ => bug!("bound region is not anonymous"),
81 impl BoundRegionKind {
82 pub fn is_named(&self) -> bool {
84 BoundRegionKind::BrNamed(_, name) => name != kw::UnderscoreLifetime,
90 /// Defines the kinds of types.
92 /// N.B., if you change this, you'll probably want to change the corresponding
93 /// AST structure in `librustc_ast/ast.rs` as well.
94 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
96 #[rustc_diagnostic_item = "TyKind"]
97 pub enum TyKind<'tcx> {
98 /// The primitive boolean type. Written as `bool`.
101 /// The primitive character type; holds a Unicode scalar value
102 /// (a non-surrogate code point). Written as `char`.
105 /// A primitive signed integer type. For example, `i32`.
108 /// A primitive unsigned integer type. For example, `u32`.
111 /// A primitive floating-point type. For example, `f64`.
114 /// Algebraic data types (ADT). For example: structures, enumerations and unions.
116 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
117 /// That is, even after substitution it is possible that there are type
118 /// variables. This happens when the `Adt` corresponds to an ADT
119 /// definition and not a concrete use of it.
120 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
122 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
125 /// The pointee of a string slice. Written as `str`.
128 /// An array with the given length. Written as `[T; n]`.
129 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
131 /// The pointee of an array slice. Written as `[T]`.
134 /// A raw pointer. Written as `*mut T` or `*const T`
135 RawPtr(TypeAndMut<'tcx>),
137 /// A reference; a pointer with an associated lifetime. Written as
138 /// `&'a mut T` or `&'a T`.
139 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
141 /// The anonymous type of a function declaration/definition. Each
142 /// function has a unique type, which is output (for a function
143 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
145 /// For example the type of `bar` here:
148 /// fn foo() -> i32 { 1 }
149 /// let bar = foo; // bar: fn() -> i32 {foo}
151 FnDef(DefId, SubstsRef<'tcx>),
153 /// A pointer to a function. Written as `fn() -> i32`.
155 /// For example the type of `bar` here:
158 /// fn foo() -> i32 { 1 }
159 /// let bar: fn() -> i32 = foo;
161 FnPtr(PolyFnSig<'tcx>),
163 /// A trait, defined with `trait`.
164 Dynamic(&'tcx List<Binder<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
166 /// The anonymous type of a closure. Used to represent the type of
168 Closure(DefId, SubstsRef<'tcx>),
170 /// The anonymous type of a generator. Used to represent the type of
172 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
174 /// A type representing the types stored inside a generator.
175 /// This should only appear in GeneratorInteriors.
176 GeneratorWitness(Binder<&'tcx List<Ty<'tcx>>>),
178 /// The never type `!`.
181 /// A tuple type. For example, `(i32, bool)`.
182 /// Use `TyS::tuple_fields` to iterate over the field types.
183 Tuple(SubstsRef<'tcx>),
185 /// The projection of an associated type. For example,
186 /// `<T as Trait<..>>::N`.
187 Projection(ProjectionTy<'tcx>),
189 /// Opaque (`impl Trait`) type found in a return type.
190 /// The `DefId` comes either from
191 /// * the `impl Trait` ast::Ty node,
192 /// * or the `type Foo = impl Trait` declaration
193 /// The substitutions are for the generics of the function in question.
194 /// After typeck, the concrete type can be found in the `types` map.
195 Opaque(DefId, SubstsRef<'tcx>),
197 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}`.
200 /// Bound type variable, used only when preparing a trait query.
201 Bound(ty::DebruijnIndex, BoundTy),
203 /// A placeholder type - universally quantified higher-ranked type.
204 Placeholder(ty::PlaceholderType),
206 /// A type variable used during type checking.
209 /// A placeholder for a type which could not be computed; this is
210 /// propagated to avoid useless error messages.
211 Error(DelaySpanBugEmitted),
216 pub fn is_primitive(&self) -> bool {
217 matches!(self, Bool | Char | Int(_) | Uint(_) | Float(_))
220 /// Get the article ("a" or "an") to use with this type.
221 pub fn article(&self) -> &'static str {
223 Int(_) | Float(_) | Array(_, _) => "an",
224 Adt(def, _) if def.is_enum() => "an",
225 // This should never happen, but ICEing and causing the user's code
226 // to not compile felt too harsh.
233 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
234 #[cfg(target_arch = "x86_64")]
235 static_assert_size!(TyKind<'_>, 24);
237 /// A closure can be modeled as a struct that looks like:
239 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
243 /// - 'l0...'li and T0...Tj are the generic parameters
244 /// in scope on the function that defined the closure,
245 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
246 /// is rather hackily encoded via a scalar type. See
247 /// `TyS::to_opt_closure_kind` for details.
248 /// - CS represents the *closure signature*, representing as a `fn()`
249 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
250 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
252 /// - U is a type parameter representing the types of its upvars, tupled up
253 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
254 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
256 /// So, for example, given this function:
258 /// fn foo<'a, T>(data: &'a mut T) {
259 /// do(|| data.count += 1)
262 /// the type of the closure would be something like:
264 /// struct Closure<'a, T, U>(...U);
266 /// Note that the type of the upvar is not specified in the struct.
267 /// You may wonder how the impl would then be able to use the upvar,
268 /// if it doesn't know it's type? The answer is that the impl is
269 /// (conceptually) not fully generic over Closure but rather tied to
270 /// instances with the expected upvar types:
272 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
276 /// You can see that the *impl* fully specified the type of the upvar
277 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
278 /// (Here, I am assuming that `data` is mut-borrowed.)
280 /// Now, the last question you may ask is: Why include the upvar types
281 /// in an extra type parameter? The reason for this design is that the
282 /// upvar types can reference lifetimes that are internal to the
283 /// creating function. In my example above, for example, the lifetime
284 /// `'b` represents the scope of the closure itself; this is some
285 /// subset of `foo`, probably just the scope of the call to the to
286 /// `do()`. If we just had the lifetime/type parameters from the
287 /// enclosing function, we couldn't name this lifetime `'b`. Note that
288 /// there can also be lifetimes in the types of the upvars themselves,
289 /// if one of them happens to be a reference to something that the
290 /// creating fn owns.
292 /// OK, you say, so why not create a more minimal set of parameters
293 /// that just includes the extra lifetime parameters? The answer is
294 /// primarily that it would be hard --- we don't know at the time when
295 /// we create the closure type what the full types of the upvars are,
296 /// nor do we know which are borrowed and which are not. In this
297 /// design, we can just supply a fresh type parameter and figure that
300 /// All right, you say, but why include the type parameters from the
301 /// original function then? The answer is that codegen may need them
302 /// when monomorphizing, and they may not appear in the upvars. A
303 /// closure could capture no variables but still make use of some
304 /// in-scope type parameter with a bound (e.g., if our example above
305 /// had an extra `U: Default`, and the closure called `U::default()`).
307 /// There is another reason. This design (implicitly) prohibits
308 /// closures from capturing themselves (except via a trait
309 /// object). This simplifies closure inference considerably, since it
310 /// means that when we infer the kind of a closure or its upvars, we
311 /// don't have to handle cycles where the decisions we make for
312 /// closure C wind up influencing the decisions we ought to make for
313 /// closure C (which would then require fixed point iteration to
314 /// handle). Plus it fixes an ICE. :P
318 /// Generators are handled similarly in `GeneratorSubsts`. The set of
319 /// type parameters is similar, but `CK` and `CS` are replaced by the
320 /// following type parameters:
322 /// * `GS`: The generator's "resume type", which is the type of the
323 /// argument passed to `resume`, and the type of `yield` expressions
324 /// inside the generator.
325 /// * `GY`: The "yield type", which is the type of values passed to
326 /// `yield` inside the generator.
327 /// * `GR`: The "return type", which is the type of value returned upon
328 /// completion of the generator.
329 /// * `GW`: The "generator witness".
330 #[derive(Copy, Clone, Debug, TypeFoldable)]
331 pub struct ClosureSubsts<'tcx> {
332 /// Lifetime and type parameters from the enclosing function,
333 /// concatenated with a tuple containing the types of the upvars.
335 /// These are separated out because codegen wants to pass them around
336 /// when monomorphizing.
337 pub substs: SubstsRef<'tcx>,
340 /// Struct returned by `split()`.
341 pub struct ClosureSubstsParts<'tcx, T> {
342 pub parent_substs: &'tcx [GenericArg<'tcx>],
343 pub closure_kind_ty: T,
344 pub closure_sig_as_fn_ptr_ty: T,
345 pub tupled_upvars_ty: T,
348 impl<'tcx> ClosureSubsts<'tcx> {
349 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
350 /// for the closure parent, alongside additional closure-specific components.
353 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
354 ) -> ClosureSubsts<'tcx> {
356 substs: tcx.mk_substs(
357 parts.parent_substs.iter().copied().chain(
358 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
360 .map(|&ty| ty.into()),
366 /// Divides the closure substs into their respective components.
367 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
368 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
369 match self.substs[..] {
370 [ref parent_substs @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
374 closure_sig_as_fn_ptr_ty,
378 _ => bug!("closure substs missing synthetics"),
382 /// Returns `true` only if enough of the synthetic types are known to
383 /// allow using all of the methods on `ClosureSubsts` without panicking.
385 /// Used primarily by `ty::print::pretty` to be able to handle closure
386 /// types that haven't had their synthetic types substituted in.
387 pub fn is_valid(self) -> bool {
388 self.substs.len() >= 3
389 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
392 /// Returns the substitutions of the closure's parent.
393 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
394 self.split().parent_substs
397 /// Returns an iterator over the list of types of captured paths by the closure.
398 /// In case there was a type error in figuring out the types of the captured path, an
399 /// empty iterator is returned.
401 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
402 match self.tupled_upvars_ty().kind() {
403 TyKind::Error(_) => None,
404 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
405 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
406 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
412 /// Returns the tuple type representing the upvars for this closure.
414 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
415 self.split().tupled_upvars_ty.expect_ty()
418 /// Returns the closure kind for this closure; may return a type
419 /// variable during inference. To get the closure kind during
420 /// inference, use `infcx.closure_kind(substs)`.
421 pub fn kind_ty(self) -> Ty<'tcx> {
422 self.split().closure_kind_ty.expect_ty()
425 /// Returns the `fn` pointer type representing the closure signature for this
427 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
428 // type is known at the time of the creation of `ClosureSubsts`,
429 // see `rustc_typeck::check::closure`.
430 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
431 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
434 /// Returns the closure kind for this closure; only usable outside
435 /// of an inference context, because in that context we know that
436 /// there are no type variables.
438 /// If you have an inference context, use `infcx.closure_kind()`.
439 pub fn kind(self) -> ty::ClosureKind {
440 self.kind_ty().to_opt_closure_kind().unwrap()
443 /// Extracts the signature from the closure.
444 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
445 let ty = self.sig_as_fn_ptr_ty();
447 ty::FnPtr(sig) => *sig,
448 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind()),
453 /// Similar to `ClosureSubsts`; see the above documentation for more.
454 #[derive(Copy, Clone, Debug, TypeFoldable)]
455 pub struct GeneratorSubsts<'tcx> {
456 pub substs: SubstsRef<'tcx>,
459 pub struct GeneratorSubstsParts<'tcx, T> {
460 pub parent_substs: &'tcx [GenericArg<'tcx>],
465 pub tupled_upvars_ty: T,
468 impl<'tcx> GeneratorSubsts<'tcx> {
469 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
470 /// for the generator parent, alongside additional generator-specific components.
473 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
474 ) -> GeneratorSubsts<'tcx> {
476 substs: tcx.mk_substs(
477 parts.parent_substs.iter().copied().chain(
483 parts.tupled_upvars_ty,
486 .map(|&ty| ty.into()),
492 /// Divides the generator substs into their respective components.
493 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
494 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
495 match self.substs[..] {
496 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
497 GeneratorSubstsParts {
506 _ => bug!("generator substs missing synthetics"),
510 /// Returns `true` only if enough of the synthetic types are known to
511 /// allow using all of the methods on `GeneratorSubsts` without panicking.
513 /// Used primarily by `ty::print::pretty` to be able to handle generator
514 /// types that haven't had their synthetic types substituted in.
515 pub fn is_valid(self) -> bool {
516 self.substs.len() >= 5
517 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
520 /// Returns the substitutions of the generator's parent.
521 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
522 self.split().parent_substs
525 /// This describes the types that can be contained in a generator.
526 /// It will be a type variable initially and unified in the last stages of typeck of a body.
527 /// It contains a tuple of all the types that could end up on a generator frame.
528 /// The state transformation MIR pass may only produce layouts which mention types
529 /// in this tuple. Upvars are not counted here.
530 pub fn witness(self) -> Ty<'tcx> {
531 self.split().witness.expect_ty()
534 /// Returns an iterator over the list of types of captured paths by the generator.
535 /// In case there was a type error in figuring out the types of the captured path, an
536 /// empty iterator is returned.
538 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
539 match self.tupled_upvars_ty().kind() {
540 TyKind::Error(_) => None,
541 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
542 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
543 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
549 /// Returns the tuple type representing the upvars for this generator.
551 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
552 self.split().tupled_upvars_ty.expect_ty()
555 /// Returns the type representing the resume type of the generator.
556 pub fn resume_ty(self) -> Ty<'tcx> {
557 self.split().resume_ty.expect_ty()
560 /// Returns the type representing the yield type of the generator.
561 pub fn yield_ty(self) -> Ty<'tcx> {
562 self.split().yield_ty.expect_ty()
565 /// Returns the type representing the return type of the generator.
566 pub fn return_ty(self) -> Ty<'tcx> {
567 self.split().return_ty.expect_ty()
570 /// Returns the "generator signature", which consists of its yield
571 /// and return types.
573 /// N.B., some bits of the code prefers to see this wrapped in a
574 /// binder, but it never contains bound regions. Probably this
575 /// function should be removed.
576 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
577 ty::Binder::dummy(self.sig())
580 /// Returns the "generator signature", which consists of its resume, yield
581 /// and return types.
582 pub fn sig(self) -> GenSig<'tcx> {
584 resume_ty: self.resume_ty(),
585 yield_ty: self.yield_ty(),
586 return_ty: self.return_ty(),
591 impl<'tcx> GeneratorSubsts<'tcx> {
592 /// Generator has not been resumed yet.
593 pub const UNRESUMED: usize = 0;
594 /// Generator has returned or is completed.
595 pub const RETURNED: usize = 1;
596 /// Generator has been poisoned.
597 pub const POISONED: usize = 2;
599 const UNRESUMED_NAME: &'static str = "Unresumed";
600 const RETURNED_NAME: &'static str = "Returned";
601 const POISONED_NAME: &'static str = "Panicked";
603 /// The valid variant indices of this generator.
605 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
606 // FIXME requires optimized MIR
607 let num_variants = tcx.generator_layout(def_id).unwrap().variant_fields.len();
608 VariantIdx::new(0)..VariantIdx::new(num_variants)
611 /// The discriminant for the given variant. Panics if the `variant_index` is
614 pub fn discriminant_for_variant(
618 variant_index: VariantIdx,
620 // Generators don't support explicit discriminant values, so they are
621 // the same as the variant index.
622 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
623 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
626 /// The set of all discriminants for the generator, enumerated with their
629 pub fn discriminants(
633 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
634 self.variant_range(def_id, tcx).map(move |index| {
635 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
639 /// Calls `f` with a reference to the name of the enumerator for the given
641 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
643 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
644 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
645 Self::POISONED => Cow::from(Self::POISONED_NAME),
646 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
650 /// The type of the state discriminant used in the generator type.
652 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
656 /// This returns the types of the MIR locals which had to be stored across suspension points.
657 /// It is calculated in rustc_mir::transform::generator::StateTransform.
658 /// All the types here must be in the tuple in GeneratorInterior.
660 /// The locals are grouped by their variant number. Note that some locals may
661 /// be repeated in multiple variants.
667 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
668 let layout = tcx.generator_layout(def_id).unwrap();
669 layout.variant_fields.iter().map(move |variant| {
670 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
674 /// This is the types of the fields of a generator which are not stored in a
677 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
682 #[derive(Debug, Copy, Clone)]
683 pub enum UpvarSubsts<'tcx> {
684 Closure(SubstsRef<'tcx>),
685 Generator(SubstsRef<'tcx>),
688 impl<'tcx> UpvarSubsts<'tcx> {
689 /// Returns an iterator over the list of types of captured paths by the closure/generator.
690 /// In case there was a type error in figuring out the types of the captured path, an
691 /// empty iterator is returned.
693 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
694 let tupled_tys = match self {
695 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
696 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
699 match tupled_tys.kind() {
700 TyKind::Error(_) => None,
701 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
702 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
703 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
710 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
712 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
713 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
718 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
719 #[derive(HashStable, TypeFoldable)]
720 pub enum ExistentialPredicate<'tcx> {
721 /// E.g., `Iterator`.
722 Trait(ExistentialTraitRef<'tcx>),
723 /// E.g., `Iterator::Item = T`.
724 Projection(ExistentialProjection<'tcx>),
729 impl<'tcx> ExistentialPredicate<'tcx> {
730 /// Compares via an ordering that will not change if modules are reordered or other changes are
731 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
732 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
733 use self::ExistentialPredicate::*;
734 match (*self, *other) {
735 (Trait(_), Trait(_)) => Ordering::Equal,
736 (Projection(ref a), Projection(ref b)) => {
737 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
739 (AutoTrait(ref a), AutoTrait(ref b)) => {
740 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
742 (Trait(_), _) => Ordering::Less,
743 (Projection(_), Trait(_)) => Ordering::Greater,
744 (Projection(_), _) => Ordering::Less,
745 (AutoTrait(_), _) => Ordering::Greater,
750 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
751 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
752 use crate::ty::ToPredicate;
753 match self.skip_binder() {
754 ExistentialPredicate::Trait(tr) => {
755 self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
757 ExistentialPredicate::Projection(p) => {
758 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
760 ExistentialPredicate::AutoTrait(did) => {
761 let trait_ref = self.rebind(ty::TraitRef {
763 substs: tcx.mk_substs_trait(self_ty, &[]),
765 trait_ref.without_const().to_predicate(tcx)
771 impl<'tcx> List<ty::Binder<ExistentialPredicate<'tcx>>> {
772 /// Returns the "principal `DefId`" of this set of existential predicates.
774 /// A Rust trait object type consists (in addition to a lifetime bound)
775 /// of a set of trait bounds, which are separated into any number
776 /// of auto-trait bounds, and at most one non-auto-trait bound. The
777 /// non-auto-trait bound is called the "principal" of the trait
780 /// Only the principal can have methods or type parameters (because
781 /// auto traits can have neither of them). This is important, because
782 /// it means the auto traits can be treated as an unordered set (methods
783 /// would force an order for the vtable, while relating traits with
784 /// type parameters without knowing the order to relate them in is
785 /// a rather non-trivial task).
787 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
788 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
789 /// are the set `{Sync}`.
791 /// It is also possible to have a "trivial" trait object that
792 /// consists only of auto traits, with no principal - for example,
793 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
794 /// is `{Send, Sync}`, while there is no principal. These trait objects
795 /// have a "trivial" vtable consisting of just the size, alignment,
797 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
799 .map_bound(|this| match this {
800 ExistentialPredicate::Trait(tr) => Some(tr),
806 pub fn principal_def_id(&self) -> Option<DefId> {
807 self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
811 pub fn projection_bounds<'a>(
813 ) -> impl Iterator<Item = ty::Binder<ExistentialProjection<'tcx>>> + 'a {
814 self.iter().filter_map(|predicate| {
816 .map_bound(|pred| match pred {
817 ExistentialPredicate::Projection(projection) => Some(projection),
825 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
826 self.iter().filter_map(|predicate| match predicate.skip_binder() {
827 ExistentialPredicate::AutoTrait(did) => Some(did),
833 /// A complete reference to a trait. These take numerous guises in syntax,
834 /// but perhaps the most recognizable form is in a where-clause:
838 /// This would be represented by a trait-reference where the `DefId` is the
839 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
840 /// and `U` as parameter 1.
842 /// Trait references also appear in object types like `Foo<U>`, but in
843 /// that case the `Self` parameter is absent from the substitutions.
844 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
845 #[derive(HashStable, TypeFoldable)]
846 pub struct TraitRef<'tcx> {
848 pub substs: SubstsRef<'tcx>,
851 impl<'tcx> TraitRef<'tcx> {
852 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
853 TraitRef { def_id, substs }
856 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
857 /// are the parameters defined on trait.
858 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
859 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
863 pub fn self_ty(&self) -> Ty<'tcx> {
864 self.substs.type_at(0)
870 substs: SubstsRef<'tcx>,
871 ) -> ty::TraitRef<'tcx> {
872 let defs = tcx.generics_of(trait_id);
874 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
878 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
880 impl<'tcx> PolyTraitRef<'tcx> {
881 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
882 self.map_bound_ref(|tr| tr.self_ty())
885 pub fn def_id(&self) -> DefId {
886 self.skip_binder().def_id
889 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
890 self.map_bound(|trait_ref| ty::TraitPredicate { trait_ref })
894 /// An existential reference to a trait, where `Self` is erased.
895 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
897 /// exists T. T: Trait<'a, 'b, X, Y>
899 /// The substitutions don't include the erased `Self`, only trait
900 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
901 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
902 #[derive(HashStable, TypeFoldable)]
903 pub struct ExistentialTraitRef<'tcx> {
905 pub substs: SubstsRef<'tcx>,
908 impl<'tcx> ExistentialTraitRef<'tcx> {
909 pub fn erase_self_ty(
911 trait_ref: ty::TraitRef<'tcx>,
912 ) -> ty::ExistentialTraitRef<'tcx> {
913 // Assert there is a Self.
914 trait_ref.substs.type_at(0);
916 ty::ExistentialTraitRef {
917 def_id: trait_ref.def_id,
918 substs: tcx.intern_substs(&trait_ref.substs[1..]),
922 /// Object types don't have a self type specified. Therefore, when
923 /// we convert the principal trait-ref into a normal trait-ref,
924 /// you must give *some* self type. A common choice is `mk_err()`
925 /// or some placeholder type.
926 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
927 // otherwise the escaping vars would be captured by the binder
928 // debug_assert!(!self_ty.has_escaping_bound_vars());
930 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
934 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
936 impl<'tcx> PolyExistentialTraitRef<'tcx> {
937 pub fn def_id(&self) -> DefId {
938 self.skip_binder().def_id
941 /// Object types don't have a self type specified. Therefore, when
942 /// we convert the principal trait-ref into a normal trait-ref,
943 /// you must give *some* self type. A common choice is `mk_err()`
944 /// or some placeholder type.
945 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
946 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
950 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
951 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
952 /// (which would be represented by the type `PolyTraitRef ==
953 /// Binder<TraitRef>`). Note that when we instantiate,
954 /// erase, or otherwise "discharge" these bound vars, we change the
955 /// type from `Binder<T>` to just `T` (see
956 /// e.g., `liberate_late_bound_regions`).
958 /// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro.
959 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
960 pub struct Binder<T>(T);
963 /// Wraps `value` in a binder, asserting that `value` does not
964 /// contain any bound vars that would be bound by the
965 /// binder. This is commonly used to 'inject' a value T into a
966 /// different binding level.
967 pub fn dummy<'tcx>(value: T) -> Binder<T>
969 T: TypeFoldable<'tcx>,
971 debug_assert!(!value.has_escaping_bound_vars());
975 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
976 pub fn bind(value: T) -> Binder<T> {
980 /// Wraps `value` in a binder without actually binding any currently
981 /// unbound variables.
983 /// Note that this will shift all debrujin indices of escaping bound variables
984 /// by 1 to avoid accidential captures.
985 pub fn wrap_nonbinding(tcx: TyCtxt<'tcx>, value: T) -> Binder<T>
987 T: TypeFoldable<'tcx>,
989 if value.has_escaping_bound_vars() {
990 Binder::bind(super::fold::shift_vars(tcx, value, 1))
996 /// Skips the binder and returns the "bound" value. This is a
997 /// risky thing to do because it's easy to get confused about
998 /// De Bruijn indices and the like. It is usually better to
999 /// discharge the binder using `no_bound_vars` or
1000 /// `replace_late_bound_regions` or something like
1001 /// that. `skip_binder` is only valid when you are either
1002 /// extracting data that has nothing to do with bound vars, you
1003 /// are doing some sort of test that does not involve bound
1004 /// regions, or you are being very careful about your depth
1007 /// Some examples where `skip_binder` is reasonable:
1009 /// - extracting the `DefId` from a PolyTraitRef;
1010 /// - comparing the self type of a PolyTraitRef to see if it is equal to
1011 /// a type parameter `X`, since the type `X` does not reference any regions
1012 pub fn skip_binder(self) -> T {
1016 pub fn as_ref(&self) -> Binder<&T> {
1020 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
1024 self.as_ref().map_bound(f)
1027 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
1034 /// Wraps a `value` in a binder, using the same bound variables as the
1035 /// current `Binder`. This should not be used if the new value *changes*
1036 /// the bound variables. Note: the (old or new) value itself does not
1037 /// necessarily need to *name* all the bound variables.
1039 /// This currently doesn't do anything different than `bind`, because we
1040 /// don't actually track bound vars. However, semantically, it is different
1041 /// because bound vars aren't allowed to change here, whereas they are
1042 /// in `bind`. This may be (debug) asserted in the future.
1043 pub fn rebind<U>(&self, value: U) -> Binder<U> {
1047 /// Unwraps and returns the value within, but only if it contains
1048 /// no bound vars at all. (In other words, if this binder --
1049 /// and indeed any enclosing binder -- doesn't bind anything at
1050 /// all.) Otherwise, returns `None`.
1052 /// (One could imagine having a method that just unwraps a single
1053 /// binder, but permits late-bound vars bound by enclosing
1054 /// binders, but that would require adjusting the debruijn
1055 /// indices, and given the shallow binding structure we often use,
1056 /// would not be that useful.)
1057 pub fn no_bound_vars<'tcx>(self) -> Option<T>
1059 T: TypeFoldable<'tcx>,
1061 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1064 /// Given two things that have the same binder level,
1065 /// and an operation that wraps on their contents, executes the operation
1066 /// and then wraps its result.
1068 /// `f` should consider bound regions at depth 1 to be free, and
1069 /// anything it produces with bound regions at depth 1 will be
1070 /// bound in the resulting return value.
1071 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
1073 F: FnOnce(T, U) -> R,
1075 Binder(f(self.0, u.0))
1078 /// Splits the contents into two things that share the same binder
1079 /// level as the original, returning two distinct binders.
1081 /// `f` should consider bound regions at depth 1 to be free, and
1082 /// anything it produces with bound regions at depth 1 will be
1083 /// bound in the resulting return values.
1084 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
1086 F: FnOnce(T) -> (U, V),
1088 let (u, v) = f(self.0);
1089 (Binder(u), Binder(v))
1093 impl<T> Binder<Option<T>> {
1094 pub fn transpose(self) -> Option<Binder<T>> {
1099 /// Represents the projection of an associated type. In explicit UFCS
1100 /// form this would be written `<T as Trait<..>>::N`.
1101 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1102 #[derive(HashStable, TypeFoldable)]
1103 pub struct ProjectionTy<'tcx> {
1104 /// The parameters of the associated item.
1105 pub substs: SubstsRef<'tcx>,
1107 /// The `DefId` of the `TraitItem` for the associated type `N`.
1109 /// Note that this is not the `DefId` of the `TraitRef` containing this
1110 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1111 pub item_def_id: DefId,
1114 impl<'tcx> ProjectionTy<'tcx> {
1115 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
1116 /// associated item named `item_name`.
1117 pub fn from_ref_and_name(
1119 trait_ref: ty::TraitRef<'tcx>,
1121 ) -> ProjectionTy<'tcx> {
1122 let item_def_id = tcx
1123 .associated_items(trait_ref.def_id)
1124 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1128 ProjectionTy { substs: trait_ref.substs, item_def_id }
1131 /// Extracts the underlying trait reference from this projection.
1132 /// For example, if this is a projection of `<T as Iterator>::Item`,
1133 /// then this function would return a `T: Iterator` trait reference.
1134 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1135 // FIXME: This method probably shouldn't exist at all, since it's not
1136 // clear what this method really intends to do. Be careful when
1137 // using this method since the resulting TraitRef additionally
1138 // contains the substs for the assoc_item, which strictly speaking
1140 let def_id = tcx.associated_item(self.item_def_id).container.id();
1141 // Include substitutions for generic arguments of associated types
1142 let assoc_item = tcx.associated_item(self.item_def_id);
1143 let substs_assoc_item = self.substs.truncate_to(tcx, tcx.generics_of(assoc_item.def_id));
1144 ty::TraitRef { def_id, substs: substs_assoc_item }
1147 pub fn self_ty(&self) -> Ty<'tcx> {
1148 self.substs.type_at(0)
1152 #[derive(Copy, Clone, Debug, TypeFoldable)]
1153 pub struct GenSig<'tcx> {
1154 pub resume_ty: Ty<'tcx>,
1155 pub yield_ty: Ty<'tcx>,
1156 pub return_ty: Ty<'tcx>,
1159 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1161 impl<'tcx> PolyGenSig<'tcx> {
1162 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1163 self.map_bound_ref(|sig| sig.resume_ty)
1165 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1166 self.map_bound_ref(|sig| sig.yield_ty)
1168 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1169 self.map_bound_ref(|sig| sig.return_ty)
1173 /// Signature of a function type, which we have arbitrarily
1174 /// decided to use to refer to the input/output types.
1176 /// - `inputs`: is the list of arguments and their modes.
1177 /// - `output`: is the return type.
1178 /// - `c_variadic`: indicates whether this is a C-variadic function.
1179 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1180 #[derive(HashStable, TypeFoldable)]
1181 pub struct FnSig<'tcx> {
1182 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1183 pub c_variadic: bool,
1184 pub unsafety: hir::Unsafety,
1188 impl<'tcx> FnSig<'tcx> {
1189 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1190 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1193 pub fn output(&self) -> Ty<'tcx> {
1194 self.inputs_and_output[self.inputs_and_output.len() - 1]
1197 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1199 fn fake() -> FnSig<'tcx> {
1201 inputs_and_output: List::empty(),
1203 unsafety: hir::Unsafety::Normal,
1204 abi: abi::Abi::Rust,
1209 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1211 impl<'tcx> PolyFnSig<'tcx> {
1213 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1214 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1217 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1218 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1220 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1221 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1224 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1225 self.map_bound_ref(|fn_sig| fn_sig.output())
1227 pub fn c_variadic(&self) -> bool {
1228 self.skip_binder().c_variadic
1230 pub fn unsafety(&self) -> hir::Unsafety {
1231 self.skip_binder().unsafety
1233 pub fn abi(&self) -> abi::Abi {
1234 self.skip_binder().abi
1238 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1240 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1241 #[derive(HashStable)]
1242 pub struct ParamTy {
1247 impl<'tcx> ParamTy {
1248 pub fn new(index: u32, name: Symbol) -> ParamTy {
1249 ParamTy { index, name }
1252 pub fn for_self() -> ParamTy {
1253 ParamTy::new(0, kw::SelfUpper)
1256 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1257 ParamTy::new(def.index, def.name)
1260 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1261 tcx.mk_ty_param(self.index, self.name)
1265 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1266 #[derive(HashStable)]
1267 pub struct ParamConst {
1272 impl<'tcx> ParamConst {
1273 pub fn new(index: u32, name: Symbol) -> ParamConst {
1274 ParamConst { index, name }
1277 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1278 ParamConst::new(def.index, def.name)
1281 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
1282 tcx.mk_const_param(self.index, self.name, ty)
1286 pub type Region<'tcx> = &'tcx RegionKind;
1288 /// Representation of regions. Note that the NLL checker uses a distinct
1289 /// representation of regions. For this reason, it internally replaces all the
1290 /// regions with inference variables -- the index of the variable is then used
1291 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1292 /// module for more information.
1294 /// ## The Region lattice within a given function
1296 /// In general, the region lattice looks like
1299 /// static ----------+-----...------+ (greatest)
1301 /// early-bound and | |
1302 /// free regions | |
1305 /// empty(root) placeholder(U1) |
1307 /// | / placeholder(Un)
1312 /// empty(Un) -------- (smallest)
1315 /// Early-bound/free regions are the named lifetimes in scope from the
1316 /// function declaration. They have relationships to one another
1317 /// determined based on the declared relationships from the
1320 /// Note that inference variables and bound regions are not included
1321 /// in this diagram. In the case of inference variables, they should
1322 /// be inferred to some other region from the diagram. In the case of
1323 /// bound regions, they are excluded because they don't make sense to
1324 /// include -- the diagram indicates the relationship between free
1327 /// ## Inference variables
1329 /// During region inference, we sometimes create inference variables,
1330 /// represented as `ReVar`. These will be inferred by the code in
1331 /// `infer::lexical_region_resolve` to some free region from the
1332 /// lattice above (the minimal region that meets the
1335 /// During NLL checking, where regions are defined differently, we
1336 /// also use `ReVar` -- in that case, the index is used to index into
1337 /// the NLL region checker's data structures. The variable may in fact
1338 /// represent either a free region or an inference variable, in that
1341 /// ## Bound Regions
1343 /// These are regions that are stored behind a binder and must be substituted
1344 /// with some concrete region before being used. There are two kind of
1345 /// bound regions: early-bound, which are bound in an item's `Generics`,
1346 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1347 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1348 /// the likes of `liberate_late_bound_regions`. The distinction exists
1349 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1351 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1352 /// outside their binder, e.g., in types passed to type inference, and
1353 /// should first be substituted (by placeholder regions, free regions,
1354 /// or region variables).
1356 /// ## Placeholder and Free Regions
1358 /// One often wants to work with bound regions without knowing their precise
1359 /// identity. For example, when checking a function, the lifetime of a borrow
1360 /// can end up being assigned to some region parameter. In these cases,
1361 /// it must be ensured that bounds on the region can't be accidentally
1362 /// assumed without being checked.
1364 /// To do this, we replace the bound regions with placeholder markers,
1365 /// which don't satisfy any relation not explicitly provided.
1367 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1368 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1369 /// to be used. These also support explicit bounds: both the internally-stored
1370 /// *scope*, which the region is assumed to outlive, as well as other
1371 /// relations stored in the `FreeRegionMap`. Note that these relations
1372 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1373 /// `resolve_regions_and_report_errors`.
1375 /// When working with higher-ranked types, some region relations aren't
1376 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1377 /// `RePlaceholder` is designed for this purpose. In these contexts,
1378 /// there's also the risk that some inference variable laying around will
1379 /// get unified with your placeholder region: if you want to check whether
1380 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1381 /// with a placeholder region `'%a`, the variable `'_` would just be
1382 /// instantiated to the placeholder region `'%a`, which is wrong because
1383 /// the inference variable is supposed to satisfy the relation
1384 /// *for every value of the placeholder region*. To ensure that doesn't
1385 /// happen, you can use `leak_check`. This is more clearly explained
1386 /// by the [rustc dev guide].
1388 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1389 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1390 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1391 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1392 pub enum RegionKind {
1393 /// Region bound in a type or fn declaration which will be
1394 /// substituted 'early' -- that is, at the same time when type
1395 /// parameters are substituted.
1396 ReEarlyBound(EarlyBoundRegion),
1398 /// Region bound in a function scope, which will be substituted when the
1399 /// function is called.
1400 ReLateBound(ty::DebruijnIndex, BoundRegion),
1402 /// When checking a function body, the types of all arguments and so forth
1403 /// that refer to bound region parameters are modified to refer to free
1404 /// region parameters.
1407 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1410 /// A region variable. Should not exist after typeck.
1413 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1414 /// Should not exist after typeck.
1415 RePlaceholder(ty::PlaceholderRegion),
1417 /// Empty lifetime is for data that is never accessed. We tag the
1418 /// empty lifetime with a universe -- the idea is that we don't
1419 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1420 /// Therefore, the `'empty` in a universe `U` is less than all
1421 /// regions visible from `U`, but not less than regions not visible
1423 ReEmpty(ty::UniverseIndex),
1425 /// Erased region, used by trait selection, in MIR and during codegen.
1429 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1430 pub struct EarlyBoundRegion {
1436 /// A **`const`** **v**ariable **ID**.
1437 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1438 pub struct ConstVid<'tcx> {
1440 pub phantom: PhantomData<&'tcx ()>,
1443 rustc_index::newtype_index! {
1444 /// A **region** (lifetime) **v**ariable **ID**.
1445 pub struct RegionVid {
1446 DEBUG_FORMAT = custom,
1450 impl Atom for RegionVid {
1451 fn index(self) -> usize {
1456 rustc_index::newtype_index! {
1457 pub struct BoundVar { .. }
1460 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1461 #[derive(HashStable)]
1462 pub struct BoundTy {
1464 pub kind: BoundTyKind,
1467 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1468 #[derive(HashStable)]
1469 pub enum BoundTyKind {
1474 impl From<BoundVar> for BoundTy {
1475 fn from(var: BoundVar) -> Self {
1476 BoundTy { var, kind: BoundTyKind::Anon }
1480 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1481 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1482 #[derive(HashStable, TypeFoldable)]
1483 pub struct ExistentialProjection<'tcx> {
1484 pub item_def_id: DefId,
1485 pub substs: SubstsRef<'tcx>,
1489 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1491 impl<'tcx> ExistentialProjection<'tcx> {
1492 /// Extracts the underlying existential trait reference from this projection.
1493 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1494 /// then this function would return a `exists T. T: Iterator` existential trait
1496 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1497 // FIXME(generic_associated_types): substs is the substs of the
1498 // associated type, which should be truncated to get the correct substs
1500 let def_id = tcx.associated_item(self.item_def_id).container.id();
1501 ty::ExistentialTraitRef { def_id, substs: self.substs }
1504 pub fn with_self_ty(
1508 ) -> ty::ProjectionPredicate<'tcx> {
1509 // otherwise the escaping regions would be captured by the binders
1510 debug_assert!(!self_ty.has_escaping_bound_vars());
1512 ty::ProjectionPredicate {
1513 projection_ty: ty::ProjectionTy {
1514 item_def_id: self.item_def_id,
1515 substs: tcx.mk_substs_trait(self_ty, self.substs),
1522 impl<'tcx> PolyExistentialProjection<'tcx> {
1523 pub fn with_self_ty(
1527 ) -> ty::PolyProjectionPredicate<'tcx> {
1528 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1531 pub fn item_def_id(&self) -> DefId {
1532 self.skip_binder().item_def_id
1536 /// Region utilities
1538 /// Is this region named by the user?
1539 pub fn has_name(&self) -> bool {
1541 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1542 RegionKind::ReLateBound(_, br) => br.kind.is_named(),
1543 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1544 RegionKind::ReStatic => true,
1545 RegionKind::ReVar(..) => false,
1546 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1547 RegionKind::ReEmpty(_) => false,
1548 RegionKind::ReErased => false,
1552 pub fn is_late_bound(&self) -> bool {
1553 matches!(*self, ty::ReLateBound(..))
1556 pub fn is_placeholder(&self) -> bool {
1557 matches!(*self, ty::RePlaceholder(..))
1560 pub fn bound_at_or_above_binder(&self, index: ty::DebruijnIndex) -> bool {
1562 ty::ReLateBound(debruijn, _) => debruijn >= index,
1567 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1568 /// innermost binder. That is, if we have something bound at `to_binder`,
1569 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1570 /// when moving a region out from inside binders:
1573 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1574 /// // Binder: D3 D2 D1 ^^
1577 /// Here, the region `'a` would have the De Bruijn index D3,
1578 /// because it is the bound 3 binders out. However, if we wanted
1579 /// to refer to that region `'a` in the second argument (the `_`),
1580 /// those two binders would not be in scope. In that case, we
1581 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1582 /// De Bruijn index of `'a` to D1 (the innermost binder).
1584 /// If we invoke `shift_out_to_binder` and the region is in fact
1585 /// bound by one of the binders we are shifting out of, that is an
1586 /// error (and should fail an assertion failure).
1587 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1589 ty::ReLateBound(debruijn, r) => {
1590 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1596 pub fn type_flags(&self) -> TypeFlags {
1597 let mut flags = TypeFlags::empty();
1601 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1602 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1603 flags = flags | TypeFlags::HAS_RE_INFER;
1605 ty::RePlaceholder(..) => {
1606 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1607 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1608 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1610 ty::ReEarlyBound(..) => {
1611 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1612 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1613 flags = flags | TypeFlags::HAS_RE_PARAM;
1615 ty::ReFree { .. } => {
1616 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1617 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1619 ty::ReEmpty(_) | ty::ReStatic => {
1620 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1622 ty::ReLateBound(..) => {
1623 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1626 flags = flags | TypeFlags::HAS_RE_ERASED;
1630 debug!("type_flags({:?}) = {:?}", self, flags);
1635 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1636 /// For example, consider the regions in this snippet of code:
1640 /// ^^ -- early bound, declared on an impl
1642 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1643 /// ^^ ^^ ^ anonymous, late-bound
1644 /// | early-bound, appears in where-clauses
1645 /// late-bound, appears only in fn args
1650 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1651 /// of the impl, and for all the other highlighted regions, it
1652 /// would return the `DefId` of the function. In other cases (not shown), this
1653 /// function might return the `DefId` of a closure.
1654 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1656 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1657 ty::ReFree(fr) => fr.scope,
1658 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1664 impl<'tcx> TyS<'tcx> {
1666 pub fn kind(&self) -> &TyKind<'tcx> {
1671 pub fn flags(&self) -> TypeFlags {
1676 pub fn is_unit(&self) -> bool {
1678 Tuple(ref tys) => tys.is_empty(),
1684 pub fn is_never(&self) -> bool {
1685 matches!(self.kind(), Never)
1688 /// Checks whether a type is definitely uninhabited. This is
1689 /// conservative: for some types that are uninhabited we return `false`,
1690 /// but we only return `true` for types that are definitely uninhabited.
1691 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1692 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1693 /// size, to account for partial initialisation. See #49298 for details.)
1694 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1695 // FIXME(varkor): we can make this less conversative by substituting concrete
1699 ty::Adt(def, _) if def.is_union() => {
1700 // For now, `union`s are never considered uninhabited.
1703 ty::Adt(def, _) => {
1704 // Any ADT is uninhabited if either:
1705 // (a) It has no variants (i.e. an empty `enum`);
1706 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1707 // one uninhabited field.
1708 def.variants.iter().all(|var| {
1709 var.fields.iter().any(|field| {
1710 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1715 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1717 ty::Array(ty, len) => {
1718 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1719 Some(0) | None => false,
1720 // If the array is definitely non-empty, it's uninhabited if
1721 // the type of its elements is uninhabited.
1722 Some(1..) => ty.conservative_is_privately_uninhabited(tcx),
1726 // References to uninitialised memory is valid for any type, including
1727 // uninhabited types, in unsafe code, so we treat all references as
1736 pub fn is_primitive(&self) -> bool {
1737 self.kind().is_primitive()
1741 pub fn is_adt(&self) -> bool {
1742 matches!(self.kind(), Adt(..))
1746 pub fn is_ref(&self) -> bool {
1747 matches!(self.kind(), Ref(..))
1751 pub fn is_ty_var(&self) -> bool {
1752 matches!(self.kind(), Infer(TyVar(_)))
1756 pub fn is_ty_infer(&self) -> bool {
1757 matches!(self.kind(), Infer(_))
1761 pub fn is_phantom_data(&self) -> bool {
1762 if let Adt(def, _) = self.kind() { def.is_phantom_data() } else { false }
1766 pub fn is_bool(&self) -> bool {
1767 *self.kind() == Bool
1770 /// Returns `true` if this type is a `str`.
1772 pub fn is_str(&self) -> bool {
1777 pub fn is_param(&self, index: u32) -> bool {
1779 ty::Param(ref data) => data.index == index,
1785 pub fn is_slice(&self) -> bool {
1787 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_) | Str),
1793 pub fn is_array(&self) -> bool {
1794 matches!(self.kind(), Array(..))
1798 pub fn is_simd(&self) -> bool {
1800 Adt(def, _) => def.repr.simd(),
1805 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1807 Array(ty, _) | Slice(ty) => ty,
1808 Str => tcx.mk_mach_uint(ty::UintTy::U8),
1809 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1813 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1815 Adt(def, substs) => {
1816 let variant = def.non_enum_variant();
1817 let f0_ty = variant.fields[0].ty(tcx, substs);
1819 match f0_ty.kind() {
1820 Array(f0_elem_ty, f0_len) => {
1821 // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112
1822 // The way we evaluate the `N` in `[T; N]` here only works since we use
1823 // `simd_size_and_type` post-monomorphization. It will probably start to ICE
1824 // if we use it in generic code. See the `simd-array-trait` ui test.
1825 (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, f0_elem_ty)
1827 _ => (variant.fields.len() as u64, f0_ty),
1830 _ => bug!("`simd_size_and_type` called on invalid type"),
1835 pub fn is_region_ptr(&self) -> bool {
1836 matches!(self.kind(), Ref(..))
1840 pub fn is_mutable_ptr(&self) -> bool {
1843 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1844 | Ref(_, _, hir::Mutability::Mut)
1848 /// Get the mutability of the reference or `None` when not a reference
1850 pub fn ref_mutability(&self) -> Option<hir::Mutability> {
1852 Ref(_, _, mutability) => Some(*mutability),
1858 pub fn is_unsafe_ptr(&self) -> bool {
1859 matches!(self.kind(), RawPtr(_))
1862 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1864 pub fn is_any_ptr(&self) -> bool {
1865 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1869 pub fn is_box(&self) -> bool {
1871 Adt(def, _) => def.is_box(),
1876 /// Panics if called on any type other than `Box<T>`.
1877 pub fn boxed_ty(&self) -> Ty<'tcx> {
1879 Adt(def, substs) if def.is_box() => substs.type_at(0),
1880 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1884 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1885 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1886 /// contents are abstract to rustc.)
1888 pub fn is_scalar(&self) -> bool {
1898 | Infer(IntVar(_) | FloatVar(_))
1902 /// Returns `true` if this type is a floating point type.
1904 pub fn is_floating_point(&self) -> bool {
1905 matches!(self.kind(), Float(_) | Infer(FloatVar(_)))
1909 pub fn is_trait(&self) -> bool {
1910 matches!(self.kind(), Dynamic(..))
1914 pub fn is_enum(&self) -> bool {
1916 Adt(adt_def, _) => adt_def.is_enum(),
1922 pub fn is_closure(&self) -> bool {
1923 matches!(self.kind(), Closure(..))
1927 pub fn is_generator(&self) -> bool {
1928 matches!(self.kind(), Generator(..))
1932 pub fn is_integral(&self) -> bool {
1933 matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_))
1937 pub fn is_fresh_ty(&self) -> bool {
1938 matches!(self.kind(), Infer(FreshTy(_)))
1942 pub fn is_fresh(&self) -> bool {
1943 matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_)))
1947 pub fn is_char(&self) -> bool {
1948 matches!(self.kind(), Char)
1952 pub fn is_numeric(&self) -> bool {
1953 self.is_integral() || self.is_floating_point()
1957 pub fn is_signed(&self) -> bool {
1958 matches!(self.kind(), Int(_))
1962 pub fn is_ptr_sized_integral(&self) -> bool {
1963 matches!(self.kind(), Int(ty::IntTy::Isize) | Uint(ty::UintTy::Usize))
1967 pub fn is_machine(&self) -> bool {
1968 matches!(self.kind(), Int(..) | Uint(..) | Float(..))
1972 pub fn has_concrete_skeleton(&self) -> bool {
1973 !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
1976 /// Returns the type and mutability of `*ty`.
1978 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1979 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
1980 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
1982 Adt(def, _) if def.is_box() => {
1983 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
1985 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl: *mutbl }),
1986 RawPtr(mt) if explicit => Some(*mt),
1991 /// Returns the type of `ty[i]`.
1992 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
1994 Array(ty, _) | Slice(ty) => Some(ty),
1999 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2001 FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
2004 // ignore errors (#54954)
2005 ty::Binder::dummy(FnSig::fake())
2007 Closure(..) => bug!(
2008 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2010 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2015 pub fn is_fn(&self) -> bool {
2016 matches!(self.kind(), FnDef(..) | FnPtr(_))
2020 pub fn is_fn_ptr(&self) -> bool {
2021 matches!(self.kind(), FnPtr(_))
2025 pub fn is_impl_trait(&self) -> bool {
2026 matches!(self.kind(), Opaque(..))
2030 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2032 Adt(adt, _) => Some(adt),
2037 /// Iterates over tuple fields.
2038 /// Panics when called on anything but a tuple.
2039 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2041 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2042 _ => bug!("tuple_fields called on non-tuple"),
2046 /// Get the `i`-th element of a tuple.
2047 /// Panics when called on anything but a tuple.
2048 pub fn tuple_element_ty(&self, i: usize) -> Option<Ty<'tcx>> {
2050 Tuple(substs) => substs.iter().nth(i).map(|field| field.expect_ty()),
2051 _ => bug!("tuple_fields called on non-tuple"),
2055 /// If the type contains variants, returns the valid range of variant indices.
2057 // FIXME: This requires the optimized MIR in the case of generators.
2059 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2061 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2062 TyKind::Generator(def_id, substs, _) => {
2063 Some(substs.as_generator().variant_range(*def_id, tcx))
2069 /// If the type contains variants, returns the variant for `variant_index`.
2070 /// Panics if `variant_index` is out of range.
2072 // FIXME: This requires the optimized MIR in the case of generators.
2074 pub fn discriminant_for_variant(
2077 variant_index: VariantIdx,
2078 ) -> Option<Discr<'tcx>> {
2080 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2081 bug!("discriminant_for_variant called on zero variant enum");
2083 TyKind::Adt(adt, _) if adt.is_enum() => {
2084 Some(adt.discriminant_for_variant(tcx, variant_index))
2086 TyKind::Generator(def_id, substs, _) => {
2087 Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
2093 /// Returns the type of the discriminant of this type.
2094 pub fn discriminant_ty(&'tcx self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2096 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2097 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2099 ty::Param(_) | ty::Projection(_) | ty::Opaque(..) | ty::Infer(ty::TyVar(_)) => {
2101 tcx.associated_items(tcx.lang_items().discriminant_kind_trait().unwrap());
2102 let discriminant_def_id = assoc_items.in_definition_order().next().unwrap().def_id;
2103 tcx.mk_projection(discriminant_def_id, tcx.mk_substs([self.into()].iter()))
2122 | ty::GeneratorWitness(..)
2126 | ty::Infer(IntVar(_) | FloatVar(_)) => tcx.types.u8,
2129 | ty::Placeholder(_)
2130 | ty::Infer(FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2131 bug!("`discriminant_ty` applied to unexpected type: {:?}", self)
2136 /// Returns the type of metadata for (potentially fat) pointers to this type.
2137 pub fn ptr_metadata_ty(&'tcx self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2138 // FIXME: should this normalize?
2139 let tail = tcx.struct_tail_without_normalization(self);
2142 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2153 | ty::GeneratorWitness(..)
2159 // If returned by `struct_tail_without_normalization` this is a unit struct
2160 // without any fields, or not a struct, and therefore is Sized.
2162 // If returned by `struct_tail_without_normalization` this is the empty tuple,
2163 // a.k.a. unit type, which is Sized
2164 | ty::Tuple(..) => tcx.types.unit,
2166 ty::Str | ty::Slice(_) => tcx.types.usize,
2167 ty::Dynamic(..) => tcx.type_of(tcx.lang_items().dyn_metadata().unwrap()),
2172 | ty::Infer(ty::TyVar(_))
2174 | ty::Placeholder(..)
2175 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2176 bug!("`ptr_metadata_ty` applied to unexpected type: {:?}", tail)
2181 /// When we create a closure, we record its kind (i.e., what trait
2182 /// it implements) into its `ClosureSubsts` using a type
2183 /// parameter. This is kind of a phantom type, except that the
2184 /// most convenient thing for us to are the integral types. This
2185 /// function converts such a special type into the closure
2186 /// kind. To go the other way, use
2187 /// `tcx.closure_kind_ty(closure_kind)`.
2189 /// Note that during type checking, we use an inference variable
2190 /// to represent the closure kind, because it has not yet been
2191 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2192 /// is complete, that type variable will be unified.
2193 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2195 Int(int_ty) => match int_ty {
2196 ty::IntTy::I8 => Some(ty::ClosureKind::Fn),
2197 ty::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2198 ty::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2199 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2202 // "Bound" types appear in canonical queries when the
2203 // closure type is not yet known
2204 Bound(..) | Infer(_) => None,
2206 Error(_) => Some(ty::ClosureKind::Fn),
2208 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2212 /// Fast path helper for testing if a type is `Sized`.
2214 /// Returning true means the type is known to be sized. Returning
2215 /// `false` means nothing -- could be sized, might not be.
2217 /// Note that we could never rely on the fact that a type such as `[_]` is
2218 /// trivially `!Sized` because we could be in a type environment with a
2219 /// bound such as `[_]: Copy`. A function with such a bound obviously never
2220 /// can be called, but that doesn't mean it shouldn't typecheck. This is why
2221 /// this method doesn't return `Option<bool>`.
2222 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2224 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2235 | ty::GeneratorWitness(..)
2239 | ty::Error(_) => true,
2241 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2243 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2245 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2247 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2249 ty::Infer(ty::TyVar(_)) => false,
2252 | ty::Placeholder(..)
2253 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2254 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)