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::fold::ValidateBoundVars;
9 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
10 use crate::ty::InferTy::{self, *};
11 use crate::ty::{self, AdtDef, DefIdTree, Discr, Term, Ty, TyCtxt, TypeFlags, TypeFoldable};
12 use crate::ty::{DelaySpanBugEmitted, List, ParamEnv};
13 use polonius_engine::Atom;
14 use rustc_data_structures::captures::Captures;
15 use rustc_data_structures::intern::Interned;
17 use rustc_hir::def_id::DefId;
18 use rustc_index::vec::Idx;
19 use rustc_macros::HashStable;
20 use rustc_span::symbol::{kw, Symbol};
21 use rustc_target::abi::VariantIdx;
22 use rustc_target::spec::abi;
24 use std::cmp::Ordering;
26 use std::marker::PhantomData;
27 use std::ops::{Deref, Range};
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: BoundRegionKind,
46 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
48 pub enum BoundRegionKind {
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
63 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
65 pub struct BoundRegion {
67 pub kind: BoundRegionKind,
70 impl BoundRegionKind {
71 pub fn is_named(&self) -> bool {
73 BoundRegionKind::BrNamed(_, name) => name != kw::UnderscoreLifetime,
79 /// Defines the kinds of types used by the type system.
81 /// Types written by the user start out as [hir::TyKind](rustc_hir::TyKind) and get
82 /// converted to this representation using `AstConv::ast_ty_to_ty`.
83 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
85 #[rustc_diagnostic_item = "TyKind"]
86 pub enum TyKind<'tcx> {
87 /// The primitive boolean type. Written as `bool`.
90 /// The primitive character type; holds a Unicode scalar value
91 /// (a non-surrogate code point). Written as `char`.
94 /// A primitive signed integer type. For example, `i32`.
97 /// A primitive unsigned integer type. For example, `u32`.
100 /// A primitive floating-point type. For example, `f64`.
103 /// Algebraic data types (ADT). For example: structures, enumerations and unions.
105 /// For example, the type `List<i32>` would be represented using the `AdtDef`
106 /// for `struct List<T>` and the substs `[i32]`.
108 /// Note that generic parameters in fields only get lazily substituted
109 /// by using something like `adt_def.all_fields().map(|field| field.ty(tcx, substs))`.
110 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
112 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
115 /// The pointee of a string slice. Written as `str`.
118 /// An array with the given length. Written as `[T; N]`.
119 Array(Ty<'tcx>, ty::Const<'tcx>),
121 /// The pointee of an array slice. Written as `[T]`.
124 /// A raw pointer. Written as `*mut T` or `*const T`
125 RawPtr(TypeAndMut<'tcx>),
127 /// A reference; a pointer with an associated lifetime. Written as
128 /// `&'a mut T` or `&'a T`.
129 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
131 /// The anonymous type of a function declaration/definition. Each
132 /// function has a unique type.
134 /// For the function `fn foo() -> i32 { 3 }` this type would be
135 /// shown to the user as `fn() -> i32 {foo}`.
137 /// 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 /// Note that both functions and closures start out as either
147 /// [FnDef] or [Closure] which can be then be coerced to this variant.
149 /// For example the type of `bar` here:
152 /// fn foo() -> i32 { 1 }
153 /// let bar: fn() -> i32 = foo;
155 FnPtr(PolyFnSig<'tcx>),
157 /// A trait object. Written as `dyn for<'b> Trait<'b, Assoc = u32> + Send + 'a`.
158 Dynamic(&'tcx List<Binder<'tcx, ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
160 /// The anonymous type of a closure. Used to represent the type of `|a| a`.
162 /// Closure substs contain both the - potentially substituted - generic parameters
163 /// of its parent and some synthetic parameters. See the documentation for
164 /// [ClosureSubsts] for more details.
165 Closure(DefId, SubstsRef<'tcx>),
167 /// The anonymous type of a generator. Used to represent the type of
170 /// For more info about generator substs, visit the documentation for
171 /// [GeneratorSubsts].
172 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
174 /// A type representing the types stored inside a generator.
175 /// This should only appear as part of the [GeneratorSubsts].
177 /// Note that the captured variables for generators are stored separately
178 /// using a tuple in the same way as for closures.
180 /// Unlike upvars, the witness can reference lifetimes from
181 /// inside of the generator itself. To deal with them in
182 /// the type of the generator, we convert them to higher ranked
183 /// lifetimes bound by the witness itself.
185 /// Looking at the following example, the witness for this generator
186 /// may end up as something like `for<'a> [Vec<i32>, &'a Vec<i32>]`:
190 /// let x = &vec![3];
195 GeneratorWitness(Binder<'tcx, &'tcx List<Ty<'tcx>>>),
197 /// The never type `!`.
200 /// A tuple type. For example, `(i32, bool)`.
201 /// Use `Ty::tuple_fields` to iterate over the field types.
202 Tuple(SubstsRef<'tcx>),
204 /// The projection of an associated type. For example,
205 /// `<T as Trait<..>>::N`.
206 Projection(ProjectionTy<'tcx>),
208 /// Opaque (`impl Trait`) type found in a return type.
210 /// The `DefId` comes either from
211 /// * the `impl Trait` ast::Ty node,
212 /// * or the `type Foo = impl Trait` declaration
214 /// For RPIT the substitutions are for the generics of the function,
215 /// while for TAIT it is used for the generic parameters of the alias.
217 /// During codegen, `tcx.type_of(def_id)` can be used to get the underlying type.
218 Opaque(DefId, SubstsRef<'tcx>),
220 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}`.
223 /// Bound type variable, used to represent the `'a` in `for<'a> fn(&'a ())`.
225 /// For canonical queries, we replace inference variables with bound variables,
226 /// so e.g. when checking whether `&'_ (): Trait<_>` holds, we canonicalize that to
227 /// `for<'a, T> &'a (): Trait<T>` and then convert the introduced bound variables
228 /// back to inference variables in a new inference context when inside of the query.
230 /// See the `rustc-dev-guide` for more details about
231 /// [higher-ranked trait bounds][1] and [canonical queries][2].
233 /// [1]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
234 /// [2]: https://rustc-dev-guide.rust-lang.org/traits/canonical-queries.html
235 Bound(ty::DebruijnIndex, BoundTy),
237 /// A placeholder type, used during higher ranked subtyping to instantiate
239 Placeholder(ty::PlaceholderType),
241 /// A type variable used during type checking.
243 /// Similar to placeholders, inference variables also live in a universe to
244 /// correctly deal with higher ranked types. Though unlike placeholders,
245 /// that universe is stored in the `InferCtxt` instead of directly
246 /// inside of the type.
249 /// A placeholder for a type which could not be computed; this is
250 /// propagated to avoid useless error messages.
251 Error(DelaySpanBugEmitted),
254 impl<'tcx> TyKind<'tcx> {
256 pub fn is_primitive(&self) -> bool {
257 matches!(self, Bool | Char | Int(_) | Uint(_) | Float(_))
260 /// Get the article ("a" or "an") to use with this type.
261 pub fn article(&self) -> &'static str {
263 Int(_) | Float(_) | Array(_, _) => "an",
264 Adt(def, _) if def.is_enum() => "an",
265 // This should never happen, but ICEing and causing the user's code
266 // to not compile felt too harsh.
273 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
274 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
275 static_assert_size!(TyKind<'_>, 32);
277 /// A closure can be modeled as a struct that looks like:
279 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
283 /// - 'l0...'li and T0...Tj are the generic parameters
284 /// in scope on the function that defined the closure,
285 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
286 /// is rather hackily encoded via a scalar type. See
287 /// `Ty::to_opt_closure_kind` for details.
288 /// - CS represents the *closure signature*, representing as a `fn()`
289 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
290 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
292 /// - U is a type parameter representing the types of its upvars, tupled up
293 /// (borrowed, if appropriate; that is, if a U field represents a by-ref upvar,
294 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
296 /// So, for example, given this function:
298 /// fn foo<'a, T>(data: &'a mut T) {
299 /// do(|| data.count += 1)
302 /// the type of the closure would be something like:
304 /// struct Closure<'a, T, U>(...U);
306 /// Note that the type of the upvar is not specified in the struct.
307 /// You may wonder how the impl would then be able to use the upvar,
308 /// if it doesn't know it's type? The answer is that the impl is
309 /// (conceptually) not fully generic over Closure but rather tied to
310 /// instances with the expected upvar types:
312 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
316 /// You can see that the *impl* fully specified the type of the upvar
317 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
318 /// (Here, I am assuming that `data` is mut-borrowed.)
320 /// Now, the last question you may ask is: Why include the upvar types
321 /// in an extra type parameter? The reason for this design is that the
322 /// upvar types can reference lifetimes that are internal to the
323 /// creating function. In my example above, for example, the lifetime
324 /// `'b` represents the scope of the closure itself; this is some
325 /// subset of `foo`, probably just the scope of the call to the to
326 /// `do()`. If we just had the lifetime/type parameters from the
327 /// enclosing function, we couldn't name this lifetime `'b`. Note that
328 /// there can also be lifetimes in the types of the upvars themselves,
329 /// if one of them happens to be a reference to something that the
330 /// creating fn owns.
332 /// OK, you say, so why not create a more minimal set of parameters
333 /// that just includes the extra lifetime parameters? The answer is
334 /// primarily that it would be hard --- we don't know at the time when
335 /// we create the closure type what the full types of the upvars are,
336 /// nor do we know which are borrowed and which are not. In this
337 /// design, we can just supply a fresh type parameter and figure that
340 /// All right, you say, but why include the type parameters from the
341 /// original function then? The answer is that codegen may need them
342 /// when monomorphizing, and they may not appear in the upvars. A
343 /// closure could capture no variables but still make use of some
344 /// in-scope type parameter with a bound (e.g., if our example above
345 /// had an extra `U: Default`, and the closure called `U::default()`).
347 /// There is another reason. This design (implicitly) prohibits
348 /// closures from capturing themselves (except via a trait
349 /// object). This simplifies closure inference considerably, since it
350 /// means that when we infer the kind of a closure or its upvars, we
351 /// don't have to handle cycles where the decisions we make for
352 /// closure C wind up influencing the decisions we ought to make for
353 /// closure C (which would then require fixed point iteration to
354 /// handle). Plus it fixes an ICE. :P
358 /// Generators are handled similarly in `GeneratorSubsts`. The set of
359 /// type parameters is similar, but `CK` and `CS` are replaced by the
360 /// following type parameters:
362 /// * `GS`: The generator's "resume type", which is the type of the
363 /// argument passed to `resume`, and the type of `yield` expressions
364 /// inside the generator.
365 /// * `GY`: The "yield type", which is the type of values passed to
366 /// `yield` inside the generator.
367 /// * `GR`: The "return type", which is the type of value returned upon
368 /// completion of the generator.
369 /// * `GW`: The "generator witness".
370 #[derive(Copy, Clone, Debug, TypeFoldable)]
371 pub struct ClosureSubsts<'tcx> {
372 /// Lifetime and type parameters from the enclosing function,
373 /// concatenated with a tuple containing the types of the upvars.
375 /// These are separated out because codegen wants to pass them around
376 /// when monomorphizing.
377 pub substs: SubstsRef<'tcx>,
380 /// Struct returned by `split()`.
381 pub struct ClosureSubstsParts<'tcx, T> {
382 pub parent_substs: &'tcx [GenericArg<'tcx>],
383 pub closure_kind_ty: T,
384 pub closure_sig_as_fn_ptr_ty: T,
385 pub tupled_upvars_ty: T,
388 impl<'tcx> ClosureSubsts<'tcx> {
389 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
390 /// for the closure parent, alongside additional closure-specific components.
393 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
394 ) -> ClosureSubsts<'tcx> {
396 substs: tcx.mk_substs(
397 parts.parent_substs.iter().copied().chain(
398 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
400 .map(|&ty| ty.into()),
406 /// Divides the closure substs into their respective components.
407 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
408 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
409 match self.substs[..] {
411 ref parent_substs @ ..,
413 closure_sig_as_fn_ptr_ty,
415 ] => ClosureSubstsParts {
418 closure_sig_as_fn_ptr_ty,
421 _ => bug!("closure substs missing synthetics"),
425 /// Returns `true` only if enough of the synthetic types are known to
426 /// allow using all of the methods on `ClosureSubsts` without panicking.
428 /// Used primarily by `ty::print::pretty` to be able to handle closure
429 /// types that haven't had their synthetic types substituted in.
430 pub fn is_valid(self) -> bool {
431 self.substs.len() >= 3
432 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
435 /// Returns the substitutions of the closure's parent.
436 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
437 self.split().parent_substs
440 /// Returns an iterator over the list of types of captured paths by the closure.
441 /// In case there was a type error in figuring out the types of the captured path, an
442 /// empty iterator is returned.
444 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
445 match self.tupled_upvars_ty().kind() {
446 TyKind::Error(_) => None,
447 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
448 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
449 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
455 /// Returns the tuple type representing the upvars for this closure.
457 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
458 self.split().tupled_upvars_ty.expect_ty()
461 /// Returns the closure kind for this closure; may return a type
462 /// variable during inference. To get the closure kind during
463 /// inference, use `infcx.closure_kind(substs)`.
464 pub fn kind_ty(self) -> Ty<'tcx> {
465 self.split().closure_kind_ty.expect_ty()
468 /// Returns the `fn` pointer type representing the closure signature for this
470 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
471 // type is known at the time of the creation of `ClosureSubsts`,
472 // see `rustc_typeck::check::closure`.
473 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
474 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
477 /// Returns the closure kind for this closure; only usable outside
478 /// of an inference context, because in that context we know that
479 /// there are no type variables.
481 /// If you have an inference context, use `infcx.closure_kind()`.
482 pub fn kind(self) -> ty::ClosureKind {
483 self.kind_ty().to_opt_closure_kind().unwrap()
486 /// Extracts the signature from the closure.
487 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
488 let ty = self.sig_as_fn_ptr_ty();
490 ty::FnPtr(sig) => *sig,
491 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind()),
496 /// Similar to `ClosureSubsts`; see the above documentation for more.
497 #[derive(Copy, Clone, Debug, TypeFoldable)]
498 pub struct GeneratorSubsts<'tcx> {
499 pub substs: SubstsRef<'tcx>,
502 pub struct GeneratorSubstsParts<'tcx, T> {
503 pub parent_substs: &'tcx [GenericArg<'tcx>],
508 pub tupled_upvars_ty: T,
511 impl<'tcx> GeneratorSubsts<'tcx> {
512 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
513 /// for the generator parent, alongside additional generator-specific components.
516 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
517 ) -> GeneratorSubsts<'tcx> {
519 substs: tcx.mk_substs(
520 parts.parent_substs.iter().copied().chain(
526 parts.tupled_upvars_ty,
529 .map(|&ty| ty.into()),
535 /// Divides the generator substs into their respective components.
536 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
537 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
538 match self.substs[..] {
539 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
540 GeneratorSubstsParts {
549 _ => bug!("generator substs missing synthetics"),
553 /// Returns `true` only if enough of the synthetic types are known to
554 /// allow using all of the methods on `GeneratorSubsts` without panicking.
556 /// Used primarily by `ty::print::pretty` to be able to handle generator
557 /// types that haven't had their synthetic types substituted in.
558 pub fn is_valid(self) -> bool {
559 self.substs.len() >= 5
560 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
563 /// Returns the substitutions of the generator's parent.
564 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
565 self.split().parent_substs
568 /// This describes the types that can be contained in a generator.
569 /// It will be a type variable initially and unified in the last stages of typeck of a body.
570 /// It contains a tuple of all the types that could end up on a generator frame.
571 /// The state transformation MIR pass may only produce layouts which mention types
572 /// in this tuple. Upvars are not counted here.
573 pub fn witness(self) -> Ty<'tcx> {
574 self.split().witness.expect_ty()
577 /// Returns an iterator over the list of types of captured paths by the generator.
578 /// In case there was a type error in figuring out the types of the captured path, an
579 /// empty iterator is returned.
581 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
582 match self.tupled_upvars_ty().kind() {
583 TyKind::Error(_) => None,
584 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
585 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
586 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
592 /// Returns the tuple type representing the upvars for this generator.
594 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
595 self.split().tupled_upvars_ty.expect_ty()
598 /// Returns the type representing the resume type of the generator.
599 pub fn resume_ty(self) -> Ty<'tcx> {
600 self.split().resume_ty.expect_ty()
603 /// Returns the type representing the yield type of the generator.
604 pub fn yield_ty(self) -> Ty<'tcx> {
605 self.split().yield_ty.expect_ty()
608 /// Returns the type representing the return type of the generator.
609 pub fn return_ty(self) -> Ty<'tcx> {
610 self.split().return_ty.expect_ty()
613 /// Returns the "generator signature", which consists of its yield
614 /// and return types.
616 /// N.B., some bits of the code prefers to see this wrapped in a
617 /// binder, but it never contains bound regions. Probably this
618 /// function should be removed.
619 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
620 ty::Binder::dummy(self.sig())
623 /// Returns the "generator signature", which consists of its resume, yield
624 /// and return types.
625 pub fn sig(self) -> GenSig<'tcx> {
627 resume_ty: self.resume_ty(),
628 yield_ty: self.yield_ty(),
629 return_ty: self.return_ty(),
634 impl<'tcx> GeneratorSubsts<'tcx> {
635 /// Generator has not been resumed yet.
636 pub const UNRESUMED: usize = 0;
637 /// Generator has returned or is completed.
638 pub const RETURNED: usize = 1;
639 /// Generator has been poisoned.
640 pub const POISONED: usize = 2;
642 const UNRESUMED_NAME: &'static str = "Unresumed";
643 const RETURNED_NAME: &'static str = "Returned";
644 const POISONED_NAME: &'static str = "Panicked";
646 /// The valid variant indices of this generator.
648 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
649 // FIXME requires optimized MIR
650 let num_variants = tcx.generator_layout(def_id).unwrap().variant_fields.len();
651 VariantIdx::new(0)..VariantIdx::new(num_variants)
654 /// The discriminant for the given variant. Panics if the `variant_index` is
657 pub fn discriminant_for_variant(
661 variant_index: VariantIdx,
663 // Generators don't support explicit discriminant values, so they are
664 // the same as the variant index.
665 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
666 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
669 /// The set of all discriminants for the generator, enumerated with their
672 pub fn discriminants(
676 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
677 self.variant_range(def_id, tcx).map(move |index| {
678 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
682 /// Calls `f` with a reference to the name of the enumerator for the given
684 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
686 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
687 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
688 Self::POISONED => Cow::from(Self::POISONED_NAME),
689 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
693 /// The type of the state discriminant used in the generator type.
695 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
699 /// This returns the types of the MIR locals which had to be stored across suspension points.
700 /// It is calculated in rustc_const_eval::transform::generator::StateTransform.
701 /// All the types here must be in the tuple in GeneratorInterior.
703 /// The locals are grouped by their variant number. Note that some locals may
704 /// be repeated in multiple variants.
710 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
711 let layout = tcx.generator_layout(def_id).unwrap();
712 layout.variant_fields.iter().map(move |variant| {
713 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
717 /// This is the types of the fields of a generator which are not stored in a
720 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
725 #[derive(Debug, Copy, Clone, HashStable)]
726 pub enum UpvarSubsts<'tcx> {
727 Closure(SubstsRef<'tcx>),
728 Generator(SubstsRef<'tcx>),
731 impl<'tcx> UpvarSubsts<'tcx> {
732 /// Returns an iterator over the list of types of captured paths by the closure/generator.
733 /// In case there was a type error in figuring out the types of the captured path, an
734 /// empty iterator is returned.
736 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
737 let tupled_tys = match self {
738 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
739 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
742 match tupled_tys.kind() {
743 TyKind::Error(_) => None,
744 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
745 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
746 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
753 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
755 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
756 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
761 /// An inline const is modeled like
763 /// const InlineConst<'l0...'li, T0...Tj, R>: R;
767 /// - 'l0...'li and T0...Tj are the generic parameters
768 /// inherited from the item that defined the inline const,
769 /// - R represents the type of the constant.
771 /// When the inline const is instantiated, `R` is substituted as the actual inferred
772 /// type of the constant. The reason that `R` is represented as an extra type parameter
773 /// is the same reason that [`ClosureSubsts`] have `CS` and `U` as type parameters:
774 /// inline const can reference lifetimes that are internal to the creating function.
775 #[derive(Copy, Clone, Debug, TypeFoldable)]
776 pub struct InlineConstSubsts<'tcx> {
777 /// Generic parameters from the enclosing item,
778 /// concatenated with the inferred type of the constant.
779 pub substs: SubstsRef<'tcx>,
782 /// Struct returned by `split()`.
783 pub struct InlineConstSubstsParts<'tcx, T> {
784 pub parent_substs: &'tcx [GenericArg<'tcx>],
788 impl<'tcx> InlineConstSubsts<'tcx> {
789 /// Construct `InlineConstSubsts` from `InlineConstSubstsParts`.
792 parts: InlineConstSubstsParts<'tcx, Ty<'tcx>>,
793 ) -> InlineConstSubsts<'tcx> {
795 substs: tcx.mk_substs(
796 parts.parent_substs.iter().copied().chain(std::iter::once(parts.ty.into())),
801 /// Divides the inline const substs into their respective components.
802 /// The ordering assumed here must match that used by `InlineConstSubsts::new` above.
803 fn split(self) -> InlineConstSubstsParts<'tcx, GenericArg<'tcx>> {
804 match self.substs[..] {
805 [ref parent_substs @ .., ty] => InlineConstSubstsParts { parent_substs, ty },
806 _ => bug!("inline const substs missing synthetics"),
810 /// Returns the substitutions of the inline const's parent.
811 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
812 self.split().parent_substs
815 /// Returns the type of this inline const.
816 pub fn ty(self) -> Ty<'tcx> {
817 self.split().ty.expect_ty()
821 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
822 #[derive(HashStable, TypeFoldable)]
823 pub enum ExistentialPredicate<'tcx> {
824 /// E.g., `Iterator`.
825 Trait(ExistentialTraitRef<'tcx>),
826 /// E.g., `Iterator::Item = T`.
827 Projection(ExistentialProjection<'tcx>),
832 impl<'tcx> ExistentialPredicate<'tcx> {
833 /// Compares via an ordering that will not change if modules are reordered or other changes are
834 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
835 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
836 use self::ExistentialPredicate::*;
837 match (*self, *other) {
838 (Trait(_), Trait(_)) => Ordering::Equal,
839 (Projection(ref a), Projection(ref b)) => {
840 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
842 (AutoTrait(ref a), AutoTrait(ref b)) => {
843 tcx.def_path_hash(*a).cmp(&tcx.def_path_hash(*b))
845 (Trait(_), _) => Ordering::Less,
846 (Projection(_), Trait(_)) => Ordering::Greater,
847 (Projection(_), _) => Ordering::Less,
848 (AutoTrait(_), _) => Ordering::Greater,
853 impl<'tcx> Binder<'tcx, ExistentialPredicate<'tcx>> {
854 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
855 use crate::ty::ToPredicate;
856 match self.skip_binder() {
857 ExistentialPredicate::Trait(tr) => {
858 self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
860 ExistentialPredicate::Projection(p) => {
861 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
863 ExistentialPredicate::AutoTrait(did) => {
864 let trait_ref = self.rebind(ty::TraitRef {
866 substs: tcx.mk_substs_trait(self_ty, &[]),
868 trait_ref.without_const().to_predicate(tcx)
874 impl<'tcx> List<ty::Binder<'tcx, ExistentialPredicate<'tcx>>> {
875 /// Returns the "principal `DefId`" of this set of existential predicates.
877 /// A Rust trait object type consists (in addition to a lifetime bound)
878 /// of a set of trait bounds, which are separated into any number
879 /// of auto-trait bounds, and at most one non-auto-trait bound. The
880 /// non-auto-trait bound is called the "principal" of the trait
883 /// Only the principal can have methods or type parameters (because
884 /// auto traits can have neither of them). This is important, because
885 /// it means the auto traits can be treated as an unordered set (methods
886 /// would force an order for the vtable, while relating traits with
887 /// type parameters without knowing the order to relate them in is
888 /// a rather non-trivial task).
890 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
891 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
892 /// are the set `{Sync}`.
894 /// It is also possible to have a "trivial" trait object that
895 /// consists only of auto traits, with no principal - for example,
896 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
897 /// is `{Send, Sync}`, while there is no principal. These trait objects
898 /// have a "trivial" vtable consisting of just the size, alignment,
900 pub fn principal(&self) -> Option<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> {
902 .map_bound(|this| match this {
903 ExistentialPredicate::Trait(tr) => Some(tr),
909 pub fn principal_def_id(&self) -> Option<DefId> {
910 self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
914 pub fn projection_bounds<'a>(
916 ) -> impl Iterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> + 'a {
917 self.iter().filter_map(|predicate| {
919 .map_bound(|pred| match pred {
920 ExistentialPredicate::Projection(projection) => Some(projection),
928 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
929 self.iter().filter_map(|predicate| match predicate.skip_binder() {
930 ExistentialPredicate::AutoTrait(did) => Some(did),
936 /// A complete reference to a trait. These take numerous guises in syntax,
937 /// but perhaps the most recognizable form is in a where-clause:
941 /// This would be represented by a trait-reference where the `DefId` is the
942 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
943 /// and `U` as parameter 1.
945 /// Trait references also appear in object types like `Foo<U>`, but in
946 /// that case the `Self` parameter is absent from the substitutions.
947 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
948 #[derive(HashStable, TypeFoldable)]
949 pub struct TraitRef<'tcx> {
951 pub substs: SubstsRef<'tcx>,
954 impl<'tcx> TraitRef<'tcx> {
955 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
956 TraitRef { def_id, substs }
959 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
960 /// are the parameters defined on trait.
961 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> Binder<'tcx, TraitRef<'tcx>> {
962 ty::Binder::dummy(TraitRef {
964 substs: InternalSubsts::identity_for_item(tcx, def_id),
969 pub fn self_ty(&self) -> Ty<'tcx> {
970 self.substs.type_at(0)
976 substs: SubstsRef<'tcx>,
977 ) -> ty::TraitRef<'tcx> {
978 let defs = tcx.generics_of(trait_id);
980 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
984 pub type PolyTraitRef<'tcx> = Binder<'tcx, TraitRef<'tcx>>;
986 impl<'tcx> PolyTraitRef<'tcx> {
987 pub fn self_ty(&self) -> Binder<'tcx, Ty<'tcx>> {
988 self.map_bound_ref(|tr| tr.self_ty())
991 pub fn def_id(&self) -> DefId {
992 self.skip_binder().def_id
995 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
996 self.map_bound(|trait_ref| ty::TraitPredicate {
998 constness: ty::BoundConstness::NotConst,
999 polarity: ty::ImplPolarity::Positive,
1004 /// An existential reference to a trait, where `Self` is erased.
1005 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
1007 /// exists T. T: Trait<'a, 'b, X, Y>
1009 /// The substitutions don't include the erased `Self`, only trait
1010 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
1011 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1012 #[derive(HashStable, TypeFoldable)]
1013 pub struct ExistentialTraitRef<'tcx> {
1015 pub substs: SubstsRef<'tcx>,
1018 impl<'tcx> ExistentialTraitRef<'tcx> {
1019 pub fn erase_self_ty(
1021 trait_ref: ty::TraitRef<'tcx>,
1022 ) -> ty::ExistentialTraitRef<'tcx> {
1023 // Assert there is a Self.
1024 trait_ref.substs.type_at(0);
1026 ty::ExistentialTraitRef {
1027 def_id: trait_ref.def_id,
1028 substs: tcx.intern_substs(&trait_ref.substs[1..]),
1032 /// Object types don't have a self type specified. Therefore, when
1033 /// we convert the principal trait-ref into a normal trait-ref,
1034 /// you must give *some* self type. A common choice is `mk_err()`
1035 /// or some placeholder type.
1036 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
1037 // otherwise the escaping vars would be captured by the binder
1038 // debug_assert!(!self_ty.has_escaping_bound_vars());
1040 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
1044 pub type PolyExistentialTraitRef<'tcx> = Binder<'tcx, ExistentialTraitRef<'tcx>>;
1046 impl<'tcx> PolyExistentialTraitRef<'tcx> {
1047 pub fn def_id(&self) -> DefId {
1048 self.skip_binder().def_id
1051 /// Object types don't have a self type specified. Therefore, when
1052 /// we convert the principal trait-ref into a normal trait-ref,
1053 /// you must give *some* self type. A common choice is `mk_err()`
1054 /// or some placeholder type.
1055 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
1056 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
1060 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1061 #[derive(HashStable)]
1062 pub enum BoundVariableKind {
1064 Region(BoundRegionKind),
1068 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
1069 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
1070 /// (which would be represented by the type `PolyTraitRef ==
1071 /// Binder<'tcx, TraitRef>`). Note that when we instantiate,
1072 /// erase, or otherwise "discharge" these bound vars, we change the
1073 /// type from `Binder<'tcx, T>` to just `T` (see
1074 /// e.g., `liberate_late_bound_regions`).
1076 /// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro.
1077 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
1078 pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>);
1080 impl<'tcx, T> Binder<'tcx, T>
1082 T: TypeFoldable<'tcx>,
1084 /// Wraps `value` in a binder, asserting that `value` does not
1085 /// contain any bound vars that would be bound by the
1086 /// binder. This is commonly used to 'inject' a value T into a
1087 /// different binding level.
1088 pub fn dummy(value: T) -> Binder<'tcx, T> {
1089 assert!(!value.has_escaping_bound_vars());
1090 Binder(value, ty::List::empty())
1093 pub fn bind_with_vars(value: T, vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> {
1094 if cfg!(debug_assertions) {
1095 let mut validator = ValidateBoundVars::new(vars);
1096 value.visit_with(&mut validator);
1102 impl<'tcx, T> Binder<'tcx, T> {
1103 /// Skips the binder and returns the "bound" value. This is a
1104 /// risky thing to do because it's easy to get confused about
1105 /// De Bruijn indices and the like. It is usually better to
1106 /// discharge the binder using `no_bound_vars` or
1107 /// `replace_late_bound_regions` or something like
1108 /// that. `skip_binder` is only valid when you are either
1109 /// extracting data that has nothing to do with bound vars, you
1110 /// are doing some sort of test that does not involve bound
1111 /// regions, or you are being very careful about your depth
1114 /// Some examples where `skip_binder` is reasonable:
1116 /// - extracting the `DefId` from a PolyTraitRef;
1117 /// - comparing the self type of a PolyTraitRef to see if it is equal to
1118 /// a type parameter `X`, since the type `X` does not reference any regions
1119 pub fn skip_binder(self) -> T {
1123 pub fn bound_vars(&self) -> &'tcx List<BoundVariableKind> {
1127 pub fn as_ref(&self) -> Binder<'tcx, &T> {
1128 Binder(&self.0, self.1)
1131 pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U>
1135 let value = f(&self.0);
1136 Binder(value, self.1)
1139 pub fn map_bound_ref<F, U: TypeFoldable<'tcx>>(&self, f: F) -> Binder<'tcx, U>
1143 self.as_ref().map_bound(f)
1146 pub fn map_bound<F, U: TypeFoldable<'tcx>>(self, f: F) -> Binder<'tcx, U>
1150 let value = f(self.0);
1151 if cfg!(debug_assertions) {
1152 let mut validator = ValidateBoundVars::new(self.1);
1153 value.visit_with(&mut validator);
1155 Binder(value, self.1)
1158 pub fn try_map_bound<F, U: TypeFoldable<'tcx>, E>(self, f: F) -> Result<Binder<'tcx, U>, E>
1160 F: FnOnce(T) -> Result<U, E>,
1162 let value = f(self.0)?;
1163 if cfg!(debug_assertions) {
1164 let mut validator = ValidateBoundVars::new(self.1);
1165 value.visit_with(&mut validator);
1167 Ok(Binder(value, self.1))
1170 /// Wraps a `value` in a binder, using the same bound variables as the
1171 /// current `Binder`. This should not be used if the new value *changes*
1172 /// the bound variables. Note: the (old or new) value itself does not
1173 /// necessarily need to *name* all the bound variables.
1175 /// This currently doesn't do anything different than `bind`, because we
1176 /// don't actually track bound vars. However, semantically, it is different
1177 /// because bound vars aren't allowed to change here, whereas they are
1178 /// in `bind`. This may be (debug) asserted in the future.
1179 pub fn rebind<U>(&self, value: U) -> Binder<'tcx, U>
1181 U: TypeFoldable<'tcx>,
1183 if cfg!(debug_assertions) {
1184 let mut validator = ValidateBoundVars::new(self.bound_vars());
1185 value.visit_with(&mut validator);
1187 Binder(value, self.1)
1190 /// Unwraps and returns the value within, but only if it contains
1191 /// no bound vars at all. (In other words, if this binder --
1192 /// and indeed any enclosing binder -- doesn't bind anything at
1193 /// all.) Otherwise, returns `None`.
1195 /// (One could imagine having a method that just unwraps a single
1196 /// binder, but permits late-bound vars bound by enclosing
1197 /// binders, but that would require adjusting the debruijn
1198 /// indices, and given the shallow binding structure we often use,
1199 /// would not be that useful.)
1200 pub fn no_bound_vars(self) -> Option<T>
1202 T: TypeFoldable<'tcx>,
1204 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1207 /// Splits the contents into two things that share the same binder
1208 /// level as the original, returning two distinct binders.
1210 /// `f` should consider bound regions at depth 1 to be free, and
1211 /// anything it produces with bound regions at depth 1 will be
1212 /// bound in the resulting return values.
1213 pub fn split<U, V, F>(self, f: F) -> (Binder<'tcx, U>, Binder<'tcx, V>)
1215 F: FnOnce(T) -> (U, V),
1217 let (u, v) = f(self.0);
1218 (Binder(u, self.1), Binder(v, self.1))
1222 impl<'tcx, T> Binder<'tcx, Option<T>> {
1223 pub fn transpose(self) -> Option<Binder<'tcx, T>> {
1224 let bound_vars = self.1;
1225 self.0.map(|v| Binder(v, bound_vars))
1229 /// Represents the projection of an associated type. In explicit UFCS
1230 /// form this would be written `<T as Trait<..>>::N`.
1231 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1232 #[derive(HashStable, TypeFoldable)]
1233 pub struct ProjectionTy<'tcx> {
1234 /// The parameters of the associated item.
1235 pub substs: SubstsRef<'tcx>,
1237 /// The `DefId` of the `TraitItem` for the associated type `N`.
1239 /// Note that this is not the `DefId` of the `TraitRef` containing this
1240 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1241 pub item_def_id: DefId,
1244 impl<'tcx> ProjectionTy<'tcx> {
1245 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
1246 tcx.associated_item(self.item_def_id).container.id()
1249 /// Extracts the underlying trait reference and own substs from this projection.
1250 /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
1251 /// then this function would return a `T: Iterator` trait reference and `['a]` as the own substs
1252 pub fn trait_ref_and_own_substs(
1255 ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) {
1256 let def_id = tcx.associated_item(self.item_def_id).container.id();
1257 let trait_generics = tcx.generics_of(def_id);
1259 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, trait_generics) },
1260 &self.substs[trait_generics.count()..],
1264 /// Extracts the underlying trait reference from this projection.
1265 /// For example, if this is a projection of `<T as Iterator>::Item`,
1266 /// then this function would return a `T: Iterator` trait reference.
1268 /// WARNING: This will drop the substs for generic associated types
1269 /// consider calling [Self::trait_ref_and_own_substs] to get those
1271 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1272 let def_id = self.trait_def_id(tcx);
1273 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1276 pub fn self_ty(&self) -> Ty<'tcx> {
1277 self.substs.type_at(0)
1281 #[derive(Copy, Clone, Debug, TypeFoldable)]
1282 pub struct GenSig<'tcx> {
1283 pub resume_ty: Ty<'tcx>,
1284 pub yield_ty: Ty<'tcx>,
1285 pub return_ty: Ty<'tcx>,
1288 pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>;
1290 /// Signature of a function type, which we have arbitrarily
1291 /// decided to use to refer to the input/output types.
1293 /// - `inputs`: is the list of arguments and their modes.
1294 /// - `output`: is the return type.
1295 /// - `c_variadic`: indicates whether this is a C-variadic function.
1296 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1297 #[derive(HashStable, TypeFoldable)]
1298 pub struct FnSig<'tcx> {
1299 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1300 pub c_variadic: bool,
1301 pub unsafety: hir::Unsafety,
1305 impl<'tcx> FnSig<'tcx> {
1306 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1307 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1310 pub fn output(&self) -> Ty<'tcx> {
1311 self.inputs_and_output[self.inputs_and_output.len() - 1]
1314 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1316 fn fake() -> FnSig<'tcx> {
1318 inputs_and_output: List::empty(),
1320 unsafety: hir::Unsafety::Normal,
1321 abi: abi::Abi::Rust,
1326 pub type PolyFnSig<'tcx> = Binder<'tcx, FnSig<'tcx>>;
1328 impl<'tcx> PolyFnSig<'tcx> {
1330 pub fn inputs(&self) -> Binder<'tcx, &'tcx [Ty<'tcx>]> {
1331 self.map_bound_ref_unchecked(|fn_sig| fn_sig.inputs())
1334 pub fn input(&self, index: usize) -> ty::Binder<'tcx, Ty<'tcx>> {
1335 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1337 pub fn inputs_and_output(&self) -> ty::Binder<'tcx, &'tcx List<Ty<'tcx>>> {
1338 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1341 pub fn output(&self) -> ty::Binder<'tcx, Ty<'tcx>> {
1342 self.map_bound_ref(|fn_sig| fn_sig.output())
1344 pub fn c_variadic(&self) -> bool {
1345 self.skip_binder().c_variadic
1347 pub fn unsafety(&self) -> hir::Unsafety {
1348 self.skip_binder().unsafety
1350 pub fn abi(&self) -> abi::Abi {
1351 self.skip_binder().abi
1355 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<'tcx, FnSig<'tcx>>>;
1357 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1358 #[derive(HashStable)]
1359 pub struct ParamTy {
1364 impl<'tcx> ParamTy {
1365 pub fn new(index: u32, name: Symbol) -> ParamTy {
1366 ParamTy { index, name }
1369 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1370 ParamTy::new(def.index, def.name)
1374 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1375 tcx.mk_ty_param(self.index, self.name)
1379 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1380 #[derive(HashStable)]
1381 pub struct ParamConst {
1387 pub fn new(index: u32, name: Symbol) -> ParamConst {
1388 ParamConst { index, name }
1391 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1392 ParamConst::new(def.index, def.name)
1396 /// Use this rather than `TyKind`, whenever possible.
1397 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
1398 #[cfg_attr(not(bootstrap), rustc_pass_by_value)]
1399 pub struct Region<'tcx>(pub Interned<'tcx, RegionKind>);
1401 impl<'tcx> Deref for Region<'tcx> {
1402 type Target = RegionKind;
1404 fn deref(&self) -> &RegionKind {
1409 impl<'tcx> fmt::Debug for Region<'tcx> {
1410 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1411 write!(f, "{:?}", self.kind())
1415 /// Representation of regions. Note that the NLL checker uses a distinct
1416 /// representation of regions. For this reason, it internally replaces all the
1417 /// regions with inference variables -- the index of the variable is then used
1418 /// to index into internal NLL data structures. See `rustc_const_eval::borrow_check`
1419 /// module for more information.
1421 /// Note: operations are on the wrapper `Region` type, which is interned,
1422 /// rather than this type.
1424 /// ## The Region lattice within a given function
1426 /// In general, the region lattice looks like
1429 /// static ----------+-----...------+ (greatest)
1431 /// early-bound and | |
1432 /// free regions | |
1435 /// empty(root) placeholder(U1) |
1437 /// | / placeholder(Un)
1442 /// empty(Un) -------- (smallest)
1445 /// Early-bound/free regions are the named lifetimes in scope from the
1446 /// function declaration. They have relationships to one another
1447 /// determined based on the declared relationships from the
1450 /// Note that inference variables and bound regions are not included
1451 /// in this diagram. In the case of inference variables, they should
1452 /// be inferred to some other region from the diagram. In the case of
1453 /// bound regions, they are excluded because they don't make sense to
1454 /// include -- the diagram indicates the relationship between free
1457 /// ## Inference variables
1459 /// During region inference, we sometimes create inference variables,
1460 /// represented as `ReVar`. These will be inferred by the code in
1461 /// `infer::lexical_region_resolve` to some free region from the
1462 /// lattice above (the minimal region that meets the
1465 /// During NLL checking, where regions are defined differently, we
1466 /// also use `ReVar` -- in that case, the index is used to index into
1467 /// the NLL region checker's data structures. The variable may in fact
1468 /// represent either a free region or an inference variable, in that
1471 /// ## Bound Regions
1473 /// These are regions that are stored behind a binder and must be substituted
1474 /// with some concrete region before being used. There are two kind of
1475 /// bound regions: early-bound, which are bound in an item's `Generics`,
1476 /// and are substituted by an `InternalSubsts`, and late-bound, which are part of
1477 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1478 /// the likes of `liberate_late_bound_regions`. The distinction exists
1479 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1481 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1482 /// outside their binder, e.g., in types passed to type inference, and
1483 /// should first be substituted (by placeholder regions, free regions,
1484 /// or region variables).
1486 /// ## Placeholder and Free Regions
1488 /// One often wants to work with bound regions without knowing their precise
1489 /// identity. For example, when checking a function, the lifetime of a borrow
1490 /// can end up being assigned to some region parameter. In these cases,
1491 /// it must be ensured that bounds on the region can't be accidentally
1492 /// assumed without being checked.
1494 /// To do this, we replace the bound regions with placeholder markers,
1495 /// which don't satisfy any relation not explicitly provided.
1497 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1498 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1499 /// to be used. These also support explicit bounds: both the internally-stored
1500 /// *scope*, which the region is assumed to outlive, as well as other
1501 /// relations stored in the `FreeRegionMap`. Note that these relations
1502 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1503 /// `resolve_regions_and_report_errors`.
1505 /// When working with higher-ranked types, some region relations aren't
1506 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1507 /// `RePlaceholder` is designed for this purpose. In these contexts,
1508 /// there's also the risk that some inference variable laying around will
1509 /// get unified with your placeholder region: if you want to check whether
1510 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1511 /// with a placeholder region `'%a`, the variable `'_` would just be
1512 /// instantiated to the placeholder region `'%a`, which is wrong because
1513 /// the inference variable is supposed to satisfy the relation
1514 /// *for every value of the placeholder region*. To ensure that doesn't
1515 /// happen, you can use `leak_check`. This is more clearly explained
1516 /// by the [rustc dev guide].
1518 /// [1]: https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1519 /// [2]: https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1520 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1521 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1522 pub enum RegionKind {
1523 /// Region bound in a type or fn declaration which will be
1524 /// substituted 'early' -- that is, at the same time when type
1525 /// parameters are substituted.
1526 ReEarlyBound(EarlyBoundRegion),
1528 /// Region bound in a function scope, which will be substituted when the
1529 /// function is called.
1530 ReLateBound(ty::DebruijnIndex, BoundRegion),
1532 /// When checking a function body, the types of all arguments and so forth
1533 /// that refer to bound region parameters are modified to refer to free
1534 /// region parameters.
1537 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1540 /// A region variable. Should not exist outside of type inference.
1543 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1544 /// Should not exist outside of type inference.
1545 RePlaceholder(ty::PlaceholderRegion),
1547 /// Empty lifetime is for data that is never accessed. We tag the
1548 /// empty lifetime with a universe -- the idea is that we don't
1549 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1550 /// Therefore, the `'empty` in a universe `U` is less than all
1551 /// regions visible from `U`, but not less than regions not visible
1553 ReEmpty(ty::UniverseIndex),
1555 /// Erased region, used by trait selection, in MIR and during codegen.
1559 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1560 pub struct EarlyBoundRegion {
1566 /// A **`const`** **v**ariable **ID**.
1567 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1568 pub struct ConstVid<'tcx> {
1570 pub phantom: PhantomData<&'tcx ()>,
1573 rustc_index::newtype_index! {
1574 /// A **region** (lifetime) **v**ariable **ID**.
1575 pub struct RegionVid {
1576 DEBUG_FORMAT = custom,
1580 impl Atom for RegionVid {
1581 fn index(self) -> usize {
1586 rustc_index::newtype_index! {
1587 pub struct BoundVar { .. }
1590 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1591 #[derive(HashStable)]
1592 pub struct BoundTy {
1594 pub kind: BoundTyKind,
1597 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1598 #[derive(HashStable)]
1599 pub enum BoundTyKind {
1604 impl From<BoundVar> for BoundTy {
1605 fn from(var: BoundVar) -> Self {
1606 BoundTy { var, kind: BoundTyKind::Anon }
1610 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1611 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1612 #[derive(HashStable, TypeFoldable)]
1613 pub struct ExistentialProjection<'tcx> {
1614 pub item_def_id: DefId,
1615 pub substs: SubstsRef<'tcx>,
1616 pub term: Term<'tcx>,
1619 pub type PolyExistentialProjection<'tcx> = Binder<'tcx, ExistentialProjection<'tcx>>;
1621 impl<'tcx> ExistentialProjection<'tcx> {
1622 /// Extracts the underlying existential trait reference from this projection.
1623 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1624 /// then this function would return an `exists T. T: Iterator` existential trait
1626 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
1627 let def_id = tcx.associated_item(self.item_def_id).container.id();
1628 let subst_count = tcx.generics_of(def_id).count() - 1;
1629 let substs = tcx.intern_substs(&self.substs[..subst_count]);
1630 ty::ExistentialTraitRef { def_id, substs }
1633 pub fn with_self_ty(
1637 ) -> ty::ProjectionPredicate<'tcx> {
1638 // otherwise the escaping regions would be captured by the binders
1639 debug_assert!(!self_ty.has_escaping_bound_vars());
1641 ty::ProjectionPredicate {
1642 projection_ty: ty::ProjectionTy {
1643 item_def_id: self.item_def_id,
1644 substs: tcx.mk_substs_trait(self_ty, self.substs),
1650 pub fn erase_self_ty(
1652 projection_predicate: ty::ProjectionPredicate<'tcx>,
1654 // Assert there is a Self.
1655 projection_predicate.projection_ty.substs.type_at(0);
1658 item_def_id: projection_predicate.projection_ty.item_def_id,
1659 substs: tcx.intern_substs(&projection_predicate.projection_ty.substs[1..]),
1660 term: projection_predicate.term,
1665 impl<'tcx> PolyExistentialProjection<'tcx> {
1666 pub fn with_self_ty(
1670 ) -> ty::PolyProjectionPredicate<'tcx> {
1671 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1674 pub fn item_def_id(&self) -> DefId {
1675 self.skip_binder().item_def_id
1679 /// Region utilities
1680 impl<'tcx> Region<'tcx> {
1681 pub fn kind(self) -> RegionKind {
1685 /// Is this region named by the user?
1686 pub fn has_name(self) -> bool {
1688 ty::ReEarlyBound(ebr) => ebr.has_name(),
1689 ty::ReLateBound(_, br) => br.kind.is_named(),
1690 ty::ReFree(fr) => fr.bound_region.is_named(),
1691 ty::ReStatic => true,
1692 ty::ReVar(..) => false,
1693 ty::RePlaceholder(placeholder) => placeholder.name.is_named(),
1694 ty::ReEmpty(_) => false,
1695 ty::ReErased => false,
1700 pub fn is_static(self) -> bool {
1701 matches!(*self, ty::ReStatic)
1705 pub fn is_erased(self) -> bool {
1706 matches!(*self, ty::ReErased)
1710 pub fn is_late_bound(self) -> bool {
1711 matches!(*self, ty::ReLateBound(..))
1715 pub fn is_placeholder(self) -> bool {
1716 matches!(*self, ty::RePlaceholder(..))
1720 pub fn is_empty(self) -> bool {
1721 matches!(*self, ty::ReEmpty(..))
1725 pub fn bound_at_or_above_binder(self, index: ty::DebruijnIndex) -> bool {
1727 ty::ReLateBound(debruijn, _) => debruijn >= index,
1732 pub fn type_flags(self) -> TypeFlags {
1733 let mut flags = TypeFlags::empty();
1737 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1738 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1739 flags = flags | TypeFlags::HAS_RE_INFER;
1741 ty::RePlaceholder(..) => {
1742 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1743 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1744 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1746 ty::ReEarlyBound(..) => {
1747 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1748 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1749 flags = flags | TypeFlags::HAS_RE_PARAM;
1751 ty::ReFree { .. } => {
1752 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1753 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1755 ty::ReEmpty(_) | ty::ReStatic => {
1756 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1758 ty::ReLateBound(..) => {
1759 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1762 flags = flags | TypeFlags::HAS_RE_ERASED;
1766 debug!("type_flags({:?}) = {:?}", self, flags);
1771 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1772 /// For example, consider the regions in this snippet of code:
1776 /// ^^ -- early bound, declared on an impl
1778 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1779 /// ^^ ^^ ^ anonymous, late-bound
1780 /// | early-bound, appears in where-clauses
1781 /// late-bound, appears only in fn args
1786 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1787 /// of the impl, and for all the other highlighted regions, it
1788 /// would return the `DefId` of the function. In other cases (not shown), this
1789 /// function might return the `DefId` of a closure.
1790 pub fn free_region_binding_scope(self, tcx: TyCtxt<'_>) -> DefId {
1792 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1793 ty::ReFree(fr) => fr.scope,
1794 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1800 impl<'tcx> Ty<'tcx> {
1802 pub fn kind(self) -> &'tcx TyKind<'tcx> {
1807 pub fn flags(self) -> TypeFlags {
1812 pub fn is_unit(self) -> bool {
1814 Tuple(ref tys) => tys.is_empty(),
1820 pub fn is_never(self) -> bool {
1821 matches!(self.kind(), Never)
1825 pub fn is_primitive(self) -> bool {
1826 self.kind().is_primitive()
1830 pub fn is_adt(self) -> bool {
1831 matches!(self.kind(), Adt(..))
1835 pub fn is_ref(self) -> bool {
1836 matches!(self.kind(), Ref(..))
1840 pub fn is_ty_var(self) -> bool {
1841 matches!(self.kind(), Infer(TyVar(_)))
1845 pub fn ty_vid(self) -> Option<ty::TyVid> {
1847 &Infer(TyVar(vid)) => Some(vid),
1853 pub fn is_ty_infer(self) -> bool {
1854 matches!(self.kind(), Infer(_))
1858 pub fn is_phantom_data(self) -> bool {
1859 if let Adt(def, _) = self.kind() { def.is_phantom_data() } else { false }
1863 pub fn is_bool(self) -> bool {
1864 *self.kind() == Bool
1867 /// Returns `true` if this type is a `str`.
1869 pub fn is_str(self) -> bool {
1874 pub fn is_param(self, index: u32) -> bool {
1876 ty::Param(ref data) => data.index == index,
1882 pub fn is_slice(self) -> bool {
1884 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_) | Str),
1890 pub fn is_array(self) -> bool {
1891 matches!(self.kind(), Array(..))
1895 pub fn is_simd(self) -> bool {
1897 Adt(def, _) => def.repr.simd(),
1902 pub fn sequence_element_type(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1904 Array(ty, _) | Slice(ty) => *ty,
1905 Str => tcx.types.u8,
1906 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1910 pub fn simd_size_and_type(self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1912 Adt(def, substs) => {
1913 assert!(def.repr.simd(), "`simd_size_and_type` called on non-SIMD type");
1914 let variant = def.non_enum_variant();
1915 let f0_ty = variant.fields[0].ty(tcx, substs);
1917 match f0_ty.kind() {
1918 // If the first field is an array, we assume it is the only field and its
1919 // elements are the SIMD components.
1920 Array(f0_elem_ty, f0_len) => {
1921 // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112
1922 // The way we evaluate the `N` in `[T; N]` here only works since we use
1923 // `simd_size_and_type` post-monomorphization. It will probably start to ICE
1924 // if we use it in generic code. See the `simd-array-trait` ui test.
1925 (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, *f0_elem_ty)
1927 // Otherwise, the fields of this Adt are the SIMD components (and we assume they
1928 // all have the same type).
1929 _ => (variant.fields.len() as u64, f0_ty),
1932 _ => bug!("`simd_size_and_type` called on invalid type"),
1937 pub fn is_region_ptr(self) -> bool {
1938 matches!(self.kind(), Ref(..))
1942 pub fn is_mutable_ptr(self) -> bool {
1945 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1946 | Ref(_, _, hir::Mutability::Mut)
1950 /// Get the mutability of the reference or `None` when not a reference
1952 pub fn ref_mutability(self) -> Option<hir::Mutability> {
1954 Ref(_, _, mutability) => Some(*mutability),
1960 pub fn is_unsafe_ptr(self) -> bool {
1961 matches!(self.kind(), RawPtr(_))
1964 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1966 pub fn is_any_ptr(self) -> bool {
1967 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1971 pub fn is_box(self) -> bool {
1973 Adt(def, _) => def.is_box(),
1978 /// Panics if called on any type other than `Box<T>`.
1979 pub fn boxed_ty(self) -> Ty<'tcx> {
1981 Adt(def, substs) if def.is_box() => substs.type_at(0),
1982 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1986 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1987 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1988 /// contents are abstract to rustc.)
1990 pub fn is_scalar(self) -> bool {
2000 | Infer(IntVar(_) | FloatVar(_))
2004 /// Returns `true` if this type is a floating point type.
2006 pub fn is_floating_point(self) -> bool {
2007 matches!(self.kind(), Float(_) | Infer(FloatVar(_)))
2011 pub fn is_trait(self) -> bool {
2012 matches!(self.kind(), Dynamic(..))
2016 pub fn is_enum(self) -> bool {
2017 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_enum())
2021 pub fn is_union(self) -> bool {
2022 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_union())
2026 pub fn is_closure(self) -> bool {
2027 matches!(self.kind(), Closure(..))
2031 pub fn is_generator(self) -> bool {
2032 matches!(self.kind(), Generator(..))
2036 pub fn is_integral(self) -> bool {
2037 matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_))
2041 pub fn is_fresh_ty(self) -> bool {
2042 matches!(self.kind(), Infer(FreshTy(_)))
2046 pub fn is_fresh(self) -> bool {
2047 matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_)))
2051 pub fn is_char(self) -> bool {
2052 matches!(self.kind(), Char)
2056 pub fn is_numeric(self) -> bool {
2057 self.is_integral() || self.is_floating_point()
2061 pub fn is_signed(self) -> bool {
2062 matches!(self.kind(), Int(_))
2066 pub fn is_ptr_sized_integral(self) -> bool {
2067 matches!(self.kind(), Int(ty::IntTy::Isize) | Uint(ty::UintTy::Usize))
2071 pub fn has_concrete_skeleton(self) -> bool {
2072 !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
2075 /// Returns the type and mutability of `*ty`.
2077 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2078 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2079 pub fn builtin_deref(self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2081 Adt(def, _) if def.is_box() => {
2082 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2084 Ref(_, ty, mutbl) => Some(TypeAndMut { ty: *ty, mutbl: *mutbl }),
2085 RawPtr(mt) if explicit => Some(*mt),
2090 /// Returns the type of `ty[i]`.
2091 pub fn builtin_index(self) -> Option<Ty<'tcx>> {
2093 Array(ty, _) | Slice(ty) => Some(*ty),
2098 pub fn fn_sig(self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2100 FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
2103 // ignore errors (#54954)
2104 ty::Binder::dummy(FnSig::fake())
2106 Closure(..) => bug!(
2107 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2109 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2114 pub fn is_fn(self) -> bool {
2115 matches!(self.kind(), FnDef(..) | FnPtr(_))
2119 pub fn is_fn_ptr(self) -> bool {
2120 matches!(self.kind(), FnPtr(_))
2124 pub fn is_impl_trait(self) -> bool {
2125 matches!(self.kind(), Opaque(..))
2129 pub fn ty_adt_def(self) -> Option<&'tcx AdtDef> {
2131 Adt(adt, _) => Some(adt),
2136 /// Iterates over tuple fields.
2137 /// Panics when called on anything but a tuple.
2138 pub fn tuple_fields(self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2140 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2141 _ => bug!("tuple_fields called on non-tuple"),
2145 /// Get the `i`-th element of a tuple.
2146 /// Panics when called on anything but a tuple.
2147 pub fn tuple_element_ty(self, i: usize) -> Option<Ty<'tcx>> {
2149 Tuple(substs) => substs.iter().nth(i).map(|field| field.expect_ty()),
2150 _ => bug!("tuple_fields called on non-tuple"),
2154 /// If the type contains variants, returns the valid range of variant indices.
2156 // FIXME: This requires the optimized MIR in the case of generators.
2158 pub fn variant_range(self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2160 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2161 TyKind::Generator(def_id, substs, _) => {
2162 Some(substs.as_generator().variant_range(*def_id, tcx))
2168 /// If the type contains variants, returns the variant for `variant_index`.
2169 /// Panics if `variant_index` is out of range.
2171 // FIXME: This requires the optimized MIR in the case of generators.
2173 pub fn discriminant_for_variant(
2176 variant_index: VariantIdx,
2177 ) -> Option<Discr<'tcx>> {
2179 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2180 // This can actually happen during CTFE, see
2181 // https://github.com/rust-lang/rust/issues/89765.
2184 TyKind::Adt(adt, _) if adt.is_enum() => {
2185 Some(adt.discriminant_for_variant(tcx, variant_index))
2187 TyKind::Generator(def_id, substs, _) => {
2188 Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
2194 /// Returns the type of the discriminant of this type.
2195 pub fn discriminant_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2197 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2198 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2200 ty::Param(_) | ty::Projection(_) | ty::Opaque(..) | ty::Infer(ty::TyVar(_)) => {
2201 let assoc_items = tcx.associated_item_def_ids(
2202 tcx.require_lang_item(hir::LangItem::DiscriminantKind, None),
2204 tcx.mk_projection(assoc_items[0], tcx.intern_substs(&[self.into()]))
2223 | ty::GeneratorWitness(..)
2227 | ty::Infer(IntVar(_) | FloatVar(_)) => tcx.types.u8,
2230 | ty::Placeholder(_)
2231 | ty::Infer(FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2232 bug!("`discriminant_ty` applied to unexpected type: {:?}", self)
2237 /// Returns the type of metadata for (potentially fat) pointers to this type.
2238 pub fn ptr_metadata_ty(
2241 normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
2243 let tail = tcx.struct_tail_with_normalize(self, normalize);
2246 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2257 | ty::GeneratorWitness(..)
2263 // If returned by `struct_tail_without_normalization` this is a unit struct
2264 // without any fields, or not a struct, and therefore is Sized.
2266 // If returned by `struct_tail_without_normalization` this is the empty tuple,
2267 // a.k.a. unit type, which is Sized
2268 | ty::Tuple(..) => tcx.types.unit,
2270 ty::Str | ty::Slice(_) => tcx.types.usize,
2271 ty::Dynamic(..) => {
2272 let dyn_metadata = tcx.lang_items().dyn_metadata().unwrap();
2273 tcx.type_of(dyn_metadata).subst(tcx, &[tail.into()])
2279 | ty::Infer(ty::TyVar(_))
2281 | ty::Placeholder(..)
2282 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2283 bug!("`ptr_metadata_ty` applied to unexpected type: {:?}", tail)
2288 /// When we create a closure, we record its kind (i.e., what trait
2289 /// it implements) into its `ClosureSubsts` using a type
2290 /// parameter. This is kind of a phantom type, except that the
2291 /// most convenient thing for us to are the integral types. This
2292 /// function converts such a special type into the closure
2293 /// kind. To go the other way, use
2294 /// `tcx.closure_kind_ty(closure_kind)`.
2296 /// Note that during type checking, we use an inference variable
2297 /// to represent the closure kind, because it has not yet been
2298 /// inferred. Once upvar inference (in `rustc_typeck/src/check/upvar.rs`)
2299 /// is complete, that type variable will be unified.
2300 pub fn to_opt_closure_kind(self) -> Option<ty::ClosureKind> {
2302 Int(int_ty) => match int_ty {
2303 ty::IntTy::I8 => Some(ty::ClosureKind::Fn),
2304 ty::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2305 ty::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2306 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2309 // "Bound" types appear in canonical queries when the
2310 // closure type is not yet known
2311 Bound(..) | Infer(_) => None,
2313 Error(_) => Some(ty::ClosureKind::Fn),
2315 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2319 /// Fast path helper for testing if a type is `Sized`.
2321 /// Returning true means the type is known to be sized. Returning
2322 /// `false` means nothing -- could be sized, might not be.
2324 /// Note that we could never rely on the fact that a type such as `[_]` is
2325 /// trivially `!Sized` because we could be in a type environment with a
2326 /// bound such as `[_]: Copy`. A function with such a bound obviously never
2327 /// can be called, but that doesn't mean it shouldn't typecheck. This is why
2328 /// this method doesn't return `Option<bool>`.
2329 pub fn is_trivially_sized(self, tcx: TyCtxt<'tcx>) -> bool {
2331 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2342 | ty::GeneratorWitness(..)
2346 | ty::Error(_) => true,
2348 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2350 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2352 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2354 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2356 ty::Infer(ty::TyVar(_)) => false,
2359 | ty::Placeholder(..)
2360 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2361 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2367 /// Extra information about why we ended up with a particular variance.
2368 /// This is only used to add more information to error messages, and
2369 /// has no effect on soundness. While choosing the 'wrong' `VarianceDiagInfo`
2370 /// may lead to confusing notes in error messages, it will never cause
2371 /// a miscompilation or unsoundness.
2373 /// When in doubt, use `VarianceDiagInfo::default()`
2374 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
2375 pub enum VarianceDiagInfo<'tcx> {
2376 /// No additional information - this is the default.
2377 /// We will not add any additional information to error messages.
2380 /// We switched our variance because a generic argument occurs inside
2381 /// the invariant generic argument of another type.
2383 /// The generic type containing the generic parameter
2384 /// that changes the variance (e.g. `*mut T`, `MyStruct<T>`)
2386 /// The index of the generic parameter being used
2387 /// (e.g. `0` for `*mut T`, `1` for `MyStruct<'CovariantParam, 'InvariantParam>`)
2392 impl<'tcx> VarianceDiagInfo<'tcx> {
2393 /// Mirrors `Variance::xform` - used to 'combine' the existing
2394 /// and new `VarianceDiagInfo`s when our variance changes.
2395 pub fn xform(self, other: VarianceDiagInfo<'tcx>) -> VarianceDiagInfo<'tcx> {
2396 // For now, just use the first `VarianceDiagInfo::Invariant` that we see
2398 VarianceDiagInfo::None => other,
2399 VarianceDiagInfo::Invariant { .. } => self,