1 //! This module contains `TyKind` and its major components.
3 #![allow(rustc::usage_of_ty_tykind)]
8 use crate::infer::canonical::Canonical;
9 use crate::middle::region;
10 use crate::mir::interpret::ConstValue;
11 use crate::mir::interpret::{LitToConstInput, Scalar};
12 use crate::mir::Promoted;
13 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
15 self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness,
17 use crate::ty::{List, ParamEnv, ParamEnvAnd, TyS};
18 use polonius_engine::Atom;
19 use rustc_ast::ast::{self, Ident};
20 use rustc_data_structures::captures::Captures;
22 use rustc_hir::def_id::{DefId, LocalDefId};
23 use rustc_index::vec::Idx;
24 use rustc_macros::HashStable;
25 use rustc_span::symbol::{kw, Symbol};
26 use rustc_target::abi::{Size, VariantIdx};
27 use rustc_target::spec::abi;
29 use std::cmp::Ordering;
30 use std::marker::PhantomData;
33 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
34 #[derive(HashStable, TypeFoldable, Lift)]
35 pub struct TypeAndMut<'tcx> {
37 pub mutbl: hir::Mutability,
40 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable, RustcDecodable, Copy)]
42 /// A "free" region `fr` can be interpreted as "some region
43 /// at least as big as the scope `fr.scope`".
44 pub struct FreeRegion {
46 pub bound_region: BoundRegion,
49 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable, RustcDecodable, Copy)]
51 pub enum BoundRegion {
52 /// An anonymous region parameter for a given fn (&T)
55 /// Named region parameters for functions (a in &'a T)
57 /// The `DefId` is needed to distinguish free regions in
58 /// the event of shadowing.
59 BrNamed(DefId, Symbol),
61 /// Anonymous region for the implicit env pointer parameter
67 pub fn is_named(&self) -> bool {
69 BoundRegion::BrNamed(_, name) => name != kw::UnderscoreLifetime,
74 /// When canonicalizing, we replace unbound inference variables and free
75 /// regions with anonymous late bound regions. This method asserts that
76 /// we have an anonymous late bound region, which hence may refer to
77 /// a canonical variable.
78 pub fn assert_bound_var(&self) -> BoundVar {
80 BoundRegion::BrAnon(var) => BoundVar::from_u32(var),
81 _ => bug!("bound region is not anonymous"),
86 /// N.B., if you change this, you'll probably want to change the corresponding
87 /// AST structure in `librustc_ast/ast.rs` as well.
88 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, Debug)]
90 #[rustc_diagnostic_item = "TyKind"]
91 pub enum TyKind<'tcx> {
92 /// The primitive boolean type. Written as `bool`.
95 /// The primitive character type; holds a Unicode scalar value
96 /// (a non-surrogate code point). Written as `char`.
99 /// A primitive signed integer type. For example, `i32`.
102 /// A primitive unsigned integer type. For example, `u32`.
105 /// A primitive floating-point type. For example, `f64`.
108 /// Structures, enumerations and unions.
110 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
111 /// That is, even after substitution it is possible that there are type
112 /// variables. This happens when the `Adt` corresponds to an ADT
113 /// definition and not a concrete use of it.
114 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
116 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
119 /// The pointee of a string slice. Written as `str`.
122 /// An array with the given length. Written as `[T; n]`.
123 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
125 /// The pointee of an array slice. Written as `[T]`.
128 /// A raw pointer. Written as `*mut T` or `*const T`
129 RawPtr(TypeAndMut<'tcx>),
131 /// A reference; a pointer with an associated lifetime. Written as
132 /// `&'a mut T` or `&'a T`.
133 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
135 /// The anonymous type of a function declaration/definition. Each
136 /// function has a unique type, which is output (for a function
137 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
139 /// For example the type of `bar` here:
142 /// fn foo() -> i32 { 1 }
143 /// let bar = foo; // bar: fn() -> i32 {foo}
145 FnDef(DefId, SubstsRef<'tcx>),
147 /// A pointer to a function. Written as `fn() -> i32`.
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, defined with `trait`.
158 Dynamic(Binder<&'tcx List<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
160 /// The anonymous type of a closure. Used to represent the type of
162 Closure(DefId, SubstsRef<'tcx>),
164 /// The anonymous type of a generator. Used to represent the type of
166 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
168 /// A type representin the types stored inside a generator.
169 /// This should only appear in GeneratorInteriors.
170 GeneratorWitness(Binder<&'tcx List<Ty<'tcx>>>),
172 /// The never type `!`
175 /// A tuple type. For example, `(i32, bool)`.
176 /// Use `TyS::tuple_fields` to iterate over the field types.
177 Tuple(SubstsRef<'tcx>),
179 /// The projection of an associated type. For example,
180 /// `<T as Trait<..>>::N`.
181 Projection(ProjectionTy<'tcx>),
183 /// A placeholder type used when we do not have enough information
184 /// to normalize the projection of an associated type to an
185 /// existing concrete type. Currently only used with chalk-engine.
186 UnnormalizedProjection(ProjectionTy<'tcx>),
188 /// Opaque (`impl Trait`) type found in a return type.
189 /// The `DefId` comes either from
190 /// * the `impl Trait` ast::Ty node,
191 /// * or the `type Foo = impl Trait` declaration
192 /// The substitutions are for the generics of the function in question.
193 /// After typeck, the concrete type can be found in the `types` map.
194 Opaque(DefId, SubstsRef<'tcx>),
196 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
199 /// Bound type variable, used only when preparing a trait query.
200 Bound(ty::DebruijnIndex, BoundTy),
202 /// A placeholder type - universally quantified higher-ranked type.
203 Placeholder(ty::PlaceholderType),
205 /// A type variable used during type checking.
208 /// A placeholder for a type which could not be computed; this is
209 /// propagated to avoid useless error messages.
213 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
214 #[cfg(target_arch = "x86_64")]
215 static_assert_size!(TyKind<'_>, 24);
217 /// A closure can be modeled as a struct that looks like:
219 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
223 /// - 'l0...'li and T0...Tj are the generic parameters
224 /// in scope on the function that defined the closure,
225 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
226 /// is rather hackily encoded via a scalar type. See
227 /// `TyS::to_opt_closure_kind` for details.
228 /// - CS represents the *closure signature*, representing as a `fn()`
229 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
230 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
232 /// - U is a type parameter representing the types of its upvars, tupled up
233 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
234 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
236 /// So, for example, given this function:
238 /// fn foo<'a, T>(data: &'a mut T) {
239 /// do(|| data.count += 1)
242 /// the type of the closure would be something like:
244 /// struct Closure<'a, T, U>(...U);
246 /// Note that the type of the upvar is not specified in the struct.
247 /// You may wonder how the impl would then be able to use the upvar,
248 /// if it doesn't know it's type? The answer is that the impl is
249 /// (conceptually) not fully generic over Closure but rather tied to
250 /// instances with the expected upvar types:
252 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
256 /// You can see that the *impl* fully specified the type of the upvar
257 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
258 /// (Here, I am assuming that `data` is mut-borrowed.)
260 /// Now, the last question you may ask is: Why include the upvar types
261 /// in an extra type parameter? The reason for this design is that the
262 /// upvar types can reference lifetimes that are internal to the
263 /// creating function. In my example above, for example, the lifetime
264 /// `'b` represents the scope of the closure itself; this is some
265 /// subset of `foo`, probably just the scope of the call to the to
266 /// `do()`. If we just had the lifetime/type parameters from the
267 /// enclosing function, we couldn't name this lifetime `'b`. Note that
268 /// there can also be lifetimes in the types of the upvars themselves,
269 /// if one of them happens to be a reference to something that the
270 /// creating fn owns.
272 /// OK, you say, so why not create a more minimal set of parameters
273 /// that just includes the extra lifetime parameters? The answer is
274 /// primarily that it would be hard --- we don't know at the time when
275 /// we create the closure type what the full types of the upvars are,
276 /// nor do we know which are borrowed and which are not. In this
277 /// design, we can just supply a fresh type parameter and figure that
280 /// All right, you say, but why include the type parameters from the
281 /// original function then? The answer is that codegen may need them
282 /// when monomorphizing, and they may not appear in the upvars. A
283 /// closure could capture no variables but still make use of some
284 /// in-scope type parameter with a bound (e.g., if our example above
285 /// had an extra `U: Default`, and the closure called `U::default()`).
287 /// There is another reason. This design (implicitly) prohibits
288 /// closures from capturing themselves (except via a trait
289 /// object). This simplifies closure inference considerably, since it
290 /// means that when we infer the kind of a closure or its upvars, we
291 /// don't have to handle cycles where the decisions we make for
292 /// closure C wind up influencing the decisions we ought to make for
293 /// closure C (which would then require fixed point iteration to
294 /// handle). Plus it fixes an ICE. :P
298 /// Generators are handled similarly in `GeneratorSubsts`. The set of
299 /// type parameters is similar, but `CK` and `CS` are replaced by the
300 /// following type parameters:
302 /// * `GS`: The generator's "resume type", which is the type of the
303 /// argument passed to `resume`, and the type of `yield` expressions
304 /// inside the generator.
305 /// * `GY`: The "yield type", which is the type of values passed to
306 /// `yield` inside the generator.
307 /// * `GR`: The "return type", which is the type of value returned upon
308 /// completion of the generator.
309 /// * `GW`: The "generator witness".
310 #[derive(Copy, Clone, Debug, TypeFoldable)]
311 pub struct ClosureSubsts<'tcx> {
312 /// Lifetime and type parameters from the enclosing function,
313 /// concatenated with a tuple containing the types of the upvars.
315 /// These are separated out because codegen wants to pass them around
316 /// when monomorphizing.
317 pub substs: SubstsRef<'tcx>,
320 /// Struct returned by `split()`. Note that these are subslices of the
321 /// parent slice and not canonical substs themselves.
322 struct SplitClosureSubsts<'tcx> {
323 closure_kind_ty: GenericArg<'tcx>,
324 closure_sig_as_fn_ptr_ty: GenericArg<'tcx>,
325 tupled_upvars_ty: GenericArg<'tcx>,
328 impl<'tcx> ClosureSubsts<'tcx> {
329 /// Divides the closure substs into their respective
330 /// components. Single source of truth with respect to the
332 fn split(self) -> SplitClosureSubsts<'tcx> {
333 match self.substs[..] {
334 [.., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
335 SplitClosureSubsts { closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty }
337 _ => bug!("closure substs missing synthetics"),
341 /// Returns `true` only if enough of the synthetic types are known to
342 /// allow using all of the methods on `ClosureSubsts` without panicking.
344 /// Used primarily by `ty::print::pretty` to be able to handle closure
345 /// types that haven't had their synthetic types substituted in.
346 pub fn is_valid(self) -> bool {
347 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
351 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
352 self.split().tupled_upvars_ty.expect_ty().tuple_fields()
355 /// Returns the closure kind for this closure; may return a type
356 /// variable during inference. To get the closure kind during
357 /// inference, use `infcx.closure_kind(substs)`.
358 pub fn kind_ty(self) -> Ty<'tcx> {
359 self.split().closure_kind_ty.expect_ty()
362 /// Returns the `fn` pointer type representing the closure signature for this
364 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
365 // type is known at the time of the creation of `ClosureSubsts`,
366 // see `rustc_typeck::check::closure`.
367 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
368 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
371 /// Returns the closure kind for this closure; only usable outside
372 /// of an inference context, because in that context we know that
373 /// there are no type variables.
375 /// If you have an inference context, use `infcx.closure_kind()`.
376 pub fn kind(self) -> ty::ClosureKind {
377 self.kind_ty().to_opt_closure_kind().unwrap()
380 /// Extracts the signature from the closure.
381 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
382 let ty = self.sig_as_fn_ptr_ty();
384 ty::FnPtr(sig) => sig,
385 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
390 /// Similar to `ClosureSubsts`; see the above documentation for more.
391 #[derive(Copy, Clone, Debug, TypeFoldable)]
392 pub struct GeneratorSubsts<'tcx> {
393 pub substs: SubstsRef<'tcx>,
396 struct SplitGeneratorSubsts<'tcx> {
397 resume_ty: GenericArg<'tcx>,
398 yield_ty: GenericArg<'tcx>,
399 return_ty: GenericArg<'tcx>,
400 witness: GenericArg<'tcx>,
401 tupled_upvars_ty: GenericArg<'tcx>,
404 impl<'tcx> GeneratorSubsts<'tcx> {
405 fn split(self) -> SplitGeneratorSubsts<'tcx> {
406 match self.substs[..] {
407 [.., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
408 SplitGeneratorSubsts { resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty }
410 _ => bug!("generator substs missing synthetics"),
414 /// Returns `true` only if enough of the synthetic types are known to
415 /// allow using all of the methods on `GeneratorSubsts` without panicking.
417 /// Used primarily by `ty::print::pretty` to be able to handle generator
418 /// types that haven't had their synthetic types substituted in.
419 pub fn is_valid(self) -> bool {
420 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
423 /// This describes the types that can be contained in a generator.
424 /// It will be a type variable initially and unified in the last stages of typeck of a body.
425 /// It contains a tuple of all the types that could end up on a generator frame.
426 /// The state transformation MIR pass may only produce layouts which mention types
427 /// in this tuple. Upvars are not counted here.
428 pub fn witness(self) -> Ty<'tcx> {
429 self.split().witness.expect_ty()
433 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
434 self.split().tupled_upvars_ty.expect_ty().tuple_fields()
437 /// Returns the type representing the resume type of the generator.
438 pub fn resume_ty(self) -> Ty<'tcx> {
439 self.split().resume_ty.expect_ty()
442 /// Returns the type representing the yield type of the generator.
443 pub fn yield_ty(self) -> Ty<'tcx> {
444 self.split().yield_ty.expect_ty()
447 /// Returns the type representing the return type of the generator.
448 pub fn return_ty(self) -> Ty<'tcx> {
449 self.split().return_ty.expect_ty()
452 /// Returns the "generator signature", which consists of its yield
453 /// and return types.
455 /// N.B., some bits of the code prefers to see this wrapped in a
456 /// binder, but it never contains bound regions. Probably this
457 /// function should be removed.
458 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
459 ty::Binder::dummy(self.sig())
462 /// Returns the "generator signature", which consists of its resume, yield
463 /// and return types.
464 pub fn sig(self) -> GenSig<'tcx> {
466 resume_ty: self.resume_ty(),
467 yield_ty: self.yield_ty(),
468 return_ty: self.return_ty(),
473 impl<'tcx> GeneratorSubsts<'tcx> {
474 /// Generator has not been resumed yet.
475 pub const UNRESUMED: usize = 0;
476 /// Generator has returned or is completed.
477 pub const RETURNED: usize = 1;
478 /// Generator has been poisoned.
479 pub const POISONED: usize = 2;
481 const UNRESUMED_NAME: &'static str = "Unresumed";
482 const RETURNED_NAME: &'static str = "Returned";
483 const POISONED_NAME: &'static str = "Panicked";
485 /// The valid variant indices of this generator.
487 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
488 // FIXME requires optimized MIR
489 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
490 VariantIdx::new(0)..VariantIdx::new(num_variants)
493 /// The discriminant for the given variant. Panics if the `variant_index` is
496 pub fn discriminant_for_variant(
500 variant_index: VariantIdx,
502 // Generators don't support explicit discriminant values, so they are
503 // the same as the variant index.
504 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
505 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
508 /// The set of all discriminants for the generator, enumerated with their
511 pub fn discriminants(
515 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
516 self.variant_range(def_id, tcx).map(move |index| {
517 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
521 /// Calls `f` with a reference to the name of the enumerator for the given
524 pub fn variant_name(self, v: VariantIdx) -> Cow<'static, str> {
526 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
527 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
528 Self::POISONED => Cow::from(Self::POISONED_NAME),
529 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
533 /// The type of the state discriminant used in the generator type.
535 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
539 /// This returns the types of the MIR locals which had to be stored across suspension points.
540 /// It is calculated in rustc_mir::transform::generator::StateTransform.
541 /// All the types here must be in the tuple in GeneratorInterior.
543 /// The locals are grouped by their variant number. Note that some locals may
544 /// be repeated in multiple variants.
550 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
551 let layout = tcx.generator_layout(def_id);
552 layout.variant_fields.iter().map(move |variant| {
553 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
557 /// This is the types of the fields of a generator which are not stored in a
560 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
565 #[derive(Debug, Copy, Clone)]
566 pub enum UpvarSubsts<'tcx> {
567 Closure(SubstsRef<'tcx>),
568 Generator(SubstsRef<'tcx>),
571 impl<'tcx> UpvarSubsts<'tcx> {
573 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
574 let tupled_upvars_ty = match self {
575 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
576 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
578 tupled_upvars_ty.expect_ty().tuple_fields()
582 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, RustcEncodable, RustcDecodable)]
583 #[derive(HashStable, TypeFoldable)]
584 pub enum ExistentialPredicate<'tcx> {
585 /// E.g., `Iterator`.
586 Trait(ExistentialTraitRef<'tcx>),
587 /// E.g., `Iterator::Item = T`.
588 Projection(ExistentialProjection<'tcx>),
593 impl<'tcx> ExistentialPredicate<'tcx> {
594 /// Compares via an ordering that will not change if modules are reordered or other changes are
595 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
596 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
597 use self::ExistentialPredicate::*;
598 match (*self, *other) {
599 (Trait(_), Trait(_)) => Ordering::Equal,
600 (Projection(ref a), Projection(ref b)) => {
601 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
603 (AutoTrait(ref a), AutoTrait(ref b)) => {
604 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
606 (Trait(_), _) => Ordering::Less,
607 (Projection(_), Trait(_)) => Ordering::Greater,
608 (Projection(_), _) => Ordering::Less,
609 (AutoTrait(_), _) => Ordering::Greater,
614 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
615 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
616 use crate::ty::ToPredicate;
617 match *self.skip_binder() {
618 ExistentialPredicate::Trait(tr) => {
619 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate()
621 ExistentialPredicate::Projection(p) => {
622 ty::Predicate::Projection(Binder(p.with_self_ty(tcx, self_ty)))
624 ExistentialPredicate::AutoTrait(did) => {
626 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
627 trait_ref.without_const().to_predicate()
633 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx List<ExistentialPredicate<'tcx>> {}
635 impl<'tcx> List<ExistentialPredicate<'tcx>> {
636 /// Returns the "principal `DefId`" of this set of existential predicates.
638 /// A Rust trait object type consists (in addition to a lifetime bound)
639 /// of a set of trait bounds, which are separated into any number
640 /// of auto-trait bounds, and at most one non-auto-trait bound. The
641 /// non-auto-trait bound is called the "principal" of the trait
644 /// Only the principal can have methods or type parameters (because
645 /// auto traits can have neither of them). This is important, because
646 /// it means the auto traits can be treated as an unordered set (methods
647 /// would force an order for the vtable, while relating traits with
648 /// type parameters without knowing the order to relate them in is
649 /// a rather non-trivial task).
651 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
652 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
653 /// are the set `{Sync}`.
655 /// It is also possible to have a "trivial" trait object that
656 /// consists only of auto traits, with no principal - for example,
657 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
658 /// is `{Send, Sync}`, while there is no principal. These trait objects
659 /// have a "trivial" vtable consisting of just the size, alignment,
661 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
663 ExistentialPredicate::Trait(tr) => Some(tr),
668 pub fn principal_def_id(&self) -> Option<DefId> {
669 self.principal().map(|trait_ref| trait_ref.def_id)
673 pub fn projection_bounds<'a>(
675 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
676 self.iter().filter_map(|predicate| match *predicate {
677 ExistentialPredicate::Projection(projection) => Some(projection),
683 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
684 self.iter().filter_map(|predicate| match *predicate {
685 ExistentialPredicate::AutoTrait(did) => Some(did),
691 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
692 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
693 self.skip_binder().principal().map(Binder::bind)
696 pub fn principal_def_id(&self) -> Option<DefId> {
697 self.skip_binder().principal_def_id()
701 pub fn projection_bounds<'a>(
703 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
704 self.skip_binder().projection_bounds().map(Binder::bind)
708 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
709 self.skip_binder().auto_traits()
714 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
715 self.skip_binder().iter().cloned().map(Binder::bind)
719 /// A complete reference to a trait. These take numerous guises in syntax,
720 /// but perhaps the most recognizable form is in a where-clause:
724 /// This would be represented by a trait-reference where the `DefId` is the
725 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
726 /// and `U` as parameter 1.
728 /// Trait references also appear in object types like `Foo<U>`, but in
729 /// that case the `Self` parameter is absent from the substitutions.
731 /// Note that a `TraitRef` introduces a level of region binding, to
732 /// account for higher-ranked trait bounds like `T: for<'a> Foo<&'a U>`
733 /// or higher-ranked object types.
734 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
735 #[derive(HashStable, TypeFoldable)]
736 pub struct TraitRef<'tcx> {
738 pub substs: SubstsRef<'tcx>,
741 impl<'tcx> TraitRef<'tcx> {
742 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
743 TraitRef { def_id, substs }
746 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
747 /// are the parameters defined on trait.
748 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
749 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
753 pub fn self_ty(&self) -> Ty<'tcx> {
754 self.substs.type_at(0)
757 pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> + 'a {
758 // Select only the "input types" from a trait-reference. For
759 // now this is all the types that appear in the
760 // trait-reference, but it should eventually exclude
768 substs: SubstsRef<'tcx>,
769 ) -> ty::TraitRef<'tcx> {
770 let defs = tcx.generics_of(trait_id);
772 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
776 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
778 impl<'tcx> PolyTraitRef<'tcx> {
779 pub fn self_ty(&self) -> Ty<'tcx> {
780 self.skip_binder().self_ty()
783 pub fn def_id(&self) -> DefId {
784 self.skip_binder().def_id
787 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
788 // Note that we preserve binding levels
789 Binder(ty::TraitPredicate { trait_ref: *self.skip_binder() })
793 /// An existential reference to a trait, where `Self` is erased.
794 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
796 /// exists T. T: Trait<'a, 'b, X, Y>
798 /// The substitutions don't include the erased `Self`, only trait
799 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
800 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
801 #[derive(HashStable, TypeFoldable)]
802 pub struct ExistentialTraitRef<'tcx> {
804 pub substs: SubstsRef<'tcx>,
807 impl<'tcx> ExistentialTraitRef<'tcx> {
808 pub fn input_types<'b>(&'b self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> + 'b {
809 // Select only the "input types" from a trait-reference. For
810 // now this is all the types that appear in the
811 // trait-reference, but it should eventually exclude
816 pub fn erase_self_ty(
818 trait_ref: ty::TraitRef<'tcx>,
819 ) -> ty::ExistentialTraitRef<'tcx> {
820 // Assert there is a Self.
821 trait_ref.substs.type_at(0);
823 ty::ExistentialTraitRef {
824 def_id: trait_ref.def_id,
825 substs: tcx.intern_substs(&trait_ref.substs[1..]),
829 /// Object types don't have a self type specified. Therefore, when
830 /// we convert the principal trait-ref into a normal trait-ref,
831 /// you must give *some* self type. A common choice is `mk_err()`
832 /// or some placeholder type.
833 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
834 // otherwise the escaping vars would be captured by the binder
835 // debug_assert!(!self_ty.has_escaping_bound_vars());
837 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
841 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
843 impl<'tcx> PolyExistentialTraitRef<'tcx> {
844 pub fn def_id(&self) -> DefId {
845 self.skip_binder().def_id
848 /// Object types don't have a self type specified. Therefore, when
849 /// we convert the principal trait-ref into a normal trait-ref,
850 /// you must give *some* self type. A common choice is `mk_err()`
851 /// or some placeholder type.
852 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
853 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
857 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
858 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
859 /// (which would be represented by the type `PolyTraitRef ==
860 /// Binder<TraitRef>`). Note that when we instantiate,
861 /// erase, or otherwise "discharge" these bound vars, we change the
862 /// type from `Binder<T>` to just `T` (see
863 /// e.g., `liberate_late_bound_regions`).
864 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
865 pub struct Binder<T>(T);
868 /// Wraps `value` in a binder, asserting that `value` does not
869 /// contain any bound vars that would be bound by the
870 /// binder. This is commonly used to 'inject' a value T into a
871 /// different binding level.
872 pub fn dummy<'tcx>(value: T) -> Binder<T>
874 T: TypeFoldable<'tcx>,
876 debug_assert!(!value.has_escaping_bound_vars());
880 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
881 pub fn bind(value: T) -> Binder<T> {
885 /// Skips the binder and returns the "bound" value. This is a
886 /// risky thing to do because it's easy to get confused about
887 /// De Bruijn indices and the like. It is usually better to
888 /// discharge the binder using `no_bound_vars` or
889 /// `replace_late_bound_regions` or something like
890 /// that. `skip_binder` is only valid when you are either
891 /// extracting data that has nothing to do with bound vars, you
892 /// are doing some sort of test that does not involve bound
893 /// regions, or you are being very careful about your depth
896 /// Some examples where `skip_binder` is reasonable:
898 /// - extracting the `DefId` from a PolyTraitRef;
899 /// - comparing the self type of a PolyTraitRef to see if it is equal to
900 /// a type parameter `X`, since the type `X` does not reference any regions
901 pub fn skip_binder(&self) -> &T {
905 pub fn as_ref(&self) -> Binder<&T> {
909 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
913 self.as_ref().map_bound(f)
916 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
923 /// Unwraps and returns the value within, but only if it contains
924 /// no bound vars at all. (In other words, if this binder --
925 /// and indeed any enclosing binder -- doesn't bind anything at
926 /// all.) Otherwise, returns `None`.
928 /// (One could imagine having a method that just unwraps a single
929 /// binder, but permits late-bound vars bound by enclosing
930 /// binders, but that would require adjusting the debruijn
931 /// indices, and given the shallow binding structure we often use,
932 /// would not be that useful.)
933 pub fn no_bound_vars<'tcx>(self) -> Option<T>
935 T: TypeFoldable<'tcx>,
937 if self.skip_binder().has_escaping_bound_vars() {
940 Some(self.skip_binder().clone())
944 /// Given two things that have the same binder level,
945 /// and an operation that wraps on their contents, executes the operation
946 /// and then wraps its result.
948 /// `f` should consider bound regions at depth 1 to be free, and
949 /// anything it produces with bound regions at depth 1 will be
950 /// bound in the resulting return value.
951 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
953 F: FnOnce(T, U) -> R,
955 Binder(f(self.0, u.0))
958 /// Splits the contents into two things that share the same binder
959 /// level as the original, returning two distinct binders.
961 /// `f` should consider bound regions at depth 1 to be free, and
962 /// anything it produces with bound regions at depth 1 will be
963 /// bound in the resulting return values.
964 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
966 F: FnOnce(T) -> (U, V),
968 let (u, v) = f(self.0);
969 (Binder(u), Binder(v))
973 /// Represents the projection of an associated type. In explicit UFCS
974 /// form this would be written `<T as Trait<..>>::N`.
975 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
976 #[derive(HashStable, TypeFoldable)]
977 pub struct ProjectionTy<'tcx> {
978 /// The parameters of the associated item.
979 pub substs: SubstsRef<'tcx>,
981 /// The `DefId` of the `TraitItem` for the associated type `N`.
983 /// Note that this is not the `DefId` of the `TraitRef` containing this
984 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
985 pub item_def_id: DefId,
988 impl<'tcx> ProjectionTy<'tcx> {
989 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
990 /// associated item named `item_name`.
991 pub fn from_ref_and_name(
993 trait_ref: ty::TraitRef<'tcx>,
995 ) -> ProjectionTy<'tcx> {
996 let item_def_id = tcx
997 .associated_items(trait_ref.def_id)
998 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
1002 ProjectionTy { substs: trait_ref.substs, item_def_id }
1005 /// Extracts the underlying trait reference from this projection.
1006 /// For example, if this is a projection of `<T as Iterator>::Item`,
1007 /// then this function would return a `T: Iterator` trait reference.
1008 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1009 let def_id = tcx.associated_item(self.item_def_id).container.id();
1010 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1013 pub fn self_ty(&self) -> Ty<'tcx> {
1014 self.substs.type_at(0)
1018 #[derive(Clone, Debug, TypeFoldable)]
1019 pub struct GenSig<'tcx> {
1020 pub resume_ty: Ty<'tcx>,
1021 pub yield_ty: Ty<'tcx>,
1022 pub return_ty: Ty<'tcx>,
1025 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1027 impl<'tcx> PolyGenSig<'tcx> {
1028 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1029 self.map_bound_ref(|sig| sig.resume_ty)
1031 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1032 self.map_bound_ref(|sig| sig.yield_ty)
1034 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1035 self.map_bound_ref(|sig| sig.return_ty)
1039 /// Signature of a function type, which we have arbitrarily
1040 /// decided to use to refer to the input/output types.
1042 /// - `inputs`: is the list of arguments and their modes.
1043 /// - `output`: is the return type.
1044 /// - `c_variadic`: indicates whether this is a C-variadic function.
1045 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1046 #[derive(HashStable, TypeFoldable)]
1047 pub struct FnSig<'tcx> {
1048 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1049 pub c_variadic: bool,
1050 pub unsafety: hir::Unsafety,
1054 impl<'tcx> FnSig<'tcx> {
1055 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1056 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1059 pub fn output(&self) -> Ty<'tcx> {
1060 self.inputs_and_output[self.inputs_and_output.len() - 1]
1063 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1065 fn fake() -> FnSig<'tcx> {
1067 inputs_and_output: List::empty(),
1069 unsafety: hir::Unsafety::Normal,
1070 abi: abi::Abi::Rust,
1075 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1077 impl<'tcx> PolyFnSig<'tcx> {
1079 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1080 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1083 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1084 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1086 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1087 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1090 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1091 self.map_bound_ref(|fn_sig| fn_sig.output())
1093 pub fn c_variadic(&self) -> bool {
1094 self.skip_binder().c_variadic
1096 pub fn unsafety(&self) -> hir::Unsafety {
1097 self.skip_binder().unsafety
1099 pub fn abi(&self) -> abi::Abi {
1100 self.skip_binder().abi
1104 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1106 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1107 #[derive(HashStable)]
1108 pub struct ParamTy {
1113 impl<'tcx> ParamTy {
1114 pub fn new(index: u32, name: Symbol) -> ParamTy {
1115 ParamTy { index, name }
1118 pub fn for_self() -> ParamTy {
1119 ParamTy::new(0, kw::SelfUpper)
1122 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1123 ParamTy::new(def.index, def.name)
1126 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1127 tcx.mk_ty_param(self.index, self.name)
1131 #[derive(Copy, Clone, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
1132 #[derive(HashStable)]
1133 pub struct ParamConst {
1138 impl<'tcx> ParamConst {
1139 pub fn new(index: u32, name: Symbol) -> ParamConst {
1140 ParamConst { index, name }
1143 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1144 ParamConst::new(def.index, def.name)
1147 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Const<'tcx> {
1148 tcx.mk_const_param(self.index, self.name, ty)
1152 rustc_index::newtype_index! {
1153 /// A [De Bruijn index][dbi] is a standard means of representing
1154 /// regions (and perhaps later types) in a higher-ranked setting. In
1155 /// particular, imagine a type like this:
1157 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1160 /// | +------------+ 0 | |
1162 /// +--------------------------------+ 1 |
1164 /// +------------------------------------------+ 0
1166 /// In this type, there are two binders (the outer fn and the inner
1167 /// fn). We need to be able to determine, for any given region, which
1168 /// fn type it is bound by, the inner or the outer one. There are
1169 /// various ways you can do this, but a De Bruijn index is one of the
1170 /// more convenient and has some nice properties. The basic idea is to
1171 /// count the number of binders, inside out. Some examples should help
1172 /// clarify what I mean.
1174 /// Let's start with the reference type `&'b isize` that is the first
1175 /// argument to the inner function. This region `'b` is assigned a De
1176 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1177 /// fn). The region `'a` that appears in the second argument type (`&'a
1178 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1179 /// second-innermost binder". (These indices are written on the arrays
1180 /// in the diagram).
1182 /// What is interesting is that De Bruijn index attached to a particular
1183 /// variable will vary depending on where it appears. For example,
1184 /// the final type `&'a char` also refers to the region `'a` declared on
1185 /// the outermost fn. But this time, this reference is not nested within
1186 /// any other binders (i.e., it is not an argument to the inner fn, but
1187 /// rather the outer one). Therefore, in this case, it is assigned a
1188 /// De Bruijn index of 0, because the innermost binder in that location
1189 /// is the outer fn.
1191 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1192 #[derive(HashStable)]
1193 pub struct DebruijnIndex {
1194 DEBUG_FORMAT = "DebruijnIndex({})",
1195 const INNERMOST = 0,
1199 pub type Region<'tcx> = &'tcx RegionKind;
1201 /// Representation of (lexical) regions. Note that the NLL checker
1202 /// uses a distinct representation of regions. For this reason, it
1203 /// internally replaces all the regions with inference variables --
1204 /// the index of the variable is then used to index into internal NLL
1205 /// data structures. See `rustc_mir::borrow_check` module for more
1208 /// ## The Region lattice within a given function
1210 /// In general, the (lexical, and hence deprecated) region lattice
1214 /// static ----------+-----...------+ (greatest)
1216 /// early-bound and | |
1217 /// free regions | |
1219 /// scope regions | |
1221 /// empty(root) placeholder(U1) |
1223 /// | / placeholder(Un)
1228 /// empty(Un) -------- (smallest)
1231 /// Early-bound/free regions are the named lifetimes in scope from the
1232 /// function declaration. They have relationships to one another
1233 /// determined based on the declared relationships from the
1234 /// function. They all collectively outlive the scope regions. (See
1235 /// `RegionRelations` type, and particularly
1236 /// `crate::infer::outlives::free_region_map::FreeRegionMap`.)
1238 /// The scope regions are related to one another based on the AST
1239 /// structure. (See `RegionRelations` type, and particularly the
1240 /// `rustc_middle::middle::region::ScopeTree`.)
1242 /// Note that inference variables and bound regions are not included
1243 /// in this diagram. In the case of inference variables, they should
1244 /// be inferred to some other region from the diagram. In the case of
1245 /// bound regions, they are excluded because they don't make sense to
1246 /// include -- the diagram indicates the relationship between free
1249 /// ## Inference variables
1251 /// During region inference, we sometimes create inference variables,
1252 /// represented as `ReVar`. These will be inferred by the code in
1253 /// `infer::lexical_region_resolve` to some free region from the
1254 /// lattice above (the minimal region that meets the
1257 /// During NLL checking, where regions are defined differently, we
1258 /// also use `ReVar` -- in that case, the index is used to index into
1259 /// the NLL region checker's data structures. The variable may in fact
1260 /// represent either a free region or an inference variable, in that
1263 /// ## Bound Regions
1265 /// These are regions that are stored behind a binder and must be substituted
1266 /// with some concrete region before being used. There are two kind of
1267 /// bound regions: early-bound, which are bound in an item's `Generics`,
1268 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1269 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1270 /// the likes of `liberate_late_bound_regions`. The distinction exists
1271 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1273 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1274 /// outside their binder, e.g., in types passed to type inference, and
1275 /// should first be substituted (by placeholder regions, free regions,
1276 /// or region variables).
1278 /// ## Placeholder and Free Regions
1280 /// One often wants to work with bound regions without knowing their precise
1281 /// identity. For example, when checking a function, the lifetime of a borrow
1282 /// can end up being assigned to some region parameter. In these cases,
1283 /// it must be ensured that bounds on the region can't be accidentally
1284 /// assumed without being checked.
1286 /// To do this, we replace the bound regions with placeholder markers,
1287 /// which don't satisfy any relation not explicitly provided.
1289 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1290 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1291 /// to be used. These also support explicit bounds: both the internally-stored
1292 /// *scope*, which the region is assumed to outlive, as well as other
1293 /// relations stored in the `FreeRegionMap`. Note that these relations
1294 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1295 /// `resolve_regions_and_report_errors`.
1297 /// When working with higher-ranked types, some region relations aren't
1298 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1299 /// `RePlaceholder` is designed for this purpose. In these contexts,
1300 /// there's also the risk that some inference variable laying around will
1301 /// get unified with your placeholder region: if you want to check whether
1302 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1303 /// with a placeholder region `'%a`, the variable `'_` would just be
1304 /// instantiated to the placeholder region `'%a`, which is wrong because
1305 /// the inference variable is supposed to satisfy the relation
1306 /// *for every value of the placeholder region*. To ensure that doesn't
1307 /// happen, you can use `leak_check`. This is more clearly explained
1308 /// by the [rustc dev guide].
1310 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1311 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1312 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1313 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable, PartialOrd, Ord)]
1314 pub enum RegionKind {
1315 /// Region bound in a type or fn declaration which will be
1316 /// substituted 'early' -- that is, at the same time when type
1317 /// parameters are substituted.
1318 ReEarlyBound(EarlyBoundRegion),
1320 /// Region bound in a function scope, which will be substituted when the
1321 /// function is called.
1322 ReLateBound(DebruijnIndex, BoundRegion),
1324 /// When checking a function body, the types of all arguments and so forth
1325 /// that refer to bound region parameters are modified to refer to free
1326 /// region parameters.
1329 /// A concrete region naming some statically determined scope
1330 /// (e.g., an expression or sequence of statements) within the
1331 /// current function.
1332 ReScope(region::Scope),
1334 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1337 /// A region variable. Should not exist after typeck.
1340 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1341 /// Should not exist after typeck.
1342 RePlaceholder(ty::PlaceholderRegion),
1344 /// Empty lifetime is for data that is never accessed. We tag the
1345 /// empty lifetime with a universe -- the idea is that we don't
1346 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1347 /// Therefore, the `'empty` in a universe `U` is less than all
1348 /// regions visible from `U`, but not less than regions not visible
1350 ReEmpty(ty::UniverseIndex),
1352 /// Erased region, used by trait selection, in MIR and during codegen.
1356 impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
1358 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, PartialOrd, Ord)]
1359 pub struct EarlyBoundRegion {
1365 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1370 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1371 pub struct ConstVid<'tcx> {
1373 pub phantom: PhantomData<&'tcx ()>,
1376 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1381 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1382 pub struct FloatVid {
1386 rustc_index::newtype_index! {
1387 pub struct RegionVid {
1388 DEBUG_FORMAT = custom,
1392 impl Atom for RegionVid {
1393 fn index(self) -> usize {
1398 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1399 #[derive(HashStable)]
1405 /// A `FreshTy` is one that is generated as a replacement for an
1406 /// unbound type variable. This is convenient for caching etc. See
1407 /// `infer::freshen` for more details.
1413 rustc_index::newtype_index! {
1414 pub struct BoundVar { .. }
1417 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1418 #[derive(HashStable)]
1419 pub struct BoundTy {
1421 pub kind: BoundTyKind,
1424 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1425 #[derive(HashStable)]
1426 pub enum BoundTyKind {
1431 impl From<BoundVar> for BoundTy {
1432 fn from(var: BoundVar) -> Self {
1433 BoundTy { var, kind: BoundTyKind::Anon }
1437 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1438 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1439 #[derive(HashStable, TypeFoldable)]
1440 pub struct ExistentialProjection<'tcx> {
1441 pub item_def_id: DefId,
1442 pub substs: SubstsRef<'tcx>,
1446 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1448 impl<'tcx> ExistentialProjection<'tcx> {
1449 /// Extracts the underlying existential trait reference from this projection.
1450 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1451 /// then this function would return a `exists T. T: Iterator` existential trait
1453 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1454 let def_id = tcx.associated_item(self.item_def_id).container.id();
1455 ty::ExistentialTraitRef { def_id, substs: self.substs }
1458 pub fn with_self_ty(
1462 ) -> ty::ProjectionPredicate<'tcx> {
1463 // otherwise the escaping regions would be captured by the binders
1464 debug_assert!(!self_ty.has_escaping_bound_vars());
1466 ty::ProjectionPredicate {
1467 projection_ty: ty::ProjectionTy {
1468 item_def_id: self.item_def_id,
1469 substs: tcx.mk_substs_trait(self_ty, self.substs),
1476 impl<'tcx> PolyExistentialProjection<'tcx> {
1477 pub fn with_self_ty(
1481 ) -> ty::PolyProjectionPredicate<'tcx> {
1482 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1485 pub fn item_def_id(&self) -> DefId {
1486 self.skip_binder().item_def_id
1490 impl DebruijnIndex {
1491 /// Returns the resulting index when this value is moved into
1492 /// `amount` number of new binders. So, e.g., if you had
1494 /// for<'a> fn(&'a x)
1496 /// and you wanted to change it to
1498 /// for<'a> fn(for<'b> fn(&'a x))
1500 /// you would need to shift the index for `'a` into a new binder.
1502 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1503 DebruijnIndex::from_u32(self.as_u32() + amount)
1506 /// Update this index in place by shifting it "in" through
1507 /// `amount` number of binders.
1508 pub fn shift_in(&mut self, amount: u32) {
1509 *self = self.shifted_in(amount);
1512 /// Returns the resulting index when this value is moved out from
1513 /// `amount` number of new binders.
1515 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1516 DebruijnIndex::from_u32(self.as_u32() - amount)
1519 /// Update in place by shifting out from `amount` binders.
1520 pub fn shift_out(&mut self, amount: u32) {
1521 *self = self.shifted_out(amount);
1524 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1525 /// innermost binder. That is, if we have something bound at `to_binder`,
1526 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1527 /// when moving a region out from inside binders:
1530 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1531 /// // Binder: D3 D2 D1 ^^
1534 /// Here, the region `'a` would have the De Bruijn index D3,
1535 /// because it is the bound 3 binders out. However, if we wanted
1536 /// to refer to that region `'a` in the second argument (the `_`),
1537 /// those two binders would not be in scope. In that case, we
1538 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1539 /// De Bruijn index of `'a` to D1 (the innermost binder).
1541 /// If we invoke `shift_out_to_binder` and the region is in fact
1542 /// bound by one of the binders we are shifting out of, that is an
1543 /// error (and should fail an assertion failure).
1544 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1545 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1549 /// Region utilities
1551 /// Is this region named by the user?
1552 pub fn has_name(&self) -> bool {
1554 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1555 RegionKind::ReLateBound(_, br) => br.is_named(),
1556 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1557 RegionKind::ReScope(..) => false,
1558 RegionKind::ReStatic => true,
1559 RegionKind::ReVar(..) => false,
1560 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1561 RegionKind::ReEmpty(_) => false,
1562 RegionKind::ReErased => false,
1566 pub fn is_late_bound(&self) -> bool {
1568 ty::ReLateBound(..) => true,
1573 pub fn is_placeholder(&self) -> bool {
1575 ty::RePlaceholder(..) => true,
1580 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1582 ty::ReLateBound(debruijn, _) => debruijn >= index,
1587 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1588 /// innermost binder. That is, if we have something bound at `to_binder`,
1589 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1590 /// when moving a region out from inside binders:
1593 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1594 /// // Binder: D3 D2 D1 ^^
1597 /// Here, the region `'a` would have the De Bruijn index D3,
1598 /// because it is the bound 3 binders out. However, if we wanted
1599 /// to refer to that region `'a` in the second argument (the `_`),
1600 /// those two binders would not be in scope. In that case, we
1601 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1602 /// De Bruijn index of `'a` to D1 (the innermost binder).
1604 /// If we invoke `shift_out_to_binder` and the region is in fact
1605 /// bound by one of the binders we are shifting out of, that is an
1606 /// error (and should fail an assertion failure).
1607 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1609 ty::ReLateBound(debruijn, r) => {
1610 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1616 pub fn type_flags(&self) -> TypeFlags {
1617 let mut flags = TypeFlags::empty();
1621 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1622 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1623 flags = flags | TypeFlags::HAS_RE_INFER;
1624 flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
1625 flags = flags | TypeFlags::STILL_FURTHER_SPECIALIZABLE;
1627 ty::RePlaceholder(..) => {
1628 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1629 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1630 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1631 flags = flags | TypeFlags::STILL_FURTHER_SPECIALIZABLE;
1633 ty::ReEarlyBound(..) => {
1634 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1635 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1636 flags = flags | TypeFlags::HAS_RE_PARAM;
1637 flags = flags | TypeFlags::STILL_FURTHER_SPECIALIZABLE;
1639 ty::ReFree { .. } | ty::ReScope { .. } => {
1640 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1641 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1643 ty::ReEmpty(_) | ty::ReStatic => {
1644 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1646 ty::ReLateBound(..) => {
1647 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1650 flags = flags | TypeFlags::HAS_RE_ERASED;
1654 debug!("type_flags({:?}) = {:?}", self, flags);
1659 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1660 /// For example, consider the regions in this snippet of code:
1664 /// ^^ -- early bound, declared on an impl
1666 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1667 /// ^^ ^^ ^ anonymous, late-bound
1668 /// | early-bound, appears in where-clauses
1669 /// late-bound, appears only in fn args
1674 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1675 /// of the impl, and for all the other highlighted regions, it
1676 /// would return the `DefId` of the function. In other cases (not shown), this
1677 /// function might return the `DefId` of a closure.
1678 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1680 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1681 ty::ReFree(fr) => fr.scope,
1682 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1688 impl<'tcx> TyS<'tcx> {
1690 pub fn is_unit(&self) -> bool {
1692 Tuple(ref tys) => tys.is_empty(),
1698 pub fn is_never(&self) -> bool {
1705 /// Checks whether a type is definitely uninhabited. This is
1706 /// conservative: for some types that are uninhabited we return `false`,
1707 /// but we only return `true` for types that are definitely uninhabited.
1708 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1709 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1710 /// size, to account for partial initialisation. See #49298 for details.)
1711 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1712 // FIXME(varkor): we can make this less conversative by substituting concrete
1716 ty::Adt(def, _) if def.is_union() => {
1717 // For now, `union`s are never considered uninhabited.
1720 ty::Adt(def, _) => {
1721 // Any ADT is uninhabited if either:
1722 // (a) It has no variants (i.e. an empty `enum`);
1723 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1724 // one uninhabited field.
1725 def.variants.iter().all(|var| {
1726 var.fields.iter().any(|field| {
1727 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1732 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1734 ty::Array(ty, len) => {
1735 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1736 // If the array is definitely non-empty, it's uninhabited if
1737 // the type of its elements is uninhabited.
1738 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1743 // References to uninitialised memory is valid for any type, including
1744 // uninhabited types, in unsafe code, so we treat all references as
1753 pub fn is_primitive(&self) -> bool {
1755 Bool | Char | Int(_) | Uint(_) | Float(_) => true,
1761 pub fn is_ty_var(&self) -> bool {
1763 Infer(TyVar(_)) => true,
1769 pub fn is_ty_infer(&self) -> bool {
1777 pub fn is_phantom_data(&self) -> bool {
1778 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1782 pub fn is_bool(&self) -> bool {
1786 /// Returns `true` if this type is a `str`.
1788 pub fn is_str(&self) -> bool {
1793 pub fn is_param(&self, index: u32) -> bool {
1795 ty::Param(ref data) => data.index == index,
1801 pub fn is_slice(&self) -> bool {
1803 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1804 Slice(_) | Str => true,
1812 pub fn is_simd(&self) -> bool {
1814 Adt(def, _) => def.repr.simd(),
1819 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1821 Array(ty, _) | Slice(ty) => ty,
1822 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1823 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1827 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1829 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1830 _ => bug!("`simd_type` called on invalid type"),
1834 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1835 // Parameter currently unused, but probably needed in the future to
1836 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1838 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1839 _ => bug!("`simd_size` called on invalid type"),
1843 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1845 Adt(def, substs) => {
1846 let variant = def.non_enum_variant();
1847 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1849 _ => bug!("`simd_size_and_type` called on invalid type"),
1854 pub fn is_region_ptr(&self) -> bool {
1862 pub fn is_mutable_ptr(&self) -> bool {
1864 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1865 | Ref(_, _, hir::Mutability::Mut) => true,
1871 pub fn is_unsafe_ptr(&self) -> bool {
1878 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1880 pub fn is_any_ptr(&self) -> bool {
1881 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1884 /// Returns `true` if this type is an `Arc<T>`.
1886 pub fn is_arc(&self) -> bool {
1888 Adt(def, _) => def.is_arc(),
1893 /// Returns `true` if this type is an `Rc<T>`.
1895 pub fn is_rc(&self) -> bool {
1897 Adt(def, _) => def.is_rc(),
1903 pub fn is_box(&self) -> bool {
1905 Adt(def, _) => def.is_box(),
1910 /// Panics if called on any type other than `Box<T>`.
1911 pub fn boxed_ty(&self) -> Ty<'tcx> {
1913 Adt(def, substs) if def.is_box() => substs.type_at(0),
1914 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1918 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1919 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1920 /// contents are abstract to rustc.)
1922 pub fn is_scalar(&self) -> bool {
1924 Bool | Char | Int(_) | Float(_) | Uint(_) | Infer(IntVar(_)) | Infer(FloatVar(_))
1925 | FnDef(..) | FnPtr(_) | RawPtr(_) => true,
1930 /// Returns `true` if this type is a floating point type.
1932 pub fn is_floating_point(&self) -> bool {
1934 Float(_) | Infer(FloatVar(_)) => true,
1940 pub fn is_trait(&self) -> bool {
1942 Dynamic(..) => true,
1948 pub fn is_enum(&self) -> bool {
1950 Adt(adt_def, _) => adt_def.is_enum(),
1956 pub fn is_closure(&self) -> bool {
1958 Closure(..) => true,
1964 pub fn is_generator(&self) -> bool {
1966 Generator(..) => true,
1972 pub fn is_integral(&self) -> bool {
1974 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
1980 pub fn is_fresh_ty(&self) -> bool {
1982 Infer(FreshTy(_)) => true,
1988 pub fn is_fresh(&self) -> bool {
1990 Infer(FreshTy(_)) => true,
1991 Infer(FreshIntTy(_)) => true,
1992 Infer(FreshFloatTy(_)) => true,
1998 pub fn is_char(&self) -> bool {
2006 pub fn is_numeric(&self) -> bool {
2007 self.is_integral() || self.is_floating_point()
2011 pub fn is_signed(&self) -> bool {
2019 pub fn is_ptr_sized_integral(&self) -> bool {
2021 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
2027 pub fn is_machine(&self) -> bool {
2029 Int(..) | Uint(..) | Float(..) => true,
2035 pub fn has_concrete_skeleton(&self) -> bool {
2037 Param(_) | Infer(_) | Error => false,
2042 /// Returns the type and mutability of `*ty`.
2044 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2045 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2046 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2048 Adt(def, _) if def.is_box() => {
2049 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2051 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2052 RawPtr(mt) if explicit => Some(mt),
2057 /// Returns the type of `ty[i]`.
2058 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2060 Array(ty, _) | Slice(ty) => Some(ty),
2065 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2067 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2070 // ignore errors (#54954)
2071 ty::Binder::dummy(FnSig::fake())
2073 Closure(..) => bug!(
2074 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2076 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2081 pub fn is_fn(&self) -> bool {
2083 FnDef(..) | FnPtr(_) => true,
2089 pub fn is_fn_ptr(&self) -> bool {
2097 pub fn is_impl_trait(&self) -> bool {
2105 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2107 Adt(adt, _) => Some(adt),
2112 /// Iterates over tuple fields.
2113 /// Panics when called on anything but a tuple.
2114 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2116 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2117 _ => bug!("tuple_fields called on non-tuple"),
2121 /// If the type contains variants, returns the valid range of variant indices.
2123 // FIXME: This requires the optimized MIR in the case of generators.
2125 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2127 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2128 TyKind::Generator(def_id, substs, _) => {
2129 Some(substs.as_generator().variant_range(def_id, tcx))
2135 /// If the type contains variants, returns the variant for `variant_index`.
2136 /// Panics if `variant_index` is out of range.
2138 // FIXME: This requires the optimized MIR in the case of generators.
2140 pub fn discriminant_for_variant(
2143 variant_index: VariantIdx,
2144 ) -> Option<Discr<'tcx>> {
2146 TyKind::Adt(adt, _) => Some(adt.discriminant_for_variant(tcx, variant_index)),
2147 TyKind::Generator(def_id, substs, _) => {
2148 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2154 /// When we create a closure, we record its kind (i.e., what trait
2155 /// it implements) into its `ClosureSubsts` using a type
2156 /// parameter. This is kind of a phantom type, except that the
2157 /// most convenient thing for us to are the integral types. This
2158 /// function converts such a special type into the closure
2159 /// kind. To go the other way, use
2160 /// `tcx.closure_kind_ty(closure_kind)`.
2162 /// Note that during type checking, we use an inference variable
2163 /// to represent the closure kind, because it has not yet been
2164 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2165 /// is complete, that type variable will be unified.
2166 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2168 Int(int_ty) => match int_ty {
2169 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2170 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2171 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2172 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2175 // "Bound" types appear in canonical queries when the
2176 // closure type is not yet known
2177 Bound(..) | Infer(_) => None,
2179 Error => Some(ty::ClosureKind::Fn),
2181 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2185 /// Fast path helper for testing if a type is `Sized`.
2187 /// Returning true means the type is known to be sized. Returning
2188 /// `false` means nothing -- could be sized, might not be.
2189 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2191 ty::Infer(ty::IntVar(_))
2192 | ty::Infer(ty::FloatVar(_))
2203 | ty::GeneratorWitness(..)
2207 | ty::Error => true,
2209 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2211 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2213 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2215 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2217 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
2219 ty::Infer(ty::TyVar(_)) => false,
2222 | ty::Placeholder(..)
2223 | ty::Infer(ty::FreshTy(_))
2224 | ty::Infer(ty::FreshIntTy(_))
2225 | ty::Infer(ty::FreshFloatTy(_)) => {
2226 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2232 /// Typed constant value.
2233 #[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
2234 #[derive(HashStable)]
2235 pub struct Const<'tcx> {
2238 pub val: ConstKind<'tcx>,
2241 #[cfg(target_arch = "x86_64")]
2242 static_assert_size!(Const<'_>, 48);
2244 impl<'tcx> Const<'tcx> {
2245 /// Literals and const generic parameters are eagerly converted to a constant, everything else
2246 /// becomes `Unevaluated`.
2247 pub fn from_anon_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx Self {
2248 debug!("Const::from_anon_const(id={:?})", def_id);
2250 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2252 let body_id = match tcx.hir().get(hir_id) {
2253 hir::Node::AnonConst(ac) => ac.body,
2255 tcx.def_span(def_id.to_def_id()),
2256 "from_anon_const can only process anonymous constants"
2260 let expr = &tcx.hir().body(body_id).value;
2262 let ty = tcx.type_of(def_id.to_def_id());
2264 let lit_input = match expr.kind {
2265 hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
2266 hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind {
2267 hir::ExprKind::Lit(ref lit) => {
2268 Some(LitToConstInput { lit: &lit.node, ty, neg: true })
2275 if let Some(lit_input) = lit_input {
2276 // If an error occurred, ignore that it's a literal and leave reporting the error up to
2278 if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
2281 tcx.sess.delay_span_bug(expr.span, "Const::from_anon_const: couldn't lit_to_const");
2285 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
2286 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
2287 let expr = match &expr.kind {
2288 hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
2289 block.expr.as_ref().unwrap()
2294 use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
2295 let val = match expr.kind {
2296 ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
2297 // Find the name and index of the const parameter by indexing the generics of
2298 // the parent item and construct a `ParamConst`.
2299 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2300 let item_id = tcx.hir().get_parent_node(hir_id);
2301 let item_def_id = tcx.hir().local_def_id(item_id);
2302 let generics = tcx.generics_of(item_def_id);
2303 let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
2304 let name = tcx.hir().name(hir_id);
2305 ty::ConstKind::Param(ty::ParamConst::new(index, name))
2307 _ => ty::ConstKind::Unevaluated(
2309 InternalSubsts::identity_for_item(tcx, def_id.to_def_id()),
2314 tcx.mk_const(ty::Const { val, ty })
2318 /// Interns the given value as a constant.
2319 pub fn from_value(tcx: TyCtxt<'tcx>, val: ConstValue<'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
2320 tcx.mk_const(Self { val: ConstKind::Value(val), ty })
2324 /// Interns the given scalar as a constant.
2325 pub fn from_scalar(tcx: TyCtxt<'tcx>, val: Scalar, ty: Ty<'tcx>) -> &'tcx Self {
2326 Self::from_value(tcx, ConstValue::Scalar(val), ty)
2330 /// Creates a constant with the given integer value and interns it.
2331 pub fn from_bits(tcx: TyCtxt<'tcx>, bits: u128, ty: ParamEnvAnd<'tcx, Ty<'tcx>>) -> &'tcx Self {
2334 .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
2336 Self::from_scalar(tcx, Scalar::from_uint(bits, size), ty.value)
2340 /// Creates an interned zst constant.
2341 pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
2342 Self::from_scalar(tcx, Scalar::zst(), ty)
2346 /// Creates an interned bool constant.
2347 pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> &'tcx Self {
2348 Self::from_bits(tcx, v as u128, ParamEnv::empty().and(tcx.types.bool))
2352 /// Creates an interned usize constant.
2353 pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> &'tcx Self {
2354 Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize))
2358 /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of
2359 /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it
2360 /// contains const generic parameters or pointers).
2361 pub fn try_eval_bits(
2364 param_env: ParamEnv<'tcx>,
2367 assert_eq!(self.ty, ty);
2368 let size = tcx.layout_of(param_env.with_reveal_all().and(ty)).ok()?.size;
2369 // if `ty` does not depend on generic parameters, use an empty param_env
2370 self.eval(tcx, param_env).val.try_to_bits(size)
2374 /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the
2375 /// unevaluated constant.
2376 pub fn eval(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> &Const<'tcx> {
2377 let try_const_eval = |did, param_env: ParamEnv<'tcx>, substs, promoted| {
2378 let param_env_and_substs = param_env.with_reveal_all().and(substs);
2380 // Avoid querying `tcx.const_eval(...)` with any e.g. inference vars.
2381 if param_env_and_substs.has_local_value() {
2385 let (param_env, substs) = param_env_and_substs.into_parts();
2387 // try to resolve e.g. associated constants to their definition on an impl, and then
2388 // evaluate the const.
2389 tcx.const_eval_resolve(param_env, did, substs, promoted, None)
2391 .map(|val| Const::from_value(tcx, val, self.ty))
2395 ConstKind::Unevaluated(did, substs, promoted) => {
2396 // HACK(eddyb) when substs contain e.g. inference variables,
2397 // attempt using identity substs instead, that will succeed
2398 // when the expression doesn't depend on any parameters.
2399 // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
2400 // we can call `infcx.const_eval_resolve` which handles inference variables.
2401 if substs.has_local_value() {
2402 let identity_substs = InternalSubsts::identity_for_item(tcx, did);
2403 // The `ParamEnv` needs to match the `identity_substs`.
2404 let identity_param_env = tcx.param_env(did);
2405 match try_const_eval(did, identity_param_env, identity_substs, promoted) {
2406 Some(ct) => ct.subst(tcx, substs),
2410 try_const_eval(did, param_env, substs, promoted).unwrap_or(self)
2418 pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> {
2419 self.try_eval_bits(tcx, param_env, tcx.types.bool).and_then(|v| match v {
2427 pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> {
2428 self.try_eval_bits(tcx, param_env, tcx.types.usize).map(|v| v as u64)
2432 /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
2433 pub fn eval_bits(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {
2434 self.try_eval_bits(tcx, param_env, ty)
2435 .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self))
2439 /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`.
2440 pub fn eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 {
2441 self.eval_bits(tcx, param_env, tcx.types.usize) as u64
2445 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx Const<'tcx> {}
2447 /// Represents a constant in Rust.
2448 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
2449 #[derive(HashStable)]
2450 pub enum ConstKind<'tcx> {
2451 /// A const generic parameter.
2454 /// Infer the value of the const.
2455 Infer(InferConst<'tcx>),
2457 /// Bound const variable, used only when preparing a trait query.
2458 Bound(DebruijnIndex, BoundVar),
2460 /// A placeholder const - universally quantified higher-ranked const.
2461 Placeholder(ty::PlaceholderConst),
2463 /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
2464 /// variants when the code is monomorphic enough for that.
2465 Unevaluated(DefId, SubstsRef<'tcx>, Option<Promoted>),
2467 /// Used to hold computed value.
2468 Value(ConstValue<'tcx>),
2471 #[cfg(target_arch = "x86_64")]
2472 static_assert_size!(ConstKind<'_>, 40);
2474 impl<'tcx> ConstKind<'tcx> {
2476 pub fn try_to_scalar(&self) -> Option<Scalar> {
2477 if let ConstKind::Value(val) = self { val.try_to_scalar() } else { None }
2481 pub fn try_to_bits(&self, size: Size) -> Option<u128> {
2482 if let ConstKind::Value(val) = self { val.try_to_bits(size) } else { None }
2486 /// An inference variable for a const, for use in const generics.
2487 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
2488 #[derive(HashStable)]
2489 pub enum InferConst<'tcx> {
2490 /// Infer the value of the const.
2491 Var(ConstVid<'tcx>),
2492 /// A fresh const variable. See `infer::freshen` for more details.