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;
20 use rustc_data_structures::captures::Captures;
21 use rustc_errors::ErrorReported;
23 use rustc_hir::def_id::{DefId, LocalDefId};
24 use rustc_index::vec::Idx;
25 use rustc_macros::HashStable;
26 use rustc_span::symbol::{kw, Ident, Symbol};
27 use rustc_target::abi::{Size, VariantIdx};
28 use rustc_target::spec::abi;
30 use std::cmp::Ordering;
31 use std::marker::PhantomData;
34 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
35 #[derive(HashStable, TypeFoldable, Lift)]
36 pub struct TypeAndMut<'tcx> {
38 pub mutbl: hir::Mutability,
41 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable, RustcDecodable, Copy)]
43 /// A "free" region `fr` can be interpreted as "some region
44 /// at least as big as the scope `fr.scope`".
45 pub struct FreeRegion {
47 pub bound_region: BoundRegion,
50 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable, RustcDecodable, Copy)]
52 pub enum BoundRegion {
53 /// An anonymous region parameter for a given fn (&T)
56 /// Named region parameters for functions (a in &'a T)
58 /// The `DefId` is needed to distinguish free regions in
59 /// the event of shadowing.
60 BrNamed(DefId, Symbol),
62 /// Anonymous region for the implicit env pointer parameter
68 pub fn is_named(&self) -> bool {
70 BoundRegion::BrNamed(_, name) => name != kw::UnderscoreLifetime,
75 /// When canonicalizing, we replace unbound inference variables and free
76 /// regions with anonymous late bound regions. This method asserts that
77 /// we have an anonymous late bound region, which hence may refer to
78 /// a canonical variable.
79 pub fn assert_bound_var(&self) -> BoundVar {
81 BoundRegion::BrAnon(var) => BoundVar::from_u32(var),
82 _ => bug!("bound region is not anonymous"),
87 /// N.B., if you change this, you'll probably want to change the corresponding
88 /// AST structure in `librustc_ast/ast.rs` as well.
89 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, Debug)]
91 #[rustc_diagnostic_item = "TyKind"]
92 pub enum TyKind<'tcx> {
93 /// The primitive boolean type. Written as `bool`.
96 /// The primitive character type; holds a Unicode scalar value
97 /// (a non-surrogate code point). Written as `char`.
100 /// A primitive signed integer type. For example, `i32`.
103 /// A primitive unsigned integer type. For example, `u32`.
106 /// A primitive floating-point type. For example, `f64`.
109 /// Structures, enumerations and unions.
111 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
112 /// That is, even after substitution it is possible that there are type
113 /// variables. This happens when the `Adt` corresponds to an ADT
114 /// definition and not a concrete use of it.
115 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
117 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
120 /// The pointee of a string slice. Written as `str`.
123 /// An array with the given length. Written as `[T; n]`.
124 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
126 /// The pointee of an array slice. Written as `[T]`.
129 /// A raw pointer. Written as `*mut T` or `*const T`
130 RawPtr(TypeAndMut<'tcx>),
132 /// A reference; a pointer with an associated lifetime. Written as
133 /// `&'a mut T` or `&'a T`.
134 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
136 /// The anonymous type of a function declaration/definition. Each
137 /// function has a unique type, which is output (for a function
138 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
140 /// For example the type of `bar` here:
143 /// fn foo() -> i32 { 1 }
144 /// let bar = foo; // bar: fn() -> i32 {foo}
146 FnDef(DefId, SubstsRef<'tcx>),
148 /// A pointer to a function. Written as `fn() -> i32`.
150 /// For example the type of `bar` here:
153 /// fn foo() -> i32 { 1 }
154 /// let bar: fn() -> i32 = foo;
156 FnPtr(PolyFnSig<'tcx>),
158 /// A trait, defined with `trait`.
159 Dynamic(Binder<&'tcx List<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
161 /// The anonymous type of a closure. Used to represent the type of
163 Closure(DefId, SubstsRef<'tcx>),
165 /// The anonymous type of a generator. Used to represent the type of
167 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
169 /// A type representin the types stored inside a generator.
170 /// This should only appear in GeneratorInteriors.
171 GeneratorWitness(Binder<&'tcx List<Ty<'tcx>>>),
173 /// The never type `!`
176 /// A tuple type. For example, `(i32, bool)`.
177 /// Use `TyS::tuple_fields` to iterate over the field types.
178 Tuple(SubstsRef<'tcx>),
180 /// The projection of an associated type. For example,
181 /// `<T as Trait<..>>::N`.
182 Projection(ProjectionTy<'tcx>),
184 /// Opaque (`impl Trait`) type found in a return type.
185 /// The `DefId` comes either from
186 /// * the `impl Trait` ast::Ty node,
187 /// * or the `type Foo = impl Trait` declaration
188 /// The substitutions are for the generics of the function in question.
189 /// After typeck, the concrete type can be found in the `types` map.
190 Opaque(DefId, SubstsRef<'tcx>),
192 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
195 /// Bound type variable, used only when preparing a trait query.
196 Bound(ty::DebruijnIndex, BoundTy),
198 /// A placeholder type - universally quantified higher-ranked type.
199 Placeholder(ty::PlaceholderType),
201 /// A type variable used during type checking.
204 /// A placeholder for a type which could not be computed; this is
205 /// propagated to avoid useless error messages.
209 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
210 #[cfg(target_arch = "x86_64")]
211 static_assert_size!(TyKind<'_>, 24);
213 /// A closure can be modeled as a struct that looks like:
215 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
219 /// - 'l0...'li and T0...Tj are the generic parameters
220 /// in scope on the function that defined the closure,
221 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
222 /// is rather hackily encoded via a scalar type. See
223 /// `TyS::to_opt_closure_kind` for details.
224 /// - CS represents the *closure signature*, representing as a `fn()`
225 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
226 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
228 /// - U is a type parameter representing the types of its upvars, tupled up
229 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
230 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
232 /// So, for example, given this function:
234 /// fn foo<'a, T>(data: &'a mut T) {
235 /// do(|| data.count += 1)
238 /// the type of the closure would be something like:
240 /// struct Closure<'a, T, U>(...U);
242 /// Note that the type of the upvar is not specified in the struct.
243 /// You may wonder how the impl would then be able to use the upvar,
244 /// if it doesn't know it's type? The answer is that the impl is
245 /// (conceptually) not fully generic over Closure but rather tied to
246 /// instances with the expected upvar types:
248 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
252 /// You can see that the *impl* fully specified the type of the upvar
253 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
254 /// (Here, I am assuming that `data` is mut-borrowed.)
256 /// Now, the last question you may ask is: Why include the upvar types
257 /// in an extra type parameter? The reason for this design is that the
258 /// upvar types can reference lifetimes that are internal to the
259 /// creating function. In my example above, for example, the lifetime
260 /// `'b` represents the scope of the closure itself; this is some
261 /// subset of `foo`, probably just the scope of the call to the to
262 /// `do()`. If we just had the lifetime/type parameters from the
263 /// enclosing function, we couldn't name this lifetime `'b`. Note that
264 /// there can also be lifetimes in the types of the upvars themselves,
265 /// if one of them happens to be a reference to something that the
266 /// creating fn owns.
268 /// OK, you say, so why not create a more minimal set of parameters
269 /// that just includes the extra lifetime parameters? The answer is
270 /// primarily that it would be hard --- we don't know at the time when
271 /// we create the closure type what the full types of the upvars are,
272 /// nor do we know which are borrowed and which are not. In this
273 /// design, we can just supply a fresh type parameter and figure that
276 /// All right, you say, but why include the type parameters from the
277 /// original function then? The answer is that codegen may need them
278 /// when monomorphizing, and they may not appear in the upvars. A
279 /// closure could capture no variables but still make use of some
280 /// in-scope type parameter with a bound (e.g., if our example above
281 /// had an extra `U: Default`, and the closure called `U::default()`).
283 /// There is another reason. This design (implicitly) prohibits
284 /// closures from capturing themselves (except via a trait
285 /// object). This simplifies closure inference considerably, since it
286 /// means that when we infer the kind of a closure or its upvars, we
287 /// don't have to handle cycles where the decisions we make for
288 /// closure C wind up influencing the decisions we ought to make for
289 /// closure C (which would then require fixed point iteration to
290 /// handle). Plus it fixes an ICE. :P
294 /// Generators are handled similarly in `GeneratorSubsts`. The set of
295 /// type parameters is similar, but `CK` and `CS` are replaced by the
296 /// following type parameters:
298 /// * `GS`: The generator's "resume type", which is the type of the
299 /// argument passed to `resume`, and the type of `yield` expressions
300 /// inside the generator.
301 /// * `GY`: The "yield type", which is the type of values passed to
302 /// `yield` inside the generator.
303 /// * `GR`: The "return type", which is the type of value returned upon
304 /// completion of the generator.
305 /// * `GW`: The "generator witness".
306 #[derive(Copy, Clone, Debug, TypeFoldable)]
307 pub struct ClosureSubsts<'tcx> {
308 /// Lifetime and type parameters from the enclosing function,
309 /// concatenated with a tuple containing the types of the upvars.
311 /// These are separated out because codegen wants to pass them around
312 /// when monomorphizing.
313 pub substs: SubstsRef<'tcx>,
316 /// Struct returned by `split()`. Note that these are subslices of the
317 /// parent slice and not canonical substs themselves.
318 struct SplitClosureSubsts<'tcx> {
319 closure_kind_ty: GenericArg<'tcx>,
320 closure_sig_as_fn_ptr_ty: GenericArg<'tcx>,
321 tupled_upvars_ty: GenericArg<'tcx>,
324 impl<'tcx> ClosureSubsts<'tcx> {
325 /// Divides the closure substs into their respective
326 /// components. Single source of truth with respect to the
328 fn split(self) -> SplitClosureSubsts<'tcx> {
329 match self.substs[..] {
330 [.., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
331 SplitClosureSubsts { closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty }
333 _ => bug!("closure substs missing synthetics"),
337 /// Returns `true` only if enough of the synthetic types are known to
338 /// allow using all of the methods on `ClosureSubsts` without panicking.
340 /// Used primarily by `ty::print::pretty` to be able to handle closure
341 /// types that haven't had their synthetic types substituted in.
342 pub fn is_valid(self) -> bool {
343 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
347 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
348 self.split().tupled_upvars_ty.expect_ty().tuple_fields()
351 /// Returns the closure kind for this closure; may return a type
352 /// variable during inference. To get the closure kind during
353 /// inference, use `infcx.closure_kind(substs)`.
354 pub fn kind_ty(self) -> Ty<'tcx> {
355 self.split().closure_kind_ty.expect_ty()
358 /// Returns the `fn` pointer type representing the closure signature for this
360 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
361 // type is known at the time of the creation of `ClosureSubsts`,
362 // see `rustc_typeck::check::closure`.
363 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
364 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
367 /// Returns the closure kind for this closure; only usable outside
368 /// of an inference context, because in that context we know that
369 /// there are no type variables.
371 /// If you have an inference context, use `infcx.closure_kind()`.
372 pub fn kind(self) -> ty::ClosureKind {
373 self.kind_ty().to_opt_closure_kind().unwrap()
376 /// Extracts the signature from the closure.
377 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
378 let ty = self.sig_as_fn_ptr_ty();
380 ty::FnPtr(sig) => sig,
381 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
386 /// Similar to `ClosureSubsts`; see the above documentation for more.
387 #[derive(Copy, Clone, Debug, TypeFoldable)]
388 pub struct GeneratorSubsts<'tcx> {
389 pub substs: SubstsRef<'tcx>,
392 struct SplitGeneratorSubsts<'tcx> {
393 resume_ty: GenericArg<'tcx>,
394 yield_ty: GenericArg<'tcx>,
395 return_ty: GenericArg<'tcx>,
396 witness: GenericArg<'tcx>,
397 tupled_upvars_ty: GenericArg<'tcx>,
400 impl<'tcx> GeneratorSubsts<'tcx> {
401 fn split(self) -> SplitGeneratorSubsts<'tcx> {
402 match self.substs[..] {
403 [.., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
404 SplitGeneratorSubsts { resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty }
406 _ => bug!("generator substs missing synthetics"),
410 /// Returns `true` only if enough of the synthetic types are known to
411 /// allow using all of the methods on `GeneratorSubsts` without panicking.
413 /// Used primarily by `ty::print::pretty` to be able to handle generator
414 /// types that haven't had their synthetic types substituted in.
415 pub fn is_valid(self) -> bool {
416 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
419 /// This describes the types that can be contained in a generator.
420 /// It will be a type variable initially and unified in the last stages of typeck of a body.
421 /// It contains a tuple of all the types that could end up on a generator frame.
422 /// The state transformation MIR pass may only produce layouts which mention types
423 /// in this tuple. Upvars are not counted here.
424 pub fn witness(self) -> Ty<'tcx> {
425 self.split().witness.expect_ty()
429 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
430 self.split().tupled_upvars_ty.expect_ty().tuple_fields()
433 /// Returns the type representing the resume type of the generator.
434 pub fn resume_ty(self) -> Ty<'tcx> {
435 self.split().resume_ty.expect_ty()
438 /// Returns the type representing the yield type of the generator.
439 pub fn yield_ty(self) -> Ty<'tcx> {
440 self.split().yield_ty.expect_ty()
443 /// Returns the type representing the return type of the generator.
444 pub fn return_ty(self) -> Ty<'tcx> {
445 self.split().return_ty.expect_ty()
448 /// Returns the "generator signature", which consists of its yield
449 /// and return types.
451 /// N.B., some bits of the code prefers to see this wrapped in a
452 /// binder, but it never contains bound regions. Probably this
453 /// function should be removed.
454 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
455 ty::Binder::dummy(self.sig())
458 /// Returns the "generator signature", which consists of its resume, yield
459 /// and return types.
460 pub fn sig(self) -> GenSig<'tcx> {
462 resume_ty: self.resume_ty(),
463 yield_ty: self.yield_ty(),
464 return_ty: self.return_ty(),
469 impl<'tcx> GeneratorSubsts<'tcx> {
470 /// Generator has not been resumed yet.
471 pub const UNRESUMED: usize = 0;
472 /// Generator has returned or is completed.
473 pub const RETURNED: usize = 1;
474 /// Generator has been poisoned.
475 pub const POISONED: usize = 2;
477 const UNRESUMED_NAME: &'static str = "Unresumed";
478 const RETURNED_NAME: &'static str = "Returned";
479 const POISONED_NAME: &'static str = "Panicked";
481 /// The valid variant indices of this generator.
483 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
484 // FIXME requires optimized MIR
485 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
486 VariantIdx::new(0)..VariantIdx::new(num_variants)
489 /// The discriminant for the given variant. Panics if the `variant_index` is
492 pub fn discriminant_for_variant(
496 variant_index: VariantIdx,
498 // Generators don't support explicit discriminant values, so they are
499 // the same as the variant index.
500 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
501 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
504 /// The set of all discriminants for the generator, enumerated with their
507 pub fn discriminants(
511 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
512 self.variant_range(def_id, tcx).map(move |index| {
513 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
517 /// Calls `f` with a reference to the name of the enumerator for the given
520 pub fn variant_name(self, v: VariantIdx) -> Cow<'static, str> {
522 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
523 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
524 Self::POISONED => Cow::from(Self::POISONED_NAME),
525 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
529 /// The type of the state discriminant used in the generator type.
531 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
535 /// This returns the types of the MIR locals which had to be stored across suspension points.
536 /// It is calculated in rustc_mir::transform::generator::StateTransform.
537 /// All the types here must be in the tuple in GeneratorInterior.
539 /// The locals are grouped by their variant number. Note that some locals may
540 /// be repeated in multiple variants.
546 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
547 let layout = tcx.generator_layout(def_id);
548 layout.variant_fields.iter().map(move |variant| {
549 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
553 /// This is the types of the fields of a generator which are not stored in a
556 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
561 #[derive(Debug, Copy, Clone)]
562 pub enum UpvarSubsts<'tcx> {
563 Closure(SubstsRef<'tcx>),
564 Generator(SubstsRef<'tcx>),
567 impl<'tcx> UpvarSubsts<'tcx> {
569 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
570 let tupled_upvars_ty = match self {
571 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
572 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
574 tupled_upvars_ty.expect_ty().tuple_fields()
578 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, RustcEncodable, RustcDecodable)]
579 #[derive(HashStable, TypeFoldable)]
580 pub enum ExistentialPredicate<'tcx> {
581 /// E.g., `Iterator`.
582 Trait(ExistentialTraitRef<'tcx>),
583 /// E.g., `Iterator::Item = T`.
584 Projection(ExistentialProjection<'tcx>),
589 impl<'tcx> ExistentialPredicate<'tcx> {
590 /// Compares via an ordering that will not change if modules are reordered or other changes are
591 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
592 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
593 use self::ExistentialPredicate::*;
594 match (*self, *other) {
595 (Trait(_), Trait(_)) => Ordering::Equal,
596 (Projection(ref a), Projection(ref b)) => {
597 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
599 (AutoTrait(ref a), AutoTrait(ref b)) => {
600 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
602 (Trait(_), _) => Ordering::Less,
603 (Projection(_), Trait(_)) => Ordering::Greater,
604 (Projection(_), _) => Ordering::Less,
605 (AutoTrait(_), _) => Ordering::Greater,
610 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
611 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
612 use crate::ty::ToPredicate;
613 match *self.skip_binder() {
614 ExistentialPredicate::Trait(tr) => {
615 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate()
617 ExistentialPredicate::Projection(p) => {
618 ty::PredicateKind::Projection(Binder(p.with_self_ty(tcx, self_ty)))
620 ExistentialPredicate::AutoTrait(did) => {
622 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
623 trait_ref.without_const().to_predicate()
629 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx List<ExistentialPredicate<'tcx>> {}
631 impl<'tcx> List<ExistentialPredicate<'tcx>> {
632 /// Returns the "principal `DefId`" of this set of existential predicates.
634 /// A Rust trait object type consists (in addition to a lifetime bound)
635 /// of a set of trait bounds, which are separated into any number
636 /// of auto-trait bounds, and at most one non-auto-trait bound. The
637 /// non-auto-trait bound is called the "principal" of the trait
640 /// Only the principal can have methods or type parameters (because
641 /// auto traits can have neither of them). This is important, because
642 /// it means the auto traits can be treated as an unordered set (methods
643 /// would force an order for the vtable, while relating traits with
644 /// type parameters without knowing the order to relate them in is
645 /// a rather non-trivial task).
647 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
648 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
649 /// are the set `{Sync}`.
651 /// It is also possible to have a "trivial" trait object that
652 /// consists only of auto traits, with no principal - for example,
653 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
654 /// is `{Send, Sync}`, while there is no principal. These trait objects
655 /// have a "trivial" vtable consisting of just the size, alignment,
657 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
659 ExistentialPredicate::Trait(tr) => Some(tr),
664 pub fn principal_def_id(&self) -> Option<DefId> {
665 self.principal().map(|trait_ref| trait_ref.def_id)
669 pub fn projection_bounds<'a>(
671 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
672 self.iter().filter_map(|predicate| match *predicate {
673 ExistentialPredicate::Projection(projection) => Some(projection),
679 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
680 self.iter().filter_map(|predicate| match *predicate {
681 ExistentialPredicate::AutoTrait(did) => Some(did),
687 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
688 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
689 self.skip_binder().principal().map(Binder::bind)
692 pub fn principal_def_id(&self) -> Option<DefId> {
693 self.skip_binder().principal_def_id()
697 pub fn projection_bounds<'a>(
699 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
700 self.skip_binder().projection_bounds().map(Binder::bind)
704 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
705 self.skip_binder().auto_traits()
710 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
711 self.skip_binder().iter().cloned().map(Binder::bind)
715 /// A complete reference to a trait. These take numerous guises in syntax,
716 /// but perhaps the most recognizable form is in a where-clause:
720 /// This would be represented by a trait-reference where the `DefId` is the
721 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
722 /// and `U` as parameter 1.
724 /// Trait references also appear in object types like `Foo<U>`, but in
725 /// that case the `Self` parameter is absent from the substitutions.
727 /// Note that a `TraitRef` introduces a level of region binding, to
728 /// account for higher-ranked trait bounds like `T: for<'a> Foo<&'a U>`
729 /// or higher-ranked object types.
730 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
731 #[derive(HashStable, TypeFoldable)]
732 pub struct TraitRef<'tcx> {
734 pub substs: SubstsRef<'tcx>,
737 impl<'tcx> TraitRef<'tcx> {
738 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
739 TraitRef { def_id, substs }
742 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
743 /// are the parameters defined on trait.
744 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
745 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
749 pub fn self_ty(&self) -> Ty<'tcx> {
750 self.substs.type_at(0)
756 substs: SubstsRef<'tcx>,
757 ) -> ty::TraitRef<'tcx> {
758 let defs = tcx.generics_of(trait_id);
760 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
764 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
766 impl<'tcx> PolyTraitRef<'tcx> {
767 pub fn self_ty(&self) -> Ty<'tcx> {
768 self.skip_binder().self_ty()
771 pub fn def_id(&self) -> DefId {
772 self.skip_binder().def_id
775 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
776 // Note that we preserve binding levels
777 Binder(ty::TraitPredicate { trait_ref: *self.skip_binder() })
781 /// An existential reference to a trait, where `Self` is erased.
782 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
784 /// exists T. T: Trait<'a, 'b, X, Y>
786 /// The substitutions don't include the erased `Self`, only trait
787 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
788 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
789 #[derive(HashStable, TypeFoldable)]
790 pub struct ExistentialTraitRef<'tcx> {
792 pub substs: SubstsRef<'tcx>,
795 impl<'tcx> ExistentialTraitRef<'tcx> {
796 pub fn erase_self_ty(
798 trait_ref: ty::TraitRef<'tcx>,
799 ) -> ty::ExistentialTraitRef<'tcx> {
800 // Assert there is a Self.
801 trait_ref.substs.type_at(0);
803 ty::ExistentialTraitRef {
804 def_id: trait_ref.def_id,
805 substs: tcx.intern_substs(&trait_ref.substs[1..]),
809 /// Object types don't have a self type specified. Therefore, when
810 /// we convert the principal trait-ref into a normal trait-ref,
811 /// you must give *some* self type. A common choice is `mk_err()`
812 /// or some placeholder type.
813 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
814 // otherwise the escaping vars would be captured by the binder
815 // debug_assert!(!self_ty.has_escaping_bound_vars());
817 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
821 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
823 impl<'tcx> PolyExistentialTraitRef<'tcx> {
824 pub fn def_id(&self) -> DefId {
825 self.skip_binder().def_id
828 /// Object types don't have a self type specified. Therefore, when
829 /// we convert the principal trait-ref into a normal trait-ref,
830 /// you must give *some* self type. A common choice is `mk_err()`
831 /// or some placeholder type.
832 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
833 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
837 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
838 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
839 /// (which would be represented by the type `PolyTraitRef ==
840 /// Binder<TraitRef>`). Note that when we instantiate,
841 /// erase, or otherwise "discharge" these bound vars, we change the
842 /// type from `Binder<T>` to just `T` (see
843 /// e.g., `liberate_late_bound_regions`).
844 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
845 pub struct Binder<T>(T);
848 /// Wraps `value` in a binder, asserting that `value` does not
849 /// contain any bound vars that would be bound by the
850 /// binder. This is commonly used to 'inject' a value T into a
851 /// different binding level.
852 pub fn dummy<'tcx>(value: T) -> Binder<T>
854 T: TypeFoldable<'tcx>,
856 debug_assert!(!value.has_escaping_bound_vars());
860 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
861 pub fn bind(value: T) -> Binder<T> {
865 /// Skips the binder and returns the "bound" value. This is a
866 /// risky thing to do because it's easy to get confused about
867 /// De Bruijn indices and the like. It is usually better to
868 /// discharge the binder using `no_bound_vars` or
869 /// `replace_late_bound_regions` or something like
870 /// that. `skip_binder` is only valid when you are either
871 /// extracting data that has nothing to do with bound vars, you
872 /// are doing some sort of test that does not involve bound
873 /// regions, or you are being very careful about your depth
876 /// Some examples where `skip_binder` is reasonable:
878 /// - extracting the `DefId` from a PolyTraitRef;
879 /// - comparing the self type of a PolyTraitRef to see if it is equal to
880 /// a type parameter `X`, since the type `X` does not reference any regions
881 pub fn skip_binder(&self) -> &T {
885 pub fn as_ref(&self) -> Binder<&T> {
889 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
893 self.as_ref().map_bound(f)
896 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
903 /// Unwraps and returns the value within, but only if it contains
904 /// no bound vars at all. (In other words, if this binder --
905 /// and indeed any enclosing binder -- doesn't bind anything at
906 /// all.) Otherwise, returns `None`.
908 /// (One could imagine having a method that just unwraps a single
909 /// binder, but permits late-bound vars bound by enclosing
910 /// binders, but that would require adjusting the debruijn
911 /// indices, and given the shallow binding structure we often use,
912 /// would not be that useful.)
913 pub fn no_bound_vars<'tcx>(self) -> Option<T>
915 T: TypeFoldable<'tcx>,
917 if self.skip_binder().has_escaping_bound_vars() {
920 Some(self.skip_binder().clone())
924 /// Given two things that have the same binder level,
925 /// and an operation that wraps on their contents, executes the operation
926 /// and then wraps its result.
928 /// `f` should consider bound regions at depth 1 to be free, and
929 /// anything it produces with bound regions at depth 1 will be
930 /// bound in the resulting return value.
931 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
933 F: FnOnce(T, U) -> R,
935 Binder(f(self.0, u.0))
938 /// Splits the contents into two things that share the same binder
939 /// level as the original, returning two distinct binders.
941 /// `f` should consider bound regions at depth 1 to be free, and
942 /// anything it produces with bound regions at depth 1 will be
943 /// bound in the resulting return values.
944 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
946 F: FnOnce(T) -> (U, V),
948 let (u, v) = f(self.0);
949 (Binder(u), Binder(v))
953 /// Represents the projection of an associated type. In explicit UFCS
954 /// form this would be written `<T as Trait<..>>::N`.
955 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
956 #[derive(HashStable, TypeFoldable)]
957 pub struct ProjectionTy<'tcx> {
958 /// The parameters of the associated item.
959 pub substs: SubstsRef<'tcx>,
961 /// The `DefId` of the `TraitItem` for the associated type `N`.
963 /// Note that this is not the `DefId` of the `TraitRef` containing this
964 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
965 pub item_def_id: DefId,
968 impl<'tcx> ProjectionTy<'tcx> {
969 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
970 /// associated item named `item_name`.
971 pub fn from_ref_and_name(
973 trait_ref: ty::TraitRef<'tcx>,
975 ) -> ProjectionTy<'tcx> {
976 let item_def_id = tcx
977 .associated_items(trait_ref.def_id)
978 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
982 ProjectionTy { substs: trait_ref.substs, item_def_id }
985 /// Extracts the underlying trait reference from this projection.
986 /// For example, if this is a projection of `<T as Iterator>::Item`,
987 /// then this function would return a `T: Iterator` trait reference.
988 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
989 let def_id = tcx.associated_item(self.item_def_id).container.id();
990 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
993 pub fn self_ty(&self) -> Ty<'tcx> {
994 self.substs.type_at(0)
998 #[derive(Clone, Debug, TypeFoldable)]
999 pub struct GenSig<'tcx> {
1000 pub resume_ty: Ty<'tcx>,
1001 pub yield_ty: Ty<'tcx>,
1002 pub return_ty: Ty<'tcx>,
1005 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1007 impl<'tcx> PolyGenSig<'tcx> {
1008 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1009 self.map_bound_ref(|sig| sig.resume_ty)
1011 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1012 self.map_bound_ref(|sig| sig.yield_ty)
1014 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1015 self.map_bound_ref(|sig| sig.return_ty)
1019 /// Signature of a function type, which we have arbitrarily
1020 /// decided to use to refer to the input/output types.
1022 /// - `inputs`: is the list of arguments and their modes.
1023 /// - `output`: is the return type.
1024 /// - `c_variadic`: indicates whether this is a C-variadic function.
1025 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1026 #[derive(HashStable, TypeFoldable)]
1027 pub struct FnSig<'tcx> {
1028 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1029 pub c_variadic: bool,
1030 pub unsafety: hir::Unsafety,
1034 impl<'tcx> FnSig<'tcx> {
1035 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1036 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1039 pub fn output(&self) -> Ty<'tcx> {
1040 self.inputs_and_output[self.inputs_and_output.len() - 1]
1043 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1045 fn fake() -> FnSig<'tcx> {
1047 inputs_and_output: List::empty(),
1049 unsafety: hir::Unsafety::Normal,
1050 abi: abi::Abi::Rust,
1055 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1057 impl<'tcx> PolyFnSig<'tcx> {
1059 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1060 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1063 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1064 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1066 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1067 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1070 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1071 self.map_bound_ref(|fn_sig| fn_sig.output())
1073 pub fn c_variadic(&self) -> bool {
1074 self.skip_binder().c_variadic
1076 pub fn unsafety(&self) -> hir::Unsafety {
1077 self.skip_binder().unsafety
1079 pub fn abi(&self) -> abi::Abi {
1080 self.skip_binder().abi
1084 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1086 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1087 #[derive(HashStable)]
1088 pub struct ParamTy {
1093 impl<'tcx> ParamTy {
1094 pub fn new(index: u32, name: Symbol) -> ParamTy {
1095 ParamTy { index, name }
1098 pub fn for_self() -> ParamTy {
1099 ParamTy::new(0, kw::SelfUpper)
1102 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1103 ParamTy::new(def.index, def.name)
1106 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1107 tcx.mk_ty_param(self.index, self.name)
1111 #[derive(Copy, Clone, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
1112 #[derive(HashStable)]
1113 pub struct ParamConst {
1118 impl<'tcx> ParamConst {
1119 pub fn new(index: u32, name: Symbol) -> ParamConst {
1120 ParamConst { index, name }
1123 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1124 ParamConst::new(def.index, def.name)
1127 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Const<'tcx> {
1128 tcx.mk_const_param(self.index, self.name, ty)
1132 rustc_index::newtype_index! {
1133 /// A [De Bruijn index][dbi] is a standard means of representing
1134 /// regions (and perhaps later types) in a higher-ranked setting. In
1135 /// particular, imagine a type like this:
1137 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1140 /// | +------------+ 0 | |
1142 /// +--------------------------------+ 1 |
1144 /// +------------------------------------------+ 0
1146 /// In this type, there are two binders (the outer fn and the inner
1147 /// fn). We need to be able to determine, for any given region, which
1148 /// fn type it is bound by, the inner or the outer one. There are
1149 /// various ways you can do this, but a De Bruijn index is one of the
1150 /// more convenient and has some nice properties. The basic idea is to
1151 /// count the number of binders, inside out. Some examples should help
1152 /// clarify what I mean.
1154 /// Let's start with the reference type `&'b isize` that is the first
1155 /// argument to the inner function. This region `'b` is assigned a De
1156 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1157 /// fn). The region `'a` that appears in the second argument type (`&'a
1158 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1159 /// second-innermost binder". (These indices are written on the arrays
1160 /// in the diagram).
1162 /// What is interesting is that De Bruijn index attached to a particular
1163 /// variable will vary depending on where it appears. For example,
1164 /// the final type `&'a char` also refers to the region `'a` declared on
1165 /// the outermost fn. But this time, this reference is not nested within
1166 /// any other binders (i.e., it is not an argument to the inner fn, but
1167 /// rather the outer one). Therefore, in this case, it is assigned a
1168 /// De Bruijn index of 0, because the innermost binder in that location
1169 /// is the outer fn.
1171 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1172 #[derive(HashStable)]
1173 pub struct DebruijnIndex {
1174 DEBUG_FORMAT = "DebruijnIndex({})",
1175 const INNERMOST = 0,
1179 pub type Region<'tcx> = &'tcx RegionKind;
1181 /// Representation of (lexical) regions. Note that the NLL checker
1182 /// uses a distinct representation of regions. For this reason, it
1183 /// internally replaces all the regions with inference variables --
1184 /// the index of the variable is then used to index into internal NLL
1185 /// data structures. See `rustc_mir::borrow_check` module for more
1188 /// ## The Region lattice within a given function
1190 /// In general, the (lexical, and hence deprecated) region lattice
1194 /// static ----------+-----...------+ (greatest)
1196 /// early-bound and | |
1197 /// free regions | |
1199 /// scope regions | |
1201 /// empty(root) placeholder(U1) |
1203 /// | / placeholder(Un)
1208 /// empty(Un) -------- (smallest)
1211 /// Early-bound/free regions are the named lifetimes in scope from the
1212 /// function declaration. They have relationships to one another
1213 /// determined based on the declared relationships from the
1214 /// function. They all collectively outlive the scope regions. (See
1215 /// `RegionRelations` type, and particularly
1216 /// `crate::infer::outlives::free_region_map::FreeRegionMap`.)
1218 /// The scope regions are related to one another based on the AST
1219 /// structure. (See `RegionRelations` type, and particularly the
1220 /// `rustc_middle::middle::region::ScopeTree`.)
1222 /// Note that inference variables and bound regions are not included
1223 /// in this diagram. In the case of inference variables, they should
1224 /// be inferred to some other region from the diagram. In the case of
1225 /// bound regions, they are excluded because they don't make sense to
1226 /// include -- the diagram indicates the relationship between free
1229 /// ## Inference variables
1231 /// During region inference, we sometimes create inference variables,
1232 /// represented as `ReVar`. These will be inferred by the code in
1233 /// `infer::lexical_region_resolve` to some free region from the
1234 /// lattice above (the minimal region that meets the
1237 /// During NLL checking, where regions are defined differently, we
1238 /// also use `ReVar` -- in that case, the index is used to index into
1239 /// the NLL region checker's data structures. The variable may in fact
1240 /// represent either a free region or an inference variable, in that
1243 /// ## Bound Regions
1245 /// These are regions that are stored behind a binder and must be substituted
1246 /// with some concrete region before being used. There are two kind of
1247 /// bound regions: early-bound, which are bound in an item's `Generics`,
1248 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1249 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1250 /// the likes of `liberate_late_bound_regions`. The distinction exists
1251 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1253 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1254 /// outside their binder, e.g., in types passed to type inference, and
1255 /// should first be substituted (by placeholder regions, free regions,
1256 /// or region variables).
1258 /// ## Placeholder and Free Regions
1260 /// One often wants to work with bound regions without knowing their precise
1261 /// identity. For example, when checking a function, the lifetime of a borrow
1262 /// can end up being assigned to some region parameter. In these cases,
1263 /// it must be ensured that bounds on the region can't be accidentally
1264 /// assumed without being checked.
1266 /// To do this, we replace the bound regions with placeholder markers,
1267 /// which don't satisfy any relation not explicitly provided.
1269 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1270 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1271 /// to be used. These also support explicit bounds: both the internally-stored
1272 /// *scope*, which the region is assumed to outlive, as well as other
1273 /// relations stored in the `FreeRegionMap`. Note that these relations
1274 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1275 /// `resolve_regions_and_report_errors`.
1277 /// When working with higher-ranked types, some region relations aren't
1278 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1279 /// `RePlaceholder` is designed for this purpose. In these contexts,
1280 /// there's also the risk that some inference variable laying around will
1281 /// get unified with your placeholder region: if you want to check whether
1282 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1283 /// with a placeholder region `'%a`, the variable `'_` would just be
1284 /// instantiated to the placeholder region `'%a`, which is wrong because
1285 /// the inference variable is supposed to satisfy the relation
1286 /// *for every value of the placeholder region*. To ensure that doesn't
1287 /// happen, you can use `leak_check`. This is more clearly explained
1288 /// by the [rustc dev guide].
1290 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1291 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1292 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1293 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable, PartialOrd, Ord)]
1294 pub enum RegionKind {
1295 /// Region bound in a type or fn declaration which will be
1296 /// substituted 'early' -- that is, at the same time when type
1297 /// parameters are substituted.
1298 ReEarlyBound(EarlyBoundRegion),
1300 /// Region bound in a function scope, which will be substituted when the
1301 /// function is called.
1302 ReLateBound(DebruijnIndex, BoundRegion),
1304 /// When checking a function body, the types of all arguments and so forth
1305 /// that refer to bound region parameters are modified to refer to free
1306 /// region parameters.
1309 /// A concrete region naming some statically determined scope
1310 /// (e.g., an expression or sequence of statements) within the
1311 /// current function.
1312 ReScope(region::Scope),
1314 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1317 /// A region variable. Should not exist after typeck.
1320 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1321 /// Should not exist after typeck.
1322 RePlaceholder(ty::PlaceholderRegion),
1324 /// Empty lifetime is for data that is never accessed. We tag the
1325 /// empty lifetime with a universe -- the idea is that we don't
1326 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1327 /// Therefore, the `'empty` in a universe `U` is less than all
1328 /// regions visible from `U`, but not less than regions not visible
1330 ReEmpty(ty::UniverseIndex),
1332 /// Erased region, used by trait selection, in MIR and during codegen.
1336 impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
1338 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, PartialOrd, Ord)]
1339 pub struct EarlyBoundRegion {
1345 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1350 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1351 pub struct ConstVid<'tcx> {
1353 pub phantom: PhantomData<&'tcx ()>,
1356 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1361 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1362 pub struct FloatVid {
1366 rustc_index::newtype_index! {
1367 pub struct RegionVid {
1368 DEBUG_FORMAT = custom,
1372 impl Atom for RegionVid {
1373 fn index(self) -> usize {
1378 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1379 #[derive(HashStable)]
1385 /// A `FreshTy` is one that is generated as a replacement for an
1386 /// unbound type variable. This is convenient for caching etc. See
1387 /// `infer::freshen` for more details.
1393 rustc_index::newtype_index! {
1394 pub struct BoundVar { .. }
1397 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1398 #[derive(HashStable)]
1399 pub struct BoundTy {
1401 pub kind: BoundTyKind,
1404 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1405 #[derive(HashStable)]
1406 pub enum BoundTyKind {
1411 impl From<BoundVar> for BoundTy {
1412 fn from(var: BoundVar) -> Self {
1413 BoundTy { var, kind: BoundTyKind::Anon }
1417 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1418 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1419 #[derive(HashStable, TypeFoldable)]
1420 pub struct ExistentialProjection<'tcx> {
1421 pub item_def_id: DefId,
1422 pub substs: SubstsRef<'tcx>,
1426 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1428 impl<'tcx> ExistentialProjection<'tcx> {
1429 /// Extracts the underlying existential trait reference from this projection.
1430 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1431 /// then this function would return a `exists T. T: Iterator` existential trait
1433 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1434 let def_id = tcx.associated_item(self.item_def_id).container.id();
1435 ty::ExistentialTraitRef { def_id, substs: self.substs }
1438 pub fn with_self_ty(
1442 ) -> ty::ProjectionPredicate<'tcx> {
1443 // otherwise the escaping regions would be captured by the binders
1444 debug_assert!(!self_ty.has_escaping_bound_vars());
1446 ty::ProjectionPredicate {
1447 projection_ty: ty::ProjectionTy {
1448 item_def_id: self.item_def_id,
1449 substs: tcx.mk_substs_trait(self_ty, self.substs),
1456 impl<'tcx> PolyExistentialProjection<'tcx> {
1457 pub fn with_self_ty(
1461 ) -> ty::PolyProjectionPredicate<'tcx> {
1462 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1465 pub fn item_def_id(&self) -> DefId {
1466 self.skip_binder().item_def_id
1470 impl DebruijnIndex {
1471 /// Returns the resulting index when this value is moved into
1472 /// `amount` number of new binders. So, e.g., if you had
1474 /// for<'a> fn(&'a x)
1476 /// and you wanted to change it to
1478 /// for<'a> fn(for<'b> fn(&'a x))
1480 /// you would need to shift the index for `'a` into a new binder.
1482 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1483 DebruijnIndex::from_u32(self.as_u32() + amount)
1486 /// Update this index in place by shifting it "in" through
1487 /// `amount` number of binders.
1488 pub fn shift_in(&mut self, amount: u32) {
1489 *self = self.shifted_in(amount);
1492 /// Returns the resulting index when this value is moved out from
1493 /// `amount` number of new binders.
1495 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1496 DebruijnIndex::from_u32(self.as_u32() - amount)
1499 /// Update in place by shifting out from `amount` binders.
1500 pub fn shift_out(&mut self, amount: u32) {
1501 *self = self.shifted_out(amount);
1504 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1505 /// innermost binder. That is, if we have something bound at `to_binder`,
1506 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1507 /// when moving a region out from inside binders:
1510 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1511 /// // Binder: D3 D2 D1 ^^
1514 /// Here, the region `'a` would have the De Bruijn index D3,
1515 /// because it is the bound 3 binders out. However, if we wanted
1516 /// to refer to that region `'a` in the second argument (the `_`),
1517 /// those two binders would not be in scope. In that case, we
1518 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1519 /// De Bruijn index of `'a` to D1 (the innermost binder).
1521 /// If we invoke `shift_out_to_binder` and the region is in fact
1522 /// bound by one of the binders we are shifting out of, that is an
1523 /// error (and should fail an assertion failure).
1524 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1525 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1529 /// Region utilities
1531 /// Is this region named by the user?
1532 pub fn has_name(&self) -> bool {
1534 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1535 RegionKind::ReLateBound(_, br) => br.is_named(),
1536 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1537 RegionKind::ReScope(..) => false,
1538 RegionKind::ReStatic => true,
1539 RegionKind::ReVar(..) => false,
1540 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1541 RegionKind::ReEmpty(_) => false,
1542 RegionKind::ReErased => false,
1546 pub fn is_late_bound(&self) -> bool {
1548 ty::ReLateBound(..) => true,
1553 pub fn is_placeholder(&self) -> bool {
1555 ty::RePlaceholder(..) => true,
1560 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1562 ty::ReLateBound(debruijn, _) => debruijn >= index,
1567 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1568 /// innermost binder. That is, if we have something bound at `to_binder`,
1569 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1570 /// when moving a region out from inside binders:
1573 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1574 /// // Binder: D3 D2 D1 ^^
1577 /// Here, the region `'a` would have the De Bruijn index D3,
1578 /// because it is the bound 3 binders out. However, if we wanted
1579 /// to refer to that region `'a` in the second argument (the `_`),
1580 /// those two binders would not be in scope. In that case, we
1581 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1582 /// De Bruijn index of `'a` to D1 (the innermost binder).
1584 /// If we invoke `shift_out_to_binder` and the region is in fact
1585 /// bound by one of the binders we are shifting out of, that is an
1586 /// error (and should fail an assertion failure).
1587 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1589 ty::ReLateBound(debruijn, r) => {
1590 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1596 pub fn type_flags(&self) -> TypeFlags {
1597 let mut flags = TypeFlags::empty();
1601 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1602 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1603 flags = flags | TypeFlags::HAS_RE_INFER;
1604 flags = flags | TypeFlags::STILL_FURTHER_SPECIALIZABLE;
1606 ty::RePlaceholder(..) => {
1607 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1608 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1609 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1610 flags = flags | TypeFlags::STILL_FURTHER_SPECIALIZABLE;
1612 ty::ReEarlyBound(..) => {
1613 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1614 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1615 flags = flags | TypeFlags::HAS_RE_PARAM;
1616 flags = flags | TypeFlags::STILL_FURTHER_SPECIALIZABLE;
1618 ty::ReFree { .. } | ty::ReScope { .. } => {
1619 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1620 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1622 ty::ReEmpty(_) | ty::ReStatic => {
1623 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1625 ty::ReLateBound(..) => {
1626 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1629 flags = flags | TypeFlags::HAS_RE_ERASED;
1633 debug!("type_flags({:?}) = {:?}", self, flags);
1638 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1639 /// For example, consider the regions in this snippet of code:
1643 /// ^^ -- early bound, declared on an impl
1645 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1646 /// ^^ ^^ ^ anonymous, late-bound
1647 /// | early-bound, appears in where-clauses
1648 /// late-bound, appears only in fn args
1653 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1654 /// of the impl, and for all the other highlighted regions, it
1655 /// would return the `DefId` of the function. In other cases (not shown), this
1656 /// function might return the `DefId` of a closure.
1657 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1659 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1660 ty::ReFree(fr) => fr.scope,
1661 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1667 impl<'tcx> TyS<'tcx> {
1669 pub fn is_unit(&self) -> bool {
1671 Tuple(ref tys) => tys.is_empty(),
1677 pub fn is_never(&self) -> bool {
1684 /// Checks whether a type is definitely uninhabited. This is
1685 /// conservative: for some types that are uninhabited we return `false`,
1686 /// but we only return `true` for types that are definitely uninhabited.
1687 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1688 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1689 /// size, to account for partial initialisation. See #49298 for details.)
1690 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1691 // FIXME(varkor): we can make this less conversative by substituting concrete
1695 ty::Adt(def, _) if def.is_union() => {
1696 // For now, `union`s are never considered uninhabited.
1699 ty::Adt(def, _) => {
1700 // Any ADT is uninhabited if either:
1701 // (a) It has no variants (i.e. an empty `enum`);
1702 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1703 // one uninhabited field.
1704 def.variants.iter().all(|var| {
1705 var.fields.iter().any(|field| {
1706 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1711 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1713 ty::Array(ty, len) => {
1714 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1715 // If the array is definitely non-empty, it's uninhabited if
1716 // the type of its elements is uninhabited.
1717 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1722 // References to uninitialised memory is valid for any type, including
1723 // uninhabited types, in unsafe code, so we treat all references as
1732 pub fn is_primitive(&self) -> bool {
1734 Bool | Char | Int(_) | Uint(_) | Float(_) => true,
1740 pub fn is_ty_var(&self) -> bool {
1742 Infer(TyVar(_)) => true,
1748 pub fn is_ty_infer(&self) -> bool {
1756 pub fn is_phantom_data(&self) -> bool {
1757 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1761 pub fn is_bool(&self) -> bool {
1765 /// Returns `true` if this type is a `str`.
1767 pub fn is_str(&self) -> bool {
1772 pub fn is_param(&self, index: u32) -> bool {
1774 ty::Param(ref data) => data.index == index,
1780 pub fn is_slice(&self) -> bool {
1782 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1783 Slice(_) | Str => true,
1791 pub fn is_simd(&self) -> bool {
1793 Adt(def, _) => def.repr.simd(),
1798 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1800 Array(ty, _) | Slice(ty) => ty,
1801 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1802 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1806 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1808 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1809 _ => bug!("`simd_type` called on invalid type"),
1813 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1814 // Parameter currently unused, but probably needed in the future to
1815 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1817 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1818 _ => bug!("`simd_size` called on invalid type"),
1822 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1824 Adt(def, substs) => {
1825 let variant = def.non_enum_variant();
1826 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1828 _ => bug!("`simd_size_and_type` called on invalid type"),
1833 pub fn is_region_ptr(&self) -> bool {
1841 pub fn is_mutable_ptr(&self) -> bool {
1843 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1844 | Ref(_, _, hir::Mutability::Mut) => true,
1850 pub fn is_unsafe_ptr(&self) -> bool {
1857 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1859 pub fn is_any_ptr(&self) -> bool {
1860 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1864 pub fn is_box(&self) -> bool {
1866 Adt(def, _) => def.is_box(),
1871 /// Panics if called on any type other than `Box<T>`.
1872 pub fn boxed_ty(&self) -> Ty<'tcx> {
1874 Adt(def, substs) if def.is_box() => substs.type_at(0),
1875 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1879 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1880 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1881 /// contents are abstract to rustc.)
1883 pub fn is_scalar(&self) -> bool {
1890 | Infer(IntVar(_) | FloatVar(_))
1893 | RawPtr(_) => true,
1898 /// Returns `true` if this type is a floating point type.
1900 pub fn is_floating_point(&self) -> bool {
1902 Float(_) | Infer(FloatVar(_)) => true,
1908 pub fn is_trait(&self) -> bool {
1910 Dynamic(..) => true,
1916 pub fn is_enum(&self) -> bool {
1918 Adt(adt_def, _) => adt_def.is_enum(),
1924 pub fn is_closure(&self) -> bool {
1926 Closure(..) => true,
1932 pub fn is_generator(&self) -> bool {
1934 Generator(..) => true,
1940 pub fn is_integral(&self) -> bool {
1942 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
1948 pub fn is_fresh_ty(&self) -> bool {
1950 Infer(FreshTy(_)) => true,
1956 pub fn is_fresh(&self) -> bool {
1958 Infer(FreshTy(_)) => true,
1959 Infer(FreshIntTy(_)) => true,
1960 Infer(FreshFloatTy(_)) => true,
1966 pub fn is_char(&self) -> bool {
1974 pub fn is_numeric(&self) -> bool {
1975 self.is_integral() || self.is_floating_point()
1979 pub fn is_signed(&self) -> bool {
1987 pub fn is_ptr_sized_integral(&self) -> bool {
1989 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
1995 pub fn is_machine(&self) -> bool {
1997 Int(..) | Uint(..) | Float(..) => true,
2003 pub fn has_concrete_skeleton(&self) -> bool {
2005 Param(_) | Infer(_) | Error => false,
2010 /// Returns the type and mutability of `*ty`.
2012 /// The parameter `explicit` indicates if this is an *explicit* dereference.
2013 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
2014 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
2016 Adt(def, _) if def.is_box() => {
2017 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
2019 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2020 RawPtr(mt) if explicit => Some(mt),
2025 /// Returns the type of `ty[i]`.
2026 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2028 Array(ty, _) | Slice(ty) => Some(ty),
2033 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2035 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2038 // ignore errors (#54954)
2039 ty::Binder::dummy(FnSig::fake())
2041 Closure(..) => bug!(
2042 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2044 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2049 pub fn is_fn(&self) -> bool {
2051 FnDef(..) | FnPtr(_) => true,
2057 pub fn is_fn_ptr(&self) -> bool {
2065 pub fn is_impl_trait(&self) -> bool {
2073 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2075 Adt(adt, _) => Some(adt),
2080 /// Iterates over tuple fields.
2081 /// Panics when called on anything but a tuple.
2082 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2084 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2085 _ => bug!("tuple_fields called on non-tuple"),
2089 /// If the type contains variants, returns the valid range of variant indices.
2091 // FIXME: This requires the optimized MIR in the case of generators.
2093 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2095 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2096 TyKind::Generator(def_id, substs, _) => {
2097 Some(substs.as_generator().variant_range(def_id, tcx))
2103 /// If the type contains variants, returns the variant for `variant_index`.
2104 /// Panics if `variant_index` is out of range.
2106 // FIXME: This requires the optimized MIR in the case of generators.
2108 pub fn discriminant_for_variant(
2111 variant_index: VariantIdx,
2112 ) -> Option<Discr<'tcx>> {
2114 TyKind::Adt(adt, _) => Some(adt.discriminant_for_variant(tcx, variant_index)),
2115 TyKind::Generator(def_id, substs, _) => {
2116 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2122 /// When we create a closure, we record its kind (i.e., what trait
2123 /// it implements) into its `ClosureSubsts` using a type
2124 /// parameter. This is kind of a phantom type, except that the
2125 /// most convenient thing for us to are the integral types. This
2126 /// function converts such a special type into the closure
2127 /// kind. To go the other way, use
2128 /// `tcx.closure_kind_ty(closure_kind)`.
2130 /// Note that during type checking, we use an inference variable
2131 /// to represent the closure kind, because it has not yet been
2132 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2133 /// is complete, that type variable will be unified.
2134 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2136 Int(int_ty) => match int_ty {
2137 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2138 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2139 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2140 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2143 // "Bound" types appear in canonical queries when the
2144 // closure type is not yet known
2145 Bound(..) | Infer(_) => None,
2147 Error => Some(ty::ClosureKind::Fn),
2149 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2153 /// Fast path helper for testing if a type is `Sized`.
2155 /// Returning true means the type is known to be sized. Returning
2156 /// `false` means nothing -- could be sized, might not be.
2157 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2159 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2170 | ty::GeneratorWitness(..)
2174 | ty::Error => true,
2176 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2178 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2180 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2182 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2184 ty::Infer(ty::TyVar(_)) => false,
2187 | ty::Placeholder(..)
2188 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2189 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2195 /// Typed constant value.
2196 #[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
2197 #[derive(HashStable)]
2198 pub struct Const<'tcx> {
2201 pub val: ConstKind<'tcx>,
2204 #[cfg(target_arch = "x86_64")]
2205 static_assert_size!(Const<'_>, 48);
2207 impl<'tcx> Const<'tcx> {
2208 /// Literals and const generic parameters are eagerly converted to a constant, everything else
2209 /// becomes `Unevaluated`.
2210 pub fn from_anon_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx Self {
2211 debug!("Const::from_anon_const(id={:?})", def_id);
2213 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2215 let body_id = match tcx.hir().get(hir_id) {
2216 hir::Node::AnonConst(ac) => ac.body,
2218 tcx.def_span(def_id.to_def_id()),
2219 "from_anon_const can only process anonymous constants"
2223 let expr = &tcx.hir().body(body_id).value;
2225 let ty = tcx.type_of(def_id.to_def_id());
2227 let lit_input = match expr.kind {
2228 hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
2229 hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind {
2230 hir::ExprKind::Lit(ref lit) => {
2231 Some(LitToConstInput { lit: &lit.node, ty, neg: true })
2238 if let Some(lit_input) = lit_input {
2239 // If an error occurred, ignore that it's a literal and leave reporting the error up to
2241 if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
2244 tcx.sess.delay_span_bug(expr.span, "Const::from_anon_const: couldn't lit_to_const");
2248 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
2249 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
2250 let expr = match &expr.kind {
2251 hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
2252 block.expr.as_ref().unwrap()
2257 use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
2258 let val = match expr.kind {
2259 ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
2260 // Find the name and index of the const parameter by indexing the generics of
2261 // the parent item and construct a `ParamConst`.
2262 let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
2263 let item_id = tcx.hir().get_parent_node(hir_id);
2264 let item_def_id = tcx.hir().local_def_id(item_id);
2265 let generics = tcx.generics_of(item_def_id.to_def_id());
2267 generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id).to_def_id()];
2268 let name = tcx.hir().name(hir_id);
2269 ty::ConstKind::Param(ty::ParamConst::new(index, name))
2271 _ => ty::ConstKind::Unevaluated(
2273 InternalSubsts::identity_for_item(tcx, def_id.to_def_id()),
2278 tcx.mk_const(ty::Const { val, ty })
2282 /// Interns the given value as a constant.
2283 pub fn from_value(tcx: TyCtxt<'tcx>, val: ConstValue<'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
2284 tcx.mk_const(Self { val: ConstKind::Value(val), ty })
2288 /// Interns the given scalar as a constant.
2289 pub fn from_scalar(tcx: TyCtxt<'tcx>, val: Scalar, ty: Ty<'tcx>) -> &'tcx Self {
2290 Self::from_value(tcx, ConstValue::Scalar(val), ty)
2294 /// Creates a constant with the given integer value and interns it.
2295 pub fn from_bits(tcx: TyCtxt<'tcx>, bits: u128, ty: ParamEnvAnd<'tcx, Ty<'tcx>>) -> &'tcx Self {
2298 .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
2300 Self::from_scalar(tcx, Scalar::from_uint(bits, size), ty.value)
2304 /// Creates an interned zst constant.
2305 pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
2306 Self::from_scalar(tcx, Scalar::zst(), ty)
2310 /// Creates an interned bool constant.
2311 pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> &'tcx Self {
2312 Self::from_bits(tcx, v as u128, ParamEnv::empty().and(tcx.types.bool))
2316 /// Creates an interned usize constant.
2317 pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> &'tcx Self {
2318 Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize))
2322 /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of
2323 /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it
2324 /// contains const generic parameters or pointers).
2325 pub fn try_eval_bits(
2328 param_env: ParamEnv<'tcx>,
2331 assert_eq!(self.ty, ty);
2332 let size = tcx.layout_of(param_env.with_reveal_all().and(ty)).ok()?.size;
2333 // if `ty` does not depend on generic parameters, use an empty param_env
2334 self.eval(tcx, param_env).val.try_to_bits(size)
2338 /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the
2339 /// unevaluated constant.
2340 pub fn eval(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> &Const<'tcx> {
2341 if let ConstKind::Unevaluated(did, substs, promoted) = self.val {
2342 use crate::mir::interpret::ErrorHandled;
2344 let param_env_and_substs = param_env.with_reveal_all().and(substs);
2346 // HACK(eddyb) this erases lifetimes even though `const_eval_resolve`
2347 // also does later, but we want to do it before checking for
2348 // inference variables.
2349 let param_env_and_substs = tcx.erase_regions(¶m_env_and_substs);
2351 // HACK(eddyb) when the query key would contain inference variables,
2352 // attempt using identity substs and `ParamEnv` instead, that will succeed
2353 // when the expression doesn't depend on any parameters.
2354 // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
2355 // we can call `infcx.const_eval_resolve` which handles inference variables.
2356 let param_env_and_substs = if param_env_and_substs.needs_infer() {
2357 tcx.param_env(did).and(InternalSubsts::identity_for_item(tcx, did))
2359 param_env_and_substs
2362 // FIXME(eddyb) maybe the `const_eval_*` methods should take
2363 // `ty::ParamEnvAnd<SubstsRef>` instead of having them separate.
2364 let (param_env, substs) = param_env_and_substs.into_parts();
2365 // try to resolve e.g. associated constants to their definition on an impl, and then
2366 // evaluate the const.
2367 match tcx.const_eval_resolve(param_env, did, substs, promoted, None) {
2368 // NOTE(eddyb) `val` contains no lifetimes/types/consts,
2369 // and we use the original type, so nothing from `substs`
2370 // (which may be identity substs, see above),
2371 // can leak through `val` into the const we return.
2372 Ok(val) => Const::from_value(tcx, val, self.ty),
2373 Err(ErrorHandled::TooGeneric | ErrorHandled::Linted) => self,
2374 Err(ErrorHandled::Reported(ErrorReported)) => {
2375 tcx.mk_const(ty::Const { val: ty::ConstKind::Error, ty: self.ty })
2384 pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> {
2385 self.try_eval_bits(tcx, param_env, tcx.types.bool).and_then(|v| match v {
2393 pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> {
2394 self.try_eval_bits(tcx, param_env, tcx.types.usize).map(|v| v as u64)
2398 /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
2399 pub fn eval_bits(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {
2400 self.try_eval_bits(tcx, param_env, ty)
2401 .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self))
2405 /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`.
2406 pub fn eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 {
2407 self.eval_bits(tcx, param_env, tcx.types.usize) as u64
2411 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx Const<'tcx> {}
2413 /// Represents a constant in Rust.
2414 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
2415 #[derive(HashStable)]
2416 pub enum ConstKind<'tcx> {
2417 /// A const generic parameter.
2420 /// Infer the value of the const.
2421 Infer(InferConst<'tcx>),
2423 /// Bound const variable, used only when preparing a trait query.
2424 Bound(DebruijnIndex, BoundVar),
2426 /// A placeholder const - universally quantified higher-ranked const.
2427 Placeholder(ty::PlaceholderConst),
2429 /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
2430 /// variants when the code is monomorphic enough for that.
2431 Unevaluated(DefId, SubstsRef<'tcx>, Option<Promoted>),
2433 /// Used to hold computed value.
2434 Value(ConstValue<'tcx>),
2436 /// A placeholder for a const which could not be computed; this is
2437 /// propagated to avoid useless error messages.
2441 #[cfg(target_arch = "x86_64")]
2442 static_assert_size!(ConstKind<'_>, 40);
2444 impl<'tcx> ConstKind<'tcx> {
2446 pub fn try_to_scalar(&self) -> Option<Scalar> {
2447 if let ConstKind::Value(val) = self { val.try_to_scalar() } else { None }
2451 pub fn try_to_bits(&self, size: Size) -> Option<u128> {
2452 if let ConstKind::Value(val) = self { val.try_to_bits(size) } else { None }
2456 /// An inference variable for a const, for use in const generics.
2457 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
2458 #[derive(HashStable)]
2459 pub enum InferConst<'tcx> {
2460 /// Infer the value of the const.
2461 Var(ConstVid<'tcx>),
2462 /// A fresh const variable. See `infer::freshen` for more details.