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::mir::interpret::ConstValue;
10 use crate::mir::interpret::{LitToConstInput, Scalar};
11 use crate::mir::Promoted;
12 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
14 self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness,
16 use crate::ty::{List, ParamEnv, ParamEnvAnd, TyS};
17 use polonius_engine::Atom;
19 use rustc_data_structures::captures::Captures;
20 use rustc_errors::ErrorReported;
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, Ident, Symbol};
26 use rustc_target::abi::{Size, VariantIdx};
27 use rustc_target::spec::abi;
29 use std::cmp::Ordering;
30 use std::marker::PhantomData;
32 use ty::util::IntTypeExt;
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.
206 Error(DelaySpanBugEmitted),
209 /// A type that is not publicly constructable. This prevents people from making `TyKind::Error`
210 /// except through `tcx.err*()`.
211 #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
212 #[derive(RustcEncodable, RustcDecodable, HashStable)]
213 pub struct DelaySpanBugEmitted(pub(super) ());
215 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
216 #[cfg(target_arch = "x86_64")]
217 static_assert_size!(TyKind<'_>, 24);
219 /// A closure can be modeled as a struct that looks like:
221 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
225 /// - 'l0...'li and T0...Tj are the generic parameters
226 /// in scope on the function that defined the closure,
227 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
228 /// is rather hackily encoded via a scalar type. See
229 /// `TyS::to_opt_closure_kind` for details.
230 /// - CS represents the *closure signature*, representing as a `fn()`
231 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
232 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
234 /// - U is a type parameter representing the types of its upvars, tupled up
235 /// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar,
236 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
238 /// So, for example, given this function:
240 /// fn foo<'a, T>(data: &'a mut T) {
241 /// do(|| data.count += 1)
244 /// the type of the closure would be something like:
246 /// struct Closure<'a, T, U>(...U);
248 /// Note that the type of the upvar is not specified in the struct.
249 /// You may wonder how the impl would then be able to use the upvar,
250 /// if it doesn't know it's type? The answer is that the impl is
251 /// (conceptually) not fully generic over Closure but rather tied to
252 /// instances with the expected upvar types:
254 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
258 /// You can see that the *impl* fully specified the type of the upvar
259 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
260 /// (Here, I am assuming that `data` is mut-borrowed.)
262 /// Now, the last question you may ask is: Why include the upvar types
263 /// in an extra type parameter? The reason for this design is that the
264 /// upvar types can reference lifetimes that are internal to the
265 /// creating function. In my example above, for example, the lifetime
266 /// `'b` represents the scope of the closure itself; this is some
267 /// subset of `foo`, probably just the scope of the call to the to
268 /// `do()`. If we just had the lifetime/type parameters from the
269 /// enclosing function, we couldn't name this lifetime `'b`. Note that
270 /// there can also be lifetimes in the types of the upvars themselves,
271 /// if one of them happens to be a reference to something that the
272 /// creating fn owns.
274 /// OK, you say, so why not create a more minimal set of parameters
275 /// that just includes the extra lifetime parameters? The answer is
276 /// primarily that it would be hard --- we don't know at the time when
277 /// we create the closure type what the full types of the upvars are,
278 /// nor do we know which are borrowed and which are not. In this
279 /// design, we can just supply a fresh type parameter and figure that
282 /// All right, you say, but why include the type parameters from the
283 /// original function then? The answer is that codegen may need them
284 /// when monomorphizing, and they may not appear in the upvars. A
285 /// closure could capture no variables but still make use of some
286 /// in-scope type parameter with a bound (e.g., if our example above
287 /// had an extra `U: Default`, and the closure called `U::default()`).
289 /// There is another reason. This design (implicitly) prohibits
290 /// closures from capturing themselves (except via a trait
291 /// object). This simplifies closure inference considerably, since it
292 /// means that when we infer the kind of a closure or its upvars, we
293 /// don't have to handle cycles where the decisions we make for
294 /// closure C wind up influencing the decisions we ought to make for
295 /// closure C (which would then require fixed point iteration to
296 /// handle). Plus it fixes an ICE. :P
300 /// Generators are handled similarly in `GeneratorSubsts`. The set of
301 /// type parameters is similar, but `CK` and `CS` are replaced by the
302 /// following type parameters:
304 /// * `GS`: The generator's "resume type", which is the type of the
305 /// argument passed to `resume`, and the type of `yield` expressions
306 /// inside the generator.
307 /// * `GY`: The "yield type", which is the type of values passed to
308 /// `yield` inside the generator.
309 /// * `GR`: The "return type", which is the type of value returned upon
310 /// completion of the generator.
311 /// * `GW`: The "generator witness".
312 #[derive(Copy, Clone, Debug, TypeFoldable)]
313 pub struct ClosureSubsts<'tcx> {
314 /// Lifetime and type parameters from the enclosing function,
315 /// concatenated with a tuple containing the types of the upvars.
317 /// These are separated out because codegen wants to pass them around
318 /// when monomorphizing.
319 pub substs: SubstsRef<'tcx>,
322 /// Struct returned by `split()`. Note that these are subslices of the
323 /// parent slice and not canonical substs themselves.
324 struct SplitClosureSubsts<'tcx> {
325 closure_kind_ty: GenericArg<'tcx>,
326 closure_sig_as_fn_ptr_ty: GenericArg<'tcx>,
327 tupled_upvars_ty: GenericArg<'tcx>,
330 impl<'tcx> ClosureSubsts<'tcx> {
331 /// Divides the closure substs into their respective
332 /// components. Single source of truth with respect to the
334 fn split(self) -> SplitClosureSubsts<'tcx> {
335 match self.substs[..] {
336 [.., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
337 SplitClosureSubsts { closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty }
339 _ => bug!("closure substs missing synthetics"),
343 /// Returns `true` only if enough of the synthetic types are known to
344 /// allow using all of the methods on `ClosureSubsts` without panicking.
346 /// Used primarily by `ty::print::pretty` to be able to handle closure
347 /// types that haven't had their synthetic types substituted in.
348 pub fn is_valid(self) -> bool {
349 self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
353 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
354 self.split().tupled_upvars_ty.expect_ty().tuple_fields()
357 /// Returns the closure kind for this closure; may return a type
358 /// variable during inference. To get the closure kind during
359 /// inference, use `infcx.closure_kind(substs)`.
360 pub fn kind_ty(self) -> Ty<'tcx> {
361 self.split().closure_kind_ty.expect_ty()
364 /// Returns the `fn` pointer type representing the closure signature for this
366 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
367 // type is known at the time of the creation of `ClosureSubsts`,
368 // see `rustc_typeck::check::closure`.
369 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
370 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
373 /// Returns the closure kind for this closure; only usable outside
374 /// of an inference context, because in that context we know that
375 /// there are no type variables.
377 /// If you have an inference context, use `infcx.closure_kind()`.
378 pub fn kind(self) -> ty::ClosureKind {
379 self.kind_ty().to_opt_closure_kind().unwrap()
382 /// Extracts the signature from the closure.
383 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
384 let ty = self.sig_as_fn_ptr_ty();
386 ty::FnPtr(sig) => sig,
387 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind),
392 /// Similar to `ClosureSubsts`; see the above documentation for more.
393 #[derive(Copy, Clone, Debug, TypeFoldable)]
394 pub struct GeneratorSubsts<'tcx> {
395 pub substs: SubstsRef<'tcx>,
398 struct SplitGeneratorSubsts<'tcx> {
399 resume_ty: GenericArg<'tcx>,
400 yield_ty: GenericArg<'tcx>,
401 return_ty: GenericArg<'tcx>,
402 witness: GenericArg<'tcx>,
403 tupled_upvars_ty: GenericArg<'tcx>,
406 impl<'tcx> GeneratorSubsts<'tcx> {
407 fn split(self) -> SplitGeneratorSubsts<'tcx> {
408 match self.substs[..] {
409 [.., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
410 SplitGeneratorSubsts { resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty }
412 _ => bug!("generator substs missing synthetics"),
416 /// Returns `true` only if enough of the synthetic types are known to
417 /// allow using all of the methods on `GeneratorSubsts` without panicking.
419 /// Used primarily by `ty::print::pretty` to be able to handle generator
420 /// types that haven't had their synthetic types substituted in.
421 pub fn is_valid(self) -> bool {
422 self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_))
425 /// This describes the types that can be contained in a generator.
426 /// It will be a type variable initially and unified in the last stages of typeck of a body.
427 /// It contains a tuple of all the types that could end up on a generator frame.
428 /// The state transformation MIR pass may only produce layouts which mention types
429 /// in this tuple. Upvars are not counted here.
430 pub fn witness(self) -> Ty<'tcx> {
431 self.split().witness.expect_ty()
435 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
436 self.split().tupled_upvars_ty.expect_ty().tuple_fields()
439 /// Returns the type representing the resume type of the generator.
440 pub fn resume_ty(self) -> Ty<'tcx> {
441 self.split().resume_ty.expect_ty()
444 /// Returns the type representing the yield type of the generator.
445 pub fn yield_ty(self) -> Ty<'tcx> {
446 self.split().yield_ty.expect_ty()
449 /// Returns the type representing the return type of the generator.
450 pub fn return_ty(self) -> Ty<'tcx> {
451 self.split().return_ty.expect_ty()
454 /// Returns the "generator signature", which consists of its yield
455 /// and return types.
457 /// N.B., some bits of the code prefers to see this wrapped in a
458 /// binder, but it never contains bound regions. Probably this
459 /// function should be removed.
460 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
461 ty::Binder::dummy(self.sig())
464 /// Returns the "generator signature", which consists of its resume, yield
465 /// and return types.
466 pub fn sig(self) -> GenSig<'tcx> {
468 resume_ty: self.resume_ty(),
469 yield_ty: self.yield_ty(),
470 return_ty: self.return_ty(),
475 impl<'tcx> GeneratorSubsts<'tcx> {
476 /// Generator has not been resumed yet.
477 pub const UNRESUMED: usize = 0;
478 /// Generator has returned or is completed.
479 pub const RETURNED: usize = 1;
480 /// Generator has been poisoned.
481 pub const POISONED: usize = 2;
483 const UNRESUMED_NAME: &'static str = "Unresumed";
484 const RETURNED_NAME: &'static str = "Returned";
485 const POISONED_NAME: &'static str = "Panicked";
487 /// The valid variant indices of this generator.
489 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
490 // FIXME requires optimized MIR
491 let num_variants = tcx.generator_layout(def_id).variant_fields.len();
492 VariantIdx::new(0)..VariantIdx::new(num_variants)
495 /// The discriminant for the given variant. Panics if the `variant_index` is
498 pub fn discriminant_for_variant(
502 variant_index: VariantIdx,
504 // Generators don't support explicit discriminant values, so they are
505 // the same as the variant index.
506 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
507 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
510 /// The set of all discriminants for the generator, enumerated with their
513 pub fn discriminants(
517 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
518 self.variant_range(def_id, tcx).map(move |index| {
519 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
523 /// Calls `f` with a reference to the name of the enumerator for the given
525 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
527 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
528 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
529 Self::POISONED => Cow::from(Self::POISONED_NAME),
530 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
534 /// The type of the state discriminant used in the generator type.
536 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
540 /// This returns the types of the MIR locals which had to be stored across suspension points.
541 /// It is calculated in rustc_mir::transform::generator::StateTransform.
542 /// All the types here must be in the tuple in GeneratorInterior.
544 /// The locals are grouped by their variant number. Note that some locals may
545 /// be repeated in multiple variants.
551 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
552 let layout = tcx.generator_layout(def_id);
553 layout.variant_fields.iter().map(move |variant| {
554 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
558 /// This is the types of the fields of a generator which are not stored in a
561 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
566 #[derive(Debug, Copy, Clone)]
567 pub enum UpvarSubsts<'tcx> {
568 Closure(SubstsRef<'tcx>),
569 Generator(SubstsRef<'tcx>),
572 impl<'tcx> UpvarSubsts<'tcx> {
574 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
575 let tupled_upvars_ty = match self {
576 UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty,
577 UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty,
579 tupled_upvars_ty.expect_ty().tuple_fields()
583 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, RustcEncodable, RustcDecodable)]
584 #[derive(HashStable, TypeFoldable)]
585 pub enum ExistentialPredicate<'tcx> {
586 /// E.g., `Iterator`.
587 Trait(ExistentialTraitRef<'tcx>),
588 /// E.g., `Iterator::Item = T`.
589 Projection(ExistentialProjection<'tcx>),
594 impl<'tcx> ExistentialPredicate<'tcx> {
595 /// Compares via an ordering that will not change if modules are reordered or other changes are
596 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
597 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
598 use self::ExistentialPredicate::*;
599 match (*self, *other) {
600 (Trait(_), Trait(_)) => Ordering::Equal,
601 (Projection(ref a), Projection(ref b)) => {
602 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
604 (AutoTrait(ref a), AutoTrait(ref b)) => {
605 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
607 (Trait(_), _) => Ordering::Less,
608 (Projection(_), Trait(_)) => Ordering::Greater,
609 (Projection(_), _) => Ordering::Less,
610 (AutoTrait(_), _) => Ordering::Greater,
615 impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
616 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
617 use crate::ty::ToPredicate;
618 match self.skip_binder() {
619 ExistentialPredicate::Trait(tr) => {
620 Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
622 ExistentialPredicate::Projection(p) => {
623 ty::PredicateKind::Projection(Binder(p.with_self_ty(tcx, self_ty)))
626 ExistentialPredicate::AutoTrait(did) => {
628 Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) });
629 trait_ref.without_const().to_predicate(tcx)
635 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx List<ExistentialPredicate<'tcx>> {}
637 impl<'tcx> List<ExistentialPredicate<'tcx>> {
638 /// Returns the "principal `DefId`" of this set of existential predicates.
640 /// A Rust trait object type consists (in addition to a lifetime bound)
641 /// of a set of trait bounds, which are separated into any number
642 /// of auto-trait bounds, and at most one non-auto-trait bound. The
643 /// non-auto-trait bound is called the "principal" of the trait
646 /// Only the principal can have methods or type parameters (because
647 /// auto traits can have neither of them). This is important, because
648 /// it means the auto traits can be treated as an unordered set (methods
649 /// would force an order for the vtable, while relating traits with
650 /// type parameters without knowing the order to relate them in is
651 /// a rather non-trivial task).
653 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
654 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
655 /// are the set `{Sync}`.
657 /// It is also possible to have a "trivial" trait object that
658 /// consists only of auto traits, with no principal - for example,
659 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
660 /// is `{Send, Sync}`, while there is no principal. These trait objects
661 /// have a "trivial" vtable consisting of just the size, alignment,
663 pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> {
665 ExistentialPredicate::Trait(tr) => Some(tr),
670 pub fn principal_def_id(&self) -> Option<DefId> {
671 self.principal().map(|trait_ref| trait_ref.def_id)
675 pub fn projection_bounds<'a>(
677 ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a {
678 self.iter().filter_map(|predicate| match predicate {
679 ExistentialPredicate::Projection(projection) => Some(projection),
685 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
686 self.iter().filter_map(|predicate| match predicate {
687 ExistentialPredicate::AutoTrait(did) => Some(did),
693 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
694 pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
695 self.skip_binder().principal().map(Binder::bind)
698 pub fn principal_def_id(&self) -> Option<DefId> {
699 self.skip_binder().principal_def_id()
703 pub fn projection_bounds<'a>(
705 ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a {
706 self.skip_binder().projection_bounds().map(Binder::bind)
710 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
711 self.skip_binder().auto_traits()
716 ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx {
717 self.skip_binder().iter().map(Binder::bind)
721 /// A complete reference to a trait. These take numerous guises in syntax,
722 /// but perhaps the most recognizable form is in a where-clause:
726 /// This would be represented by a trait-reference where the `DefId` is the
727 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
728 /// and `U` as parameter 1.
730 /// Trait references also appear in object types like `Foo<U>`, but in
731 /// that case the `Self` parameter is absent from the substitutions.
732 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
733 #[derive(HashStable, TypeFoldable)]
734 pub struct TraitRef<'tcx> {
736 pub substs: SubstsRef<'tcx>,
739 impl<'tcx> TraitRef<'tcx> {
740 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
741 TraitRef { def_id, substs }
744 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
745 /// are the parameters defined on trait.
746 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
747 TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
751 pub fn self_ty(&self) -> Ty<'tcx> {
752 self.substs.type_at(0)
758 substs: SubstsRef<'tcx>,
759 ) -> ty::TraitRef<'tcx> {
760 let defs = tcx.generics_of(trait_id);
762 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
766 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
768 impl<'tcx> PolyTraitRef<'tcx> {
769 pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
770 self.map_bound_ref(|tr| tr.self_ty())
773 pub fn def_id(&self) -> DefId {
774 self.skip_binder().def_id
777 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
778 // Note that we preserve binding levels
779 Binder(ty::TraitPredicate { trait_ref: self.skip_binder() })
783 /// An existential reference to a trait, where `Self` is erased.
784 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
786 /// exists T. T: Trait<'a, 'b, X, Y>
788 /// The substitutions don't include the erased `Self`, only trait
789 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
790 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
791 #[derive(HashStable, TypeFoldable)]
792 pub struct ExistentialTraitRef<'tcx> {
794 pub substs: SubstsRef<'tcx>,
797 impl<'tcx> ExistentialTraitRef<'tcx> {
798 pub fn erase_self_ty(
800 trait_ref: ty::TraitRef<'tcx>,
801 ) -> ty::ExistentialTraitRef<'tcx> {
802 // Assert there is a Self.
803 trait_ref.substs.type_at(0);
805 ty::ExistentialTraitRef {
806 def_id: trait_ref.def_id,
807 substs: tcx.intern_substs(&trait_ref.substs[1..]),
811 /// Object types don't have a self type specified. Therefore, when
812 /// we convert the principal trait-ref into a normal trait-ref,
813 /// you must give *some* self type. A common choice is `mk_err()`
814 /// or some placeholder type.
815 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
816 // otherwise the escaping vars would be captured by the binder
817 // debug_assert!(!self_ty.has_escaping_bound_vars());
819 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
823 pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>;
825 impl<'tcx> PolyExistentialTraitRef<'tcx> {
826 pub fn def_id(&self) -> DefId {
827 self.skip_binder().def_id
830 /// Object types don't have a self type specified. Therefore, when
831 /// we convert the principal trait-ref into a normal trait-ref,
832 /// you must give *some* self type. A common choice is `mk_err()`
833 /// or some placeholder type.
834 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
835 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
839 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
840 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
841 /// (which would be represented by the type `PolyTraitRef ==
842 /// Binder<TraitRef>`). Note that when we instantiate,
843 /// erase, or otherwise "discharge" these bound vars, we change the
844 /// type from `Binder<T>` to just `T` (see
845 /// e.g., `liberate_late_bound_regions`).
846 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
847 pub struct Binder<T>(T);
850 /// Wraps `value` in a binder, asserting that `value` does not
851 /// contain any bound vars that would be bound by the
852 /// binder. This is commonly used to 'inject' a value T into a
853 /// different binding level.
854 pub fn dummy<'tcx>(value: T) -> Binder<T>
856 T: TypeFoldable<'tcx>,
858 debug_assert!(!value.has_escaping_bound_vars());
862 /// Wraps `value` in a binder, binding higher-ranked vars (if any).
863 pub fn bind(value: T) -> Binder<T> {
867 /// Skips the binder and returns the "bound" value. This is a
868 /// risky thing to do because it's easy to get confused about
869 /// De Bruijn indices and the like. It is usually better to
870 /// discharge the binder using `no_bound_vars` or
871 /// `replace_late_bound_regions` or something like
872 /// that. `skip_binder` is only valid when you are either
873 /// extracting data that has nothing to do with bound vars, you
874 /// are doing some sort of test that does not involve bound
875 /// regions, or you are being very careful about your depth
878 /// Some examples where `skip_binder` is reasonable:
880 /// - extracting the `DefId` from a PolyTraitRef;
881 /// - comparing the self type of a PolyTraitRef to see if it is equal to
882 /// a type parameter `X`, since the type `X` does not reference any regions
883 pub fn skip_binder(self) -> T {
887 pub fn as_ref(&self) -> Binder<&T> {
891 pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U>
895 self.as_ref().map_bound(f)
898 pub fn map_bound<F, U>(self, f: F) -> Binder<U>
905 /// Unwraps and returns the value within, but only if it contains
906 /// no bound vars at all. (In other words, if this binder --
907 /// and indeed any enclosing binder -- doesn't bind anything at
908 /// all.) Otherwise, returns `None`.
910 /// (One could imagine having a method that just unwraps a single
911 /// binder, but permits late-bound vars bound by enclosing
912 /// binders, but that would require adjusting the debruijn
913 /// indices, and given the shallow binding structure we often use,
914 /// would not be that useful.)
915 pub fn no_bound_vars<'tcx>(self) -> Option<T>
917 T: TypeFoldable<'tcx>,
919 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
922 /// Given two things that have the same binder level,
923 /// and an operation that wraps on their contents, executes the operation
924 /// and then wraps its result.
926 /// `f` should consider bound regions at depth 1 to be free, and
927 /// anything it produces with bound regions at depth 1 will be
928 /// bound in the resulting return value.
929 pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R>
931 F: FnOnce(T, U) -> R,
933 Binder(f(self.0, u.0))
936 /// Splits the contents into two things that share the same binder
937 /// level as the original, returning two distinct binders.
939 /// `f` should consider bound regions at depth 1 to be free, and
940 /// anything it produces with bound regions at depth 1 will be
941 /// bound in the resulting return values.
942 pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>)
944 F: FnOnce(T) -> (U, V),
946 let (u, v) = f(self.0);
947 (Binder(u), Binder(v))
951 /// Represents the projection of an associated type. In explicit UFCS
952 /// form this would be written `<T as Trait<..>>::N`.
953 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
954 #[derive(HashStable, TypeFoldable)]
955 pub struct ProjectionTy<'tcx> {
956 /// The parameters of the associated item.
957 pub substs: SubstsRef<'tcx>,
959 /// The `DefId` of the `TraitItem` for the associated type `N`.
961 /// Note that this is not the `DefId` of the `TraitRef` containing this
962 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
963 pub item_def_id: DefId,
966 impl<'tcx> ProjectionTy<'tcx> {
967 /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the
968 /// associated item named `item_name`.
969 pub fn from_ref_and_name(
971 trait_ref: ty::TraitRef<'tcx>,
973 ) -> ProjectionTy<'tcx> {
974 let item_def_id = tcx
975 .associated_items(trait_ref.def_id)
976 .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id)
980 ProjectionTy { substs: trait_ref.substs, item_def_id }
983 /// Extracts the underlying trait reference from this projection.
984 /// For example, if this is a projection of `<T as Iterator>::Item`,
985 /// then this function would return a `T: Iterator` trait reference.
986 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
987 let def_id = tcx.associated_item(self.item_def_id).container.id();
988 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
991 pub fn self_ty(&self) -> Ty<'tcx> {
992 self.substs.type_at(0)
996 #[derive(Copy, Clone, Debug, TypeFoldable)]
997 pub struct GenSig<'tcx> {
998 pub resume_ty: Ty<'tcx>,
999 pub yield_ty: Ty<'tcx>,
1000 pub return_ty: Ty<'tcx>,
1003 pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
1005 impl<'tcx> PolyGenSig<'tcx> {
1006 pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> {
1007 self.map_bound_ref(|sig| sig.resume_ty)
1009 pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
1010 self.map_bound_ref(|sig| sig.yield_ty)
1012 pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
1013 self.map_bound_ref(|sig| sig.return_ty)
1017 /// Signature of a function type, which we have arbitrarily
1018 /// decided to use to refer to the input/output types.
1020 /// - `inputs`: is the list of arguments and their modes.
1021 /// - `output`: is the return type.
1022 /// - `c_variadic`: indicates whether this is a C-variadic function.
1023 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1024 #[derive(HashStable, TypeFoldable)]
1025 pub struct FnSig<'tcx> {
1026 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1027 pub c_variadic: bool,
1028 pub unsafety: hir::Unsafety,
1032 impl<'tcx> FnSig<'tcx> {
1033 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1034 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1037 pub fn output(&self) -> Ty<'tcx> {
1038 self.inputs_and_output[self.inputs_and_output.len() - 1]
1041 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1043 fn fake() -> FnSig<'tcx> {
1045 inputs_and_output: List::empty(),
1047 unsafety: hir::Unsafety::Normal,
1048 abi: abi::Abi::Rust,
1053 pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
1055 impl<'tcx> PolyFnSig<'tcx> {
1057 pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> {
1058 self.map_bound_ref(|fn_sig| fn_sig.inputs())
1061 pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
1062 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1064 pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> {
1065 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1068 pub fn output(&self) -> ty::Binder<Ty<'tcx>> {
1069 self.map_bound_ref(|fn_sig| fn_sig.output())
1071 pub fn c_variadic(&self) -> bool {
1072 self.skip_binder().c_variadic
1074 pub fn unsafety(&self) -> hir::Unsafety {
1075 self.skip_binder().unsafety
1077 pub fn abi(&self) -> abi::Abi {
1078 self.skip_binder().abi
1082 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
1084 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1085 #[derive(HashStable)]
1086 pub struct ParamTy {
1091 impl<'tcx> ParamTy {
1092 pub fn new(index: u32, name: Symbol) -> ParamTy {
1093 ParamTy { index, name }
1096 pub fn for_self() -> ParamTy {
1097 ParamTy::new(0, kw::SelfUpper)
1100 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1101 ParamTy::new(def.index, def.name)
1104 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1105 tcx.mk_ty_param(self.index, self.name)
1109 #[derive(Copy, Clone, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
1110 #[derive(HashStable)]
1111 pub struct ParamConst {
1116 impl<'tcx> ParamConst {
1117 pub fn new(index: u32, name: Symbol) -> ParamConst {
1118 ParamConst { index, name }
1121 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1122 ParamConst::new(def.index, def.name)
1125 pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Const<'tcx> {
1126 tcx.mk_const_param(self.index, self.name, ty)
1130 rustc_index::newtype_index! {
1131 /// A [De Bruijn index][dbi] is a standard means of representing
1132 /// regions (and perhaps later types) in a higher-ranked setting. In
1133 /// particular, imagine a type like this:
1135 /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
1138 /// | +------------+ 0 | |
1140 /// +--------------------------------+ 1 |
1142 /// +------------------------------------------+ 0
1144 /// In this type, there are two binders (the outer fn and the inner
1145 /// fn). We need to be able to determine, for any given region, which
1146 /// fn type it is bound by, the inner or the outer one. There are
1147 /// various ways you can do this, but a De Bruijn index is one of the
1148 /// more convenient and has some nice properties. The basic idea is to
1149 /// count the number of binders, inside out. Some examples should help
1150 /// clarify what I mean.
1152 /// Let's start with the reference type `&'b isize` that is the first
1153 /// argument to the inner function. This region `'b` is assigned a De
1154 /// Bruijn index of 0, meaning "the innermost binder" (in this case, a
1155 /// fn). The region `'a` that appears in the second argument type (`&'a
1156 /// isize`) would then be assigned a De Bruijn index of 1, meaning "the
1157 /// second-innermost binder". (These indices are written on the arrays
1158 /// in the diagram).
1160 /// What is interesting is that De Bruijn index attached to a particular
1161 /// variable will vary depending on where it appears. For example,
1162 /// the final type `&'a char` also refers to the region `'a` declared on
1163 /// the outermost fn. But this time, this reference is not nested within
1164 /// any other binders (i.e., it is not an argument to the inner fn, but
1165 /// rather the outer one). Therefore, in this case, it is assigned a
1166 /// De Bruijn index of 0, because the innermost binder in that location
1167 /// is the outer fn.
1169 /// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
1170 #[derive(HashStable)]
1171 pub struct DebruijnIndex {
1172 DEBUG_FORMAT = "DebruijnIndex({})",
1173 const INNERMOST = 0,
1177 pub type Region<'tcx> = &'tcx RegionKind;
1179 /// Representation of regions. Note that the NLL checker uses a distinct
1180 /// representation of regions. For this reason, it internally replaces all the
1181 /// regions with inference variables -- the index of the variable is then used
1182 /// to index into internal NLL data structures. See `rustc_mir::borrow_check`
1183 /// module for more information.
1185 /// ## The Region lattice within a given function
1187 /// In general, the region lattice looks like
1190 /// static ----------+-----...------+ (greatest)
1192 /// early-bound and | |
1193 /// free regions | |
1196 /// empty(root) placeholder(U1) |
1198 /// | / placeholder(Un)
1203 /// empty(Un) -------- (smallest)
1206 /// Early-bound/free regions are the named lifetimes in scope from the
1207 /// function declaration. They have relationships to one another
1208 /// determined based on the declared relationships from the
1211 /// Note that inference variables and bound regions are not included
1212 /// in this diagram. In the case of inference variables, they should
1213 /// be inferred to some other region from the diagram. In the case of
1214 /// bound regions, they are excluded because they don't make sense to
1215 /// include -- the diagram indicates the relationship between free
1218 /// ## Inference variables
1220 /// During region inference, we sometimes create inference variables,
1221 /// represented as `ReVar`. These will be inferred by the code in
1222 /// `infer::lexical_region_resolve` to some free region from the
1223 /// lattice above (the minimal region that meets the
1226 /// During NLL checking, where regions are defined differently, we
1227 /// also use `ReVar` -- in that case, the index is used to index into
1228 /// the NLL region checker's data structures. The variable may in fact
1229 /// represent either a free region or an inference variable, in that
1232 /// ## Bound Regions
1234 /// These are regions that are stored behind a binder and must be substituted
1235 /// with some concrete region before being used. There are two kind of
1236 /// bound regions: early-bound, which are bound in an item's `Generics`,
1237 /// and are substituted by a `InternalSubsts`, and late-bound, which are part of
1238 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1239 /// the likes of `liberate_late_bound_regions`. The distinction exists
1240 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1242 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1243 /// outside their binder, e.g., in types passed to type inference, and
1244 /// should first be substituted (by placeholder regions, free regions,
1245 /// or region variables).
1247 /// ## Placeholder and Free Regions
1249 /// One often wants to work with bound regions without knowing their precise
1250 /// identity. For example, when checking a function, the lifetime of a borrow
1251 /// can end up being assigned to some region parameter. In these cases,
1252 /// it must be ensured that bounds on the region can't be accidentally
1253 /// assumed without being checked.
1255 /// To do this, we replace the bound regions with placeholder markers,
1256 /// which don't satisfy any relation not explicitly provided.
1258 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1259 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1260 /// to be used. These also support explicit bounds: both the internally-stored
1261 /// *scope*, which the region is assumed to outlive, as well as other
1262 /// relations stored in the `FreeRegionMap`. Note that these relations
1263 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1264 /// `resolve_regions_and_report_errors`.
1266 /// When working with higher-ranked types, some region relations aren't
1267 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1268 /// `RePlaceholder` is designed for this purpose. In these contexts,
1269 /// there's also the risk that some inference variable laying around will
1270 /// get unified with your placeholder region: if you want to check whether
1271 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1272 /// with a placeholder region `'%a`, the variable `'_` would just be
1273 /// instantiated to the placeholder region `'%a`, which is wrong because
1274 /// the inference variable is supposed to satisfy the relation
1275 /// *for every value of the placeholder region*. To ensure that doesn't
1276 /// happen, you can use `leak_check`. This is more clearly explained
1277 /// by the [rustc dev guide].
1279 /// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1280 /// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1281 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1282 #[derive(Clone, PartialEq, Eq, Hash, Copy, RustcEncodable, RustcDecodable, PartialOrd, Ord)]
1283 pub enum RegionKind {
1284 /// Region bound in a type or fn declaration which will be
1285 /// substituted 'early' -- that is, at the same time when type
1286 /// parameters are substituted.
1287 ReEarlyBound(EarlyBoundRegion),
1289 /// Region bound in a function scope, which will be substituted when the
1290 /// function is called.
1291 ReLateBound(DebruijnIndex, BoundRegion),
1293 /// When checking a function body, the types of all arguments and so forth
1294 /// that refer to bound region parameters are modified to refer to free
1295 /// region parameters.
1298 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1301 /// A region variable. Should not exist after typeck.
1304 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1305 /// Should not exist after typeck.
1306 RePlaceholder(ty::PlaceholderRegion),
1308 /// Empty lifetime is for data that is never accessed. We tag the
1309 /// empty lifetime with a universe -- the idea is that we don't
1310 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1311 /// Therefore, the `'empty` in a universe `U` is less than all
1312 /// regions visible from `U`, but not less than regions not visible
1314 ReEmpty(ty::UniverseIndex),
1316 /// Erased region, used by trait selection, in MIR and during codegen.
1320 impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
1322 #[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, PartialOrd, Ord)]
1323 pub struct EarlyBoundRegion {
1329 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1334 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1335 pub struct ConstVid<'tcx> {
1337 pub phantom: PhantomData<&'tcx ()>,
1340 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1345 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1346 pub struct FloatVid {
1350 rustc_index::newtype_index! {
1351 pub struct RegionVid {
1352 DEBUG_FORMAT = custom,
1356 impl Atom for RegionVid {
1357 fn index(self) -> usize {
1362 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
1363 #[derive(HashStable)]
1369 /// A `FreshTy` is one that is generated as a replacement for an
1370 /// unbound type variable. This is convenient for caching etc. See
1371 /// `infer::freshen` for more details.
1377 rustc_index::newtype_index! {
1378 pub struct BoundVar { .. }
1381 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1382 #[derive(HashStable)]
1383 pub struct BoundTy {
1385 pub kind: BoundTyKind,
1388 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1389 #[derive(HashStable)]
1390 pub enum BoundTyKind {
1395 impl From<BoundVar> for BoundTy {
1396 fn from(var: BoundVar) -> Self {
1397 BoundTy { var, kind: BoundTyKind::Anon }
1401 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1402 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
1403 #[derive(HashStable, TypeFoldable)]
1404 pub struct ExistentialProjection<'tcx> {
1405 pub item_def_id: DefId,
1406 pub substs: SubstsRef<'tcx>,
1410 pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>;
1412 impl<'tcx> ExistentialProjection<'tcx> {
1413 /// Extracts the underlying existential trait reference from this projection.
1414 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1415 /// then this function would return a `exists T. T: Iterator` existential trait
1417 pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> {
1418 let def_id = tcx.associated_item(self.item_def_id).container.id();
1419 ty::ExistentialTraitRef { def_id, substs: self.substs }
1422 pub fn with_self_ty(
1426 ) -> ty::ProjectionPredicate<'tcx> {
1427 // otherwise the escaping regions would be captured by the binders
1428 debug_assert!(!self_ty.has_escaping_bound_vars());
1430 ty::ProjectionPredicate {
1431 projection_ty: ty::ProjectionTy {
1432 item_def_id: self.item_def_id,
1433 substs: tcx.mk_substs_trait(self_ty, self.substs),
1440 impl<'tcx> PolyExistentialProjection<'tcx> {
1441 pub fn with_self_ty(
1445 ) -> ty::PolyProjectionPredicate<'tcx> {
1446 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1449 pub fn item_def_id(&self) -> DefId {
1450 self.skip_binder().item_def_id
1454 impl DebruijnIndex {
1455 /// Returns the resulting index when this value is moved into
1456 /// `amount` number of new binders. So, e.g., if you had
1458 /// for<'a> fn(&'a x)
1460 /// and you wanted to change it to
1462 /// for<'a> fn(for<'b> fn(&'a x))
1464 /// you would need to shift the index for `'a` into a new binder.
1466 pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
1467 DebruijnIndex::from_u32(self.as_u32() + amount)
1470 /// Update this index in place by shifting it "in" through
1471 /// `amount` number of binders.
1472 pub fn shift_in(&mut self, amount: u32) {
1473 *self = self.shifted_in(amount);
1476 /// Returns the resulting index when this value is moved out from
1477 /// `amount` number of new binders.
1479 pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
1480 DebruijnIndex::from_u32(self.as_u32() - amount)
1483 /// Update in place by shifting out from `amount` binders.
1484 pub fn shift_out(&mut self, amount: u32) {
1485 *self = self.shifted_out(amount);
1488 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1489 /// innermost binder. That is, if we have something bound at `to_binder`,
1490 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1491 /// when moving a region out from inside binders:
1494 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1495 /// // Binder: D3 D2 D1 ^^
1498 /// Here, the region `'a` would have the De Bruijn index D3,
1499 /// because it is the bound 3 binders out. However, if we wanted
1500 /// to refer to that region `'a` in the second argument (the `_`),
1501 /// those two binders would not be in scope. In that case, we
1502 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1503 /// De Bruijn index of `'a` to D1 (the innermost binder).
1505 /// If we invoke `shift_out_to_binder` and the region is in fact
1506 /// bound by one of the binders we are shifting out of, that is an
1507 /// error (and should fail an assertion failure).
1508 pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
1509 self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
1513 /// Region utilities
1515 /// Is this region named by the user?
1516 pub fn has_name(&self) -> bool {
1518 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1519 RegionKind::ReLateBound(_, br) => br.is_named(),
1520 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1521 RegionKind::ReStatic => true,
1522 RegionKind::ReVar(..) => false,
1523 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1524 RegionKind::ReEmpty(_) => false,
1525 RegionKind::ReErased => false,
1529 pub fn is_late_bound(&self) -> bool {
1531 ty::ReLateBound(..) => true,
1536 pub fn is_placeholder(&self) -> bool {
1538 ty::RePlaceholder(..) => true,
1543 pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
1545 ty::ReLateBound(debruijn, _) => debruijn >= index,
1550 /// Adjusts any De Bruijn indices so as to make `to_binder` the
1551 /// innermost binder. That is, if we have something bound at `to_binder`,
1552 /// it will now be bound at INNERMOST. This is an appropriate thing to do
1553 /// when moving a region out from inside binders:
1556 /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
1557 /// // Binder: D3 D2 D1 ^^
1560 /// Here, the region `'a` would have the De Bruijn index D3,
1561 /// because it is the bound 3 binders out. However, if we wanted
1562 /// to refer to that region `'a` in the second argument (the `_`),
1563 /// those two binders would not be in scope. In that case, we
1564 /// might invoke `shift_out_to_binder(D3)`. This would adjust the
1565 /// De Bruijn index of `'a` to D1 (the innermost binder).
1567 /// If we invoke `shift_out_to_binder` and the region is in fact
1568 /// bound by one of the binders we are shifting out of, that is an
1569 /// error (and should fail an assertion failure).
1570 pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind {
1572 ty::ReLateBound(debruijn, r) => {
1573 ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r)
1579 pub fn type_flags(&self) -> TypeFlags {
1580 let mut flags = TypeFlags::empty();
1584 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1585 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1586 flags = flags | TypeFlags::HAS_RE_INFER;
1588 ty::RePlaceholder(..) => {
1589 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1590 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1591 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1593 ty::ReEarlyBound(..) => {
1594 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1595 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1596 flags = flags | TypeFlags::HAS_RE_PARAM;
1598 ty::ReFree { .. } => {
1599 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1600 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1602 ty::ReEmpty(_) | ty::ReStatic => {
1603 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1605 ty::ReLateBound(..) => {
1606 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1609 flags = flags | TypeFlags::HAS_RE_ERASED;
1613 debug!("type_flags({:?}) = {:?}", self, flags);
1618 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1619 /// For example, consider the regions in this snippet of code:
1623 /// ^^ -- early bound, declared on an impl
1625 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1626 /// ^^ ^^ ^ anonymous, late-bound
1627 /// | early-bound, appears in where-clauses
1628 /// late-bound, appears only in fn args
1633 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1634 /// of the impl, and for all the other highlighted regions, it
1635 /// would return the `DefId` of the function. In other cases (not shown), this
1636 /// function might return the `DefId` of a closure.
1637 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1639 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1640 ty::ReFree(fr) => fr.scope,
1641 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1647 impl<'tcx> TyS<'tcx> {
1649 pub fn is_unit(&self) -> bool {
1651 Tuple(ref tys) => tys.is_empty(),
1657 pub fn is_never(&self) -> bool {
1664 /// Checks whether a type is definitely uninhabited. This is
1665 /// conservative: for some types that are uninhabited we return `false`,
1666 /// but we only return `true` for types that are definitely uninhabited.
1667 /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
1668 /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
1669 /// size, to account for partial initialisation. See #49298 for details.)
1670 pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool {
1671 // FIXME(varkor): we can make this less conversative by substituting concrete
1675 ty::Adt(def, _) if def.is_union() => {
1676 // For now, `union`s are never considered uninhabited.
1679 ty::Adt(def, _) => {
1680 // Any ADT is uninhabited if either:
1681 // (a) It has no variants (i.e. an empty `enum`);
1682 // (b) Each of its variants (a single one in the case of a `struct`) has at least
1683 // one uninhabited field.
1684 def.variants.iter().all(|var| {
1685 var.fields.iter().any(|field| {
1686 tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx)
1691 self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx))
1693 ty::Array(ty, len) => {
1694 match len.try_eval_usize(tcx, ParamEnv::empty()) {
1695 // If the array is definitely non-empty, it's uninhabited if
1696 // the type of its elements is uninhabited.
1697 Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx),
1702 // References to uninitialised memory is valid for any type, including
1703 // uninhabited types, in unsafe code, so we treat all references as
1712 pub fn is_primitive(&self) -> bool {
1714 Bool | Char | Int(_) | Uint(_) | Float(_) => true,
1720 pub fn is_ty_var(&self) -> bool {
1722 Infer(TyVar(_)) => true,
1728 pub fn is_ty_infer(&self) -> bool {
1736 pub fn is_phantom_data(&self) -> bool {
1737 if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false }
1741 pub fn is_bool(&self) -> bool {
1745 /// Returns `true` if this type is a `str`.
1747 pub fn is_str(&self) -> bool {
1752 pub fn is_param(&self, index: u32) -> bool {
1754 ty::Param(ref data) => data.index == index,
1760 pub fn is_slice(&self) -> bool {
1762 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind {
1763 Slice(_) | Str => true,
1771 pub fn is_simd(&self) -> bool {
1773 Adt(def, _) => def.repr.simd(),
1778 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1780 Array(ty, _) | Slice(ty) => ty,
1781 Str => tcx.mk_mach_uint(ast::UintTy::U8),
1782 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1786 pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1788 Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
1789 _ => bug!("`simd_type` called on invalid type"),
1793 pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
1794 // Parameter currently unused, but probably needed in the future to
1795 // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
1797 Adt(def, _) => def.non_enum_variant().fields.len() as u64,
1798 _ => bug!("`simd_size` called on invalid type"),
1802 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1804 Adt(def, substs) => {
1805 let variant = def.non_enum_variant();
1806 (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
1808 _ => bug!("`simd_size_and_type` called on invalid type"),
1813 pub fn is_region_ptr(&self) -> bool {
1821 pub fn is_mutable_ptr(&self) -> bool {
1823 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1824 | Ref(_, _, hir::Mutability::Mut) => true,
1830 pub fn is_unsafe_ptr(&self) -> bool {
1837 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1839 pub fn is_any_ptr(&self) -> bool {
1840 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1844 pub fn is_box(&self) -> bool {
1846 Adt(def, _) => def.is_box(),
1851 /// Panics if called on any type other than `Box<T>`.
1852 pub fn boxed_ty(&self) -> Ty<'tcx> {
1854 Adt(def, substs) if def.is_box() => substs.type_at(0),
1855 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1859 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1860 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1861 /// contents are abstract to rustc.)
1863 pub fn is_scalar(&self) -> bool {
1870 | Infer(IntVar(_) | FloatVar(_))
1873 | RawPtr(_) => true,
1878 /// Returns `true` if this type is a floating point type.
1880 pub fn is_floating_point(&self) -> bool {
1882 Float(_) | Infer(FloatVar(_)) => true,
1888 pub fn is_trait(&self) -> bool {
1890 Dynamic(..) => true,
1896 pub fn is_enum(&self) -> bool {
1898 Adt(adt_def, _) => adt_def.is_enum(),
1904 pub fn is_closure(&self) -> bool {
1906 Closure(..) => true,
1912 pub fn is_generator(&self) -> bool {
1914 Generator(..) => true,
1920 pub fn is_integral(&self) -> bool {
1922 Infer(IntVar(_)) | Int(_) | Uint(_) => true,
1928 pub fn is_fresh_ty(&self) -> bool {
1930 Infer(FreshTy(_)) => true,
1936 pub fn is_fresh(&self) -> bool {
1938 Infer(FreshTy(_)) => true,
1939 Infer(FreshIntTy(_)) => true,
1940 Infer(FreshFloatTy(_)) => true,
1946 pub fn is_char(&self) -> bool {
1954 pub fn is_numeric(&self) -> bool {
1955 self.is_integral() || self.is_floating_point()
1959 pub fn is_signed(&self) -> bool {
1967 pub fn is_ptr_sized_integral(&self) -> bool {
1969 Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true,
1975 pub fn is_machine(&self) -> bool {
1977 Int(..) | Uint(..) | Float(..) => true,
1983 pub fn has_concrete_skeleton(&self) -> bool {
1985 Param(_) | Infer(_) | Error(_) => false,
1990 /// Returns the type and mutability of `*ty`.
1992 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1993 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
1994 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
1996 Adt(def, _) if def.is_box() => {
1997 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
1999 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }),
2000 RawPtr(mt) if explicit => Some(mt),
2005 /// Returns the type of `ty[i]`.
2006 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2008 Array(ty, _) | Slice(ty) => Some(ty),
2013 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2015 FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs),
2018 // ignore errors (#54954)
2019 ty::Binder::dummy(FnSig::fake())
2021 Closure(..) => bug!(
2022 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2024 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2029 pub fn is_fn(&self) -> bool {
2031 FnDef(..) | FnPtr(_) => true,
2037 pub fn is_fn_ptr(&self) -> bool {
2045 pub fn is_impl_trait(&self) -> bool {
2053 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2055 Adt(adt, _) => Some(adt),
2060 /// Iterates over tuple fields.
2061 /// Panics when called on anything but a tuple.
2062 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2064 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2065 _ => bug!("tuple_fields called on non-tuple"),
2069 /// If the type contains variants, returns the valid range of variant indices.
2071 // FIXME: This requires the optimized MIR in the case of generators.
2073 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2075 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2076 TyKind::Generator(def_id, substs, _) => {
2077 Some(substs.as_generator().variant_range(def_id, tcx))
2083 /// If the type contains variants, returns the variant for `variant_index`.
2084 /// Panics if `variant_index` is out of range.
2086 // FIXME: This requires the optimized MIR in the case of generators.
2088 pub fn discriminant_for_variant(
2091 variant_index: VariantIdx,
2092 ) -> Option<Discr<'tcx>> {
2094 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2095 bug!("discriminant_for_variant called on zero variant enum");
2097 TyKind::Adt(adt, _) if adt.is_enum() => {
2098 Some(adt.discriminant_for_variant(tcx, variant_index))
2100 TyKind::Generator(def_id, substs, _) => {
2101 Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index))
2107 /// Returns the type of the discriminant of this type.
2108 pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2110 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2111 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2113 // This can only be `0`, for now, so `u8` will suffice.
2119 /// When we create a closure, we record its kind (i.e., what trait
2120 /// it implements) into its `ClosureSubsts` using a type
2121 /// parameter. This is kind of a phantom type, except that the
2122 /// most convenient thing for us to are the integral types. This
2123 /// function converts such a special type into the closure
2124 /// kind. To go the other way, use
2125 /// `tcx.closure_kind_ty(closure_kind)`.
2127 /// Note that during type checking, we use an inference variable
2128 /// to represent the closure kind, because it has not yet been
2129 /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`)
2130 /// is complete, that type variable will be unified.
2131 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2133 Int(int_ty) => match int_ty {
2134 ast::IntTy::I8 => Some(ty::ClosureKind::Fn),
2135 ast::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2136 ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2137 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2140 // "Bound" types appear in canonical queries when the
2141 // closure type is not yet known
2142 Bound(..) | Infer(_) => None,
2144 Error(_) => Some(ty::ClosureKind::Fn),
2146 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2150 /// Fast path helper for testing if a type is `Sized`.
2152 /// Returning true means the type is known to be sized. Returning
2153 /// `false` means nothing -- could be sized, might not be.
2154 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2156 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2167 | ty::GeneratorWitness(..)
2171 | ty::Error(_) => true,
2173 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2175 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2177 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2179 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2181 ty::Infer(ty::TyVar(_)) => false,
2184 | ty::Placeholder(..)
2185 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2186 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2191 /// Is this a zero-sized type?
2192 pub fn is_zst(&'tcx self, tcx: TyCtxt<'tcx>, did: DefId) -> bool {
2193 tcx.layout_of(tcx.param_env(did).and(self)).map(|layout| layout.is_zst()).unwrap_or(false)
2197 /// Typed constant value.
2198 #[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
2199 #[derive(HashStable)]
2200 pub struct Const<'tcx> {
2203 pub val: ConstKind<'tcx>,
2206 #[cfg(target_arch = "x86_64")]
2207 static_assert_size!(Const<'_>, 48);
2209 impl<'tcx> Const<'tcx> {
2210 /// Literals and const generic parameters are eagerly converted to a constant, everything else
2211 /// becomes `Unevaluated`.
2212 pub fn from_anon_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx Self {
2213 Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::dummy(def_id))
2216 pub fn from_opt_const_arg_anon_const(
2218 def: ty::WithOptConstParam<LocalDefId>,
2220 debug!("Const::from_anon_const(def={:?})", def);
2222 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
2224 let body_id = match tcx.hir().get(hir_id) {
2225 hir::Node::AnonConst(ac) => ac.body,
2227 tcx.def_span(def.did.to_def_id()),
2228 "from_anon_const can only process anonymous constants"
2232 let expr = &tcx.hir().body(body_id).value;
2234 let ty = tcx.type_of(def.ty_def_id());
2236 let lit_input = match expr.kind {
2237 hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
2238 hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => match expr.kind {
2239 hir::ExprKind::Lit(ref lit) => {
2240 Some(LitToConstInput { lit: &lit.node, ty, neg: true })
2247 if let Some(lit_input) = lit_input {
2248 // If an error occurred, ignore that it's a literal and leave reporting the error up to
2250 if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
2253 tcx.sess.delay_span_bug(expr.span, "Const::from_anon_const: couldn't lit_to_const");
2257 // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
2258 // currently have to be wrapped in curly brackets, so it's necessary to special-case.
2259 let expr = match &expr.kind {
2260 hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => {
2261 block.expr.as_ref().unwrap()
2266 use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
2267 let val = match expr.kind {
2268 ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
2269 // Find the name and index of the const parameter by indexing the generics of
2270 // the parent item and construct a `ParamConst`.
2271 let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
2272 let item_id = tcx.hir().get_parent_node(hir_id);
2273 let item_def_id = tcx.hir().local_def_id(item_id);
2274 let generics = tcx.generics_of(item_def_id.to_def_id());
2276 generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id).to_def_id()];
2277 let name = tcx.hir().name(hir_id);
2278 ty::ConstKind::Param(ty::ParamConst::new(index, name))
2280 _ => ty::ConstKind::Unevaluated(
2282 InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
2287 tcx.mk_const(ty::Const { val, ty })
2291 /// Interns the given value as a constant.
2292 pub fn from_value(tcx: TyCtxt<'tcx>, val: ConstValue<'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
2293 tcx.mk_const(Self { val: ConstKind::Value(val), ty })
2297 /// Interns the given scalar as a constant.
2298 pub fn from_scalar(tcx: TyCtxt<'tcx>, val: Scalar, ty: Ty<'tcx>) -> &'tcx Self {
2299 Self::from_value(tcx, ConstValue::Scalar(val), ty)
2303 /// Creates a constant with the given integer value and interns it.
2304 pub fn from_bits(tcx: TyCtxt<'tcx>, bits: u128, ty: ParamEnvAnd<'tcx, Ty<'tcx>>) -> &'tcx Self {
2307 .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e))
2309 Self::from_scalar(tcx, Scalar::from_uint(bits, size), ty.value)
2313 /// Creates an interned zst constant.
2314 pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Self {
2315 Self::from_scalar(tcx, Scalar::zst(), ty)
2319 /// Creates an interned bool constant.
2320 pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> &'tcx Self {
2321 Self::from_bits(tcx, v as u128, ParamEnv::empty().and(tcx.types.bool))
2325 /// Creates an interned usize constant.
2326 pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> &'tcx Self {
2327 Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize))
2331 /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of
2332 /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it
2333 /// contains const generic parameters or pointers).
2334 pub fn try_eval_bits(
2337 param_env: ParamEnv<'tcx>,
2340 assert_eq!(self.ty, ty);
2341 let size = tcx.layout_of(param_env.with_reveal_all().and(ty)).ok()?.size;
2342 // if `ty` does not depend on generic parameters, use an empty param_env
2343 self.eval(tcx, param_env).val.try_to_bits(size)
2347 /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the
2348 /// unevaluated constant.
2349 pub fn eval(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> &Const<'tcx> {
2350 if let ConstKind::Unevaluated(def, substs, promoted) = self.val {
2351 use crate::mir::interpret::ErrorHandled;
2353 let param_env_and_substs = param_env.with_reveal_all().and(substs);
2355 // HACK(eddyb) this erases lifetimes even though `const_eval_resolve`
2356 // also does later, but we want to do it before checking for
2357 // inference variables.
2358 let param_env_and_substs = tcx.erase_regions(¶m_env_and_substs);
2360 // HACK(eddyb) when the query key would contain inference variables,
2361 // attempt using identity substs and `ParamEnv` instead, that will succeed
2362 // when the expression doesn't depend on any parameters.
2363 // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
2364 // we can call `infcx.const_eval_resolve` which handles inference variables.
2365 let param_env_and_substs = if param_env_and_substs.needs_infer() {
2366 tcx.param_env(def.did).and(InternalSubsts::identity_for_item(tcx, def.did))
2368 param_env_and_substs
2371 // FIXME(eddyb) maybe the `const_eval_*` methods should take
2372 // `ty::ParamEnvAnd<SubstsRef>` instead of having them separate.
2373 let (param_env, substs) = param_env_and_substs.into_parts();
2374 // try to resolve e.g. associated constants to their definition on an impl, and then
2375 // evaluate the const.
2376 match tcx.const_eval_resolve(param_env, def, substs, promoted, None) {
2377 // NOTE(eddyb) `val` contains no lifetimes/types/consts,
2378 // and we use the original type, so nothing from `substs`
2379 // (which may be identity substs, see above),
2380 // can leak through `val` into the const we return.
2381 Ok(val) => Const::from_value(tcx, val, self.ty),
2382 Err(ErrorHandled::TooGeneric | ErrorHandled::Linted) => self,
2383 Err(ErrorHandled::Reported(ErrorReported)) => tcx.const_error(self.ty),
2391 pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> {
2392 self.try_eval_bits(tcx, param_env, tcx.types.bool).and_then(|v| match v {
2400 pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> {
2401 self.try_eval_bits(tcx, param_env, tcx.types.usize).map(|v| v as u64)
2405 /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
2406 pub fn eval_bits(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 {
2407 self.try_eval_bits(tcx, param_env, ty)
2408 .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self))
2412 /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`.
2413 pub fn eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 {
2414 self.eval_bits(tcx, param_env, tcx.types.usize) as u64
2418 /// Represents a constant in Rust.
2419 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
2420 #[derive(HashStable)]
2421 pub enum ConstKind<'tcx> {
2422 /// A const generic parameter.
2425 /// Infer the value of the const.
2426 Infer(InferConst<'tcx>),
2428 /// Bound const variable, used only when preparing a trait query.
2429 Bound(DebruijnIndex, BoundVar),
2431 /// A placeholder const - universally quantified higher-ranked const.
2432 Placeholder(ty::PlaceholderConst),
2434 /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
2435 /// variants when the code is monomorphic enough for that.
2436 Unevaluated(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>, Option<Promoted>),
2438 /// Used to hold computed value.
2439 Value(ConstValue<'tcx>),
2441 /// A placeholder for a const which could not be computed; this is
2442 /// propagated to avoid useless error messages.
2443 Error(DelaySpanBugEmitted),
2446 #[cfg(target_arch = "x86_64")]
2447 static_assert_size!(ConstKind<'_>, 40);
2449 impl<'tcx> ConstKind<'tcx> {
2451 pub fn try_to_scalar(&self) -> Option<Scalar> {
2452 if let ConstKind::Value(val) = self { val.try_to_scalar() } else { None }
2456 pub fn try_to_bits(&self, size: Size) -> Option<u128> {
2457 if let ConstKind::Value(val) = self { val.try_to_bits(size) } else { None }
2461 /// An inference variable for a const, for use in const generics.
2462 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
2463 #[derive(HashStable)]
2464 pub enum InferConst<'tcx> {
2465 /// Infer the value of the const.
2466 Var(ConstVid<'tcx>),
2467 /// A fresh const variable. See `infer::freshen` for more details.