1 //! This module contains `TyKind` and its major components.
3 #![allow(rustc::usage_of_ty_tykind)]
5 use crate::infer::canonical::Canonical;
6 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
7 use crate::ty::visit::ValidateBoundVars;
8 use crate::ty::InferTy::*;
10 self, AdtDef, DefIdTree, Discr, Term, Ty, TyCtxt, TypeFlags, TypeSuperVisitable, TypeVisitable,
13 use crate::ty::{List, ParamEnv};
14 use polonius_engine::Atom;
15 use rustc_data_structures::captures::Captures;
16 use rustc_data_structures::intern::Interned;
18 use rustc_hir::def_id::DefId;
19 use rustc_index::vec::Idx;
20 use rustc_macros::HashStable;
21 use rustc_span::symbol::{kw, Symbol};
22 use rustc_target::abi::VariantIdx;
23 use rustc_target::spec::abi;
25 use std::cmp::Ordering;
27 use std::marker::PhantomData;
28 use std::ops::{ControlFlow, Deref, Range};
29 use ty::util::IntTypeExt;
31 use rustc_type_ir::sty::TyKind::*;
32 use rustc_type_ir::RegionKind as IrRegionKind;
33 use rustc_type_ir::TyKind as IrTyKind;
35 // Re-export the `TyKind` from `rustc_type_ir` here for convenience
36 #[rustc_diagnostic_item = "TyKind"]
37 pub type TyKind<'tcx> = IrTyKind<TyCtxt<'tcx>>;
38 pub type RegionKind<'tcx> = IrRegionKind<TyCtxt<'tcx>>;
40 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
41 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
42 pub struct TypeAndMut<'tcx> {
44 pub mutbl: hir::Mutability,
47 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
49 /// A "free" region `fr` can be interpreted as "some region
50 /// at least as big as the scope `fr.scope`".
51 pub struct FreeRegion {
53 pub bound_region: BoundRegionKind,
56 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
58 pub enum BoundRegionKind {
59 /// An anonymous region parameter for a given fn (&T)
62 /// Named region parameters for functions (a in &'a T)
64 /// The `DefId` is needed to distinguish free regions in
65 /// the event of shadowing.
66 BrNamed(DefId, Symbol),
68 /// Anonymous region for the implicit env pointer parameter
73 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
75 pub struct BoundRegion {
77 pub kind: BoundRegionKind,
80 impl BoundRegionKind {
81 pub fn is_named(&self) -> bool {
83 BoundRegionKind::BrNamed(_, name) => name != kw::UnderscoreLifetime,
90 fn article(&self) -> &'static str;
93 impl<'tcx> Article for TyKind<'tcx> {
94 /// Get the article ("a" or "an") to use with this type.
95 fn article(&self) -> &'static str {
97 Int(_) | Float(_) | Array(_, _) => "an",
98 Adt(def, _) if def.is_enum() => "an",
99 // This should never happen, but ICEing and causing the user's code
100 // to not compile felt too harsh.
107 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
108 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
109 static_assert_size!(TyKind<'_>, 32);
111 /// A closure can be modeled as a struct that looks like:
112 /// ```ignore (illustrative)
113 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
117 /// - 'l0...'li and T0...Tj are the generic parameters
118 /// in scope on the function that defined the closure,
119 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
120 /// is rather hackily encoded via a scalar type. See
121 /// `Ty::to_opt_closure_kind` for details.
122 /// - CS represents the *closure signature*, representing as a `fn()`
123 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
124 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
126 /// - U is a type parameter representing the types of its upvars, tupled up
127 /// (borrowed, if appropriate; that is, if a U field represents a by-ref upvar,
128 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
130 /// So, for example, given this function:
131 /// ```ignore (illustrative)
132 /// fn foo<'a, T>(data: &'a mut T) {
133 /// do(|| data.count += 1)
136 /// the type of the closure would be something like:
137 /// ```ignore (illustrative)
138 /// struct Closure<'a, T, U>(...U);
140 /// Note that the type of the upvar is not specified in the struct.
141 /// You may wonder how the impl would then be able to use the upvar,
142 /// if it doesn't know it's type? The answer is that the impl is
143 /// (conceptually) not fully generic over Closure but rather tied to
144 /// instances with the expected upvar types:
145 /// ```ignore (illustrative)
146 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
150 /// You can see that the *impl* fully specified the type of the upvar
151 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
152 /// (Here, I am assuming that `data` is mut-borrowed.)
154 /// Now, the last question you may ask is: Why include the upvar types
155 /// in an extra type parameter? The reason for this design is that the
156 /// upvar types can reference lifetimes that are internal to the
157 /// creating function. In my example above, for example, the lifetime
158 /// `'b` represents the scope of the closure itself; this is some
159 /// subset of `foo`, probably just the scope of the call to the to
160 /// `do()`. If we just had the lifetime/type parameters from the
161 /// enclosing function, we couldn't name this lifetime `'b`. Note that
162 /// there can also be lifetimes in the types of the upvars themselves,
163 /// if one of them happens to be a reference to something that the
164 /// creating fn owns.
166 /// OK, you say, so why not create a more minimal set of parameters
167 /// that just includes the extra lifetime parameters? The answer is
168 /// primarily that it would be hard --- we don't know at the time when
169 /// we create the closure type what the full types of the upvars are,
170 /// nor do we know which are borrowed and which are not. In this
171 /// design, we can just supply a fresh type parameter and figure that
174 /// All right, you say, but why include the type parameters from the
175 /// original function then? The answer is that codegen may need them
176 /// when monomorphizing, and they may not appear in the upvars. A
177 /// closure could capture no variables but still make use of some
178 /// in-scope type parameter with a bound (e.g., if our example above
179 /// had an extra `U: Default`, and the closure called `U::default()`).
181 /// There is another reason. This design (implicitly) prohibits
182 /// closures from capturing themselves (except via a trait
183 /// object). This simplifies closure inference considerably, since it
184 /// means that when we infer the kind of a closure or its upvars, we
185 /// don't have to handle cycles where the decisions we make for
186 /// closure C wind up influencing the decisions we ought to make for
187 /// closure C (which would then require fixed point iteration to
188 /// handle). Plus it fixes an ICE. :P
192 /// Generators are handled similarly in `GeneratorSubsts`. The set of
193 /// type parameters is similar, but `CK` and `CS` are replaced by the
194 /// following type parameters:
196 /// * `GS`: The generator's "resume type", which is the type of the
197 /// argument passed to `resume`, and the type of `yield` expressions
198 /// inside the generator.
199 /// * `GY`: The "yield type", which is the type of values passed to
200 /// `yield` inside the generator.
201 /// * `GR`: The "return type", which is the type of value returned upon
202 /// completion of the generator.
203 /// * `GW`: The "generator witness".
204 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
205 pub struct ClosureSubsts<'tcx> {
206 /// Lifetime and type parameters from the enclosing function,
207 /// concatenated with a tuple containing the types of the upvars.
209 /// These are separated out because codegen wants to pass them around
210 /// when monomorphizing.
211 pub substs: SubstsRef<'tcx>,
214 /// Struct returned by `split()`.
215 pub struct ClosureSubstsParts<'tcx, T> {
216 pub parent_substs: &'tcx [GenericArg<'tcx>],
217 pub closure_kind_ty: T,
218 pub closure_sig_as_fn_ptr_ty: T,
219 pub tupled_upvars_ty: T,
222 impl<'tcx> ClosureSubsts<'tcx> {
223 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
224 /// for the closure parent, alongside additional closure-specific components.
227 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
228 ) -> ClosureSubsts<'tcx> {
230 substs: tcx.mk_substs(
231 parts.parent_substs.iter().copied().chain(
232 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
234 .map(|&ty| ty.into()),
240 /// Divides the closure substs into their respective components.
241 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
242 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
243 match self.substs[..] {
245 ref parent_substs @ ..,
247 closure_sig_as_fn_ptr_ty,
249 ] => ClosureSubstsParts {
252 closure_sig_as_fn_ptr_ty,
255 _ => bug!("closure substs missing synthetics"),
259 /// Returns `true` only if enough of the synthetic types are known to
260 /// allow using all of the methods on `ClosureSubsts` without panicking.
262 /// Used primarily by `ty::print::pretty` to be able to handle closure
263 /// types that haven't had their synthetic types substituted in.
264 pub fn is_valid(self) -> bool {
265 self.substs.len() >= 3
266 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
269 /// Returns the substitutions of the closure's parent.
270 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
271 self.split().parent_substs
274 /// Returns an iterator over the list of types of captured paths by the closure.
275 /// In case there was a type error in figuring out the types of the captured path, an
276 /// empty iterator is returned.
278 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
279 match self.tupled_upvars_ty().kind() {
280 TyKind::Error(_) => None,
281 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
282 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
283 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
289 /// Returns the tuple type representing the upvars for this closure.
291 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
292 self.split().tupled_upvars_ty.expect_ty()
295 /// Returns the closure kind for this closure; may return a type
296 /// variable during inference. To get the closure kind during
297 /// inference, use `infcx.closure_kind(substs)`.
298 pub fn kind_ty(self) -> Ty<'tcx> {
299 self.split().closure_kind_ty.expect_ty()
302 /// Returns the `fn` pointer type representing the closure signature for this
304 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
305 // type is known at the time of the creation of `ClosureSubsts`,
306 // see `rustc_typeck::check::closure`.
307 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
308 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
311 /// Returns the closure kind for this closure; only usable outside
312 /// of an inference context, because in that context we know that
313 /// there are no type variables.
315 /// If you have an inference context, use `infcx.closure_kind()`.
316 pub fn kind(self) -> ty::ClosureKind {
317 self.kind_ty().to_opt_closure_kind().unwrap()
320 /// Extracts the signature from the closure.
321 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
322 let ty = self.sig_as_fn_ptr_ty();
324 ty::FnPtr(sig) => *sig,
325 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind()),
330 /// Similar to `ClosureSubsts`; see the above documentation for more.
331 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
332 pub struct GeneratorSubsts<'tcx> {
333 pub substs: SubstsRef<'tcx>,
336 pub struct GeneratorSubstsParts<'tcx, T> {
337 pub parent_substs: &'tcx [GenericArg<'tcx>],
342 pub tupled_upvars_ty: T,
345 impl<'tcx> GeneratorSubsts<'tcx> {
346 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
347 /// for the generator parent, alongside additional generator-specific components.
350 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
351 ) -> GeneratorSubsts<'tcx> {
353 substs: tcx.mk_substs(
354 parts.parent_substs.iter().copied().chain(
360 parts.tupled_upvars_ty,
363 .map(|&ty| ty.into()),
369 /// Divides the generator substs into their respective components.
370 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
371 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
372 match self.substs[..] {
373 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
374 GeneratorSubstsParts {
383 _ => bug!("generator substs missing synthetics"),
387 /// Returns `true` only if enough of the synthetic types are known to
388 /// allow using all of the methods on `GeneratorSubsts` without panicking.
390 /// Used primarily by `ty::print::pretty` to be able to handle generator
391 /// types that haven't had their synthetic types substituted in.
392 pub fn is_valid(self) -> bool {
393 self.substs.len() >= 5
394 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
397 /// Returns the substitutions of the generator's parent.
398 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
399 self.split().parent_substs
402 /// This describes the types that can be contained in a generator.
403 /// It will be a type variable initially and unified in the last stages of typeck of a body.
404 /// It contains a tuple of all the types that could end up on a generator frame.
405 /// The state transformation MIR pass may only produce layouts which mention types
406 /// in this tuple. Upvars are not counted here.
407 pub fn witness(self) -> Ty<'tcx> {
408 self.split().witness.expect_ty()
411 /// Returns an iterator over the list of types of captured paths by the generator.
412 /// In case there was a type error in figuring out the types of the captured path, an
413 /// empty iterator is returned.
415 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
416 match self.tupled_upvars_ty().kind() {
417 TyKind::Error(_) => None,
418 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
419 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
420 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
426 /// Returns the tuple type representing the upvars for this generator.
428 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
429 self.split().tupled_upvars_ty.expect_ty()
432 /// Returns the type representing the resume type of the generator.
433 pub fn resume_ty(self) -> Ty<'tcx> {
434 self.split().resume_ty.expect_ty()
437 /// Returns the type representing the yield type of the generator.
438 pub fn yield_ty(self) -> Ty<'tcx> {
439 self.split().yield_ty.expect_ty()
442 /// Returns the type representing the return type of the generator.
443 pub fn return_ty(self) -> Ty<'tcx> {
444 self.split().return_ty.expect_ty()
447 /// Returns the "generator signature", which consists of its yield
448 /// and return types.
450 /// N.B., some bits of the code prefers to see this wrapped in a
451 /// binder, but it never contains bound regions. Probably this
452 /// function should be removed.
453 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
454 ty::Binder::dummy(self.sig())
457 /// Returns the "generator signature", which consists of its resume, yield
458 /// and return types.
459 pub fn sig(self) -> GenSig<'tcx> {
461 resume_ty: self.resume_ty(),
462 yield_ty: self.yield_ty(),
463 return_ty: self.return_ty(),
468 impl<'tcx> GeneratorSubsts<'tcx> {
469 /// Generator has not been resumed yet.
470 pub const UNRESUMED: usize = 0;
471 /// Generator has returned or is completed.
472 pub const RETURNED: usize = 1;
473 /// Generator has been poisoned.
474 pub const POISONED: usize = 2;
476 const UNRESUMED_NAME: &'static str = "Unresumed";
477 const RETURNED_NAME: &'static str = "Returned";
478 const POISONED_NAME: &'static str = "Panicked";
480 /// The valid variant indices of this generator.
482 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
483 // FIXME requires optimized MIR
484 let num_variants = tcx.generator_layout(def_id).unwrap().variant_fields.len();
485 VariantIdx::new(0)..VariantIdx::new(num_variants)
488 /// The discriminant for the given variant. Panics if the `variant_index` is
491 pub fn discriminant_for_variant(
495 variant_index: VariantIdx,
497 // Generators don't support explicit discriminant values, so they are
498 // the same as the variant index.
499 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
500 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
503 /// The set of all discriminants for the generator, enumerated with their
506 pub fn discriminants(
510 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
511 self.variant_range(def_id, tcx).map(move |index| {
512 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
516 /// Calls `f` with a reference to the name of the enumerator for the given
518 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
520 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
521 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
522 Self::POISONED => Cow::from(Self::POISONED_NAME),
523 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
527 /// The type of the state discriminant used in the generator type.
529 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
533 /// This returns the types of the MIR locals which had to be stored across suspension points.
534 /// It is calculated in rustc_mir_transform::generator::StateTransform.
535 /// All the types here must be in the tuple in GeneratorInterior.
537 /// The locals are grouped by their variant number. Note that some locals may
538 /// be repeated in multiple variants.
544 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
545 let layout = tcx.generator_layout(def_id).unwrap();
546 layout.variant_fields.iter().map(move |variant| {
549 .map(move |field| EarlyBinder(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, HashStable)]
562 pub enum UpvarSubsts<'tcx> {
563 Closure(SubstsRef<'tcx>),
564 Generator(SubstsRef<'tcx>),
567 impl<'tcx> UpvarSubsts<'tcx> {
568 /// Returns an iterator over the list of types of captured paths by the closure/generator.
569 /// In case there was a type error in figuring out the types of the captured path, an
570 /// empty iterator is returned.
572 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
573 let tupled_tys = match self {
574 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
575 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
578 match tupled_tys.kind() {
579 TyKind::Error(_) => None,
580 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
581 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
582 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
589 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
591 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
592 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
597 /// An inline const is modeled like
598 /// ```ignore (illustrative)
599 /// const InlineConst<'l0...'li, T0...Tj, R>: R;
603 /// - 'l0...'li and T0...Tj are the generic parameters
604 /// inherited from the item that defined the inline const,
605 /// - R represents the type of the constant.
607 /// When the inline const is instantiated, `R` is substituted as the actual inferred
608 /// type of the constant. The reason that `R` is represented as an extra type parameter
609 /// is the same reason that [`ClosureSubsts`] have `CS` and `U` as type parameters:
610 /// inline const can reference lifetimes that are internal to the creating function.
611 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
612 pub struct InlineConstSubsts<'tcx> {
613 /// Generic parameters from the enclosing item,
614 /// concatenated with the inferred type of the constant.
615 pub substs: SubstsRef<'tcx>,
618 /// Struct returned by `split()`.
619 pub struct InlineConstSubstsParts<'tcx, T> {
620 pub parent_substs: &'tcx [GenericArg<'tcx>],
624 impl<'tcx> InlineConstSubsts<'tcx> {
625 /// Construct `InlineConstSubsts` from `InlineConstSubstsParts`.
628 parts: InlineConstSubstsParts<'tcx, Ty<'tcx>>,
629 ) -> InlineConstSubsts<'tcx> {
631 substs: tcx.mk_substs(
632 parts.parent_substs.iter().copied().chain(std::iter::once(parts.ty.into())),
637 /// Divides the inline const substs into their respective components.
638 /// The ordering assumed here must match that used by `InlineConstSubsts::new` above.
639 fn split(self) -> InlineConstSubstsParts<'tcx, GenericArg<'tcx>> {
640 match self.substs[..] {
641 [ref parent_substs @ .., ty] => InlineConstSubstsParts { parent_substs, ty },
642 _ => bug!("inline const substs missing synthetics"),
646 /// Returns the substitutions of the inline const's parent.
647 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
648 self.split().parent_substs
651 /// Returns the type of this inline const.
652 pub fn ty(self) -> Ty<'tcx> {
653 self.split().ty.expect_ty()
657 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
658 #[derive(HashStable, TypeFoldable, TypeVisitable)]
659 pub enum ExistentialPredicate<'tcx> {
660 /// E.g., `Iterator`.
661 Trait(ExistentialTraitRef<'tcx>),
662 /// E.g., `Iterator::Item = T`.
663 Projection(ExistentialProjection<'tcx>),
668 impl<'tcx> ExistentialPredicate<'tcx> {
669 /// Compares via an ordering that will not change if modules are reordered or other changes are
670 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
671 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
672 use self::ExistentialPredicate::*;
673 match (*self, *other) {
674 (Trait(_), Trait(_)) => Ordering::Equal,
675 (Projection(ref a), Projection(ref b)) => {
676 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
678 (AutoTrait(ref a), AutoTrait(ref b)) => {
679 tcx.def_path_hash(*a).cmp(&tcx.def_path_hash(*b))
681 (Trait(_), _) => Ordering::Less,
682 (Projection(_), Trait(_)) => Ordering::Greater,
683 (Projection(_), _) => Ordering::Less,
684 (AutoTrait(_), _) => Ordering::Greater,
689 impl<'tcx> Binder<'tcx, ExistentialPredicate<'tcx>> {
690 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
691 use crate::ty::ToPredicate;
692 match self.skip_binder() {
693 ExistentialPredicate::Trait(tr) => {
694 self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
696 ExistentialPredicate::Projection(p) => {
697 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
699 ExistentialPredicate::AutoTrait(did) => {
700 let trait_ref = self.rebind(ty::TraitRef {
702 substs: tcx.mk_substs_trait(self_ty, &[]),
704 trait_ref.without_const().to_predicate(tcx)
710 impl<'tcx> List<ty::Binder<'tcx, ExistentialPredicate<'tcx>>> {
711 /// Returns the "principal `DefId`" of this set of existential predicates.
713 /// A Rust trait object type consists (in addition to a lifetime bound)
714 /// of a set of trait bounds, which are separated into any number
715 /// of auto-trait bounds, and at most one non-auto-trait bound. The
716 /// non-auto-trait bound is called the "principal" of the trait
719 /// Only the principal can have methods or type parameters (because
720 /// auto traits can have neither of them). This is important, because
721 /// it means the auto traits can be treated as an unordered set (methods
722 /// would force an order for the vtable, while relating traits with
723 /// type parameters without knowing the order to relate them in is
724 /// a rather non-trivial task).
726 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
727 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
728 /// are the set `{Sync}`.
730 /// It is also possible to have a "trivial" trait object that
731 /// consists only of auto traits, with no principal - for example,
732 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
733 /// is `{Send, Sync}`, while there is no principal. These trait objects
734 /// have a "trivial" vtable consisting of just the size, alignment,
736 pub fn principal(&self) -> Option<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> {
738 .map_bound(|this| match this {
739 ExistentialPredicate::Trait(tr) => Some(tr),
745 pub fn principal_def_id(&self) -> Option<DefId> {
746 self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
750 pub fn projection_bounds<'a>(
752 ) -> impl Iterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> + 'a {
753 self.iter().filter_map(|predicate| {
755 .map_bound(|pred| match pred {
756 ExistentialPredicate::Projection(projection) => Some(projection),
764 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + Captures<'tcx> + 'a {
765 self.iter().filter_map(|predicate| match predicate.skip_binder() {
766 ExistentialPredicate::AutoTrait(did) => Some(did),
772 /// A complete reference to a trait. These take numerous guises in syntax,
773 /// but perhaps the most recognizable form is in a where-clause:
774 /// ```ignore (illustrative)
777 /// This would be represented by a trait-reference where the `DefId` is the
778 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
779 /// and `U` as parameter 1.
781 /// Trait references also appear in object types like `Foo<U>`, but in
782 /// that case the `Self` parameter is absent from the substitutions.
783 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
784 #[derive(HashStable, TypeFoldable, TypeVisitable)]
785 pub struct TraitRef<'tcx> {
787 pub substs: SubstsRef<'tcx>,
790 impl<'tcx> TraitRef<'tcx> {
791 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
792 TraitRef { def_id, substs }
795 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
796 /// are the parameters defined on trait.
797 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> Binder<'tcx, TraitRef<'tcx>> {
798 ty::Binder::dummy(TraitRef {
800 substs: InternalSubsts::identity_for_item(tcx, def_id),
805 pub fn self_ty(&self) -> Ty<'tcx> {
806 self.substs.type_at(0)
812 substs: SubstsRef<'tcx>,
813 ) -> ty::TraitRef<'tcx> {
814 let defs = tcx.generics_of(trait_id);
815 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
819 pub type PolyTraitRef<'tcx> = Binder<'tcx, TraitRef<'tcx>>;
821 impl<'tcx> PolyTraitRef<'tcx> {
822 pub fn self_ty(&self) -> Binder<'tcx, Ty<'tcx>> {
823 self.map_bound_ref(|tr| tr.self_ty())
826 pub fn def_id(&self) -> DefId {
827 self.skip_binder().def_id
830 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
831 self.map_bound(|trait_ref| ty::TraitPredicate {
833 constness: ty::BoundConstness::NotConst,
834 polarity: ty::ImplPolarity::Positive,
838 /// Same as [`PolyTraitRef::to_poly_trait_predicate`] but sets a negative polarity instead.
839 pub fn to_poly_trait_predicate_negative_polarity(&self) -> ty::PolyTraitPredicate<'tcx> {
840 self.map_bound(|trait_ref| ty::TraitPredicate {
842 constness: ty::BoundConstness::NotConst,
843 polarity: ty::ImplPolarity::Negative,
848 /// An existential reference to a trait, where `Self` is erased.
849 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
850 /// ```ignore (illustrative)
851 /// exists T. T: Trait<'a, 'b, X, Y>
853 /// The substitutions don't include the erased `Self`, only trait
854 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
855 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
856 #[derive(HashStable, TypeFoldable, TypeVisitable)]
857 pub struct ExistentialTraitRef<'tcx> {
859 pub substs: SubstsRef<'tcx>,
862 impl<'tcx> ExistentialTraitRef<'tcx> {
863 pub fn erase_self_ty(
865 trait_ref: ty::TraitRef<'tcx>,
866 ) -> ty::ExistentialTraitRef<'tcx> {
867 // Assert there is a Self.
868 trait_ref.substs.type_at(0);
870 ty::ExistentialTraitRef {
871 def_id: trait_ref.def_id,
872 substs: tcx.intern_substs(&trait_ref.substs[1..]),
876 /// Object types don't have a self type specified. Therefore, when
877 /// we convert the principal trait-ref into a normal trait-ref,
878 /// you must give *some* self type. A common choice is `mk_err()`
879 /// or some placeholder type.
880 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
881 // otherwise the escaping vars would be captured by the binder
882 // debug_assert!(!self_ty.has_escaping_bound_vars());
884 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
888 pub type PolyExistentialTraitRef<'tcx> = Binder<'tcx, ExistentialTraitRef<'tcx>>;
890 impl<'tcx> PolyExistentialTraitRef<'tcx> {
891 pub fn def_id(&self) -> DefId {
892 self.skip_binder().def_id
895 /// Object types don't have a self type specified. Therefore, when
896 /// we convert the principal trait-ref into a normal trait-ref,
897 /// you must give *some* self type. A common choice is `mk_err()`
898 /// or some placeholder type.
899 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
900 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
904 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
905 #[derive(Encodable, Decodable, HashStable)]
906 pub struct EarlyBinder<T>(pub T);
908 impl<T> EarlyBinder<T> {
909 pub fn as_ref(&self) -> EarlyBinder<&T> {
913 pub fn map_bound_ref<F, U>(&self, f: F) -> EarlyBinder<U>
917 self.as_ref().map_bound(f)
920 pub fn map_bound<F, U>(self, f: F) -> EarlyBinder<U>
924 let value = f(self.0);
928 pub fn try_map_bound<F, U, E>(self, f: F) -> Result<EarlyBinder<U>, E>
930 F: FnOnce(T) -> Result<U, E>,
932 let value = f(self.0)?;
933 Ok(EarlyBinder(value))
937 impl<T> EarlyBinder<Option<T>> {
938 pub fn transpose(self) -> Option<EarlyBinder<T>> {
939 self.0.map(|v| EarlyBinder(v))
943 impl<T, U> EarlyBinder<(T, U)> {
944 pub fn transpose_tuple2(self) -> (EarlyBinder<T>, EarlyBinder<U>) {
945 (EarlyBinder(self.0.0), EarlyBinder(self.0.1))
949 pub struct EarlyBinderIter<T> {
953 impl<T: IntoIterator> EarlyBinder<T> {
954 pub fn transpose_iter(self) -> EarlyBinderIter<T::IntoIter> {
955 EarlyBinderIter { t: self.0.into_iter() }
959 impl<T: Iterator> Iterator for EarlyBinderIter<T> {
960 type Item = EarlyBinder<T::Item>;
962 fn next(&mut self) -> Option<Self::Item> {
963 self.t.next().map(|i| EarlyBinder(i))
967 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
968 #[derive(HashStable)]
969 pub enum BoundVariableKind {
971 Region(BoundRegionKind),
975 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
976 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
977 /// (which would be represented by the type `PolyTraitRef ==
978 /// Binder<'tcx, TraitRef>`). Note that when we instantiate,
979 /// erase, or otherwise "discharge" these bound vars, we change the
980 /// type from `Binder<'tcx, T>` to just `T` (see
981 /// e.g., `liberate_late_bound_regions`).
983 /// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro.
984 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
985 pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>);
987 impl<'tcx, T> Binder<'tcx, T>
989 T: TypeVisitable<'tcx>,
991 /// Wraps `value` in a binder, asserting that `value` does not
992 /// contain any bound vars that would be bound by the
993 /// binder. This is commonly used to 'inject' a value T into a
994 /// different binding level.
995 pub fn dummy(value: T) -> Binder<'tcx, T> {
996 assert!(!value.has_escaping_bound_vars());
997 Binder(value, ty::List::empty())
1000 pub fn bind_with_vars(value: T, vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> {
1001 if cfg!(debug_assertions) {
1002 let mut validator = ValidateBoundVars::new(vars);
1003 value.visit_with(&mut validator);
1009 impl<'tcx, T> Binder<'tcx, T> {
1010 /// Skips the binder and returns the "bound" value. This is a
1011 /// risky thing to do because it's easy to get confused about
1012 /// De Bruijn indices and the like. It is usually better to
1013 /// discharge the binder using `no_bound_vars` or
1014 /// `replace_late_bound_regions` or something like
1015 /// that. `skip_binder` is only valid when you are either
1016 /// extracting data that has nothing to do with bound vars, you
1017 /// are doing some sort of test that does not involve bound
1018 /// regions, or you are being very careful about your depth
1021 /// Some examples where `skip_binder` is reasonable:
1023 /// - extracting the `DefId` from a PolyTraitRef;
1024 /// - comparing the self type of a PolyTraitRef to see if it is equal to
1025 /// a type parameter `X`, since the type `X` does not reference any regions
1026 pub fn skip_binder(self) -> T {
1030 pub fn bound_vars(&self) -> &'tcx List<BoundVariableKind> {
1034 pub fn as_ref(&self) -> Binder<'tcx, &T> {
1035 Binder(&self.0, self.1)
1038 pub fn as_deref(&self) -> Binder<'tcx, &T::Target>
1042 Binder(&self.0, self.1)
1045 pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U>
1049 let value = f(&self.0);
1050 Binder(value, self.1)
1053 pub fn map_bound_ref<F, U: TypeVisitable<'tcx>>(&self, f: F) -> Binder<'tcx, U>
1057 self.as_ref().map_bound(f)
1060 pub fn map_bound<F, U: TypeVisitable<'tcx>>(self, f: F) -> Binder<'tcx, U>
1064 let value = f(self.0);
1065 if cfg!(debug_assertions) {
1066 let mut validator = ValidateBoundVars::new(self.1);
1067 value.visit_with(&mut validator);
1069 Binder(value, self.1)
1072 pub fn try_map_bound<F, U: TypeVisitable<'tcx>, E>(self, f: F) -> Result<Binder<'tcx, U>, E>
1074 F: FnOnce(T) -> Result<U, E>,
1076 let value = f(self.0)?;
1077 if cfg!(debug_assertions) {
1078 let mut validator = ValidateBoundVars::new(self.1);
1079 value.visit_with(&mut validator);
1081 Ok(Binder(value, self.1))
1084 /// Wraps a `value` in a binder, using the same bound variables as the
1085 /// current `Binder`. This should not be used if the new value *changes*
1086 /// the bound variables. Note: the (old or new) value itself does not
1087 /// necessarily need to *name* all the bound variables.
1089 /// This currently doesn't do anything different than `bind`, because we
1090 /// don't actually track bound vars. However, semantically, it is different
1091 /// because bound vars aren't allowed to change here, whereas they are
1092 /// in `bind`. This may be (debug) asserted in the future.
1093 pub fn rebind<U>(&self, value: U) -> Binder<'tcx, U>
1095 U: TypeVisitable<'tcx>,
1097 if cfg!(debug_assertions) {
1098 let mut validator = ValidateBoundVars::new(self.bound_vars());
1099 value.visit_with(&mut validator);
1101 Binder(value, self.1)
1104 /// Unwraps and returns the value within, but only if it contains
1105 /// no bound vars at all. (In other words, if this binder --
1106 /// and indeed any enclosing binder -- doesn't bind anything at
1107 /// all.) Otherwise, returns `None`.
1109 /// (One could imagine having a method that just unwraps a single
1110 /// binder, but permits late-bound vars bound by enclosing
1111 /// binders, but that would require adjusting the debruijn
1112 /// indices, and given the shallow binding structure we often use,
1113 /// would not be that useful.)
1114 pub fn no_bound_vars(self) -> Option<T>
1116 T: TypeVisitable<'tcx>,
1118 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1121 /// Splits the contents into two things that share the same binder
1122 /// level as the original, returning two distinct binders.
1124 /// `f` should consider bound regions at depth 1 to be free, and
1125 /// anything it produces with bound regions at depth 1 will be
1126 /// bound in the resulting return values.
1127 pub fn split<U, V, F>(self, f: F) -> (Binder<'tcx, U>, Binder<'tcx, V>)
1129 F: FnOnce(T) -> (U, V),
1131 let (u, v) = f(self.0);
1132 (Binder(u, self.1), Binder(v, self.1))
1136 impl<'tcx, T> Binder<'tcx, Option<T>> {
1137 pub fn transpose(self) -> Option<Binder<'tcx, T>> {
1138 let bound_vars = self.1;
1139 self.0.map(|v| Binder(v, bound_vars))
1143 /// Represents the projection of an associated type. In explicit UFCS
1144 /// form this would be written `<T as Trait<..>>::N`.
1145 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1146 #[derive(HashStable, TypeFoldable, TypeVisitable)]
1147 pub struct ProjectionTy<'tcx> {
1148 /// The parameters of the associated item.
1149 pub substs: SubstsRef<'tcx>,
1151 /// The `DefId` of the `TraitItem` for the associated type `N`.
1153 /// Note that this is not the `DefId` of the `TraitRef` containing this
1154 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1155 pub item_def_id: DefId,
1158 impl<'tcx> ProjectionTy<'tcx> {
1159 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
1160 tcx.associated_item(self.item_def_id).container.id()
1163 /// Extracts the underlying trait reference and own substs from this projection.
1164 /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
1165 /// then this function would return a `T: Iterator` trait reference and `['a]` as the own substs
1166 pub fn trait_ref_and_own_substs(
1169 ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) {
1170 let def_id = tcx.associated_item(self.item_def_id).container.id();
1171 let trait_generics = tcx.generics_of(def_id);
1173 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, trait_generics) },
1174 &self.substs[trait_generics.count()..],
1178 /// Extracts the underlying trait reference from this projection.
1179 /// For example, if this is a projection of `<T as Iterator>::Item`,
1180 /// then this function would return a `T: Iterator` trait reference.
1182 /// WARNING: This will drop the substs for generic associated types
1183 /// consider calling [Self::trait_ref_and_own_substs] to get those
1185 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1186 let def_id = self.trait_def_id(tcx);
1187 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1190 pub fn self_ty(&self) -> Ty<'tcx> {
1191 self.substs.type_at(0)
1195 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
1196 pub struct GenSig<'tcx> {
1197 pub resume_ty: Ty<'tcx>,
1198 pub yield_ty: Ty<'tcx>,
1199 pub return_ty: Ty<'tcx>,
1202 pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>;
1204 /// Signature of a function type, which we have arbitrarily
1205 /// decided to use to refer to the input/output types.
1207 /// - `inputs`: is the list of arguments and their modes.
1208 /// - `output`: is the return type.
1209 /// - `c_variadic`: indicates whether this is a C-variadic function.
1210 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1211 #[derive(HashStable, TypeFoldable, TypeVisitable)]
1212 pub struct FnSig<'tcx> {
1213 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1214 pub c_variadic: bool,
1215 pub unsafety: hir::Unsafety,
1219 impl<'tcx> FnSig<'tcx> {
1220 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1221 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1224 pub fn output(&self) -> Ty<'tcx> {
1225 self.inputs_and_output[self.inputs_and_output.len() - 1]
1228 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1230 fn fake() -> FnSig<'tcx> {
1232 inputs_and_output: List::empty(),
1234 unsafety: hir::Unsafety::Normal,
1235 abi: abi::Abi::Rust,
1240 pub type PolyFnSig<'tcx> = Binder<'tcx, FnSig<'tcx>>;
1242 impl<'tcx> PolyFnSig<'tcx> {
1244 pub fn inputs(&self) -> Binder<'tcx, &'tcx [Ty<'tcx>]> {
1245 self.map_bound_ref_unchecked(|fn_sig| fn_sig.inputs())
1248 pub fn input(&self, index: usize) -> ty::Binder<'tcx, Ty<'tcx>> {
1249 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1251 pub fn inputs_and_output(&self) -> ty::Binder<'tcx, &'tcx List<Ty<'tcx>>> {
1252 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1255 pub fn output(&self) -> ty::Binder<'tcx, Ty<'tcx>> {
1256 self.map_bound_ref(|fn_sig| fn_sig.output())
1258 pub fn c_variadic(&self) -> bool {
1259 self.skip_binder().c_variadic
1261 pub fn unsafety(&self) -> hir::Unsafety {
1262 self.skip_binder().unsafety
1264 pub fn abi(&self) -> abi::Abi {
1265 self.skip_binder().abi
1269 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<'tcx, FnSig<'tcx>>>;
1271 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1272 #[derive(HashStable)]
1273 pub struct ParamTy {
1278 impl<'tcx> ParamTy {
1279 pub fn new(index: u32, name: Symbol) -> ParamTy {
1280 ParamTy { index, name }
1283 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1284 ParamTy::new(def.index, def.name)
1288 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1289 tcx.mk_ty_param(self.index, self.name)
1293 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1294 #[derive(HashStable)]
1295 pub struct ParamConst {
1301 pub fn new(index: u32, name: Symbol) -> ParamConst {
1302 ParamConst { index, name }
1305 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1306 ParamConst::new(def.index, def.name)
1310 /// Use this rather than `RegionKind`, whenever possible.
1311 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
1312 #[rustc_pass_by_value]
1313 pub struct Region<'tcx>(pub Interned<'tcx, RegionKind<'tcx>>);
1315 impl<'tcx> Deref for Region<'tcx> {
1316 type Target = RegionKind<'tcx>;
1319 fn deref(&self) -> &RegionKind<'tcx> {
1324 impl<'tcx> fmt::Debug for Region<'tcx> {
1325 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1326 write!(f, "{:?}", self.kind())
1330 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, PartialOrd, Ord)]
1331 pub struct EarlyBoundRegion {
1337 impl fmt::Debug for EarlyBoundRegion {
1338 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1339 write!(f, "{}, {}", self.index, self.name)
1343 /// A **`const`** **v**ariable **ID**.
1344 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1345 pub struct ConstVid<'tcx> {
1347 pub phantom: PhantomData<&'tcx ()>,
1350 rustc_index::newtype_index! {
1351 /// A **region** (lifetime) **v**ariable **ID**.
1352 pub struct RegionVid {
1353 DEBUG_FORMAT = custom,
1357 impl Atom for RegionVid {
1358 fn index(self) -> usize {
1363 rustc_index::newtype_index! {
1364 pub struct BoundVar { .. }
1367 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1368 #[derive(HashStable)]
1369 pub struct BoundTy {
1371 pub kind: BoundTyKind,
1374 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1375 #[derive(HashStable)]
1376 pub enum BoundTyKind {
1381 impl From<BoundVar> for BoundTy {
1382 fn from(var: BoundVar) -> Self {
1383 BoundTy { var, kind: BoundTyKind::Anon }
1387 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1388 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1389 #[derive(HashStable, TypeFoldable, TypeVisitable)]
1390 pub struct ExistentialProjection<'tcx> {
1391 pub item_def_id: DefId,
1392 pub substs: SubstsRef<'tcx>,
1393 pub term: Term<'tcx>,
1396 pub type PolyExistentialProjection<'tcx> = Binder<'tcx, ExistentialProjection<'tcx>>;
1398 impl<'tcx> ExistentialProjection<'tcx> {
1399 /// Extracts the underlying existential trait reference from this projection.
1400 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1401 /// then this function would return an `exists T. T: Iterator` existential trait
1403 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
1404 let def_id = tcx.associated_item(self.item_def_id).container.id();
1405 let subst_count = tcx.generics_of(def_id).count() - 1;
1406 let substs = tcx.intern_substs(&self.substs[..subst_count]);
1407 ty::ExistentialTraitRef { def_id, substs }
1410 pub fn with_self_ty(
1414 ) -> ty::ProjectionPredicate<'tcx> {
1415 // otherwise the escaping regions would be captured by the binders
1416 debug_assert!(!self_ty.has_escaping_bound_vars());
1418 ty::ProjectionPredicate {
1419 projection_ty: ty::ProjectionTy {
1420 item_def_id: self.item_def_id,
1421 substs: tcx.mk_substs_trait(self_ty, self.substs),
1427 pub fn erase_self_ty(
1429 projection_predicate: ty::ProjectionPredicate<'tcx>,
1431 // Assert there is a Self.
1432 projection_predicate.projection_ty.substs.type_at(0);
1435 item_def_id: projection_predicate.projection_ty.item_def_id,
1436 substs: tcx.intern_substs(&projection_predicate.projection_ty.substs[1..]),
1437 term: projection_predicate.term,
1442 impl<'tcx> PolyExistentialProjection<'tcx> {
1443 pub fn with_self_ty(
1447 ) -> ty::PolyProjectionPredicate<'tcx> {
1448 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1451 pub fn item_def_id(&self) -> DefId {
1452 self.skip_binder().item_def_id
1456 /// Region utilities
1457 impl<'tcx> Region<'tcx> {
1458 pub fn kind(self) -> RegionKind<'tcx> {
1462 /// Is this region named by the user?
1463 pub fn has_name(self) -> bool {
1465 ty::ReEarlyBound(ebr) => ebr.has_name(),
1466 ty::ReLateBound(_, br) => br.kind.is_named(),
1467 ty::ReFree(fr) => fr.bound_region.is_named(),
1468 ty::ReStatic => true,
1469 ty::ReVar(..) => false,
1470 ty::RePlaceholder(placeholder) => placeholder.name.is_named(),
1471 ty::ReEmpty(_) => false,
1472 ty::ReErased => false,
1477 pub fn is_static(self) -> bool {
1478 matches!(*self, ty::ReStatic)
1482 pub fn is_erased(self) -> bool {
1483 matches!(*self, ty::ReErased)
1487 pub fn is_late_bound(self) -> bool {
1488 matches!(*self, ty::ReLateBound(..))
1492 pub fn is_placeholder(self) -> bool {
1493 matches!(*self, ty::RePlaceholder(..))
1497 pub fn is_empty(self) -> bool {
1498 matches!(*self, ty::ReEmpty(..))
1502 pub fn bound_at_or_above_binder(self, index: ty::DebruijnIndex) -> bool {
1504 ty::ReLateBound(debruijn, _) => debruijn >= index,
1509 pub fn type_flags(self) -> TypeFlags {
1510 let mut flags = TypeFlags::empty();
1514 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1515 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1516 flags = flags | TypeFlags::HAS_RE_INFER;
1518 ty::RePlaceholder(..) => {
1519 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1520 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1521 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1523 ty::ReEarlyBound(..) => {
1524 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1525 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1526 flags = flags | TypeFlags::HAS_RE_PARAM;
1528 ty::ReFree { .. } => {
1529 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1530 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
1532 ty::ReEmpty(_) | ty::ReStatic => {
1533 flags = flags | TypeFlags::HAS_FREE_REGIONS;
1535 ty::ReLateBound(..) => {
1536 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1539 flags = flags | TypeFlags::HAS_RE_ERASED;
1543 debug!("type_flags({:?}) = {:?}", self, flags);
1548 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1549 /// For example, consider the regions in this snippet of code:
1551 /// ```ignore (illustrative)
1553 /// // ^^ -- early bound, declared on an impl
1555 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1556 /// // ^^ ^^ ^ anonymous, late-bound
1557 /// // | early-bound, appears in where-clauses
1558 /// // late-bound, appears only in fn args
1563 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1564 /// of the impl, and for all the other highlighted regions, it
1565 /// would return the `DefId` of the function. In other cases (not shown), this
1566 /// function might return the `DefId` of a closure.
1567 pub fn free_region_binding_scope(self, tcx: TyCtxt<'_>) -> DefId {
1569 ty::ReEarlyBound(br) => tcx.parent(br.def_id),
1570 ty::ReFree(fr) => fr.scope,
1571 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1575 /// True for free regions other than `'static`.
1576 pub fn is_free(self) -> bool {
1577 matches!(*self, ty::ReEarlyBound(_) | ty::ReFree(_))
1580 /// True if `self` is a free region or static.
1581 pub fn is_free_or_static(self) -> bool {
1583 ty::ReStatic => true,
1584 _ => self.is_free(),
1590 impl<'tcx> Ty<'tcx> {
1592 pub fn kind(self) -> &'tcx TyKind<'tcx> {
1597 pub fn flags(self) -> TypeFlags {
1602 pub fn is_unit(self) -> bool {
1604 Tuple(ref tys) => tys.is_empty(),
1610 pub fn is_never(self) -> bool {
1611 matches!(self.kind(), Never)
1615 pub fn is_primitive(self) -> bool {
1616 self.kind().is_primitive()
1620 pub fn is_adt(self) -> bool {
1621 matches!(self.kind(), Adt(..))
1625 pub fn is_ref(self) -> bool {
1626 matches!(self.kind(), Ref(..))
1630 pub fn is_ty_var(self) -> bool {
1631 matches!(self.kind(), Infer(TyVar(_)))
1635 pub fn ty_vid(self) -> Option<ty::TyVid> {
1637 &Infer(TyVar(vid)) => Some(vid),
1643 pub fn is_ty_infer(self) -> bool {
1644 matches!(self.kind(), Infer(_))
1648 pub fn is_phantom_data(self) -> bool {
1649 if let Adt(def, _) = self.kind() { def.is_phantom_data() } else { false }
1653 pub fn is_bool(self) -> bool {
1654 *self.kind() == Bool
1657 /// Returns `true` if this type is a `str`.
1659 pub fn is_str(self) -> bool {
1664 pub fn is_param(self, index: u32) -> bool {
1666 ty::Param(ref data) => data.index == index,
1672 pub fn is_slice(self) -> bool {
1673 matches!(self.kind(), Slice(_))
1677 pub fn is_array_slice(self) -> bool {
1680 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_)),
1686 pub fn is_array(self) -> bool {
1687 matches!(self.kind(), Array(..))
1691 pub fn is_simd(self) -> bool {
1693 Adt(def, _) => def.repr().simd(),
1698 pub fn sequence_element_type(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1700 Array(ty, _) | Slice(ty) => *ty,
1701 Str => tcx.types.u8,
1702 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1706 pub fn expect_opaque_type(self) -> ty::OpaqueTypeKey<'tcx> {
1707 match *self.kind() {
1708 Opaque(def_id, substs) => ty::OpaqueTypeKey { def_id, substs },
1709 _ => bug!("`expect_opaque_type` called on non-opaque type: {}", self),
1713 pub fn simd_size_and_type(self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1715 Adt(def, substs) => {
1716 assert!(def.repr().simd(), "`simd_size_and_type` called on non-SIMD type");
1717 let variant = def.non_enum_variant();
1718 let f0_ty = variant.fields[0].ty(tcx, substs);
1720 match f0_ty.kind() {
1721 // If the first field is an array, we assume it is the only field and its
1722 // elements are the SIMD components.
1723 Array(f0_elem_ty, f0_len) => {
1724 // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112
1725 // The way we evaluate the `N` in `[T; N]` here only works since we use
1726 // `simd_size_and_type` post-monomorphization. It will probably start to ICE
1727 // if we use it in generic code. See the `simd-array-trait` ui test.
1728 (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, *f0_elem_ty)
1730 // Otherwise, the fields of this Adt are the SIMD components (and we assume they
1731 // all have the same type).
1732 _ => (variant.fields.len() as u64, f0_ty),
1735 _ => bug!("`simd_size_and_type` called on invalid type"),
1740 pub fn is_region_ptr(self) -> bool {
1741 matches!(self.kind(), Ref(..))
1745 pub fn is_mutable_ptr(self) -> bool {
1748 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1749 | Ref(_, _, hir::Mutability::Mut)
1753 /// Get the mutability of the reference or `None` when not a reference
1755 pub fn ref_mutability(self) -> Option<hir::Mutability> {
1757 Ref(_, _, mutability) => Some(*mutability),
1763 pub fn is_unsafe_ptr(self) -> bool {
1764 matches!(self.kind(), RawPtr(_))
1767 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1769 pub fn is_any_ptr(self) -> bool {
1770 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1774 pub fn is_box(self) -> bool {
1776 Adt(def, _) => def.is_box(),
1781 /// Panics if called on any type other than `Box<T>`.
1782 pub fn boxed_ty(self) -> Ty<'tcx> {
1784 Adt(def, substs) if def.is_box() => substs.type_at(0),
1785 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1789 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1790 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1791 /// contents are abstract to rustc.)
1793 pub fn is_scalar(self) -> bool {
1803 | Infer(IntVar(_) | FloatVar(_))
1807 /// Returns `true` if this type is a floating point type.
1809 pub fn is_floating_point(self) -> bool {
1810 matches!(self.kind(), Float(_) | Infer(FloatVar(_)))
1814 pub fn is_trait(self) -> bool {
1815 matches!(self.kind(), Dynamic(..))
1819 pub fn is_enum(self) -> bool {
1820 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_enum())
1824 pub fn is_union(self) -> bool {
1825 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_union())
1829 pub fn is_closure(self) -> bool {
1830 matches!(self.kind(), Closure(..))
1834 pub fn is_generator(self) -> bool {
1835 matches!(self.kind(), Generator(..))
1839 pub fn is_integral(self) -> bool {
1840 matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_))
1844 pub fn is_fresh_ty(self) -> bool {
1845 matches!(self.kind(), Infer(FreshTy(_)))
1849 pub fn is_fresh(self) -> bool {
1850 matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_)))
1854 pub fn is_char(self) -> bool {
1855 matches!(self.kind(), Char)
1859 pub fn is_numeric(self) -> bool {
1860 self.is_integral() || self.is_floating_point()
1864 pub fn is_signed(self) -> bool {
1865 matches!(self.kind(), Int(_))
1869 pub fn is_ptr_sized_integral(self) -> bool {
1870 matches!(self.kind(), Int(ty::IntTy::Isize) | Uint(ty::UintTy::Usize))
1874 pub fn has_concrete_skeleton(self) -> bool {
1875 !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
1878 /// Checks whether a type recursively contains another type
1880 /// Example: `Option<()>` contains `()`
1881 pub fn contains(self, other: Ty<'tcx>) -> bool {
1882 struct ContainsTyVisitor<'tcx>(Ty<'tcx>);
1884 impl<'tcx> TypeVisitor<'tcx> for ContainsTyVisitor<'tcx> {
1887 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1888 if self.0 == t { ControlFlow::BREAK } else { t.super_visit_with(self) }
1892 let cf = self.visit_with(&mut ContainsTyVisitor(other));
1896 /// Returns the type and mutability of `*ty`.
1898 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1899 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
1900 pub fn builtin_deref(self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
1902 Adt(def, _) if def.is_box() => {
1903 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
1905 Ref(_, ty, mutbl) => Some(TypeAndMut { ty: *ty, mutbl: *mutbl }),
1906 RawPtr(mt) if explicit => Some(*mt),
1911 /// Returns the type of `ty[i]`.
1912 pub fn builtin_index(self) -> Option<Ty<'tcx>> {
1914 Array(ty, _) | Slice(ty) => Some(*ty),
1919 pub fn fn_sig(self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
1921 FnDef(def_id, substs) => tcx.bound_fn_sig(*def_id).subst(tcx, substs),
1924 // ignore errors (#54954)
1925 ty::Binder::dummy(FnSig::fake())
1927 Closure(..) => bug!(
1928 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1930 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
1935 pub fn is_fn(self) -> bool {
1936 matches!(self.kind(), FnDef(..) | FnPtr(_))
1940 pub fn is_fn_ptr(self) -> bool {
1941 matches!(self.kind(), FnPtr(_))
1945 pub fn is_impl_trait(self) -> bool {
1946 matches!(self.kind(), Opaque(..))
1950 pub fn ty_adt_def(self) -> Option<AdtDef<'tcx>> {
1952 Adt(adt, _) => Some(*adt),
1957 /// Iterates over tuple fields.
1958 /// Panics when called on anything but a tuple.
1960 pub fn tuple_fields(self) -> &'tcx List<Ty<'tcx>> {
1962 Tuple(substs) => substs,
1963 _ => bug!("tuple_fields called on non-tuple"),
1967 /// If the type contains variants, returns the valid range of variant indices.
1969 // FIXME: This requires the optimized MIR in the case of generators.
1971 pub fn variant_range(self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
1973 TyKind::Adt(adt, _) => Some(adt.variant_range()),
1974 TyKind::Generator(def_id, substs, _) => {
1975 Some(substs.as_generator().variant_range(*def_id, tcx))
1981 /// If the type contains variants, returns the variant for `variant_index`.
1982 /// Panics if `variant_index` is out of range.
1984 // FIXME: This requires the optimized MIR in the case of generators.
1986 pub fn discriminant_for_variant(
1989 variant_index: VariantIdx,
1990 ) -> Option<Discr<'tcx>> {
1992 TyKind::Adt(adt, _) if adt.variants().is_empty() => {
1993 // This can actually happen during CTFE, see
1994 // https://github.com/rust-lang/rust/issues/89765.
1997 TyKind::Adt(adt, _) if adt.is_enum() => {
1998 Some(adt.discriminant_for_variant(tcx, variant_index))
2000 TyKind::Generator(def_id, substs, _) => {
2001 Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
2007 /// Returns the type of the discriminant of this type.
2008 pub fn discriminant_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2010 ty::Adt(adt, _) if adt.is_enum() => adt.repr().discr_type().to_ty(tcx),
2011 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2013 ty::Param(_) | ty::Projection(_) | ty::Opaque(..) | ty::Infer(ty::TyVar(_)) => {
2014 let assoc_items = tcx.associated_item_def_ids(
2015 tcx.require_lang_item(hir::LangItem::DiscriminantKind, None),
2017 tcx.mk_projection(assoc_items[0], tcx.intern_substs(&[self.into()]))
2036 | ty::GeneratorWitness(..)
2040 | ty::Infer(IntVar(_) | FloatVar(_)) => tcx.types.u8,
2043 | ty::Placeholder(_)
2044 | ty::Infer(FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2045 bug!("`discriminant_ty` applied to unexpected type: {:?}", self)
2050 /// Returns the type of metadata for (potentially fat) pointers to this type,
2051 /// and a boolean signifying if this is conditional on this type being `Sized`.
2052 pub fn ptr_metadata_ty(
2055 normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
2056 ) -> (Ty<'tcx>, bool) {
2057 let tail = tcx.struct_tail_with_normalize(self, normalize, || {});
2060 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2071 | ty::GeneratorWitness(..)
2076 // Extern types have metadata = ().
2078 // If returned by `struct_tail_without_normalization` this is a unit struct
2079 // without any fields, or not a struct, and therefore is Sized.
2081 // If returned by `struct_tail_without_normalization` this is the empty tuple,
2082 // a.k.a. unit type, which is Sized
2083 | ty::Tuple(..) => (tcx.types.unit, false),
2085 ty::Str | ty::Slice(_) => (tcx.types.usize, false),
2086 ty::Dynamic(..) => {
2087 let dyn_metadata = tcx.lang_items().dyn_metadata().unwrap();
2088 (tcx.bound_type_of(dyn_metadata).subst(tcx, &[tail.into()]), false)
2091 // type parameters only have unit metadata if they're sized, so return true
2092 // to make sure we double check this during confirmation
2093 ty::Param(_) | ty::Projection(_) | ty::Opaque(..) => (tcx.types.unit, true),
2095 ty::Infer(ty::TyVar(_))
2097 | ty::Placeholder(..)
2098 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2099 bug!("`ptr_metadata_ty` applied to unexpected type: {:?} (tail = {:?})", self, tail)
2104 /// When we create a closure, we record its kind (i.e., what trait
2105 /// it implements) into its `ClosureSubsts` using a type
2106 /// parameter. This is kind of a phantom type, except that the
2107 /// most convenient thing for us to are the integral types. This
2108 /// function converts such a special type into the closure
2109 /// kind. To go the other way, use
2110 /// `tcx.closure_kind_ty(closure_kind)`.
2112 /// Note that during type checking, we use an inference variable
2113 /// to represent the closure kind, because it has not yet been
2114 /// inferred. Once upvar inference (in `rustc_typeck/src/check/upvar.rs`)
2115 /// is complete, that type variable will be unified.
2116 pub fn to_opt_closure_kind(self) -> Option<ty::ClosureKind> {
2118 Int(int_ty) => match int_ty {
2119 ty::IntTy::I8 => Some(ty::ClosureKind::Fn),
2120 ty::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2121 ty::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2122 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2125 // "Bound" types appear in canonical queries when the
2126 // closure type is not yet known
2127 Bound(..) | Infer(_) => None,
2129 Error(_) => Some(ty::ClosureKind::Fn),
2131 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2135 /// Fast path helper for testing if a type is `Sized`.
2137 /// Returning true means the type is known to be sized. Returning
2138 /// `false` means nothing -- could be sized, might not be.
2140 /// Note that we could never rely on the fact that a type such as `[_]` is
2141 /// trivially `!Sized` because we could be in a type environment with a
2142 /// bound such as `[_]: Copy`. A function with such a bound obviously never
2143 /// can be called, but that doesn't mean it shouldn't typecheck. This is why
2144 /// this method doesn't return `Option<bool>`.
2145 pub fn is_trivially_sized(self, tcx: TyCtxt<'tcx>) -> bool {
2147 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2158 | ty::GeneratorWitness(..)
2162 | ty::Error(_) => true,
2164 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2166 ty::Tuple(tys) => tys.iter().all(|ty| ty.is_trivially_sized(tcx)),
2168 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2170 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2172 ty::Infer(ty::TyVar(_)) => false,
2175 | ty::Placeholder(..)
2176 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2177 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2182 /// Fast path helper for primitives which are always `Copy` and which
2183 /// have a side-effect-free `Clone` impl.
2185 /// Returning true means the type is known to be pure and `Copy+Clone`.
2186 /// Returning `false` means nothing -- could be `Copy`, might not be.
2188 /// This is mostly useful for optimizations, as there are the types
2189 /// on which we can replace cloning with dereferencing.
2190 pub fn is_trivially_pure_clone_copy(self) -> bool {
2192 ty::Bool | ty::Char | ty::Never => true,
2194 // These aren't even `Clone`
2195 ty::Str | ty::Slice(..) | ty::Foreign(..) | ty::Dynamic(..) => false,
2197 ty::Int(..) | ty::Uint(..) | ty::Float(..) => true,
2199 // The voldemort ZSTs are fine.
2200 ty::FnDef(..) => true,
2202 ty::Array(element_ty, _len) => element_ty.is_trivially_pure_clone_copy(),
2204 // A 100-tuple isn't "trivial", so doing this only for reasonable sizes.
2205 ty::Tuple(field_tys) => {
2206 field_tys.len() <= 3 && field_tys.iter().all(Self::is_trivially_pure_clone_copy)
2209 // Sometimes traits aren't implemented for every ABI or arity,
2210 // because we can't be generic over everything yet.
2211 ty::FnPtr(..) => false,
2213 // Definitely absolutely not copy.
2214 ty::Ref(_, _, hir::Mutability::Mut) => false,
2216 // Thin pointers & thin shared references are pure-clone-copy, but for
2217 // anything with custom metadata it might be more complicated.
2218 ty::Ref(_, _, hir::Mutability::Not) | ty::RawPtr(..) => false,
2220 ty::Generator(..) | ty::GeneratorWitness(..) => false,
2222 // Might be, but not "trivial" so just giving the safe answer.
2223 ty::Adt(..) | ty::Closure(..) | ty::Opaque(..) => false,
2225 ty::Projection(..) | ty::Param(..) | ty::Infer(..) | ty::Error(..) => false,
2227 ty::Bound(..) | ty::Placeholder(..) => {
2228 bug!("`is_trivially_pure_clone_copy` applied to unexpected type: {:?}", self);
2234 /// Extra information about why we ended up with a particular variance.
2235 /// This is only used to add more information to error messages, and
2236 /// has no effect on soundness. While choosing the 'wrong' `VarianceDiagInfo`
2237 /// may lead to confusing notes in error messages, it will never cause
2238 /// a miscompilation or unsoundness.
2240 /// When in doubt, use `VarianceDiagInfo::default()`
2241 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
2242 pub enum VarianceDiagInfo<'tcx> {
2243 /// No additional information - this is the default.
2244 /// We will not add any additional information to error messages.
2247 /// We switched our variance because a generic argument occurs inside
2248 /// the invariant generic argument of another type.
2250 /// The generic type containing the generic parameter
2251 /// that changes the variance (e.g. `*mut T`, `MyStruct<T>`)
2253 /// The index of the generic parameter being used
2254 /// (e.g. `0` for `*mut T`, `1` for `MyStruct<'CovariantParam, 'InvariantParam>`)
2259 impl<'tcx> VarianceDiagInfo<'tcx> {
2260 /// Mirrors `Variance::xform` - used to 'combine' the existing
2261 /// and new `VarianceDiagInfo`s when our variance changes.
2262 pub fn xform(self, other: VarianceDiagInfo<'tcx>) -> VarianceDiagInfo<'tcx> {
2263 // For now, just use the first `VarianceDiagInfo::Invariant` that we see
2265 VarianceDiagInfo::None => other,
2266 VarianceDiagInfo::Invariant { .. } => self,