1 //! This module contains `TyKind` and its major components.
3 #![allow(rustc::usage_of_ty_tykind)]
7 use crate::infer::canonical::Canonical;
8 use crate::ty::fold::ValidateBoundVars;
9 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
10 use crate::ty::InferTy::{self, *};
12 self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness,
14 use crate::ty::{DelaySpanBugEmitted, List, ParamEnv, TyS};
15 use polonius_engine::Atom;
16 use rustc_data_structures::captures::Captures;
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;
26 use std::marker::PhantomData;
28 use ty::util::IntTypeExt;
30 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
31 #[derive(HashStable, TypeFoldable, Lift)]
32 pub struct TypeAndMut<'tcx> {
34 pub mutbl: hir::Mutability,
37 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
39 /// A "free" region `fr` can be interpreted as "some region
40 /// at least as big as the scope `fr.scope`".
41 pub struct FreeRegion {
43 pub bound_region: BoundRegionKind,
46 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
48 pub enum BoundRegionKind {
49 /// An anonymous region parameter for a given fn (&T)
52 /// Named region parameters for functions (a in &'a T)
54 /// The `DefId` is needed to distinguish free regions in
55 /// the event of shadowing.
56 BrNamed(DefId, Symbol),
58 /// Anonymous region for the implicit env pointer parameter
63 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
65 pub struct BoundRegion {
67 pub kind: BoundRegionKind,
70 impl BoundRegionKind {
71 pub fn is_named(&self) -> bool {
73 BoundRegionKind::BrNamed(_, name) => name != kw::UnderscoreLifetime,
79 /// Defines the kinds of types.
81 /// N.B., if you change this, you'll probably want to change the corresponding
82 /// AST structure in `rustc_ast/src/ast.rs` as well.
83 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
85 #[rustc_diagnostic_item = "TyKind"]
86 pub enum TyKind<'tcx> {
87 /// The primitive boolean type. Written as `bool`.
90 /// The primitive character type; holds a Unicode scalar value
91 /// (a non-surrogate code point). Written as `char`.
94 /// A primitive signed integer type. For example, `i32`.
97 /// A primitive unsigned integer type. For example, `u32`.
100 /// A primitive floating-point type. For example, `f64`.
103 /// Algebraic data types (ADT). For example: structures, enumerations and unions.
105 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
106 /// That is, even after substitution it is possible that there are type
107 /// variables. This happens when the `Adt` corresponds to an ADT
108 /// definition and not a concrete use of it.
109 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
111 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
114 /// The pointee of a string slice. Written as `str`.
117 /// An array with the given length. Written as `[T; n]`.
118 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
120 /// The pointee of an array slice. Written as `[T]`.
123 /// A raw pointer. Written as `*mut T` or `*const T`
124 RawPtr(TypeAndMut<'tcx>),
126 /// A reference; a pointer with an associated lifetime. Written as
127 /// `&'a mut T` or `&'a T`.
128 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
130 /// The anonymous type of a function declaration/definition. Each
131 /// function has a unique type, which is output (for a function
132 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
134 /// For example the type of `bar` here:
137 /// fn foo() -> i32 { 1 }
138 /// let bar = foo; // bar: fn() -> i32 {foo}
140 FnDef(DefId, SubstsRef<'tcx>),
142 /// A pointer to a function. Written as `fn() -> i32`.
144 /// For example the type of `bar` here:
147 /// fn foo() -> i32 { 1 }
148 /// let bar: fn() -> i32 = foo;
150 FnPtr(PolyFnSig<'tcx>),
152 /// A trait object. Written as `dyn for<'b> Trait<'b, Assoc = u32> + Send + 'a`.
153 Dynamic(&'tcx List<Binder<'tcx, ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
155 /// The anonymous type of a closure. Used to represent the type of
157 Closure(DefId, SubstsRef<'tcx>),
159 /// The anonymous type of a generator. Used to represent the type of
161 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
163 /// A type representing the types stored inside a generator.
164 /// This should only appear in GeneratorInteriors.
165 GeneratorWitness(Binder<'tcx, &'tcx List<Ty<'tcx>>>),
167 /// The never type `!`.
170 /// A tuple type. For example, `(i32, bool)`.
171 /// Use `TyS::tuple_fields` to iterate over the field types.
172 Tuple(SubstsRef<'tcx>),
174 /// The projection of an associated type. For example,
175 /// `<T as Trait<..>>::N`.
176 Projection(ProjectionTy<'tcx>),
178 /// Opaque (`impl Trait`) type found in a return type.
179 /// The `DefId` comes either from
180 /// * the `impl Trait` ast::Ty node,
181 /// * or the `type Foo = impl Trait` declaration
182 /// The substitutions are for the generics of the function in question.
183 /// After typeck, the concrete type can be found in the `types` map.
184 Opaque(DefId, SubstsRef<'tcx>),
186 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}`.
189 /// Bound type variable, used only when preparing a trait query.
190 Bound(ty::DebruijnIndex, BoundTy),
192 /// A placeholder type - universally quantified higher-ranked type.
193 Placeholder(ty::PlaceholderType),
195 /// A type variable used during type checking.
198 /// A placeholder for a type which could not be computed; this is
199 /// propagated to avoid useless error messages.
200 Error(DelaySpanBugEmitted),
205 pub fn is_primitive(&self) -> bool {
206 matches!(self, Bool | Char | Int(_) | Uint(_) | Float(_))
209 /// Get the article ("a" or "an") to use with this type.
210 pub fn article(&self) -> &'static str {
212 Int(_) | Float(_) | Array(_, _) => "an",
213 Adt(def, _) if def.is_enum() => "an",
214 // This should never happen, but ICEing and causing the user's code
215 // to not compile felt too harsh.
222 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
223 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
224 static_assert_size!(TyKind<'_>, 32);
226 /// A closure can be modeled as a struct that looks like:
228 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
232 /// - 'l0...'li and T0...Tj are the generic parameters
233 /// in scope on the function that defined the closure,
234 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
235 /// is rather hackily encoded via a scalar type. See
236 /// `TyS::to_opt_closure_kind` for details.
237 /// - CS represents the *closure signature*, representing as a `fn()`
238 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
239 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
241 /// - U is a type parameter representing the types of its upvars, tupled up
242 /// (borrowed, if appropriate; that is, if a U field represents a by-ref upvar,
243 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
245 /// So, for example, given this function:
247 /// fn foo<'a, T>(data: &'a mut T) {
248 /// do(|| data.count += 1)
251 /// the type of the closure would be something like:
253 /// struct Closure<'a, T, U>(...U);
255 /// Note that the type of the upvar is not specified in the struct.
256 /// You may wonder how the impl would then be able to use the upvar,
257 /// if it doesn't know it's type? The answer is that the impl is
258 /// (conceptually) not fully generic over Closure but rather tied to
259 /// instances with the expected upvar types:
261 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
265 /// You can see that the *impl* fully specified the type of the upvar
266 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
267 /// (Here, I am assuming that `data` is mut-borrowed.)
269 /// Now, the last question you may ask is: Why include the upvar types
270 /// in an extra type parameter? The reason for this design is that the
271 /// upvar types can reference lifetimes that are internal to the
272 /// creating function. In my example above, for example, the lifetime
273 /// `'b` represents the scope of the closure itself; this is some
274 /// subset of `foo`, probably just the scope of the call to the to
275 /// `do()`. If we just had the lifetime/type parameters from the
276 /// enclosing function, we couldn't name this lifetime `'b`. Note that
277 /// there can also be lifetimes in the types of the upvars themselves,
278 /// if one of them happens to be a reference to something that the
279 /// creating fn owns.
281 /// OK, you say, so why not create a more minimal set of parameters
282 /// that just includes the extra lifetime parameters? The answer is
283 /// primarily that it would be hard --- we don't know at the time when
284 /// we create the closure type what the full types of the upvars are,
285 /// nor do we know which are borrowed and which are not. In this
286 /// design, we can just supply a fresh type parameter and figure that
289 /// All right, you say, but why include the type parameters from the
290 /// original function then? The answer is that codegen may need them
291 /// when monomorphizing, and they may not appear in the upvars. A
292 /// closure could capture no variables but still make use of some
293 /// in-scope type parameter with a bound (e.g., if our example above
294 /// had an extra `U: Default`, and the closure called `U::default()`).
296 /// There is another reason. This design (implicitly) prohibits
297 /// closures from capturing themselves (except via a trait
298 /// object). This simplifies closure inference considerably, since it
299 /// means that when we infer the kind of a closure or its upvars, we
300 /// don't have to handle cycles where the decisions we make for
301 /// closure C wind up influencing the decisions we ought to make for
302 /// closure C (which would then require fixed point iteration to
303 /// handle). Plus it fixes an ICE. :P
307 /// Generators are handled similarly in `GeneratorSubsts`. The set of
308 /// type parameters is similar, but `CK` and `CS` are replaced by the
309 /// following type parameters:
311 /// * `GS`: The generator's "resume type", which is the type of the
312 /// argument passed to `resume`, and the type of `yield` expressions
313 /// inside the generator.
314 /// * `GY`: The "yield type", which is the type of values passed to
315 /// `yield` inside the generator.
316 /// * `GR`: The "return type", which is the type of value returned upon
317 /// completion of the generator.
318 /// * `GW`: The "generator witness".
319 #[derive(Copy, Clone, Debug, TypeFoldable)]
320 pub struct ClosureSubsts<'tcx> {
321 /// Lifetime and type parameters from the enclosing function,
322 /// concatenated with a tuple containing the types of the upvars.
324 /// These are separated out because codegen wants to pass them around
325 /// when monomorphizing.
326 pub substs: SubstsRef<'tcx>,
329 /// Struct returned by `split()`.
330 pub struct ClosureSubstsParts<'tcx, T> {
331 pub parent_substs: &'tcx [GenericArg<'tcx>],
332 pub closure_kind_ty: T,
333 pub closure_sig_as_fn_ptr_ty: T,
334 pub tupled_upvars_ty: T,
337 impl<'tcx> ClosureSubsts<'tcx> {
338 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
339 /// for the closure parent, alongside additional closure-specific components.
342 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
343 ) -> ClosureSubsts<'tcx> {
345 substs: tcx.mk_substs(
346 parts.parent_substs.iter().copied().chain(
347 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
349 .map(|&ty| ty.into()),
355 /// Divides the closure substs into their respective components.
356 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
357 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
358 match self.substs[..] {
359 [ref parent_substs @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
363 closure_sig_as_fn_ptr_ty,
367 _ => bug!("closure substs missing synthetics"),
371 /// Returns `true` only if enough of the synthetic types are known to
372 /// allow using all of the methods on `ClosureSubsts` without panicking.
374 /// Used primarily by `ty::print::pretty` to be able to handle closure
375 /// types that haven't had their synthetic types substituted in.
376 pub fn is_valid(self) -> bool {
377 self.substs.len() >= 3
378 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
381 /// Returns the substitutions of the closure's parent.
382 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
383 self.split().parent_substs
386 /// Returns an iterator over the list of types of captured paths by the closure.
387 /// In case there was a type error in figuring out the types of the captured path, an
388 /// empty iterator is returned.
390 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
391 match self.tupled_upvars_ty().kind() {
392 TyKind::Error(_) => None,
393 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
394 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
395 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
401 /// Returns the tuple type representing the upvars for this closure.
403 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
404 self.split().tupled_upvars_ty.expect_ty()
407 /// Returns the closure kind for this closure; may return a type
408 /// variable during inference. To get the closure kind during
409 /// inference, use `infcx.closure_kind(substs)`.
410 pub fn kind_ty(self) -> Ty<'tcx> {
411 self.split().closure_kind_ty.expect_ty()
414 /// Returns the `fn` pointer type representing the closure signature for this
416 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
417 // type is known at the time of the creation of `ClosureSubsts`,
418 // see `rustc_typeck::check::closure`.
419 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
420 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
423 /// Returns the closure kind for this closure; only usable outside
424 /// of an inference context, because in that context we know that
425 /// there are no type variables.
427 /// If you have an inference context, use `infcx.closure_kind()`.
428 pub fn kind(self) -> ty::ClosureKind {
429 self.kind_ty().to_opt_closure_kind().unwrap()
432 /// Extracts the signature from the closure.
433 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
434 let ty = self.sig_as_fn_ptr_ty();
436 ty::FnPtr(sig) => *sig,
437 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind()),
442 /// Similar to `ClosureSubsts`; see the above documentation for more.
443 #[derive(Copy, Clone, Debug, TypeFoldable)]
444 pub struct GeneratorSubsts<'tcx> {
445 pub substs: SubstsRef<'tcx>,
448 pub struct GeneratorSubstsParts<'tcx, T> {
449 pub parent_substs: &'tcx [GenericArg<'tcx>],
454 pub tupled_upvars_ty: T,
457 impl<'tcx> GeneratorSubsts<'tcx> {
458 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
459 /// for the generator parent, alongside additional generator-specific components.
462 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
463 ) -> GeneratorSubsts<'tcx> {
465 substs: tcx.mk_substs(
466 parts.parent_substs.iter().copied().chain(
472 parts.tupled_upvars_ty,
475 .map(|&ty| ty.into()),
481 /// Divides the generator substs into their respective components.
482 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
483 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
484 match self.substs[..] {
485 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
486 GeneratorSubstsParts {
495 _ => bug!("generator substs missing synthetics"),
499 /// Returns `true` only if enough of the synthetic types are known to
500 /// allow using all of the methods on `GeneratorSubsts` without panicking.
502 /// Used primarily by `ty::print::pretty` to be able to handle generator
503 /// types that haven't had their synthetic types substituted in.
504 pub fn is_valid(self) -> bool {
505 self.substs.len() >= 5
506 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
509 /// Returns the substitutions of the generator's parent.
510 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
511 self.split().parent_substs
514 /// This describes the types that can be contained in a generator.
515 /// It will be a type variable initially and unified in the last stages of typeck of a body.
516 /// It contains a tuple of all the types that could end up on a generator frame.
517 /// The state transformation MIR pass may only produce layouts which mention types
518 /// in this tuple. Upvars are not counted here.
519 pub fn witness(self) -> Ty<'tcx> {
520 self.split().witness.expect_ty()
523 /// Returns an iterator over the list of types of captured paths by the generator.
524 /// In case there was a type error in figuring out the types of the captured path, an
525 /// empty iterator is returned.
527 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
528 match self.tupled_upvars_ty().kind() {
529 TyKind::Error(_) => None,
530 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
531 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
532 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
538 /// Returns the tuple type representing the upvars for this generator.
540 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
541 self.split().tupled_upvars_ty.expect_ty()
544 /// Returns the type representing the resume type of the generator.
545 pub fn resume_ty(self) -> Ty<'tcx> {
546 self.split().resume_ty.expect_ty()
549 /// Returns the type representing the yield type of the generator.
550 pub fn yield_ty(self) -> Ty<'tcx> {
551 self.split().yield_ty.expect_ty()
554 /// Returns the type representing the return type of the generator.
555 pub fn return_ty(self) -> Ty<'tcx> {
556 self.split().return_ty.expect_ty()
559 /// Returns the "generator signature", which consists of its yield
560 /// and return types.
562 /// N.B., some bits of the code prefers to see this wrapped in a
563 /// binder, but it never contains bound regions. Probably this
564 /// function should be removed.
565 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
566 ty::Binder::dummy(self.sig())
569 /// Returns the "generator signature", which consists of its resume, yield
570 /// and return types.
571 pub fn sig(self) -> GenSig<'tcx> {
573 resume_ty: self.resume_ty(),
574 yield_ty: self.yield_ty(),
575 return_ty: self.return_ty(),
580 impl<'tcx> GeneratorSubsts<'tcx> {
581 /// Generator has not been resumed yet.
582 pub const UNRESUMED: usize = 0;
583 /// Generator has returned or is completed.
584 pub const RETURNED: usize = 1;
585 /// Generator has been poisoned.
586 pub const POISONED: usize = 2;
588 const UNRESUMED_NAME: &'static str = "Unresumed";
589 const RETURNED_NAME: &'static str = "Returned";
590 const POISONED_NAME: &'static str = "Panicked";
592 /// The valid variant indices of this generator.
594 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
595 // FIXME requires optimized MIR
596 let num_variants = tcx.generator_layout(def_id).unwrap().variant_fields.len();
597 VariantIdx::new(0)..VariantIdx::new(num_variants)
600 /// The discriminant for the given variant. Panics if the `variant_index` is
603 pub fn discriminant_for_variant(
607 variant_index: VariantIdx,
609 // Generators don't support explicit discriminant values, so they are
610 // the same as the variant index.
611 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
612 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
615 /// The set of all discriminants for the generator, enumerated with their
618 pub fn discriminants(
622 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
623 self.variant_range(def_id, tcx).map(move |index| {
624 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
628 /// Calls `f` with a reference to the name of the enumerator for the given
630 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
632 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
633 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
634 Self::POISONED => Cow::from(Self::POISONED_NAME),
635 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
639 /// The type of the state discriminant used in the generator type.
641 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
645 /// This returns the types of the MIR locals which had to be stored across suspension points.
646 /// It is calculated in rustc_const_eval::transform::generator::StateTransform.
647 /// All the types here must be in the tuple in GeneratorInterior.
649 /// The locals are grouped by their variant number. Note that some locals may
650 /// be repeated in multiple variants.
656 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
657 let layout = tcx.generator_layout(def_id).unwrap();
658 layout.variant_fields.iter().map(move |variant| {
659 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
663 /// This is the types of the fields of a generator which are not stored in a
666 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
671 #[derive(Debug, Copy, Clone, HashStable)]
672 pub enum UpvarSubsts<'tcx> {
673 Closure(SubstsRef<'tcx>),
674 Generator(SubstsRef<'tcx>),
677 impl<'tcx> UpvarSubsts<'tcx> {
678 /// Returns an iterator over the list of types of captured paths by the closure/generator.
679 /// In case there was a type error in figuring out the types of the captured path, an
680 /// empty iterator is returned.
682 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
683 let tupled_tys = match self {
684 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
685 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
688 match tupled_tys.kind() {
689 TyKind::Error(_) => None,
690 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
691 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
692 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
699 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
701 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
702 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
707 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
708 #[derive(HashStable, TypeFoldable)]
709 pub enum ExistentialPredicate<'tcx> {
710 /// E.g., `Iterator`.
711 Trait(ExistentialTraitRef<'tcx>),
712 /// E.g., `Iterator::Item = T`.
713 Projection(ExistentialProjection<'tcx>),
718 impl<'tcx> ExistentialPredicate<'tcx> {
719 /// Compares via an ordering that will not change if modules are reordered or other changes are
720 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
721 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
722 use self::ExistentialPredicate::*;
723 match (*self, *other) {
724 (Trait(_), Trait(_)) => Ordering::Equal,
725 (Projection(ref a), Projection(ref b)) => {
726 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
728 (AutoTrait(ref a), AutoTrait(ref b)) => {
729 tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash)
731 (Trait(_), _) => Ordering::Less,
732 (Projection(_), Trait(_)) => Ordering::Greater,
733 (Projection(_), _) => Ordering::Less,
734 (AutoTrait(_), _) => Ordering::Greater,
739 impl<'tcx> Binder<'tcx, ExistentialPredicate<'tcx>> {
740 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
741 use crate::ty::ToPredicate;
742 match self.skip_binder() {
743 ExistentialPredicate::Trait(tr) => {
744 self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
746 ExistentialPredicate::Projection(p) => {
747 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
749 ExistentialPredicate::AutoTrait(did) => {
750 let trait_ref = self.rebind(ty::TraitRef {
752 substs: tcx.mk_substs_trait(self_ty, &[]),
754 trait_ref.without_const().to_predicate(tcx)
760 impl<'tcx> List<ty::Binder<'tcx, ExistentialPredicate<'tcx>>> {
761 /// Returns the "principal `DefId`" of this set of existential predicates.
763 /// A Rust trait object type consists (in addition to a lifetime bound)
764 /// of a set of trait bounds, which are separated into any number
765 /// of auto-trait bounds, and at most one non-auto-trait bound. The
766 /// non-auto-trait bound is called the "principal" of the trait
769 /// Only the principal can have methods or type parameters (because
770 /// auto traits can have neither of them). This is important, because
771 /// it means the auto traits can be treated as an unordered set (methods
772 /// would force an order for the vtable, while relating traits with
773 /// type parameters without knowing the order to relate them in is
774 /// a rather non-trivial task).
776 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
777 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
778 /// are the set `{Sync}`.
780 /// It is also possible to have a "trivial" trait object that
781 /// consists only of auto traits, with no principal - for example,
782 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
783 /// is `{Send, Sync}`, while there is no principal. These trait objects
784 /// have a "trivial" vtable consisting of just the size, alignment,
786 pub fn principal(&self) -> Option<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> {
788 .map_bound(|this| match this {
789 ExistentialPredicate::Trait(tr) => Some(tr),
795 pub fn principal_def_id(&self) -> Option<DefId> {
796 self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
800 pub fn projection_bounds<'a>(
802 ) -> impl Iterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> + 'a {
803 self.iter().filter_map(|predicate| {
805 .map_bound(|pred| match pred {
806 ExistentialPredicate::Projection(projection) => Some(projection),
814 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
815 self.iter().filter_map(|predicate| match predicate.skip_binder() {
816 ExistentialPredicate::AutoTrait(did) => Some(did),
822 /// A complete reference to a trait. These take numerous guises in syntax,
823 /// but perhaps the most recognizable form is in a where-clause:
827 /// This would be represented by a trait-reference where the `DefId` is the
828 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
829 /// and `U` as parameter 1.
831 /// Trait references also appear in object types like `Foo<U>`, but in
832 /// that case the `Self` parameter is absent from the substitutions.
833 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
834 #[derive(HashStable, TypeFoldable)]
835 pub struct TraitRef<'tcx> {
837 pub substs: SubstsRef<'tcx>,
840 impl<'tcx> TraitRef<'tcx> {
841 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
842 TraitRef { def_id, substs }
845 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
846 /// are the parameters defined on trait.
847 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> Binder<'tcx, TraitRef<'tcx>> {
848 ty::Binder::dummy(TraitRef {
850 substs: InternalSubsts::identity_for_item(tcx, def_id),
855 pub fn self_ty(&self) -> Ty<'tcx> {
856 self.substs.type_at(0)
862 substs: SubstsRef<'tcx>,
863 ) -> ty::TraitRef<'tcx> {
864 let defs = tcx.generics_of(trait_id);
866 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
870 pub type PolyTraitRef<'tcx> = Binder<'tcx, TraitRef<'tcx>>;
872 impl<'tcx> PolyTraitRef<'tcx> {
873 pub fn self_ty(&self) -> Binder<'tcx, Ty<'tcx>> {
874 self.map_bound_ref(|tr| tr.self_ty())
877 pub fn def_id(&self) -> DefId {
878 self.skip_binder().def_id
881 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
882 self.map_bound(|trait_ref| ty::TraitPredicate {
884 constness: ty::BoundConstness::NotConst,
885 polarity: ty::ImplPolarity::Positive,
890 /// An existential reference to a trait, where `Self` is erased.
891 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
893 /// exists T. T: Trait<'a, 'b, X, Y>
895 /// The substitutions don't include the erased `Self`, only trait
896 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
897 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
898 #[derive(HashStable, TypeFoldable)]
899 pub struct ExistentialTraitRef<'tcx> {
901 pub substs: SubstsRef<'tcx>,
904 impl<'tcx> ExistentialTraitRef<'tcx> {
905 pub fn erase_self_ty(
907 trait_ref: ty::TraitRef<'tcx>,
908 ) -> ty::ExistentialTraitRef<'tcx> {
909 // Assert there is a Self.
910 trait_ref.substs.type_at(0);
912 ty::ExistentialTraitRef {
913 def_id: trait_ref.def_id,
914 substs: tcx.intern_substs(&trait_ref.substs[1..]),
918 /// Object types don't have a self type specified. Therefore, when
919 /// we convert the principal trait-ref into a normal trait-ref,
920 /// you must give *some* self type. A common choice is `mk_err()`
921 /// or some placeholder type.
922 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
923 // otherwise the escaping vars would be captured by the binder
924 // debug_assert!(!self_ty.has_escaping_bound_vars());
926 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
930 pub type PolyExistentialTraitRef<'tcx> = Binder<'tcx, ExistentialTraitRef<'tcx>>;
932 impl<'tcx> PolyExistentialTraitRef<'tcx> {
933 pub fn def_id(&self) -> DefId {
934 self.skip_binder().def_id
937 /// Object types don't have a self type specified. Therefore, when
938 /// we convert the principal trait-ref into a normal trait-ref,
939 /// you must give *some* self type. A common choice is `mk_err()`
940 /// or some placeholder type.
941 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
942 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
946 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
947 #[derive(HashStable)]
948 pub enum BoundVariableKind {
950 Region(BoundRegionKind),
954 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
955 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
956 /// (which would be represented by the type `PolyTraitRef ==
957 /// Binder<'tcx, TraitRef>`). Note that when we instantiate,
958 /// erase, or otherwise "discharge" these bound vars, we change the
959 /// type from `Binder<'tcx, T>` to just `T` (see
960 /// e.g., `liberate_late_bound_regions`).
962 /// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro.
963 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
964 pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>);
966 impl<'tcx, T> Binder<'tcx, T>
968 T: TypeFoldable<'tcx>,
970 /// Wraps `value` in a binder, asserting that `value` does not
971 /// contain any bound vars that would be bound by the
972 /// binder. This is commonly used to 'inject' a value T into a
973 /// different binding level.
974 pub fn dummy(value: T) -> Binder<'tcx, T> {
975 assert!(!value.has_escaping_bound_vars());
976 Binder(value, ty::List::empty())
979 pub fn bind_with_vars(value: T, vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> {
980 if cfg!(debug_assertions) {
981 let mut validator = ValidateBoundVars::new(vars);
982 value.visit_with(&mut validator);
988 impl<'tcx, T> Binder<'tcx, T> {
989 /// Skips the binder and returns the "bound" value. This is a
990 /// risky thing to do because it's easy to get confused about
991 /// De Bruijn indices and the like. It is usually better to
992 /// discharge the binder using `no_bound_vars` or
993 /// `replace_late_bound_regions` or something like
994 /// that. `skip_binder` is only valid when you are either
995 /// extracting data that has nothing to do with bound vars, you
996 /// are doing some sort of test that does not involve bound
997 /// regions, or you are being very careful about your depth
1000 /// Some examples where `skip_binder` is reasonable:
1002 /// - extracting the `DefId` from a PolyTraitRef;
1003 /// - comparing the self type of a PolyTraitRef to see if it is equal to
1004 /// a type parameter `X`, since the type `X` does not reference any regions
1005 pub fn skip_binder(self) -> T {
1009 pub fn bound_vars(&self) -> &'tcx List<BoundVariableKind> {
1013 pub fn as_ref(&self) -> Binder<'tcx, &T> {
1014 Binder(&self.0, self.1)
1017 pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U>
1021 let value = f(&self.0);
1022 Binder(value, self.1)
1025 pub fn map_bound_ref<F, U: TypeFoldable<'tcx>>(&self, f: F) -> Binder<'tcx, U>
1029 self.as_ref().map_bound(f)
1032 pub fn map_bound<F, U: TypeFoldable<'tcx>>(self, f: F) -> Binder<'tcx, U>
1036 let value = f(self.0);
1037 if cfg!(debug_assertions) {
1038 let mut validator = ValidateBoundVars::new(self.1);
1039 value.visit_with(&mut validator);
1041 Binder(value, self.1)
1044 /// Wraps a `value` in a binder, using the same bound variables as the
1045 /// current `Binder`. This should not be used if the new value *changes*
1046 /// the bound variables. Note: the (old or new) value itself does not
1047 /// necessarily need to *name* all the bound variables.
1049 /// This currently doesn't do anything different than `bind`, because we
1050 /// don't actually track bound vars. However, semantically, it is different
1051 /// because bound vars aren't allowed to change here, whereas they are
1052 /// in `bind`. This may be (debug) asserted in the future.
1053 pub fn rebind<U>(&self, value: U) -> Binder<'tcx, U>
1055 U: TypeFoldable<'tcx>,
1057 if cfg!(debug_assertions) {
1058 let mut validator = ValidateBoundVars::new(self.bound_vars());
1059 value.visit_with(&mut validator);
1061 Binder(value, self.1)
1064 /// Unwraps and returns the value within, but only if it contains
1065 /// no bound vars at all. (In other words, if this binder --
1066 /// and indeed any enclosing binder -- doesn't bind anything at
1067 /// all.) Otherwise, returns `None`.
1069 /// (One could imagine having a method that just unwraps a single
1070 /// binder, but permits late-bound vars bound by enclosing
1071 /// binders, but that would require adjusting the debruijn
1072 /// indices, and given the shallow binding structure we often use,
1073 /// would not be that useful.)
1074 pub fn no_bound_vars(self) -> Option<T>
1076 T: TypeFoldable<'tcx>,
1078 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1081 /// Splits the contents into two things that share the same binder
1082 /// level as the original, returning two distinct binders.
1084 /// `f` should consider bound regions at depth 1 to be free, and
1085 /// anything it produces with bound regions at depth 1 will be
1086 /// bound in the resulting return values.
1087 pub fn split<U, V, F>(self, f: F) -> (Binder<'tcx, U>, Binder<'tcx, V>)
1089 F: FnOnce(T) -> (U, V),
1091 let (u, v) = f(self.0);
1092 (Binder(u, self.1), Binder(v, self.1))
1096 impl<'tcx, T> Binder<'tcx, Option<T>> {
1097 pub fn transpose(self) -> Option<Binder<'tcx, T>> {
1098 let bound_vars = self.1;
1099 self.0.map(|v| Binder(v, bound_vars))
1103 /// Represents the projection of an associated type. In explicit UFCS
1104 /// form this would be written `<T as Trait<..>>::N`.
1105 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1106 #[derive(HashStable, TypeFoldable)]
1107 pub struct ProjectionTy<'tcx> {
1108 /// The parameters of the associated item.
1109 pub substs: SubstsRef<'tcx>,
1111 /// The `DefId` of the `TraitItem` for the associated type `N`.
1113 /// Note that this is not the `DefId` of the `TraitRef` containing this
1114 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1115 pub item_def_id: DefId,
1118 impl<'tcx> ProjectionTy<'tcx> {
1119 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
1120 tcx.associated_item(self.item_def_id).container.id()
1123 /// Extracts the underlying trait reference and own substs from this projection.
1124 /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
1125 /// then this function would return a `T: Iterator` trait reference and `['a]` as the own substs
1126 pub fn trait_ref_and_own_substs(
1129 ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) {
1130 let def_id = tcx.associated_item(self.item_def_id).container.id();
1131 let trait_generics = tcx.generics_of(def_id);
1133 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, trait_generics) },
1134 &self.substs[trait_generics.count()..],
1138 /// Extracts the underlying trait reference from this projection.
1139 /// For example, if this is a projection of `<T as Iterator>::Item`,
1140 /// then this function would return a `T: Iterator` trait reference.
1142 /// WARNING: This will drop the substs for generic associated types
1143 /// consider calling [Self::trait_ref_and_own_substs] to get those
1145 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1146 let def_id = self.trait_def_id(tcx);
1147 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1150 pub fn self_ty(&self) -> Ty<'tcx> {
1151 self.substs.type_at(0)
1155 #[derive(Copy, Clone, Debug, TypeFoldable)]
1156 pub struct GenSig<'tcx> {
1157 pub resume_ty: Ty<'tcx>,
1158 pub yield_ty: Ty<'tcx>,
1159 pub return_ty: Ty<'tcx>,
1162 pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>;
1164 /// Signature of a function type, which we have arbitrarily
1165 /// decided to use to refer to the input/output types.
1167 /// - `inputs`: is the list of arguments and their modes.
1168 /// - `output`: is the return type.
1169 /// - `c_variadic`: indicates whether this is a C-variadic function.
1170 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1171 #[derive(HashStable, TypeFoldable)]
1172 pub struct FnSig<'tcx> {
1173 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1174 pub c_variadic: bool,
1175 pub unsafety: hir::Unsafety,
1179 impl<'tcx> FnSig<'tcx> {
1180 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1181 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1184 pub fn output(&self) -> Ty<'tcx> {
1185 self.inputs_and_output[self.inputs_and_output.len() - 1]
1188 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1190 fn fake() -> FnSig<'tcx> {
1192 inputs_and_output: List::empty(),
1194 unsafety: hir::Unsafety::Normal,
1195 abi: abi::Abi::Rust,
1200 pub type PolyFnSig<'tcx> = Binder<'tcx, FnSig<'tcx>>;
1202 impl<'tcx> PolyFnSig<'tcx> {
1204 pub fn inputs(&self) -> Binder<'tcx, &'tcx [Ty<'tcx>]> {
1205 self.map_bound_ref_unchecked(|fn_sig| fn_sig.inputs())
1208 pub fn input(&self, index: usize) -> ty::Binder<'tcx, Ty<'tcx>> {
1209 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1211 pub fn inputs_and_output(&self) -> ty::Binder<'tcx, &'tcx List<Ty<'tcx>>> {
1212 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1215 pub fn output(&self) -> ty::Binder<'tcx, Ty<'tcx>> {
1216 self.map_bound_ref(|fn_sig| fn_sig.output())
1218 pub fn c_variadic(&self) -> bool {
1219 self.skip_binder().c_variadic
1221 pub fn unsafety(&self) -> hir::Unsafety {
1222 self.skip_binder().unsafety
1224 pub fn abi(&self) -> abi::Abi {
1225 self.skip_binder().abi
1229 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<'tcx, FnSig<'tcx>>>;
1231 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1232 #[derive(HashStable)]
1233 pub struct ParamTy {
1238 impl<'tcx> ParamTy {
1239 pub fn new(index: u32, name: Symbol) -> ParamTy {
1240 ParamTy { index, name }
1243 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1244 ParamTy::new(def.index, def.name)
1248 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1249 tcx.mk_ty_param(self.index, self.name)
1253 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1254 #[derive(HashStable)]
1255 pub struct ParamConst {
1261 pub fn new(index: u32, name: Symbol) -> ParamConst {
1262 ParamConst { index, name }
1265 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1266 ParamConst::new(def.index, def.name)
1270 pub type Region<'tcx> = &'tcx RegionKind;
1272 /// Representation of regions. Note that the NLL checker uses a distinct
1273 /// representation of regions. For this reason, it internally replaces all the
1274 /// regions with inference variables -- the index of the variable is then used
1275 /// to index into internal NLL data structures. See `rustc_const_eval::borrow_check`
1276 /// module for more information.
1278 /// ## The Region lattice within a given function
1280 /// In general, the region lattice looks like
1283 /// static ----------+-----...------+ (greatest)
1285 /// early-bound and | |
1286 /// free regions | |
1289 /// empty(root) placeholder(U1) |
1291 /// | / placeholder(Un)
1296 /// empty(Un) -------- (smallest)
1299 /// Early-bound/free regions are the named lifetimes in scope from the
1300 /// function declaration. They have relationships to one another
1301 /// determined based on the declared relationships from the
1304 /// Note that inference variables and bound regions are not included
1305 /// in this diagram. In the case of inference variables, they should
1306 /// be inferred to some other region from the diagram. In the case of
1307 /// bound regions, they are excluded because they don't make sense to
1308 /// include -- the diagram indicates the relationship between free
1311 /// ## Inference variables
1313 /// During region inference, we sometimes create inference variables,
1314 /// represented as `ReVar`. These will be inferred by the code in
1315 /// `infer::lexical_region_resolve` to some free region from the
1316 /// lattice above (the minimal region that meets the
1319 /// During NLL checking, where regions are defined differently, we
1320 /// also use `ReVar` -- in that case, the index is used to index into
1321 /// the NLL region checker's data structures. The variable may in fact
1322 /// represent either a free region or an inference variable, in that
1325 /// ## Bound Regions
1327 /// These are regions that are stored behind a binder and must be substituted
1328 /// with some concrete region before being used. There are two kind of
1329 /// bound regions: early-bound, which are bound in an item's `Generics`,
1330 /// and are substituted by an `InternalSubsts`, and late-bound, which are part of
1331 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1332 /// the likes of `liberate_late_bound_regions`. The distinction exists
1333 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1335 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1336 /// outside their binder, e.g., in types passed to type inference, and
1337 /// should first be substituted (by placeholder regions, free regions,
1338 /// or region variables).
1340 /// ## Placeholder and Free Regions
1342 /// One often wants to work with bound regions without knowing their precise
1343 /// identity. For example, when checking a function, the lifetime of a borrow
1344 /// can end up being assigned to some region parameter. In these cases,
1345 /// it must be ensured that bounds on the region can't be accidentally
1346 /// assumed without being checked.
1348 /// To do this, we replace the bound regions with placeholder markers,
1349 /// which don't satisfy any relation not explicitly provided.
1351 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1352 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1353 /// to be used. These also support explicit bounds: both the internally-stored
1354 /// *scope*, which the region is assumed to outlive, as well as other
1355 /// relations stored in the `FreeRegionMap`. Note that these relations
1356 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1357 /// `resolve_regions_and_report_errors`.
1359 /// When working with higher-ranked types, some region relations aren't
1360 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1361 /// `RePlaceholder` is designed for this purpose. In these contexts,
1362 /// there's also the risk that some inference variable laying around will
1363 /// get unified with your placeholder region: if you want to check whether
1364 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1365 /// with a placeholder region `'%a`, the variable `'_` would just be
1366 /// instantiated to the placeholder region `'%a`, which is wrong because
1367 /// the inference variable is supposed to satisfy the relation
1368 /// *for every value of the placeholder region*. To ensure that doesn't
1369 /// happen, you can use `leak_check`. This is more clearly explained
1370 /// by the [rustc dev guide].
1372 /// [1]: https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1373 /// [2]: https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1374 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1375 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1376 pub enum RegionKind {
1377 /// Region bound in a type or fn declaration which will be
1378 /// substituted 'early' -- that is, at the same time when type
1379 /// parameters are substituted.
1380 ReEarlyBound(EarlyBoundRegion),
1382 /// Region bound in a function scope, which will be substituted when the
1383 /// function is called.
1384 ReLateBound(ty::DebruijnIndex, BoundRegion),
1386 /// When checking a function body, the types of all arguments and so forth
1387 /// that refer to bound region parameters are modified to refer to free
1388 /// region parameters.
1391 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1394 /// A region variable. Should not exist after typeck.
1397 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1398 /// Should not exist after typeck.
1399 RePlaceholder(ty::PlaceholderRegion),
1401 /// Empty lifetime is for data that is never accessed. We tag the
1402 /// empty lifetime with a universe -- the idea is that we don't
1403 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1404 /// Therefore, the `'empty` in a universe `U` is less than all
1405 /// regions visible from `U`, but not less than regions not visible
1407 ReEmpty(ty::UniverseIndex),
1409 /// Erased region, used by trait selection, in MIR and during codegen.
1413 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1414 pub struct EarlyBoundRegion {
1420 /// A **`const`** **v**ariable **ID**.
1421 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1422 pub struct ConstVid<'tcx> {
1424 pub phantom: PhantomData<&'tcx ()>,
1427 rustc_index::newtype_index! {
1428 /// A **region** (lifetime) **v**ariable **ID**.
1429 pub struct RegionVid {
1430 DEBUG_FORMAT = custom,
1434 impl Atom for RegionVid {
1435 fn index(self) -> usize {
1440 rustc_index::newtype_index! {
1441 pub struct BoundVar { .. }
1444 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1445 #[derive(HashStable)]
1446 pub struct BoundTy {
1448 pub kind: BoundTyKind,
1451 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1452 #[derive(HashStable)]
1453 pub enum BoundTyKind {
1458 impl From<BoundVar> for BoundTy {
1459 fn from(var: BoundVar) -> Self {
1460 BoundTy { var, kind: BoundTyKind::Anon }
1464 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1465 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1466 #[derive(HashStable, TypeFoldable)]
1467 pub struct ExistentialProjection<'tcx> {
1468 pub item_def_id: DefId,
1469 pub substs: SubstsRef<'tcx>,
1473 pub type PolyExistentialProjection<'tcx> = Binder<'tcx, ExistentialProjection<'tcx>>;
1475 impl<'tcx> ExistentialProjection<'tcx> {
1476 /// Extracts the underlying existential trait reference from this projection.
1477 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1478 /// then this function would return an `exists T. T: Iterator` existential trait
1480 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
1481 let def_id = tcx.associated_item(self.item_def_id).container.id();
1482 let subst_count = tcx.generics_of(def_id).count() - 1;
1483 let substs = tcx.intern_substs(&self.substs[..subst_count]);
1484 ty::ExistentialTraitRef { def_id, substs }
1487 pub fn with_self_ty(
1491 ) -> ty::ProjectionPredicate<'tcx> {
1492 // otherwise the escaping regions would be captured by the binders
1493 debug_assert!(!self_ty.has_escaping_bound_vars());
1495 ty::ProjectionPredicate {
1496 projection_ty: ty::ProjectionTy {
1497 item_def_id: self.item_def_id,
1498 substs: tcx.mk_substs_trait(self_ty, self.substs),
1504 pub fn erase_self_ty(
1506 projection_predicate: ty::ProjectionPredicate<'tcx>,
1508 // Assert there is a Self.
1509 projection_predicate.projection_ty.substs.type_at(0);
1512 item_def_id: projection_predicate.projection_ty.item_def_id,
1513 substs: tcx.intern_substs(&projection_predicate.projection_ty.substs[1..]),
1514 ty: projection_predicate.ty,
1519 impl<'tcx> PolyExistentialProjection<'tcx> {
1520 pub fn with_self_ty(
1524 ) -> ty::PolyProjectionPredicate<'tcx> {
1525 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1528 pub fn item_def_id(&self) -> DefId {
1529 self.skip_binder().item_def_id
1533 /// Region utilities
1535 /// Is this region named by the user?
1536 pub fn has_name(&self) -> bool {
1538 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1539 RegionKind::ReLateBound(_, br) => br.kind.is_named(),
1540 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1541 RegionKind::ReStatic => true,
1542 RegionKind::ReVar(..) => false,
1543 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1544 RegionKind::ReEmpty(_) => false,
1545 RegionKind::ReErased => false,
1550 pub fn is_late_bound(&self) -> bool {
1551 matches!(*self, ty::ReLateBound(..))
1555 pub fn is_placeholder(&self) -> bool {
1556 matches!(*self, ty::RePlaceholder(..))
1560 pub fn bound_at_or_above_binder(&self, index: ty::DebruijnIndex) -> bool {
1562 ty::ReLateBound(debruijn, _) => debruijn >= index,
1567 pub fn type_flags(&self) -> TypeFlags {
1568 let mut flags = TypeFlags::empty();
1572 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1573 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1574 flags = flags | TypeFlags::HAS_RE_INFER;
1576 ty::RePlaceholder(..) => {
1577 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1578 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1579 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1581 ty::ReEarlyBound(..) => {
1582 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1583 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1584 flags = flags | TypeFlags::HAS_KNOWN_RE_PARAM;
1586 ty::ReFree { .. } => {
1587 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1588 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1590 ty::ReEmpty(_) | ty::ReStatic => {
1591 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1593 ty::ReLateBound(..) => {
1594 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1597 flags = flags | TypeFlags::HAS_RE_ERASED;
1601 debug!("type_flags({:?}) = {:?}", self, flags);
1606 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1607 /// For example, consider the regions in this snippet of code:
1611 /// ^^ -- early bound, declared on an impl
1613 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1614 /// ^^ ^^ ^ anonymous, late-bound
1615 /// | early-bound, appears in where-clauses
1616 /// late-bound, appears only in fn args
1621 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1622 /// of the impl, and for all the other highlighted regions, it
1623 /// would return the `DefId` of the function. In other cases (not shown), this
1624 /// function might return the `DefId` of a closure.
1625 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1627 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1628 ty::ReFree(fr) => fr.scope,
1629 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1635 impl<'tcx> TyS<'tcx> {
1637 pub fn kind(&self) -> &TyKind<'tcx> {
1642 pub fn flags(&self) -> TypeFlags {
1647 pub fn is_unit(&self) -> bool {
1649 Tuple(ref tys) => tys.is_empty(),
1655 pub fn is_never(&self) -> bool {
1656 matches!(self.kind(), Never)
1660 pub fn is_primitive(&self) -> bool {
1661 self.kind().is_primitive()
1665 pub fn is_adt(&self) -> bool {
1666 matches!(self.kind(), Adt(..))
1670 pub fn is_ref(&self) -> bool {
1671 matches!(self.kind(), Ref(..))
1675 pub fn is_ty_var(&self) -> bool {
1676 matches!(self.kind(), Infer(TyVar(_)))
1680 pub fn ty_vid(&self) -> Option<ty::TyVid> {
1682 &Infer(TyVar(vid)) => Some(vid),
1688 pub fn is_ty_infer(&self) -> bool {
1689 matches!(self.kind(), Infer(_))
1693 pub fn is_phantom_data(&self) -> bool {
1694 if let Adt(def, _) = self.kind() { def.is_phantom_data() } else { false }
1698 pub fn is_bool(&self) -> bool {
1699 *self.kind() == Bool
1702 /// Returns `true` if this type is a `str`.
1704 pub fn is_str(&self) -> bool {
1709 pub fn is_param(&self, index: u32) -> bool {
1711 ty::Param(ref data) => data.index == index,
1717 pub fn is_slice(&self) -> bool {
1719 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_) | Str),
1725 pub fn is_array(&self) -> bool {
1726 matches!(self.kind(), Array(..))
1730 pub fn is_simd(&self) -> bool {
1732 Adt(def, _) => def.repr.simd(),
1737 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1739 Array(ty, _) | Slice(ty) => ty,
1740 Str => tcx.mk_mach_uint(ty::UintTy::U8),
1741 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1745 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1747 Adt(def, substs) => {
1748 let variant = def.non_enum_variant();
1749 let f0_ty = variant.fields[0].ty(tcx, substs);
1751 match f0_ty.kind() {
1752 Array(f0_elem_ty, f0_len) => {
1753 // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112
1754 // The way we evaluate the `N` in `[T; N]` here only works since we use
1755 // `simd_size_and_type` post-monomorphization. It will probably start to ICE
1756 // if we use it in generic code. See the `simd-array-trait` ui test.
1757 (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, f0_elem_ty)
1759 _ => (variant.fields.len() as u64, f0_ty),
1762 _ => bug!("`simd_size_and_type` called on invalid type"),
1767 pub fn is_region_ptr(&self) -> bool {
1768 matches!(self.kind(), Ref(..))
1772 pub fn is_mutable_ptr(&self) -> bool {
1775 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1776 | Ref(_, _, hir::Mutability::Mut)
1780 /// Get the mutability of the reference or `None` when not a reference
1782 pub fn ref_mutability(&self) -> Option<hir::Mutability> {
1784 Ref(_, _, mutability) => Some(*mutability),
1790 pub fn is_unsafe_ptr(&self) -> bool {
1791 matches!(self.kind(), RawPtr(_))
1794 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1796 pub fn is_any_ptr(&self) -> bool {
1797 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1801 pub fn is_box(&self) -> bool {
1803 Adt(def, _) => def.is_box(),
1808 /// Panics if called on any type other than `Box<T>`.
1809 pub fn boxed_ty(&self) -> Ty<'tcx> {
1811 Adt(def, substs) if def.is_box() => substs.type_at(0),
1812 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1816 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1817 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1818 /// contents are abstract to rustc.)
1820 pub fn is_scalar(&self) -> bool {
1830 | Infer(IntVar(_) | FloatVar(_))
1834 /// Returns `true` if this type is a floating point type.
1836 pub fn is_floating_point(&self) -> bool {
1837 matches!(self.kind(), Float(_) | Infer(FloatVar(_)))
1841 pub fn is_trait(&self) -> bool {
1842 matches!(self.kind(), Dynamic(..))
1846 pub fn is_enum(&self) -> bool {
1847 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_enum())
1851 pub fn is_union(&self) -> bool {
1852 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_union())
1856 pub fn is_closure(&self) -> bool {
1857 matches!(self.kind(), Closure(..))
1861 pub fn is_generator(&self) -> bool {
1862 matches!(self.kind(), Generator(..))
1866 pub fn is_integral(&self) -> bool {
1867 matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_))
1871 pub fn is_fresh_ty(&self) -> bool {
1872 matches!(self.kind(), Infer(FreshTy(_)))
1876 pub fn is_fresh(&self) -> bool {
1877 matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_)))
1881 pub fn is_char(&self) -> bool {
1882 matches!(self.kind(), Char)
1886 pub fn is_numeric(&self) -> bool {
1887 self.is_integral() || self.is_floating_point()
1891 pub fn is_signed(&self) -> bool {
1892 matches!(self.kind(), Int(_))
1896 pub fn is_ptr_sized_integral(&self) -> bool {
1897 matches!(self.kind(), Int(ty::IntTy::Isize) | Uint(ty::UintTy::Usize))
1901 pub fn has_concrete_skeleton(&self) -> bool {
1902 !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
1905 /// Returns the type and mutability of `*ty`.
1907 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1908 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
1909 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
1911 Adt(def, _) if def.is_box() => {
1912 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
1914 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl: *mutbl }),
1915 RawPtr(mt) if explicit => Some(*mt),
1920 /// Returns the type of `ty[i]`.
1921 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
1923 Array(ty, _) | Slice(ty) => Some(ty),
1928 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
1930 FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
1933 // ignore errors (#54954)
1934 ty::Binder::dummy(FnSig::fake())
1936 Closure(..) => bug!(
1937 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1939 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
1944 pub fn is_fn(&self) -> bool {
1945 matches!(self.kind(), FnDef(..) | FnPtr(_))
1949 pub fn is_fn_ptr(&self) -> bool {
1950 matches!(self.kind(), FnPtr(_))
1954 pub fn is_impl_trait(&self) -> bool {
1955 matches!(self.kind(), Opaque(..))
1959 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
1961 Adt(adt, _) => Some(adt),
1966 /// Iterates over tuple fields.
1967 /// Panics when called on anything but a tuple.
1968 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
1970 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
1971 _ => bug!("tuple_fields called on non-tuple"),
1975 /// Get the `i`-th element of a tuple.
1976 /// Panics when called on anything but a tuple.
1977 pub fn tuple_element_ty(&self, i: usize) -> Option<Ty<'tcx>> {
1979 Tuple(substs) => substs.iter().nth(i).map(|field| field.expect_ty()),
1980 _ => bug!("tuple_fields called on non-tuple"),
1984 /// If the type contains variants, returns the valid range of variant indices.
1986 // FIXME: This requires the optimized MIR in the case of generators.
1988 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
1990 TyKind::Adt(adt, _) => Some(adt.variant_range()),
1991 TyKind::Generator(def_id, substs, _) => {
1992 Some(substs.as_generator().variant_range(*def_id, tcx))
1998 /// If the type contains variants, returns the variant for `variant_index`.
1999 /// Panics if `variant_index` is out of range.
2001 // FIXME: This requires the optimized MIR in the case of generators.
2003 pub fn discriminant_for_variant(
2006 variant_index: VariantIdx,
2007 ) -> Option<Discr<'tcx>> {
2009 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2010 bug!("discriminant_for_variant called on zero variant enum");
2012 TyKind::Adt(adt, _) if adt.is_enum() => {
2013 Some(adt.discriminant_for_variant(tcx, variant_index))
2015 TyKind::Generator(def_id, substs, _) => {
2016 Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
2022 /// Returns the type of the discriminant of this type.
2023 pub fn discriminant_ty(&'tcx self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2025 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2026 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2028 ty::Param(_) | ty::Projection(_) | ty::Opaque(..) | ty::Infer(ty::TyVar(_)) => {
2030 tcx.associated_items(tcx.lang_items().discriminant_kind_trait().unwrap());
2031 let discriminant_def_id = assoc_items.in_definition_order().next().unwrap().def_id;
2032 tcx.mk_projection(discriminant_def_id, tcx.mk_substs([self.into()].iter()))
2051 | ty::GeneratorWitness(..)
2055 | ty::Infer(IntVar(_) | FloatVar(_)) => tcx.types.u8,
2058 | ty::Placeholder(_)
2059 | ty::Infer(FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2060 bug!("`discriminant_ty` applied to unexpected type: {:?}", self)
2065 /// Returns the type of metadata for (potentially fat) pointers to this type.
2066 pub fn ptr_metadata_ty(&'tcx self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2067 // FIXME: should this normalize?
2068 let tail = tcx.struct_tail_without_normalization(self);
2071 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2082 | ty::GeneratorWitness(..)
2088 // If returned by `struct_tail_without_normalization` this is a unit struct
2089 // without any fields, or not a struct, and therefore is Sized.
2091 // If returned by `struct_tail_without_normalization` this is the empty tuple,
2092 // a.k.a. unit type, which is Sized
2093 | ty::Tuple(..) => tcx.types.unit,
2095 ty::Str | ty::Slice(_) => tcx.types.usize,
2096 ty::Dynamic(..) => {
2097 let dyn_metadata = tcx.lang_items().dyn_metadata().unwrap();
2098 tcx.type_of(dyn_metadata).subst(tcx, &[tail.into()])
2104 | ty::Infer(ty::TyVar(_))
2106 | ty::Placeholder(..)
2107 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2108 bug!("`ptr_metadata_ty` applied to unexpected type: {:?}", tail)
2113 /// When we create a closure, we record its kind (i.e., what trait
2114 /// it implements) into its `ClosureSubsts` using a type
2115 /// parameter. This is kind of a phantom type, except that the
2116 /// most convenient thing for us to are the integral types. This
2117 /// function converts such a special type into the closure
2118 /// kind. To go the other way, use
2119 /// `tcx.closure_kind_ty(closure_kind)`.
2121 /// Note that during type checking, we use an inference variable
2122 /// to represent the closure kind, because it has not yet been
2123 /// inferred. Once upvar inference (in `rustc_typeck/src/check/upvar.rs`)
2124 /// is complete, that type variable will be unified.
2125 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2127 Int(int_ty) => match int_ty {
2128 ty::IntTy::I8 => Some(ty::ClosureKind::Fn),
2129 ty::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2130 ty::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2131 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2134 // "Bound" types appear in canonical queries when the
2135 // closure type is not yet known
2136 Bound(..) | Infer(_) => None,
2138 Error(_) => Some(ty::ClosureKind::Fn),
2140 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2144 /// Fast path helper for testing if a type is `Sized`.
2146 /// Returning true means the type is known to be sized. Returning
2147 /// `false` means nothing -- could be sized, might not be.
2149 /// Note that we could never rely on the fact that a type such as `[_]` is
2150 /// trivially `!Sized` because we could be in a type environment with a
2151 /// bound such as `[_]: Copy`. A function with such a bound obviously never
2152 /// can be called, but that doesn't mean it shouldn't typecheck. This is why
2153 /// this method doesn't return `Option<bool>`.
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)
2192 /// Extra information about why we ended up with a particular variance.
2193 /// This is only used to add more information to error messages, and
2194 /// has no effect on soundness. While choosing the 'wrong' `VarianceDiagInfo`
2195 /// may lead to confusing notes in error messages, it will never cause
2196 /// a miscompilation or unsoundness.
2198 /// When in doubt, use `VarianceDiagInfo::default()`
2199 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
2200 pub enum VarianceDiagInfo<'tcx> {
2201 /// No additional information - this is the default.
2202 /// We will not add any additional information to error messages.
2204 /// We switched our variance because a type occurs inside
2205 /// the generic argument of a mutable reference or pointer
2206 /// (`*mut T` or `&mut T`). In either case, our variance
2207 /// will always be `Invariant`.
2209 /// Tracks whether we had a mutable pointer or reference,
2210 /// for better error messages
2211 kind: VarianceDiagMutKind,
2212 /// The type parameter of the mutable pointer/reference
2213 /// (the `T` in `&mut T` or `*mut T`).
2218 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
2219 pub enum VarianceDiagMutKind {
2220 /// A mutable raw pointer (`*mut T`)
2222 /// A mutable reference (`&mut T`)
2226 impl<'tcx> VarianceDiagInfo<'tcx> {
2227 /// Mirrors `Variance::xform` - used to 'combine' the existing
2228 /// and new `VarianceDiagInfo`s when our variance changes.
2229 pub fn xform(self, other: VarianceDiagInfo<'tcx>) -> VarianceDiagInfo<'tcx> {
2230 // For now, just use the first `VarianceDiagInfo::Mut` that we see
2232 VarianceDiagInfo::None => other,
2233 VarianceDiagInfo::Mut { .. } => self,
2238 impl<'tcx> Default for VarianceDiagInfo<'tcx> {
2239 fn default() -> Self {