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, *};
11 use crate::ty::{self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable};
12 use crate::ty::{DelaySpanBugEmitted, List, ParamEnv, TyS};
13 use polonius_engine::Atom;
14 use rustc_data_structures::captures::Captures;
16 use rustc_hir::def_id::DefId;
17 use rustc_index::vec::Idx;
18 use rustc_macros::HashStable;
19 use rustc_span::symbol::{kw, Symbol};
20 use rustc_target::abi::VariantIdx;
21 use rustc_target::spec::abi;
23 use std::cmp::Ordering;
24 use std::marker::PhantomData;
26 use ty::util::IntTypeExt;
28 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
29 #[derive(HashStable, TypeFoldable, Lift)]
30 pub struct TypeAndMut<'tcx> {
32 pub mutbl: hir::Mutability,
35 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
37 /// A "free" region `fr` can be interpreted as "some region
38 /// at least as big as the scope `fr.scope`".
39 pub struct FreeRegion {
41 pub bound_region: BoundRegionKind,
44 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)]
46 pub enum BoundRegionKind {
47 /// An anonymous region parameter for a given fn (&T)
50 /// Named region parameters for functions (a in &'a T)
52 /// The `DefId` is needed to distinguish free regions in
53 /// the event of shadowing.
54 BrNamed(DefId, Symbol),
56 /// Anonymous region for the implicit env pointer parameter
61 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
63 pub struct BoundRegion {
65 pub kind: BoundRegionKind,
68 impl BoundRegionKind {
69 pub fn is_named(&self) -> bool {
71 BoundRegionKind::BrNamed(_, name) => name != kw::UnderscoreLifetime,
77 /// Defines the kinds of types.
79 /// N.B., if you change this, you'll probably want to change the corresponding
80 /// AST structure in `rustc_ast/src/ast.rs` as well.
81 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
83 #[rustc_diagnostic_item = "TyKind"]
84 pub enum TyKind<'tcx> {
85 /// The primitive boolean type. Written as `bool`.
88 /// The primitive character type; holds a Unicode scalar value
89 /// (a non-surrogate code point). Written as `char`.
92 /// A primitive signed integer type. For example, `i32`.
95 /// A primitive unsigned integer type. For example, `u32`.
98 /// A primitive floating-point type. For example, `f64`.
101 /// Algebraic data types (ADT). For example: structures, enumerations and unions.
103 /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
104 /// That is, even after substitution it is possible that there are type
105 /// variables. This happens when the `Adt` corresponds to an ADT
106 /// definition and not a concrete use of it.
107 Adt(&'tcx AdtDef, SubstsRef<'tcx>),
109 /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
112 /// The pointee of a string slice. Written as `str`.
115 /// An array with the given length. Written as `[T; n]`.
116 Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
118 /// The pointee of an array slice. Written as `[T]`.
121 /// A raw pointer. Written as `*mut T` or `*const T`
122 RawPtr(TypeAndMut<'tcx>),
124 /// A reference; a pointer with an associated lifetime. Written as
125 /// `&'a mut T` or `&'a T`.
126 Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
128 /// The anonymous type of a function declaration/definition. Each
129 /// function has a unique type, which is output (for a function
130 /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
132 /// For example the type of `bar` here:
135 /// fn foo() -> i32 { 1 }
136 /// let bar = foo; // bar: fn() -> i32 {foo}
138 FnDef(DefId, SubstsRef<'tcx>),
140 /// A pointer to a function. Written as `fn() -> i32`.
142 /// For example the type of `bar` here:
145 /// fn foo() -> i32 { 1 }
146 /// let bar: fn() -> i32 = foo;
148 FnPtr(PolyFnSig<'tcx>),
150 /// A trait object. Written as `dyn for<'b> Trait<'b, Assoc = u32> + Send + 'a`.
151 Dynamic(&'tcx List<Binder<'tcx, ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
153 /// The anonymous type of a closure. Used to represent the type of
155 Closure(DefId, SubstsRef<'tcx>),
157 /// The anonymous type of a generator. Used to represent the type of
159 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
161 /// A type representing the types stored inside a generator.
162 /// This should only appear in GeneratorInteriors.
163 GeneratorWitness(Binder<'tcx, &'tcx List<Ty<'tcx>>>),
165 /// The never type `!`.
168 /// A tuple type. For example, `(i32, bool)`.
169 /// Use `TyS::tuple_fields` to iterate over the field types.
170 Tuple(SubstsRef<'tcx>),
172 /// The projection of an associated type. For example,
173 /// `<T as Trait<..>>::N`.
174 Projection(ProjectionTy<'tcx>),
176 /// Opaque (`impl Trait`) type found in a return type.
177 /// The `DefId` comes either from
178 /// * the `impl Trait` ast::Ty node,
179 /// * or the `type Foo = impl Trait` declaration
180 /// The substitutions are for the generics of the function in question.
181 /// After typeck, the concrete type can be found in the `types` map.
182 Opaque(DefId, SubstsRef<'tcx>),
184 /// A type parameter; for example, `T` in `fn f<T>(x: T) {}`.
187 /// Bound type variable, used only when preparing a trait query.
188 Bound(ty::DebruijnIndex, BoundTy),
190 /// A placeholder type - universally quantified higher-ranked type.
191 Placeholder(ty::PlaceholderType),
193 /// A type variable used during type checking.
196 /// A placeholder for a type which could not be computed; this is
197 /// propagated to avoid useless error messages.
198 Error(DelaySpanBugEmitted),
201 impl<'tcx> TyKind<'tcx> {
203 pub fn is_primitive(&self) -> bool {
204 matches!(self, Bool | Char | Int(_) | Uint(_) | Float(_))
207 /// Get the article ("a" or "an") to use with this type.
208 pub fn article(&self) -> &'static str {
210 Int(_) | Float(_) | Array(_, _) => "an",
211 Adt(def, _) if def.is_enum() => "an",
212 // This should never happen, but ICEing and causing the user's code
213 // to not compile felt too harsh.
220 // `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
221 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
222 static_assert_size!(TyKind<'_>, 32);
224 /// A closure can be modeled as a struct that looks like:
226 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
230 /// - 'l0...'li and T0...Tj are the generic parameters
231 /// in scope on the function that defined the closure,
232 /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This
233 /// is rather hackily encoded via a scalar type. See
234 /// `TyS::to_opt_closure_kind` for details.
235 /// - CS represents the *closure signature*, representing as a `fn()`
236 /// type. For example, `fn(u32, u32) -> u32` would mean that the closure
237 /// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait
239 /// - U is a type parameter representing the types of its upvars, tupled up
240 /// (borrowed, if appropriate; that is, if a U field represents a by-ref upvar,
241 /// and the up-var has the type `Foo`, then that field of U will be `&Foo`).
243 /// So, for example, given this function:
245 /// fn foo<'a, T>(data: &'a mut T) {
246 /// do(|| data.count += 1)
249 /// the type of the closure would be something like:
251 /// struct Closure<'a, T, U>(...U);
253 /// Note that the type of the upvar is not specified in the struct.
254 /// You may wonder how the impl would then be able to use the upvar,
255 /// if it doesn't know it's type? The answer is that the impl is
256 /// (conceptually) not fully generic over Closure but rather tied to
257 /// instances with the expected upvar types:
259 /// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
263 /// You can see that the *impl* fully specified the type of the upvar
264 /// and thus knows full well that `data` has type `&'b mut &'a mut T`.
265 /// (Here, I am assuming that `data` is mut-borrowed.)
267 /// Now, the last question you may ask is: Why include the upvar types
268 /// in an extra type parameter? The reason for this design is that the
269 /// upvar types can reference lifetimes that are internal to the
270 /// creating function. In my example above, for example, the lifetime
271 /// `'b` represents the scope of the closure itself; this is some
272 /// subset of `foo`, probably just the scope of the call to the to
273 /// `do()`. If we just had the lifetime/type parameters from the
274 /// enclosing function, we couldn't name this lifetime `'b`. Note that
275 /// there can also be lifetimes in the types of the upvars themselves,
276 /// if one of them happens to be a reference to something that the
277 /// creating fn owns.
279 /// OK, you say, so why not create a more minimal set of parameters
280 /// that just includes the extra lifetime parameters? The answer is
281 /// primarily that it would be hard --- we don't know at the time when
282 /// we create the closure type what the full types of the upvars are,
283 /// nor do we know which are borrowed and which are not. In this
284 /// design, we can just supply a fresh type parameter and figure that
287 /// All right, you say, but why include the type parameters from the
288 /// original function then? The answer is that codegen may need them
289 /// when monomorphizing, and they may not appear in the upvars. A
290 /// closure could capture no variables but still make use of some
291 /// in-scope type parameter with a bound (e.g., if our example above
292 /// had an extra `U: Default`, and the closure called `U::default()`).
294 /// There is another reason. This design (implicitly) prohibits
295 /// closures from capturing themselves (except via a trait
296 /// object). This simplifies closure inference considerably, since it
297 /// means that when we infer the kind of a closure or its upvars, we
298 /// don't have to handle cycles where the decisions we make for
299 /// closure C wind up influencing the decisions we ought to make for
300 /// closure C (which would then require fixed point iteration to
301 /// handle). Plus it fixes an ICE. :P
305 /// Generators are handled similarly in `GeneratorSubsts`. The set of
306 /// type parameters is similar, but `CK` and `CS` are replaced by the
307 /// following type parameters:
309 /// * `GS`: The generator's "resume type", which is the type of the
310 /// argument passed to `resume`, and the type of `yield` expressions
311 /// inside the generator.
312 /// * `GY`: The "yield type", which is the type of values passed to
313 /// `yield` inside the generator.
314 /// * `GR`: The "return type", which is the type of value returned upon
315 /// completion of the generator.
316 /// * `GW`: The "generator witness".
317 #[derive(Copy, Clone, Debug, TypeFoldable)]
318 pub struct ClosureSubsts<'tcx> {
319 /// Lifetime and type parameters from the enclosing function,
320 /// concatenated with a tuple containing the types of the upvars.
322 /// These are separated out because codegen wants to pass them around
323 /// when monomorphizing.
324 pub substs: SubstsRef<'tcx>,
327 /// Struct returned by `split()`.
328 pub struct ClosureSubstsParts<'tcx, T> {
329 pub parent_substs: &'tcx [GenericArg<'tcx>],
330 pub closure_kind_ty: T,
331 pub closure_sig_as_fn_ptr_ty: T,
332 pub tupled_upvars_ty: T,
335 impl<'tcx> ClosureSubsts<'tcx> {
336 /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
337 /// for the closure parent, alongside additional closure-specific components.
340 parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
341 ) -> ClosureSubsts<'tcx> {
343 substs: tcx.mk_substs(
344 parts.parent_substs.iter().copied().chain(
345 [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
347 .map(|&ty| ty.into()),
353 /// Divides the closure substs into their respective components.
354 /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
355 fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
356 match self.substs[..] {
358 ref parent_substs @ ..,
360 closure_sig_as_fn_ptr_ty,
362 ] => ClosureSubstsParts {
365 closure_sig_as_fn_ptr_ty,
368 _ => bug!("closure substs missing synthetics"),
372 /// Returns `true` only if enough of the synthetic types are known to
373 /// allow using all of the methods on `ClosureSubsts` without panicking.
375 /// Used primarily by `ty::print::pretty` to be able to handle closure
376 /// types that haven't had their synthetic types substituted in.
377 pub fn is_valid(self) -> bool {
378 self.substs.len() >= 3
379 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
382 /// Returns the substitutions of the closure's parent.
383 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
384 self.split().parent_substs
387 /// Returns an iterator over the list of types of captured paths by the closure.
388 /// In case there was a type error in figuring out the types of the captured path, an
389 /// empty iterator is returned.
391 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
392 match self.tupled_upvars_ty().kind() {
393 TyKind::Error(_) => None,
394 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
395 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
396 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
402 /// Returns the tuple type representing the upvars for this closure.
404 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
405 self.split().tupled_upvars_ty.expect_ty()
408 /// Returns the closure kind for this closure; may return a type
409 /// variable during inference. To get the closure kind during
410 /// inference, use `infcx.closure_kind(substs)`.
411 pub fn kind_ty(self) -> Ty<'tcx> {
412 self.split().closure_kind_ty.expect_ty()
415 /// Returns the `fn` pointer type representing the closure signature for this
417 // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
418 // type is known at the time of the creation of `ClosureSubsts`,
419 // see `rustc_typeck::check::closure`.
420 pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
421 self.split().closure_sig_as_fn_ptr_ty.expect_ty()
424 /// Returns the closure kind for this closure; only usable outside
425 /// of an inference context, because in that context we know that
426 /// there are no type variables.
428 /// If you have an inference context, use `infcx.closure_kind()`.
429 pub fn kind(self) -> ty::ClosureKind {
430 self.kind_ty().to_opt_closure_kind().unwrap()
433 /// Extracts the signature from the closure.
434 pub fn sig(self) -> ty::PolyFnSig<'tcx> {
435 let ty = self.sig_as_fn_ptr_ty();
437 ty::FnPtr(sig) => *sig,
438 _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind()),
443 /// Similar to `ClosureSubsts`; see the above documentation for more.
444 #[derive(Copy, Clone, Debug, TypeFoldable)]
445 pub struct GeneratorSubsts<'tcx> {
446 pub substs: SubstsRef<'tcx>,
449 pub struct GeneratorSubstsParts<'tcx, T> {
450 pub parent_substs: &'tcx [GenericArg<'tcx>],
455 pub tupled_upvars_ty: T,
458 impl<'tcx> GeneratorSubsts<'tcx> {
459 /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
460 /// for the generator parent, alongside additional generator-specific components.
463 parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
464 ) -> GeneratorSubsts<'tcx> {
466 substs: tcx.mk_substs(
467 parts.parent_substs.iter().copied().chain(
473 parts.tupled_upvars_ty,
476 .map(|&ty| ty.into()),
482 /// Divides the generator substs into their respective components.
483 /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
484 fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
485 match self.substs[..] {
486 [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
487 GeneratorSubstsParts {
496 _ => bug!("generator substs missing synthetics"),
500 /// Returns `true` only if enough of the synthetic types are known to
501 /// allow using all of the methods on `GeneratorSubsts` without panicking.
503 /// Used primarily by `ty::print::pretty` to be able to handle generator
504 /// types that haven't had their synthetic types substituted in.
505 pub fn is_valid(self) -> bool {
506 self.substs.len() >= 5
507 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
510 /// Returns the substitutions of the generator's parent.
511 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
512 self.split().parent_substs
515 /// This describes the types that can be contained in a generator.
516 /// It will be a type variable initially and unified in the last stages of typeck of a body.
517 /// It contains a tuple of all the types that could end up on a generator frame.
518 /// The state transformation MIR pass may only produce layouts which mention types
519 /// in this tuple. Upvars are not counted here.
520 pub fn witness(self) -> Ty<'tcx> {
521 self.split().witness.expect_ty()
524 /// Returns an iterator over the list of types of captured paths by the generator.
525 /// In case there was a type error in figuring out the types of the captured path, an
526 /// empty iterator is returned.
528 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
529 match self.tupled_upvars_ty().kind() {
530 TyKind::Error(_) => None,
531 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
532 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
533 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
539 /// Returns the tuple type representing the upvars for this generator.
541 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
542 self.split().tupled_upvars_ty.expect_ty()
545 /// Returns the type representing the resume type of the generator.
546 pub fn resume_ty(self) -> Ty<'tcx> {
547 self.split().resume_ty.expect_ty()
550 /// Returns the type representing the yield type of the generator.
551 pub fn yield_ty(self) -> Ty<'tcx> {
552 self.split().yield_ty.expect_ty()
555 /// Returns the type representing the return type of the generator.
556 pub fn return_ty(self) -> Ty<'tcx> {
557 self.split().return_ty.expect_ty()
560 /// Returns the "generator signature", which consists of its yield
561 /// and return types.
563 /// N.B., some bits of the code prefers to see this wrapped in a
564 /// binder, but it never contains bound regions. Probably this
565 /// function should be removed.
566 pub fn poly_sig(self) -> PolyGenSig<'tcx> {
567 ty::Binder::dummy(self.sig())
570 /// Returns the "generator signature", which consists of its resume, yield
571 /// and return types.
572 pub fn sig(self) -> GenSig<'tcx> {
574 resume_ty: self.resume_ty(),
575 yield_ty: self.yield_ty(),
576 return_ty: self.return_ty(),
581 impl<'tcx> GeneratorSubsts<'tcx> {
582 /// Generator has not been resumed yet.
583 pub const UNRESUMED: usize = 0;
584 /// Generator has returned or is completed.
585 pub const RETURNED: usize = 1;
586 /// Generator has been poisoned.
587 pub const POISONED: usize = 2;
589 const UNRESUMED_NAME: &'static str = "Unresumed";
590 const RETURNED_NAME: &'static str = "Returned";
591 const POISONED_NAME: &'static str = "Panicked";
593 /// The valid variant indices of this generator.
595 pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
596 // FIXME requires optimized MIR
597 let num_variants = tcx.generator_layout(def_id).unwrap().variant_fields.len();
598 VariantIdx::new(0)..VariantIdx::new(num_variants)
601 /// The discriminant for the given variant. Panics if the `variant_index` is
604 pub fn discriminant_for_variant(
608 variant_index: VariantIdx,
610 // Generators don't support explicit discriminant values, so they are
611 // the same as the variant index.
612 assert!(self.variant_range(def_id, tcx).contains(&variant_index));
613 Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) }
616 /// The set of all discriminants for the generator, enumerated with their
619 pub fn discriminants(
623 ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> {
624 self.variant_range(def_id, tcx).map(move |index| {
625 (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) })
629 /// Calls `f` with a reference to the name of the enumerator for the given
631 pub fn variant_name(v: VariantIdx) -> Cow<'static, str> {
633 Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME),
634 Self::RETURNED => Cow::from(Self::RETURNED_NAME),
635 Self::POISONED => Cow::from(Self::POISONED_NAME),
636 _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)),
640 /// The type of the state discriminant used in the generator type.
642 pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
646 /// This returns the types of the MIR locals which had to be stored across suspension points.
647 /// It is calculated in rustc_const_eval::transform::generator::StateTransform.
648 /// All the types here must be in the tuple in GeneratorInterior.
650 /// The locals are grouped by their variant number. Note that some locals may
651 /// be repeated in multiple variants.
657 ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
658 let layout = tcx.generator_layout(def_id).unwrap();
659 layout.variant_fields.iter().map(move |variant| {
660 variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs))
664 /// This is the types of the fields of a generator which are not stored in a
667 pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
672 #[derive(Debug, Copy, Clone, HashStable)]
673 pub enum UpvarSubsts<'tcx> {
674 Closure(SubstsRef<'tcx>),
675 Generator(SubstsRef<'tcx>),
678 impl<'tcx> UpvarSubsts<'tcx> {
679 /// Returns an iterator over the list of types of captured paths by the closure/generator.
680 /// In case there was a type error in figuring out the types of the captured path, an
681 /// empty iterator is returned.
683 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
684 let tupled_tys = match self {
685 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
686 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
689 match tupled_tys.kind() {
690 TyKind::Error(_) => None,
691 TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
692 TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
693 ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
700 pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
702 UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
703 UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
708 /// An inline const is modeled like
710 /// const InlineConst<'l0...'li, T0...Tj, R>: R;
714 /// - 'l0...'li and T0...Tj are the generic parameters
715 /// inherited from the item that defined the inline const,
716 /// - R represents the type of the constant.
718 /// When the inline const is instantiated, `R` is substituted as the actual inferred
719 /// type of the constant. The reason that `R` is represented as an extra type parameter
720 /// is the same reason that [`ClosureSubsts`] have `CS` and `U` as type parameters:
721 /// inline const can reference lifetimes that are internal to the creating function.
722 #[derive(Copy, Clone, Debug, TypeFoldable)]
723 pub struct InlineConstSubsts<'tcx> {
724 /// Generic parameters from the enclosing item,
725 /// concatenated with the inferred type of the constant.
726 pub substs: SubstsRef<'tcx>,
729 /// Struct returned by `split()`.
730 pub struct InlineConstSubstsParts<'tcx, T> {
731 pub parent_substs: &'tcx [GenericArg<'tcx>],
735 impl<'tcx> InlineConstSubsts<'tcx> {
736 /// Construct `InlineConstSubsts` from `InlineConstSubstsParts`.
739 parts: InlineConstSubstsParts<'tcx, Ty<'tcx>>,
740 ) -> InlineConstSubsts<'tcx> {
742 substs: tcx.mk_substs(
743 parts.parent_substs.iter().copied().chain(std::iter::once(parts.ty.into())),
748 /// Divides the inline const substs into their respective components.
749 /// The ordering assumed here must match that used by `InlineConstSubsts::new` above.
750 fn split(self) -> InlineConstSubstsParts<'tcx, GenericArg<'tcx>> {
751 match self.substs[..] {
752 [ref parent_substs @ .., ty] => InlineConstSubstsParts { parent_substs, ty },
753 _ => bug!("inline const substs missing synthetics"),
757 /// Returns the substitutions of the inline const's parent.
758 pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
759 self.split().parent_substs
762 /// Returns the type of this inline const.
763 pub fn ty(self) -> Ty<'tcx> {
764 self.split().ty.expect_ty()
768 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]
769 #[derive(HashStable, TypeFoldable)]
770 pub enum ExistentialPredicate<'tcx> {
771 /// E.g., `Iterator`.
772 Trait(ExistentialTraitRef<'tcx>),
773 /// E.g., `Iterator::Item = T`.
774 Projection(ExistentialProjection<'tcx>),
779 impl<'tcx> ExistentialPredicate<'tcx> {
780 /// Compares via an ordering that will not change if modules are reordered or other changes are
781 /// made to the tree. In particular, this ordering is preserved across incremental compilations.
782 pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
783 use self::ExistentialPredicate::*;
784 match (*self, *other) {
785 (Trait(_), Trait(_)) => Ordering::Equal,
786 (Projection(ref a), Projection(ref b)) => {
787 tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id))
789 (AutoTrait(ref a), AutoTrait(ref b)) => {
790 tcx.def_path_hash(*a).cmp(&tcx.def_path_hash(*b))
792 (Trait(_), _) => Ordering::Less,
793 (Projection(_), Trait(_)) => Ordering::Greater,
794 (Projection(_), _) => Ordering::Less,
795 (AutoTrait(_), _) => Ordering::Greater,
800 impl<'tcx> Binder<'tcx, ExistentialPredicate<'tcx>> {
801 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
802 use crate::ty::ToPredicate;
803 match self.skip_binder() {
804 ExistentialPredicate::Trait(tr) => {
805 self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
807 ExistentialPredicate::Projection(p) => {
808 self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
810 ExistentialPredicate::AutoTrait(did) => {
811 let trait_ref = self.rebind(ty::TraitRef {
813 substs: tcx.mk_substs_trait(self_ty, &[]),
815 trait_ref.without_const().to_predicate(tcx)
821 impl<'tcx> List<ty::Binder<'tcx, ExistentialPredicate<'tcx>>> {
822 /// Returns the "principal `DefId`" of this set of existential predicates.
824 /// A Rust trait object type consists (in addition to a lifetime bound)
825 /// of a set of trait bounds, which are separated into any number
826 /// of auto-trait bounds, and at most one non-auto-trait bound. The
827 /// non-auto-trait bound is called the "principal" of the trait
830 /// Only the principal can have methods or type parameters (because
831 /// auto traits can have neither of them). This is important, because
832 /// it means the auto traits can be treated as an unordered set (methods
833 /// would force an order for the vtable, while relating traits with
834 /// type parameters without knowing the order to relate them in is
835 /// a rather non-trivial task).
837 /// For example, in the trait object `dyn fmt::Debug + Sync`, the
838 /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds
839 /// are the set `{Sync}`.
841 /// It is also possible to have a "trivial" trait object that
842 /// consists only of auto traits, with no principal - for example,
843 /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
844 /// is `{Send, Sync}`, while there is no principal. These trait objects
845 /// have a "trivial" vtable consisting of just the size, alignment,
847 pub fn principal(&self) -> Option<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> {
849 .map_bound(|this| match this {
850 ExistentialPredicate::Trait(tr) => Some(tr),
856 pub fn principal_def_id(&self) -> Option<DefId> {
857 self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
861 pub fn projection_bounds<'a>(
863 ) -> impl Iterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> + 'a {
864 self.iter().filter_map(|predicate| {
866 .map_bound(|pred| match pred {
867 ExistentialPredicate::Projection(projection) => Some(projection),
875 pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a {
876 self.iter().filter_map(|predicate| match predicate.skip_binder() {
877 ExistentialPredicate::AutoTrait(did) => Some(did),
883 /// A complete reference to a trait. These take numerous guises in syntax,
884 /// but perhaps the most recognizable form is in a where-clause:
888 /// This would be represented by a trait-reference where the `DefId` is the
889 /// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
890 /// and `U` as parameter 1.
892 /// Trait references also appear in object types like `Foo<U>`, but in
893 /// that case the `Self` parameter is absent from the substitutions.
894 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
895 #[derive(HashStable, TypeFoldable)]
896 pub struct TraitRef<'tcx> {
898 pub substs: SubstsRef<'tcx>,
901 impl<'tcx> TraitRef<'tcx> {
902 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> {
903 TraitRef { def_id, substs }
906 /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
907 /// are the parameters defined on trait.
908 pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> Binder<'tcx, TraitRef<'tcx>> {
909 ty::Binder::dummy(TraitRef {
911 substs: InternalSubsts::identity_for_item(tcx, def_id),
916 pub fn self_ty(&self) -> Ty<'tcx> {
917 self.substs.type_at(0)
923 substs: SubstsRef<'tcx>,
924 ) -> ty::TraitRef<'tcx> {
925 let defs = tcx.generics_of(trait_id);
927 ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) }
931 pub type PolyTraitRef<'tcx> = Binder<'tcx, TraitRef<'tcx>>;
933 impl<'tcx> PolyTraitRef<'tcx> {
934 pub fn self_ty(&self) -> Binder<'tcx, Ty<'tcx>> {
935 self.map_bound_ref(|tr| tr.self_ty())
938 pub fn def_id(&self) -> DefId {
939 self.skip_binder().def_id
942 pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
943 self.map_bound(|trait_ref| ty::TraitPredicate {
945 constness: ty::BoundConstness::NotConst,
946 polarity: ty::ImplPolarity::Positive,
951 /// An existential reference to a trait, where `Self` is erased.
952 /// For example, the trait object `Trait<'a, 'b, X, Y>` is:
954 /// exists T. T: Trait<'a, 'b, X, Y>
956 /// The substitutions don't include the erased `Self`, only trait
957 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
958 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
959 #[derive(HashStable, TypeFoldable)]
960 pub struct ExistentialTraitRef<'tcx> {
962 pub substs: SubstsRef<'tcx>,
965 impl<'tcx> ExistentialTraitRef<'tcx> {
966 pub fn erase_self_ty(
968 trait_ref: ty::TraitRef<'tcx>,
969 ) -> ty::ExistentialTraitRef<'tcx> {
970 // Assert there is a Self.
971 trait_ref.substs.type_at(0);
973 ty::ExistentialTraitRef {
974 def_id: trait_ref.def_id,
975 substs: tcx.intern_substs(&trait_ref.substs[1..]),
979 /// Object types don't have a self type specified. Therefore, when
980 /// we convert the principal trait-ref into a normal trait-ref,
981 /// you must give *some* self type. A common choice is `mk_err()`
982 /// or some placeholder type.
983 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> {
984 // otherwise the escaping vars would be captured by the binder
985 // debug_assert!(!self_ty.has_escaping_bound_vars());
987 ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) }
991 pub type PolyExistentialTraitRef<'tcx> = Binder<'tcx, ExistentialTraitRef<'tcx>>;
993 impl<'tcx> PolyExistentialTraitRef<'tcx> {
994 pub fn def_id(&self) -> DefId {
995 self.skip_binder().def_id
998 /// Object types don't have a self type specified. Therefore, when
999 /// we convert the principal trait-ref into a normal trait-ref,
1000 /// you must give *some* self type. A common choice is `mk_err()`
1001 /// or some placeholder type.
1002 pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> {
1003 self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty))
1007 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1008 #[derive(HashStable)]
1009 pub enum BoundVariableKind {
1011 Region(BoundRegionKind),
1015 /// Binder is a binder for higher-ranked lifetimes or types. It is part of the
1016 /// compiler's representation for things like `for<'a> Fn(&'a isize)`
1017 /// (which would be represented by the type `PolyTraitRef ==
1018 /// Binder<'tcx, TraitRef>`). Note that when we instantiate,
1019 /// erase, or otherwise "discharge" these bound vars, we change the
1020 /// type from `Binder<'tcx, T>` to just `T` (see
1021 /// e.g., `liberate_late_bound_regions`).
1023 /// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro.
1024 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
1025 pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>);
1027 impl<'tcx, T> Binder<'tcx, T>
1029 T: TypeFoldable<'tcx>,
1031 /// Wraps `value` in a binder, asserting that `value` does not
1032 /// contain any bound vars that would be bound by the
1033 /// binder. This is commonly used to 'inject' a value T into a
1034 /// different binding level.
1035 pub fn dummy(value: T) -> Binder<'tcx, T> {
1036 assert!(!value.has_escaping_bound_vars());
1037 Binder(value, ty::List::empty())
1040 pub fn bind_with_vars(value: T, vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> {
1041 if cfg!(debug_assertions) {
1042 let mut validator = ValidateBoundVars::new(vars);
1043 value.visit_with(&mut validator);
1049 impl<'tcx, T> Binder<'tcx, T> {
1050 /// Skips the binder and returns the "bound" value. This is a
1051 /// risky thing to do because it's easy to get confused about
1052 /// De Bruijn indices and the like. It is usually better to
1053 /// discharge the binder using `no_bound_vars` or
1054 /// `replace_late_bound_regions` or something like
1055 /// that. `skip_binder` is only valid when you are either
1056 /// extracting data that has nothing to do with bound vars, you
1057 /// are doing some sort of test that does not involve bound
1058 /// regions, or you are being very careful about your depth
1061 /// Some examples where `skip_binder` is reasonable:
1063 /// - extracting the `DefId` from a PolyTraitRef;
1064 /// - comparing the self type of a PolyTraitRef to see if it is equal to
1065 /// a type parameter `X`, since the type `X` does not reference any regions
1066 pub fn skip_binder(self) -> T {
1070 pub fn bound_vars(&self) -> &'tcx List<BoundVariableKind> {
1074 pub fn as_ref(&self) -> Binder<'tcx, &T> {
1075 Binder(&self.0, self.1)
1078 pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U>
1082 let value = f(&self.0);
1083 Binder(value, self.1)
1086 pub fn map_bound_ref<F, U: TypeFoldable<'tcx>>(&self, f: F) -> Binder<'tcx, U>
1090 self.as_ref().map_bound(f)
1093 pub fn map_bound<F, U: TypeFoldable<'tcx>>(self, f: F) -> Binder<'tcx, U>
1097 let value = f(self.0);
1098 if cfg!(debug_assertions) {
1099 let mut validator = ValidateBoundVars::new(self.1);
1100 value.visit_with(&mut validator);
1102 Binder(value, self.1)
1105 pub fn try_map_bound<F, U: TypeFoldable<'tcx>, E>(self, f: F) -> Result<Binder<'tcx, U>, E>
1107 F: FnOnce(T) -> Result<U, E>,
1109 let value = f(self.0)?;
1110 if cfg!(debug_assertions) {
1111 let mut validator = ValidateBoundVars::new(self.1);
1112 value.visit_with(&mut validator);
1114 Ok(Binder(value, self.1))
1117 /// Wraps a `value` in a binder, using the same bound variables as the
1118 /// current `Binder`. This should not be used if the new value *changes*
1119 /// the bound variables. Note: the (old or new) value itself does not
1120 /// necessarily need to *name* all the bound variables.
1122 /// This currently doesn't do anything different than `bind`, because we
1123 /// don't actually track bound vars. However, semantically, it is different
1124 /// because bound vars aren't allowed to change here, whereas they are
1125 /// in `bind`. This may be (debug) asserted in the future.
1126 pub fn rebind<U>(&self, value: U) -> Binder<'tcx, U>
1128 U: TypeFoldable<'tcx>,
1130 if cfg!(debug_assertions) {
1131 let mut validator = ValidateBoundVars::new(self.bound_vars());
1132 value.visit_with(&mut validator);
1134 Binder(value, self.1)
1137 /// Unwraps and returns the value within, but only if it contains
1138 /// no bound vars at all. (In other words, if this binder --
1139 /// and indeed any enclosing binder -- doesn't bind anything at
1140 /// all.) Otherwise, returns `None`.
1142 /// (One could imagine having a method that just unwraps a single
1143 /// binder, but permits late-bound vars bound by enclosing
1144 /// binders, but that would require adjusting the debruijn
1145 /// indices, and given the shallow binding structure we often use,
1146 /// would not be that useful.)
1147 pub fn no_bound_vars(self) -> Option<T>
1149 T: TypeFoldable<'tcx>,
1151 if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
1154 /// Splits the contents into two things that share the same binder
1155 /// level as the original, returning two distinct binders.
1157 /// `f` should consider bound regions at depth 1 to be free, and
1158 /// anything it produces with bound regions at depth 1 will be
1159 /// bound in the resulting return values.
1160 pub fn split<U, V, F>(self, f: F) -> (Binder<'tcx, U>, Binder<'tcx, V>)
1162 F: FnOnce(T) -> (U, V),
1164 let (u, v) = f(self.0);
1165 (Binder(u, self.1), Binder(v, self.1))
1169 impl<'tcx, T> Binder<'tcx, Option<T>> {
1170 pub fn transpose(self) -> Option<Binder<'tcx, T>> {
1171 let bound_vars = self.1;
1172 self.0.map(|v| Binder(v, bound_vars))
1176 /// Represents the projection of an associated type. In explicit UFCS
1177 /// form this would be written `<T as Trait<..>>::N`.
1178 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1179 #[derive(HashStable, TypeFoldable)]
1180 pub struct ProjectionTy<'tcx> {
1181 /// The parameters of the associated item.
1182 pub substs: SubstsRef<'tcx>,
1184 /// The `DefId` of the `TraitItem` for the associated type `N`.
1186 /// Note that this is not the `DefId` of the `TraitRef` containing this
1187 /// associated type, which is in `tcx.associated_item(item_def_id).container`.
1188 pub item_def_id: DefId,
1191 impl<'tcx> ProjectionTy<'tcx> {
1192 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
1193 tcx.associated_item(self.item_def_id).container.id()
1196 /// Extracts the underlying trait reference and own substs from this projection.
1197 /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
1198 /// then this function would return a `T: Iterator` trait reference and `['a]` as the own substs
1199 pub fn trait_ref_and_own_substs(
1202 ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) {
1203 let def_id = tcx.associated_item(self.item_def_id).container.id();
1204 let trait_generics = tcx.generics_of(def_id);
1206 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, trait_generics) },
1207 &self.substs[trait_generics.count()..],
1211 /// Extracts the underlying trait reference from this projection.
1212 /// For example, if this is a projection of `<T as Iterator>::Item`,
1213 /// then this function would return a `T: Iterator` trait reference.
1215 /// WARNING: This will drop the substs for generic associated types
1216 /// consider calling [Self::trait_ref_and_own_substs] to get those
1218 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
1219 let def_id = self.trait_def_id(tcx);
1220 ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) }
1223 pub fn self_ty(&self) -> Ty<'tcx> {
1224 self.substs.type_at(0)
1228 #[derive(Copy, Clone, Debug, TypeFoldable)]
1229 pub struct GenSig<'tcx> {
1230 pub resume_ty: Ty<'tcx>,
1231 pub yield_ty: Ty<'tcx>,
1232 pub return_ty: Ty<'tcx>,
1235 pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>;
1237 /// Signature of a function type, which we have arbitrarily
1238 /// decided to use to refer to the input/output types.
1240 /// - `inputs`: is the list of arguments and their modes.
1241 /// - `output`: is the return type.
1242 /// - `c_variadic`: indicates whether this is a C-variadic function.
1243 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1244 #[derive(HashStable, TypeFoldable)]
1245 pub struct FnSig<'tcx> {
1246 pub inputs_and_output: &'tcx List<Ty<'tcx>>,
1247 pub c_variadic: bool,
1248 pub unsafety: hir::Unsafety,
1252 impl<'tcx> FnSig<'tcx> {
1253 pub fn inputs(&self) -> &'tcx [Ty<'tcx>] {
1254 &self.inputs_and_output[..self.inputs_and_output.len() - 1]
1257 pub fn output(&self) -> Ty<'tcx> {
1258 self.inputs_and_output[self.inputs_and_output.len() - 1]
1261 // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible
1263 fn fake() -> FnSig<'tcx> {
1265 inputs_and_output: List::empty(),
1267 unsafety: hir::Unsafety::Normal,
1268 abi: abi::Abi::Rust,
1273 pub type PolyFnSig<'tcx> = Binder<'tcx, FnSig<'tcx>>;
1275 impl<'tcx> PolyFnSig<'tcx> {
1277 pub fn inputs(&self) -> Binder<'tcx, &'tcx [Ty<'tcx>]> {
1278 self.map_bound_ref_unchecked(|fn_sig| fn_sig.inputs())
1281 pub fn input(&self, index: usize) -> ty::Binder<'tcx, Ty<'tcx>> {
1282 self.map_bound_ref(|fn_sig| fn_sig.inputs()[index])
1284 pub fn inputs_and_output(&self) -> ty::Binder<'tcx, &'tcx List<Ty<'tcx>>> {
1285 self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output)
1288 pub fn output(&self) -> ty::Binder<'tcx, Ty<'tcx>> {
1289 self.map_bound_ref(|fn_sig| fn_sig.output())
1291 pub fn c_variadic(&self) -> bool {
1292 self.skip_binder().c_variadic
1294 pub fn unsafety(&self) -> hir::Unsafety {
1295 self.skip_binder().unsafety
1297 pub fn abi(&self) -> abi::Abi {
1298 self.skip_binder().abi
1302 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<'tcx, FnSig<'tcx>>>;
1304 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1305 #[derive(HashStable)]
1306 pub struct ParamTy {
1311 impl<'tcx> ParamTy {
1312 pub fn new(index: u32, name: Symbol) -> ParamTy {
1313 ParamTy { index, name }
1316 pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
1317 ParamTy::new(def.index, def.name)
1321 pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1322 tcx.mk_ty_param(self.index, self.name)
1326 #[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)]
1327 #[derive(HashStable)]
1328 pub struct ParamConst {
1334 pub fn new(index: u32, name: Symbol) -> ParamConst {
1335 ParamConst { index, name }
1338 pub fn for_def(def: &ty::GenericParamDef) -> ParamConst {
1339 ParamConst::new(def.index, def.name)
1343 pub type Region<'tcx> = &'tcx RegionKind;
1345 /// Representation of regions. Note that the NLL checker uses a distinct
1346 /// representation of regions. For this reason, it internally replaces all the
1347 /// regions with inference variables -- the index of the variable is then used
1348 /// to index into internal NLL data structures. See `rustc_const_eval::borrow_check`
1349 /// module for more information.
1351 /// ## The Region lattice within a given function
1353 /// In general, the region lattice looks like
1356 /// static ----------+-----...------+ (greatest)
1358 /// early-bound and | |
1359 /// free regions | |
1362 /// empty(root) placeholder(U1) |
1364 /// | / placeholder(Un)
1369 /// empty(Un) -------- (smallest)
1372 /// Early-bound/free regions are the named lifetimes in scope from the
1373 /// function declaration. They have relationships to one another
1374 /// determined based on the declared relationships from the
1377 /// Note that inference variables and bound regions are not included
1378 /// in this diagram. In the case of inference variables, they should
1379 /// be inferred to some other region from the diagram. In the case of
1380 /// bound regions, they are excluded because they don't make sense to
1381 /// include -- the diagram indicates the relationship between free
1384 /// ## Inference variables
1386 /// During region inference, we sometimes create inference variables,
1387 /// represented as `ReVar`. These will be inferred by the code in
1388 /// `infer::lexical_region_resolve` to some free region from the
1389 /// lattice above (the minimal region that meets the
1392 /// During NLL checking, where regions are defined differently, we
1393 /// also use `ReVar` -- in that case, the index is used to index into
1394 /// the NLL region checker's data structures. The variable may in fact
1395 /// represent either a free region or an inference variable, in that
1398 /// ## Bound Regions
1400 /// These are regions that are stored behind a binder and must be substituted
1401 /// with some concrete region before being used. There are two kind of
1402 /// bound regions: early-bound, which are bound in an item's `Generics`,
1403 /// and are substituted by an `InternalSubsts`, and late-bound, which are part of
1404 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
1405 /// the likes of `liberate_late_bound_regions`. The distinction exists
1406 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
1408 /// Unlike `Param`s, bound regions are not supposed to exist "in the wild"
1409 /// outside their binder, e.g., in types passed to type inference, and
1410 /// should first be substituted (by placeholder regions, free regions,
1411 /// or region variables).
1413 /// ## Placeholder and Free Regions
1415 /// One often wants to work with bound regions without knowing their precise
1416 /// identity. For example, when checking a function, the lifetime of a borrow
1417 /// can end up being assigned to some region parameter. In these cases,
1418 /// it must be ensured that bounds on the region can't be accidentally
1419 /// assumed without being checked.
1421 /// To do this, we replace the bound regions with placeholder markers,
1422 /// which don't satisfy any relation not explicitly provided.
1424 /// There are two kinds of placeholder regions in rustc: `ReFree` and
1425 /// `RePlaceholder`. When checking an item's body, `ReFree` is supposed
1426 /// to be used. These also support explicit bounds: both the internally-stored
1427 /// *scope*, which the region is assumed to outlive, as well as other
1428 /// relations stored in the `FreeRegionMap`. Note that these relations
1429 /// aren't checked when you `make_subregion` (or `eq_types`), only by
1430 /// `resolve_regions_and_report_errors`.
1432 /// When working with higher-ranked types, some region relations aren't
1433 /// yet known, so you can't just call `resolve_regions_and_report_errors`.
1434 /// `RePlaceholder` is designed for this purpose. In these contexts,
1435 /// there's also the risk that some inference variable laying around will
1436 /// get unified with your placeholder region: if you want to check whether
1437 /// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
1438 /// with a placeholder region `'%a`, the variable `'_` would just be
1439 /// instantiated to the placeholder region `'%a`, which is wrong because
1440 /// the inference variable is supposed to satisfy the relation
1441 /// *for every value of the placeholder region*. To ensure that doesn't
1442 /// happen, you can use `leak_check`. This is more clearly explained
1443 /// by the [rustc dev guide].
1445 /// [1]: https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
1446 /// [2]: https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
1447 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
1448 #[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)]
1449 pub enum RegionKind {
1450 /// Region bound in a type or fn declaration which will be
1451 /// substituted 'early' -- that is, at the same time when type
1452 /// parameters are substituted.
1453 ReEarlyBound(EarlyBoundRegion),
1455 /// Region bound in a function scope, which will be substituted when the
1456 /// function is called.
1457 ReLateBound(ty::DebruijnIndex, BoundRegion),
1459 /// When checking a function body, the types of all arguments and so forth
1460 /// that refer to bound region parameters are modified to refer to free
1461 /// region parameters.
1464 /// Static data that has an "infinite" lifetime. Top in the region lattice.
1467 /// A region variable. Should not exist after typeck.
1470 /// A placeholder region -- basically, the higher-ranked version of `ReFree`.
1471 /// Should not exist after typeck.
1472 RePlaceholder(ty::PlaceholderRegion),
1474 /// Empty lifetime is for data that is never accessed. We tag the
1475 /// empty lifetime with a universe -- the idea is that we don't
1476 /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable.
1477 /// Therefore, the `'empty` in a universe `U` is less than all
1478 /// regions visible from `U`, but not less than regions not visible
1480 ReEmpty(ty::UniverseIndex),
1482 /// Erased region, used by trait selection, in MIR and during codegen.
1486 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)]
1487 pub struct EarlyBoundRegion {
1493 /// A **`const`** **v**ariable **ID**.
1494 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
1495 pub struct ConstVid<'tcx> {
1497 pub phantom: PhantomData<&'tcx ()>,
1500 rustc_index::newtype_index! {
1501 /// A **region** (lifetime) **v**ariable **ID**.
1502 pub struct RegionVid {
1503 DEBUG_FORMAT = custom,
1507 impl Atom for RegionVid {
1508 fn index(self) -> usize {
1513 rustc_index::newtype_index! {
1514 pub struct BoundVar { .. }
1517 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1518 #[derive(HashStable)]
1519 pub struct BoundTy {
1521 pub kind: BoundTyKind,
1524 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1525 #[derive(HashStable)]
1526 pub enum BoundTyKind {
1531 impl From<BoundVar> for BoundTy {
1532 fn from(var: BoundVar) -> Self {
1533 BoundTy { var, kind: BoundTyKind::Anon }
1537 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
1538 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
1539 #[derive(HashStable, TypeFoldable)]
1540 pub struct ExistentialProjection<'tcx> {
1541 pub item_def_id: DefId,
1542 pub substs: SubstsRef<'tcx>,
1546 pub type PolyExistentialProjection<'tcx> = Binder<'tcx, ExistentialProjection<'tcx>>;
1548 impl<'tcx> ExistentialProjection<'tcx> {
1549 /// Extracts the underlying existential trait reference from this projection.
1550 /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`,
1551 /// then this function would return an `exists T. T: Iterator` existential trait
1553 pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
1554 let def_id = tcx.associated_item(self.item_def_id).container.id();
1555 let subst_count = tcx.generics_of(def_id).count() - 1;
1556 let substs = tcx.intern_substs(&self.substs[..subst_count]);
1557 ty::ExistentialTraitRef { def_id, substs }
1560 pub fn with_self_ty(
1564 ) -> ty::ProjectionPredicate<'tcx> {
1565 // otherwise the escaping regions would be captured by the binders
1566 debug_assert!(!self_ty.has_escaping_bound_vars());
1568 ty::ProjectionPredicate {
1569 projection_ty: ty::ProjectionTy {
1570 item_def_id: self.item_def_id,
1571 substs: tcx.mk_substs_trait(self_ty, self.substs),
1577 pub fn erase_self_ty(
1579 projection_predicate: ty::ProjectionPredicate<'tcx>,
1581 // Assert there is a Self.
1582 projection_predicate.projection_ty.substs.type_at(0);
1585 item_def_id: projection_predicate.projection_ty.item_def_id,
1586 substs: tcx.intern_substs(&projection_predicate.projection_ty.substs[1..]),
1587 ty: projection_predicate.ty,
1592 impl<'tcx> PolyExistentialProjection<'tcx> {
1593 pub fn with_self_ty(
1597 ) -> ty::PolyProjectionPredicate<'tcx> {
1598 self.map_bound(|p| p.with_self_ty(tcx, self_ty))
1601 pub fn item_def_id(&self) -> DefId {
1602 self.skip_binder().item_def_id
1606 /// Region utilities
1608 /// Is this region named by the user?
1609 pub fn has_name(&self) -> bool {
1611 RegionKind::ReEarlyBound(ebr) => ebr.has_name(),
1612 RegionKind::ReLateBound(_, br) => br.kind.is_named(),
1613 RegionKind::ReFree(fr) => fr.bound_region.is_named(),
1614 RegionKind::ReStatic => true,
1615 RegionKind::ReVar(..) => false,
1616 RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
1617 RegionKind::ReEmpty(_) => false,
1618 RegionKind::ReErased => false,
1623 pub fn is_late_bound(&self) -> bool {
1624 matches!(*self, ty::ReLateBound(..))
1628 pub fn is_placeholder(&self) -> bool {
1629 matches!(*self, ty::RePlaceholder(..))
1633 pub fn bound_at_or_above_binder(&self, index: ty::DebruijnIndex) -> bool {
1635 ty::ReLateBound(debruijn, _) => debruijn >= index,
1640 pub fn type_flags(&self) -> TypeFlags {
1641 let mut flags = TypeFlags::empty();
1645 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1646 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1647 flags = flags | TypeFlags::HAS_RE_INFER;
1649 ty::RePlaceholder(..) => {
1650 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1651 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1652 flags = flags | TypeFlags::HAS_RE_PLACEHOLDER;
1654 ty::ReEarlyBound(..) => {
1655 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1656 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1657 flags = flags | TypeFlags::HAS_KNOWN_RE_PARAM;
1659 ty::ReFree { .. } => {
1660 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1661 flags = flags | TypeFlags::HAS_KNOWN_FREE_LOCAL_REGIONS;
1663 ty::ReEmpty(_) | ty::ReStatic => {
1664 flags = flags | TypeFlags::HAS_KNOWN_FREE_REGIONS;
1666 ty::ReLateBound(..) => {
1667 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
1670 flags = flags | TypeFlags::HAS_RE_ERASED;
1674 debug!("type_flags({:?}) = {:?}", self, flags);
1679 /// Given an early-bound or free region, returns the `DefId` where it was bound.
1680 /// For example, consider the regions in this snippet of code:
1684 /// ^^ -- early bound, declared on an impl
1686 /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c
1687 /// ^^ ^^ ^ anonymous, late-bound
1688 /// | early-bound, appears in where-clauses
1689 /// late-bound, appears only in fn args
1694 /// Here, `free_region_binding_scope('a)` would return the `DefId`
1695 /// of the impl, and for all the other highlighted regions, it
1696 /// would return the `DefId` of the function. In other cases (not shown), this
1697 /// function might return the `DefId` of a closure.
1698 pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId {
1700 ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(),
1701 ty::ReFree(fr) => fr.scope,
1702 _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self),
1708 impl<'tcx> TyS<'tcx> {
1710 pub fn kind(&self) -> &TyKind<'tcx> {
1715 pub fn flags(&self) -> TypeFlags {
1720 pub fn is_unit(&self) -> bool {
1722 Tuple(ref tys) => tys.is_empty(),
1728 pub fn is_never(&self) -> bool {
1729 matches!(self.kind(), Never)
1733 pub fn is_primitive(&self) -> bool {
1734 self.kind().is_primitive()
1738 pub fn is_adt(&self) -> bool {
1739 matches!(self.kind(), Adt(..))
1743 pub fn is_ref(&self) -> bool {
1744 matches!(self.kind(), Ref(..))
1748 pub fn is_ty_var(&self) -> bool {
1749 matches!(self.kind(), Infer(TyVar(_)))
1753 pub fn ty_vid(&self) -> Option<ty::TyVid> {
1755 &Infer(TyVar(vid)) => Some(vid),
1761 pub fn is_ty_infer(&self) -> bool {
1762 matches!(self.kind(), Infer(_))
1766 pub fn is_phantom_data(&self) -> bool {
1767 if let Adt(def, _) = self.kind() { def.is_phantom_data() } else { false }
1771 pub fn is_bool(&self) -> bool {
1772 *self.kind() == Bool
1775 /// Returns `true` if this type is a `str`.
1777 pub fn is_str(&self) -> bool {
1782 pub fn is_param(&self, index: u32) -> bool {
1784 ty::Param(ref data) => data.index == index,
1790 pub fn is_slice(&self) -> bool {
1792 RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_) | Str),
1798 pub fn is_array(&self) -> bool {
1799 matches!(self.kind(), Array(..))
1803 pub fn is_simd(&self) -> bool {
1805 Adt(def, _) => def.repr.simd(),
1810 pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
1812 Array(ty, _) | Slice(ty) => ty,
1813 Str => tcx.mk_mach_uint(ty::UintTy::U8),
1814 _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
1818 pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
1820 Adt(def, substs) => {
1821 assert!(def.repr.simd(), "`simd_size_and_type` called on non-SIMD type");
1822 let variant = def.non_enum_variant();
1823 let f0_ty = variant.fields[0].ty(tcx, substs);
1825 match f0_ty.kind() {
1826 // If the first field is an array, we assume it is the only field and its
1827 // elements are the SIMD components.
1828 Array(f0_elem_ty, f0_len) => {
1829 // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112
1830 // The way we evaluate the `N` in `[T; N]` here only works since we use
1831 // `simd_size_and_type` post-monomorphization. It will probably start to ICE
1832 // if we use it in generic code. See the `simd-array-trait` ui test.
1833 (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, f0_elem_ty)
1835 // Otherwise, the fields of this Adt are the SIMD components (and we assume they
1836 // all have the same type).
1837 _ => (variant.fields.len() as u64, f0_ty),
1840 _ => bug!("`simd_size_and_type` called on invalid type"),
1845 pub fn is_region_ptr(&self) -> bool {
1846 matches!(self.kind(), Ref(..))
1850 pub fn is_mutable_ptr(&self) -> bool {
1853 RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. })
1854 | Ref(_, _, hir::Mutability::Mut)
1858 /// Get the mutability of the reference or `None` when not a reference
1860 pub fn ref_mutability(&self) -> Option<hir::Mutability> {
1862 Ref(_, _, mutability) => Some(*mutability),
1868 pub fn is_unsafe_ptr(&self) -> bool {
1869 matches!(self.kind(), RawPtr(_))
1872 /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
1874 pub fn is_any_ptr(&self) -> bool {
1875 self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
1879 pub fn is_box(&self) -> bool {
1881 Adt(def, _) => def.is_box(),
1886 /// Panics if called on any type other than `Box<T>`.
1887 pub fn boxed_ty(&self) -> Ty<'tcx> {
1889 Adt(def, substs) if def.is_box() => substs.type_at(0),
1890 _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
1894 /// A scalar type is one that denotes an atomic datum, with no sub-components.
1895 /// (A RawPtr is scalar because it represents a non-managed pointer, so its
1896 /// contents are abstract to rustc.)
1898 pub fn is_scalar(&self) -> bool {
1908 | Infer(IntVar(_) | FloatVar(_))
1912 /// Returns `true` if this type is a floating point type.
1914 pub fn is_floating_point(&self) -> bool {
1915 matches!(self.kind(), Float(_) | Infer(FloatVar(_)))
1919 pub fn is_trait(&self) -> bool {
1920 matches!(self.kind(), Dynamic(..))
1924 pub fn is_enum(&self) -> bool {
1925 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_enum())
1929 pub fn is_union(&self) -> bool {
1930 matches!(self.kind(), Adt(adt_def, _) if adt_def.is_union())
1934 pub fn is_closure(&self) -> bool {
1935 matches!(self.kind(), Closure(..))
1939 pub fn is_generator(&self) -> bool {
1940 matches!(self.kind(), Generator(..))
1944 pub fn is_integral(&self) -> bool {
1945 matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_))
1949 pub fn is_fresh_ty(&self) -> bool {
1950 matches!(self.kind(), Infer(FreshTy(_)))
1954 pub fn is_fresh(&self) -> bool {
1955 matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_)))
1959 pub fn is_char(&self) -> bool {
1960 matches!(self.kind(), Char)
1964 pub fn is_numeric(&self) -> bool {
1965 self.is_integral() || self.is_floating_point()
1969 pub fn is_signed(&self) -> bool {
1970 matches!(self.kind(), Int(_))
1974 pub fn is_ptr_sized_integral(&self) -> bool {
1975 matches!(self.kind(), Int(ty::IntTy::Isize) | Uint(ty::UintTy::Usize))
1979 pub fn has_concrete_skeleton(&self) -> bool {
1980 !matches!(self.kind(), Param(_) | Infer(_) | Error(_))
1983 /// Returns the type and mutability of `*ty`.
1985 /// The parameter `explicit` indicates if this is an *explicit* dereference.
1986 /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly.
1987 pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> {
1989 Adt(def, _) if def.is_box() => {
1990 Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not })
1992 Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl: *mutbl }),
1993 RawPtr(mt) if explicit => Some(*mt),
1998 /// Returns the type of `ty[i]`.
1999 pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
2001 Array(ty, _) | Slice(ty) => Some(ty),
2006 pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
2008 FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
2011 // ignore errors (#54954)
2012 ty::Binder::dummy(FnSig::fake())
2014 Closure(..) => bug!(
2015 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
2017 _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
2022 pub fn is_fn(&self) -> bool {
2023 matches!(self.kind(), FnDef(..) | FnPtr(_))
2027 pub fn is_fn_ptr(&self) -> bool {
2028 matches!(self.kind(), FnPtr(_))
2032 pub fn is_impl_trait(&self) -> bool {
2033 matches!(self.kind(), Opaque(..))
2037 pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> {
2039 Adt(adt, _) => Some(adt),
2044 /// Iterates over tuple fields.
2045 /// Panics when called on anything but a tuple.
2046 pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> {
2048 Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
2049 _ => bug!("tuple_fields called on non-tuple"),
2053 /// Get the `i`-th element of a tuple.
2054 /// Panics when called on anything but a tuple.
2055 pub fn tuple_element_ty(&self, i: usize) -> Option<Ty<'tcx>> {
2057 Tuple(substs) => substs.iter().nth(i).map(|field| field.expect_ty()),
2058 _ => bug!("tuple_fields called on non-tuple"),
2062 /// If the type contains variants, returns the valid range of variant indices.
2064 // FIXME: This requires the optimized MIR in the case of generators.
2066 pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
2068 TyKind::Adt(adt, _) => Some(adt.variant_range()),
2069 TyKind::Generator(def_id, substs, _) => {
2070 Some(substs.as_generator().variant_range(*def_id, tcx))
2076 /// If the type contains variants, returns the variant for `variant_index`.
2077 /// Panics if `variant_index` is out of range.
2079 // FIXME: This requires the optimized MIR in the case of generators.
2081 pub fn discriminant_for_variant(
2084 variant_index: VariantIdx,
2085 ) -> Option<Discr<'tcx>> {
2087 TyKind::Adt(adt, _) if adt.variants.is_empty() => {
2088 // This can actually happen during CTFE, see
2089 // https://github.com/rust-lang/rust/issues/89765.
2092 TyKind::Adt(adt, _) if adt.is_enum() => {
2093 Some(adt.discriminant_for_variant(tcx, variant_index))
2095 TyKind::Generator(def_id, substs, _) => {
2096 Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
2102 /// Returns the type of the discriminant of this type.
2103 pub fn discriminant_ty(&'tcx self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2105 ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx),
2106 ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
2108 ty::Param(_) | ty::Projection(_) | ty::Opaque(..) | ty::Infer(ty::TyVar(_)) => {
2109 let assoc_items = tcx.associated_item_def_ids(
2110 tcx.require_lang_item(hir::LangItem::DiscriminantKind, None),
2112 tcx.mk_projection(assoc_items[0], tcx.intern_substs(&[self.into()]))
2131 | ty::GeneratorWitness(..)
2135 | ty::Infer(IntVar(_) | FloatVar(_)) => tcx.types.u8,
2138 | ty::Placeholder(_)
2139 | ty::Infer(FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2140 bug!("`discriminant_ty` applied to unexpected type: {:?}", self)
2145 /// Returns the type of metadata for (potentially fat) pointers to this type.
2146 pub fn ptr_metadata_ty(&'tcx self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
2147 // FIXME: should this normalize?
2148 let tail = tcx.struct_tail_without_normalization(self);
2151 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2162 | ty::GeneratorWitness(..)
2168 // If returned by `struct_tail_without_normalization` this is a unit struct
2169 // without any fields, or not a struct, and therefore is Sized.
2171 // If returned by `struct_tail_without_normalization` this is the empty tuple,
2172 // a.k.a. unit type, which is Sized
2173 | ty::Tuple(..) => tcx.types.unit,
2175 ty::Str | ty::Slice(_) => tcx.types.usize,
2176 ty::Dynamic(..) => {
2177 let dyn_metadata = tcx.lang_items().dyn_metadata().unwrap();
2178 tcx.type_of(dyn_metadata).subst(tcx, &[tail.into()])
2184 | ty::Infer(ty::TyVar(_))
2186 | ty::Placeholder(..)
2187 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2188 bug!("`ptr_metadata_ty` applied to unexpected type: {:?}", tail)
2193 /// When we create a closure, we record its kind (i.e., what trait
2194 /// it implements) into its `ClosureSubsts` using a type
2195 /// parameter. This is kind of a phantom type, except that the
2196 /// most convenient thing for us to are the integral types. This
2197 /// function converts such a special type into the closure
2198 /// kind. To go the other way, use
2199 /// `tcx.closure_kind_ty(closure_kind)`.
2201 /// Note that during type checking, we use an inference variable
2202 /// to represent the closure kind, because it has not yet been
2203 /// inferred. Once upvar inference (in `rustc_typeck/src/check/upvar.rs`)
2204 /// is complete, that type variable will be unified.
2205 pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> {
2207 Int(int_ty) => match int_ty {
2208 ty::IntTy::I8 => Some(ty::ClosureKind::Fn),
2209 ty::IntTy::I16 => Some(ty::ClosureKind::FnMut),
2210 ty::IntTy::I32 => Some(ty::ClosureKind::FnOnce),
2211 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2214 // "Bound" types appear in canonical queries when the
2215 // closure type is not yet known
2216 Bound(..) | Infer(_) => None,
2218 Error(_) => Some(ty::ClosureKind::Fn),
2220 _ => bug!("cannot convert type `{:?}` to a closure kind", self),
2224 /// Fast path helper for testing if a type is `Sized`.
2226 /// Returning true means the type is known to be sized. Returning
2227 /// `false` means nothing -- could be sized, might not be.
2229 /// Note that we could never rely on the fact that a type such as `[_]` is
2230 /// trivially `!Sized` because we could be in a type environment with a
2231 /// bound such as `[_]: Copy`. A function with such a bound obviously never
2232 /// can be called, but that doesn't mean it shouldn't typecheck. This is why
2233 /// this method doesn't return `Option<bool>`.
2234 pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool {
2236 ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
2247 | ty::GeneratorWitness(..)
2251 | ty::Error(_) => true,
2253 ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
2255 ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)),
2257 ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(),
2259 ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false,
2261 ty::Infer(ty::TyVar(_)) => false,
2264 | ty::Placeholder(..)
2265 | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
2266 bug!("`is_trivially_sized` applied to unexpected type: {:?}", self)
2272 /// Extra information about why we ended up with a particular variance.
2273 /// This is only used to add more information to error messages, and
2274 /// has no effect on soundness. While choosing the 'wrong' `VarianceDiagInfo`
2275 /// may lead to confusing notes in error messages, it will never cause
2276 /// a miscompilation or unsoundness.
2278 /// When in doubt, use `VarianceDiagInfo::default()`
2279 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
2280 pub enum VarianceDiagInfo<'tcx> {
2281 /// No additional information - this is the default.
2282 /// We will not add any additional information to error messages.
2285 /// We switched our variance because a generic argument occurs inside
2286 /// the invariant generic argument of another type.
2288 /// The generic type containing the generic parameter
2289 /// that changes the variance (e.g. `*mut T`, `MyStruct<T>`)
2291 /// The index of the generic parameter being used
2292 /// (e.g. `0` for `*mut T`, `1` for `MyStruct<'CovariantParam, 'InvariantParam>`)
2297 impl<'tcx> VarianceDiagInfo<'tcx> {
2298 /// Mirrors `Variance::xform` - used to 'combine' the existing
2299 /// and new `VarianceDiagInfo`s when our variance changes.
2300 pub fn xform(self, other: VarianceDiagInfo<'tcx>) -> VarianceDiagInfo<'tcx> {
2301 // For now, just use the first `VarianceDiagInfo::Invariant` that we see
2303 VarianceDiagInfo::None => other,
2304 VarianceDiagInfo::Invariant { .. } => self,