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Diffstat (limited to 'compiler/rustc_middle/src/ty/sty.rs')
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diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs new file mode 100644 index 00000000000..c1f354c7a15 --- /dev/null +++ b/compiler/rustc_middle/src/ty/sty.rs @@ -0,0 +1,2288 @@ +//! This module contains `TyKind` and its major components. + +#![allow(rustc::usage_of_ty_tykind)] + +use self::InferTy::*; +use self::TyKind::*; + +use crate::infer::canonical::Canonical; +use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef}; +use crate::ty::{ + self, AdtDef, DefIdTree, Discr, Ty, TyCtxt, TypeFlags, TypeFoldable, WithConstness, +}; +use crate::ty::{DelaySpanBugEmitted, List, ParamEnv, TyS}; +use polonius_engine::Atom; +use rustc_ast as ast; +use rustc_data_structures::captures::Captures; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_index::vec::Idx; +use rustc_macros::HashStable; +use rustc_span::symbol::{kw, Ident, Symbol}; +use rustc_target::abi::VariantIdx; +use rustc_target::spec::abi; +use std::borrow::Cow; +use std::cmp::Ordering; +use std::marker::PhantomData; +use std::ops::Range; +use ty::util::IntTypeExt; + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, Lift)] +pub struct TypeAndMut<'tcx> { + pub ty: Ty<'tcx>, + pub mutbl: hir::Mutability, +} + +#[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)] +#[derive(HashStable)] +/// A "free" region `fr` can be interpreted as "some region +/// at least as big as the scope `fr.scope`". +pub struct FreeRegion { + pub scope: DefId, + pub bound_region: BoundRegion, +} + +#[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)] +#[derive(HashStable)] +pub enum BoundRegion { + /// An anonymous region parameter for a given fn (&T) + BrAnon(u32), + + /// Named region parameters for functions (a in &'a T) + /// + /// The `DefId` is needed to distinguish free regions in + /// the event of shadowing. + BrNamed(DefId, Symbol), + + /// Anonymous region for the implicit env pointer parameter + /// to a closure + BrEnv, +} + +impl BoundRegion { + pub fn is_named(&self) -> bool { + match *self { + BoundRegion::BrNamed(_, name) => name != kw::UnderscoreLifetime, + _ => false, + } + } + + /// When canonicalizing, we replace unbound inference variables and free + /// regions with anonymous late bound regions. This method asserts that + /// we have an anonymous late bound region, which hence may refer to + /// a canonical variable. + pub fn assert_bound_var(&self) -> BoundVar { + match *self { + BoundRegion::BrAnon(var) => BoundVar::from_u32(var), + _ => bug!("bound region is not anonymous"), + } + } +} + +/// N.B., if you change this, you'll probably want to change the corresponding +/// AST structure in `librustc_ast/ast.rs` as well. +#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)] +#[derive(HashStable)] +#[rustc_diagnostic_item = "TyKind"] +pub enum TyKind<'tcx> { + /// The primitive boolean type. Written as `bool`. + Bool, + + /// The primitive character type; holds a Unicode scalar value + /// (a non-surrogate code point). Written as `char`. + Char, + + /// A primitive signed integer type. For example, `i32`. + Int(ast::IntTy), + + /// A primitive unsigned integer type. For example, `u32`. + Uint(ast::UintTy), + + /// A primitive floating-point type. For example, `f64`. + Float(ast::FloatTy), + + /// Structures, enumerations and unions. + /// + /// InternalSubsts here, possibly against intuition, *may* contain `Param`s. + /// That is, even after substitution it is possible that there are type + /// variables. This happens when the `Adt` corresponds to an ADT + /// definition and not a concrete use of it. + Adt(&'tcx AdtDef, SubstsRef<'tcx>), + + /// An unsized FFI type that is opaque to Rust. Written as `extern type T`. + Foreign(DefId), + + /// The pointee of a string slice. Written as `str`. + Str, + + /// An array with the given length. Written as `[T; n]`. + Array(Ty<'tcx>, &'tcx ty::Const<'tcx>), + + /// The pointee of an array slice. Written as `[T]`. + Slice(Ty<'tcx>), + + /// A raw pointer. Written as `*mut T` or `*const T` + RawPtr(TypeAndMut<'tcx>), + + /// A reference; a pointer with an associated lifetime. Written as + /// `&'a mut T` or `&'a T`. + Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability), + + /// The anonymous type of a function declaration/definition. Each + /// function has a unique type, which is output (for a function + /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`. + /// + /// For example the type of `bar` here: + /// + /// ```rust + /// fn foo() -> i32 { 1 } + /// let bar = foo; // bar: fn() -> i32 {foo} + /// ``` + FnDef(DefId, SubstsRef<'tcx>), + + /// A pointer to a function. Written as `fn() -> i32`. + /// + /// For example the type of `bar` here: + /// + /// ```rust + /// fn foo() -> i32 { 1 } + /// let bar: fn() -> i32 = foo; + /// ``` + FnPtr(PolyFnSig<'tcx>), + + /// A trait, defined with `trait`. + Dynamic(Binder<&'tcx List<ExistentialPredicate<'tcx>>>, ty::Region<'tcx>), + + /// The anonymous type of a closure. Used to represent the type of + /// `|a| a`. + Closure(DefId, SubstsRef<'tcx>), + + /// The anonymous type of a generator. Used to represent the type of + /// `|a| yield a`. + Generator(DefId, SubstsRef<'tcx>, hir::Movability), + + /// A type representin the types stored inside a generator. + /// This should only appear in GeneratorInteriors. + GeneratorWitness(Binder<&'tcx List<Ty<'tcx>>>), + + /// The never type `!` + Never, + + /// A tuple type. For example, `(i32, bool)`. + /// Use `TyS::tuple_fields` to iterate over the field types. + Tuple(SubstsRef<'tcx>), + + /// The projection of an associated type. For example, + /// `<T as Trait<..>>::N`. + Projection(ProjectionTy<'tcx>), + + /// Opaque (`impl Trait`) type found in a return type. + /// The `DefId` comes either from + /// * the `impl Trait` ast::Ty node, + /// * or the `type Foo = impl Trait` declaration + /// The substitutions are for the generics of the function in question. + /// After typeck, the concrete type can be found in the `types` map. + Opaque(DefId, SubstsRef<'tcx>), + + /// A type parameter; for example, `T` in `fn f<T>(x: T) {}`. + Param(ParamTy), + + /// Bound type variable, used only when preparing a trait query. + Bound(ty::DebruijnIndex, BoundTy), + + /// A placeholder type - universally quantified higher-ranked type. + Placeholder(ty::PlaceholderType), + + /// A type variable used during type checking. + Infer(InferTy), + + /// A placeholder for a type which could not be computed; this is + /// propagated to avoid useless error messages. + Error(DelaySpanBugEmitted), +} + +impl TyKind<'tcx> { + #[inline] + pub fn is_primitive(&self) -> bool { + match self { + Bool | Char | Int(_) | Uint(_) | Float(_) => true, + _ => false, + } + } +} + +// `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger. +#[cfg(target_arch = "x86_64")] +static_assert_size!(TyKind<'_>, 24); + +/// A closure can be modeled as a struct that looks like: +/// +/// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U); +/// +/// where: +/// +/// - 'l0...'li and T0...Tj are the generic parameters +/// in scope on the function that defined the closure, +/// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This +/// is rather hackily encoded via a scalar type. See +/// `TyS::to_opt_closure_kind` for details. +/// - CS represents the *closure signature*, representing as a `fn()` +/// type. For example, `fn(u32, u32) -> u32` would mean that the closure +/// implements `CK<(u32, u32), Output = u32>`, where `CK` is the trait +/// specified above. +/// - U is a type parameter representing the types of its upvars, tupled up +/// (borrowed, if appropriate; that is, if an U field represents a by-ref upvar, +/// and the up-var has the type `Foo`, then that field of U will be `&Foo`). +/// +/// So, for example, given this function: +/// +/// fn foo<'a, T>(data: &'a mut T) { +/// do(|| data.count += 1) +/// } +/// +/// the type of the closure would be something like: +/// +/// struct Closure<'a, T, U>(...U); +/// +/// Note that the type of the upvar is not specified in the struct. +/// You may wonder how the impl would then be able to use the upvar, +/// if it doesn't know it's type? The answer is that the impl is +/// (conceptually) not fully generic over Closure but rather tied to +/// instances with the expected upvar types: +/// +/// impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> { +/// ... +/// } +/// +/// You can see that the *impl* fully specified the type of the upvar +/// and thus knows full well that `data` has type `&'b mut &'a mut T`. +/// (Here, I am assuming that `data` is mut-borrowed.) +/// +/// Now, the last question you may ask is: Why include the upvar types +/// in an extra type parameter? The reason for this design is that the +/// upvar types can reference lifetimes that are internal to the +/// creating function. In my example above, for example, the lifetime +/// `'b` represents the scope of the closure itself; this is some +/// subset of `foo`, probably just the scope of the call to the to +/// `do()`. If we just had the lifetime/type parameters from the +/// enclosing function, we couldn't name this lifetime `'b`. Note that +/// there can also be lifetimes in the types of the upvars themselves, +/// if one of them happens to be a reference to something that the +/// creating fn owns. +/// +/// OK, you say, so why not create a more minimal set of parameters +/// that just includes the extra lifetime parameters? The answer is +/// primarily that it would be hard --- we don't know at the time when +/// we create the closure type what the full types of the upvars are, +/// nor do we know which are borrowed and which are not. In this +/// design, we can just supply a fresh type parameter and figure that +/// out later. +/// +/// All right, you say, but why include the type parameters from the +/// original function then? The answer is that codegen may need them +/// when monomorphizing, and they may not appear in the upvars. A +/// closure could capture no variables but still make use of some +/// in-scope type parameter with a bound (e.g., if our example above +/// had an extra `U: Default`, and the closure called `U::default()`). +/// +/// There is another reason. This design (implicitly) prohibits +/// closures from capturing themselves (except via a trait +/// object). This simplifies closure inference considerably, since it +/// means that when we infer the kind of a closure or its upvars, we +/// don't have to handle cycles where the decisions we make for +/// closure C wind up influencing the decisions we ought to make for +/// closure C (which would then require fixed point iteration to +/// handle). Plus it fixes an ICE. :P +/// +/// ## Generators +/// +/// Generators are handled similarly in `GeneratorSubsts`. The set of +/// type parameters is similar, but `CK` and `CS` are replaced by the +/// following type parameters: +/// +/// * `GS`: The generator's "resume type", which is the type of the +/// argument passed to `resume`, and the type of `yield` expressions +/// inside the generator. +/// * `GY`: The "yield type", which is the type of values passed to +/// `yield` inside the generator. +/// * `GR`: The "return type", which is the type of value returned upon +/// completion of the generator. +/// * `GW`: The "generator witness". +#[derive(Copy, Clone, Debug, TypeFoldable)] +pub struct ClosureSubsts<'tcx> { + /// Lifetime and type parameters from the enclosing function, + /// concatenated with a tuple containing the types of the upvars. + /// + /// These are separated out because codegen wants to pass them around + /// when monomorphizing. + pub substs: SubstsRef<'tcx>, +} + +/// Struct returned by `split()`. +pub struct ClosureSubstsParts<'tcx, T> { + pub parent_substs: &'tcx [GenericArg<'tcx>], + pub closure_kind_ty: T, + pub closure_sig_as_fn_ptr_ty: T, + pub tupled_upvars_ty: T, +} + +impl<'tcx> ClosureSubsts<'tcx> { + /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs` + /// for the closure parent, alongside additional closure-specific components. + pub fn new( + tcx: TyCtxt<'tcx>, + parts: ClosureSubstsParts<'tcx, Ty<'tcx>>, + ) -> ClosureSubsts<'tcx> { + ClosureSubsts { + substs: tcx.mk_substs( + parts.parent_substs.iter().copied().chain( + [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty] + .iter() + .map(|&ty| ty.into()), + ), + ), + } + } + + /// Divides the closure substs into their respective components. + /// The ordering assumed here must match that used by `ClosureSubsts::new` above. + fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> { + match self.substs[..] { + [ref parent_substs @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => { + ClosureSubstsParts { + parent_substs, + closure_kind_ty, + closure_sig_as_fn_ptr_ty, + tupled_upvars_ty, + } + } + _ => bug!("closure substs missing synthetics"), + } + } + + /// Returns `true` only if enough of the synthetic types are known to + /// allow using all of the methods on `ClosureSubsts` without panicking. + /// + /// Used primarily by `ty::print::pretty` to be able to handle closure + /// types that haven't had their synthetic types substituted in. + pub fn is_valid(self) -> bool { + self.substs.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_)) + } + + /// Returns the substitutions of the closure's parent. + pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] { + self.split().parent_substs + } + + #[inline] + pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx { + self.tupled_upvars_ty().tuple_fields() + } + + /// Returns the tuple type representing the upvars for this closure. + #[inline] + pub fn tupled_upvars_ty(self) -> Ty<'tcx> { + self.split().tupled_upvars_ty.expect_ty() + } + + /// Returns the closure kind for this closure; may return a type + /// variable during inference. To get the closure kind during + /// inference, use `infcx.closure_kind(substs)`. + pub fn kind_ty(self) -> Ty<'tcx> { + self.split().closure_kind_ty.expect_ty() + } + + /// Returns the `fn` pointer type representing the closure signature for this + /// closure. + // FIXME(eddyb) this should be unnecessary, as the shallowly resolved + // type is known at the time of the creation of `ClosureSubsts`, + // see `rustc_typeck::check::closure`. + pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> { + self.split().closure_sig_as_fn_ptr_ty.expect_ty() + } + + /// Returns the closure kind for this closure; only usable outside + /// of an inference context, because in that context we know that + /// there are no type variables. + /// + /// If you have an inference context, use `infcx.closure_kind()`. + pub fn kind(self) -> ty::ClosureKind { + self.kind_ty().to_opt_closure_kind().unwrap() + } + + /// Extracts the signature from the closure. + pub fn sig(self) -> ty::PolyFnSig<'tcx> { + let ty = self.sig_as_fn_ptr_ty(); + match ty.kind { + ty::FnPtr(sig) => sig, + _ => bug!("closure_sig_as_fn_ptr_ty is not a fn-ptr: {:?}", ty.kind), + } + } +} + +/// Similar to `ClosureSubsts`; see the above documentation for more. +#[derive(Copy, Clone, Debug, TypeFoldable)] +pub struct GeneratorSubsts<'tcx> { + pub substs: SubstsRef<'tcx>, +} + +pub struct GeneratorSubstsParts<'tcx, T> { + pub parent_substs: &'tcx [GenericArg<'tcx>], + pub resume_ty: T, + pub yield_ty: T, + pub return_ty: T, + pub witness: T, + pub tupled_upvars_ty: T, +} + +impl<'tcx> GeneratorSubsts<'tcx> { + /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs` + /// for the generator parent, alongside additional generator-specific components. + pub fn new( + tcx: TyCtxt<'tcx>, + parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>, + ) -> GeneratorSubsts<'tcx> { + GeneratorSubsts { + substs: tcx.mk_substs( + parts.parent_substs.iter().copied().chain( + [ + parts.resume_ty, + parts.yield_ty, + parts.return_ty, + parts.witness, + parts.tupled_upvars_ty, + ] + .iter() + .map(|&ty| ty.into()), + ), + ), + } + } + + /// Divides the generator substs into their respective components. + /// The ordering assumed here must match that used by `GeneratorSubsts::new` above. + fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> { + match self.substs[..] { + [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => { + GeneratorSubstsParts { + parent_substs, + resume_ty, + yield_ty, + return_ty, + witness, + tupled_upvars_ty, + } + } + _ => bug!("generator substs missing synthetics"), + } + } + + /// Returns `true` only if enough of the synthetic types are known to + /// allow using all of the methods on `GeneratorSubsts` without panicking. + /// + /// Used primarily by `ty::print::pretty` to be able to handle generator + /// types that haven't had their synthetic types substituted in. + pub fn is_valid(self) -> bool { + self.substs.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind, Tuple(_)) + } + + /// Returns the substitutions of the generator's parent. + pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] { + self.split().parent_substs + } + + /// This describes the types that can be contained in a generator. + /// It will be a type variable initially and unified in the last stages of typeck of a body. + /// It contains a tuple of all the types that could end up on a generator frame. + /// The state transformation MIR pass may only produce layouts which mention types + /// in this tuple. Upvars are not counted here. + pub fn witness(self) -> Ty<'tcx> { + self.split().witness.expect_ty() + } + + #[inline] + pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx { + self.tupled_upvars_ty().tuple_fields() + } + + /// Returns the tuple type representing the upvars for this generator. + #[inline] + pub fn tupled_upvars_ty(self) -> Ty<'tcx> { + self.split().tupled_upvars_ty.expect_ty() + } + + /// Returns the type representing the resume type of the generator. + pub fn resume_ty(self) -> Ty<'tcx> { + self.split().resume_ty.expect_ty() + } + + /// Returns the type representing the yield type of the generator. + pub fn yield_ty(self) -> Ty<'tcx> { + self.split().yield_ty.expect_ty() + } + + /// Returns the type representing the return type of the generator. + pub fn return_ty(self) -> Ty<'tcx> { + self.split().return_ty.expect_ty() + } + + /// Returns the "generator signature", which consists of its yield + /// and return types. + /// + /// N.B., some bits of the code prefers to see this wrapped in a + /// binder, but it never contains bound regions. Probably this + /// function should be removed. + pub fn poly_sig(self) -> PolyGenSig<'tcx> { + ty::Binder::dummy(self.sig()) + } + + /// Returns the "generator signature", which consists of its resume, yield + /// and return types. + pub fn sig(self) -> GenSig<'tcx> { + ty::GenSig { + resume_ty: self.resume_ty(), + yield_ty: self.yield_ty(), + return_ty: self.return_ty(), + } + } +} + +impl<'tcx> GeneratorSubsts<'tcx> { + /// Generator has not been resumed yet. + pub const UNRESUMED: usize = 0; + /// Generator has returned or is completed. + pub const RETURNED: usize = 1; + /// Generator has been poisoned. + pub const POISONED: usize = 2; + + const UNRESUMED_NAME: &'static str = "Unresumed"; + const RETURNED_NAME: &'static str = "Returned"; + const POISONED_NAME: &'static str = "Panicked"; + + /// The valid variant indices of this generator. + #[inline] + pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> { + // FIXME requires optimized MIR + let num_variants = tcx.generator_layout(def_id).variant_fields.len(); + VariantIdx::new(0)..VariantIdx::new(num_variants) + } + + /// The discriminant for the given variant. Panics if the `variant_index` is + /// out of range. + #[inline] + pub fn discriminant_for_variant( + &self, + def_id: DefId, + tcx: TyCtxt<'tcx>, + variant_index: VariantIdx, + ) -> Discr<'tcx> { + // Generators don't support explicit discriminant values, so they are + // the same as the variant index. + assert!(self.variant_range(def_id, tcx).contains(&variant_index)); + Discr { val: variant_index.as_usize() as u128, ty: self.discr_ty(tcx) } + } + + /// The set of all discriminants for the generator, enumerated with their + /// variant indices. + #[inline] + pub fn discriminants( + self, + def_id: DefId, + tcx: TyCtxt<'tcx>, + ) -> impl Iterator<Item = (VariantIdx, Discr<'tcx>)> + Captures<'tcx> { + self.variant_range(def_id, tcx).map(move |index| { + (index, Discr { val: index.as_usize() as u128, ty: self.discr_ty(tcx) }) + }) + } + + /// Calls `f` with a reference to the name of the enumerator for the given + /// variant `v`. + pub fn variant_name(v: VariantIdx) -> Cow<'static, str> { + match v.as_usize() { + Self::UNRESUMED => Cow::from(Self::UNRESUMED_NAME), + Self::RETURNED => Cow::from(Self::RETURNED_NAME), + Self::POISONED => Cow::from(Self::POISONED_NAME), + _ => Cow::from(format!("Suspend{}", v.as_usize() - 3)), + } + } + + /// The type of the state discriminant used in the generator type. + #[inline] + pub fn discr_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + tcx.types.u32 + } + + /// This returns the types of the MIR locals which had to be stored across suspension points. + /// It is calculated in rustc_mir::transform::generator::StateTransform. + /// All the types here must be in the tuple in GeneratorInterior. + /// + /// The locals are grouped by their variant number. Note that some locals may + /// be repeated in multiple variants. + #[inline] + pub fn state_tys( + self, + def_id: DefId, + tcx: TyCtxt<'tcx>, + ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> { + let layout = tcx.generator_layout(def_id); + layout.variant_fields.iter().map(move |variant| { + variant.iter().map(move |field| layout.field_tys[*field].subst(tcx, self.substs)) + }) + } + + /// This is the types of the fields of a generator which are not stored in a + /// variant. + #[inline] + pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> { + self.upvar_tys() + } +} + +#[derive(Debug, Copy, Clone)] +pub enum UpvarSubsts<'tcx> { + Closure(SubstsRef<'tcx>), + Generator(SubstsRef<'tcx>), +} + +impl<'tcx> UpvarSubsts<'tcx> { + #[inline] + pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx { + let tupled_upvars_ty = match self { + UpvarSubsts::Closure(substs) => substs.as_closure().split().tupled_upvars_ty, + UpvarSubsts::Generator(substs) => substs.as_generator().split().tupled_upvars_ty, + }; + tupled_upvars_ty.expect_ty().tuple_fields() + } +} + +#[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable)] +pub enum ExistentialPredicate<'tcx> { + /// E.g., `Iterator`. + Trait(ExistentialTraitRef<'tcx>), + /// E.g., `Iterator::Item = T`. + Projection(ExistentialProjection<'tcx>), + /// E.g., `Send`. + AutoTrait(DefId), +} + +impl<'tcx> ExistentialPredicate<'tcx> { + /// Compares via an ordering that will not change if modules are reordered or other changes are + /// made to the tree. In particular, this ordering is preserved across incremental compilations. + pub fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering { + use self::ExistentialPredicate::*; + match (*self, *other) { + (Trait(_), Trait(_)) => Ordering::Equal, + (Projection(ref a), Projection(ref b)) => { + tcx.def_path_hash(a.item_def_id).cmp(&tcx.def_path_hash(b.item_def_id)) + } + (AutoTrait(ref a), AutoTrait(ref b)) => { + tcx.trait_def(*a).def_path_hash.cmp(&tcx.trait_def(*b).def_path_hash) + } + (Trait(_), _) => Ordering::Less, + (Projection(_), Trait(_)) => Ordering::Greater, + (Projection(_), _) => Ordering::Less, + (AutoTrait(_), _) => Ordering::Greater, + } + } +} + +impl<'tcx> Binder<ExistentialPredicate<'tcx>> { + pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> { + use crate::ty::ToPredicate; + match self.skip_binder() { + ExistentialPredicate::Trait(tr) => { + Binder(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx) + } + ExistentialPredicate::Projection(p) => { + Binder(p.with_self_ty(tcx, self_ty)).to_predicate(tcx) + } + ExistentialPredicate::AutoTrait(did) => { + let trait_ref = + Binder(ty::TraitRef { def_id: did, substs: tcx.mk_substs_trait(self_ty, &[]) }); + trait_ref.without_const().to_predicate(tcx) + } + } + } +} + +impl<'tcx> List<ExistentialPredicate<'tcx>> { + /// Returns the "principal `DefId`" of this set of existential predicates. + /// + /// A Rust trait object type consists (in addition to a lifetime bound) + /// of a set of trait bounds, which are separated into any number + /// of auto-trait bounds, and at most one non-auto-trait bound. The + /// non-auto-trait bound is called the "principal" of the trait + /// object. + /// + /// Only the principal can have methods or type parameters (because + /// auto traits can have neither of them). This is important, because + /// it means the auto traits can be treated as an unordered set (methods + /// would force an order for the vtable, while relating traits with + /// type parameters without knowing the order to relate them in is + /// a rather non-trivial task). + /// + /// For example, in the trait object `dyn fmt::Debug + Sync`, the + /// principal bound is `Some(fmt::Debug)`, while the auto-trait bounds + /// are the set `{Sync}`. + /// + /// It is also possible to have a "trivial" trait object that + /// consists only of auto traits, with no principal - for example, + /// `dyn Send + Sync`. In that case, the set of auto-trait bounds + /// is `{Send, Sync}`, while there is no principal. These trait objects + /// have a "trivial" vtable consisting of just the size, alignment, + /// and destructor. + pub fn principal(&self) -> Option<ExistentialTraitRef<'tcx>> { + match self[0] { + ExistentialPredicate::Trait(tr) => Some(tr), + _ => None, + } + } + + pub fn principal_def_id(&self) -> Option<DefId> { + self.principal().map(|trait_ref| trait_ref.def_id) + } + + #[inline] + pub fn projection_bounds<'a>( + &'a self, + ) -> impl Iterator<Item = ExistentialProjection<'tcx>> + 'a { + self.iter().filter_map(|predicate| match predicate { + ExistentialPredicate::Projection(projection) => Some(projection), + _ => None, + }) + } + + #[inline] + pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a { + self.iter().filter_map(|predicate| match predicate { + ExistentialPredicate::AutoTrait(did) => Some(did), + _ => None, + }) + } +} + +impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> { + pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> { + self.skip_binder().principal().map(Binder::bind) + } + + pub fn principal_def_id(&self) -> Option<DefId> { + self.skip_binder().principal_def_id() + } + + #[inline] + pub fn projection_bounds<'a>( + &'a self, + ) -> impl Iterator<Item = PolyExistentialProjection<'tcx>> + 'a { + self.skip_binder().projection_bounds().map(Binder::bind) + } + + #[inline] + pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + 'a { + self.skip_binder().auto_traits() + } + + pub fn iter<'a>( + &'a self, + ) -> impl DoubleEndedIterator<Item = Binder<ExistentialPredicate<'tcx>>> + 'tcx { + self.skip_binder().iter().map(Binder::bind) + } +} + +/// A complete reference to a trait. These take numerous guises in syntax, +/// but perhaps the most recognizable form is in a where-clause: +/// +/// T: Foo<U> +/// +/// This would be represented by a trait-reference where the `DefId` is the +/// `DefId` for the trait `Foo` and the substs define `T` as parameter 0, +/// and `U` as parameter 1. +/// +/// Trait references also appear in object types like `Foo<U>`, but in +/// that case the `Self` parameter is absent from the substitutions. +#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable)] +pub struct TraitRef<'tcx> { + pub def_id: DefId, + pub substs: SubstsRef<'tcx>, +} + +impl<'tcx> TraitRef<'tcx> { + pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> TraitRef<'tcx> { + TraitRef { def_id, substs } + } + + /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi` + /// are the parameters defined on trait. + pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> { + TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) } + } + + #[inline] + pub fn self_ty(&self) -> Ty<'tcx> { + self.substs.type_at(0) + } + + pub fn from_method( + tcx: TyCtxt<'tcx>, + trait_id: DefId, + substs: SubstsRef<'tcx>, + ) -> ty::TraitRef<'tcx> { + let defs = tcx.generics_of(trait_id); + + ty::TraitRef { def_id: trait_id, substs: tcx.intern_substs(&substs[..defs.params.len()]) } + } +} + +pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>; + +impl<'tcx> PolyTraitRef<'tcx> { + pub fn self_ty(&self) -> Binder<Ty<'tcx>> { + self.map_bound_ref(|tr| tr.self_ty()) + } + + pub fn def_id(&self) -> DefId { + self.skip_binder().def_id + } + + pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> { + // Note that we preserve binding levels + Binder(ty::TraitPredicate { trait_ref: self.skip_binder() }) + } +} + +/// An existential reference to a trait, where `Self` is erased. +/// For example, the trait object `Trait<'a, 'b, X, Y>` is: +/// +/// exists T. T: Trait<'a, 'b, X, Y> +/// +/// The substitutions don't include the erased `Self`, only trait +/// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above). +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable)] +pub struct ExistentialTraitRef<'tcx> { + pub def_id: DefId, + pub substs: SubstsRef<'tcx>, +} + +impl<'tcx> ExistentialTraitRef<'tcx> { + pub fn erase_self_ty( + tcx: TyCtxt<'tcx>, + trait_ref: ty::TraitRef<'tcx>, + ) -> ty::ExistentialTraitRef<'tcx> { + // Assert there is a Self. + trait_ref.substs.type_at(0); + + ty::ExistentialTraitRef { + def_id: trait_ref.def_id, + substs: tcx.intern_substs(&trait_ref.substs[1..]), + } + } + + /// Object types don't have a self type specified. Therefore, when + /// we convert the principal trait-ref into a normal trait-ref, + /// you must give *some* self type. A common choice is `mk_err()` + /// or some placeholder type. + pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::TraitRef<'tcx> { + // otherwise the escaping vars would be captured by the binder + // debug_assert!(!self_ty.has_escaping_bound_vars()); + + ty::TraitRef { def_id: self.def_id, substs: tcx.mk_substs_trait(self_ty, self.substs) } + } +} + +pub type PolyExistentialTraitRef<'tcx> = Binder<ExistentialTraitRef<'tcx>>; + +impl<'tcx> PolyExistentialTraitRef<'tcx> { + pub fn def_id(&self) -> DefId { + self.skip_binder().def_id + } + + /// Object types don't have a self type specified. Therefore, when + /// we convert the principal trait-ref into a normal trait-ref, + /// you must give *some* self type. A common choice is `mk_err()` + /// or some placeholder type. + pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::PolyTraitRef<'tcx> { + self.map_bound(|trait_ref| trait_ref.with_self_ty(tcx, self_ty)) + } +} + +/// Binder is a binder for higher-ranked lifetimes or types. It is part of the +/// compiler's representation for things like `for<'a> Fn(&'a isize)` +/// (which would be represented by the type `PolyTraitRef == +/// Binder<TraitRef>`). Note that when we instantiate, +/// erase, or otherwise "discharge" these bound vars, we change the +/// type from `Binder<T>` to just `T` (see +/// e.g., `liberate_late_bound_regions`). +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +pub struct Binder<T>(T); + +impl<T> Binder<T> { + /// Wraps `value` in a binder, asserting that `value` does not + /// contain any bound vars that would be bound by the + /// binder. This is commonly used to 'inject' a value T into a + /// different binding level. + pub fn dummy<'tcx>(value: T) -> Binder<T> + where + T: TypeFoldable<'tcx>, + { + debug_assert!(!value.has_escaping_bound_vars()); + Binder(value) + } + + /// Wraps `value` in a binder, binding higher-ranked vars (if any). + pub fn bind(value: T) -> Binder<T> { + Binder(value) + } + + /// Wraps `value` in a binder without actually binding any currently + /// unbound variables. + /// + /// Note that this will shift all debrujin indices of escaping bound variables + /// by 1 to avoid accidential captures. + pub fn wrap_nonbinding(tcx: TyCtxt<'tcx>, value: T) -> Binder<T> + where + T: TypeFoldable<'tcx>, + { + if value.has_escaping_bound_vars() { + Binder::bind(super::fold::shift_vars(tcx, &value, 1)) + } else { + Binder::dummy(value) + } + } + + /// Skips the binder and returns the "bound" value. This is a + /// risky thing to do because it's easy to get confused about + /// De Bruijn indices and the like. It is usually better to + /// discharge the binder using `no_bound_vars` or + /// `replace_late_bound_regions` or something like + /// that. `skip_binder` is only valid when you are either + /// extracting data that has nothing to do with bound vars, you + /// are doing some sort of test that does not involve bound + /// regions, or you are being very careful about your depth + /// accounting. + /// + /// Some examples where `skip_binder` is reasonable: + /// + /// - extracting the `DefId` from a PolyTraitRef; + /// - comparing the self type of a PolyTraitRef to see if it is equal to + /// a type parameter `X`, since the type `X` does not reference any regions + pub fn skip_binder(self) -> T { + self.0 + } + + pub fn as_ref(&self) -> Binder<&T> { + Binder(&self.0) + } + + pub fn map_bound_ref<F, U>(&self, f: F) -> Binder<U> + where + F: FnOnce(&T) -> U, + { + self.as_ref().map_bound(f) + } + + pub fn map_bound<F, U>(self, f: F) -> Binder<U> + where + F: FnOnce(T) -> U, + { + Binder(f(self.0)) + } + + /// Unwraps and returns the value within, but only if it contains + /// no bound vars at all. (In other words, if this binder -- + /// and indeed any enclosing binder -- doesn't bind anything at + /// all.) Otherwise, returns `None`. + /// + /// (One could imagine having a method that just unwraps a single + /// binder, but permits late-bound vars bound by enclosing + /// binders, but that would require adjusting the debruijn + /// indices, and given the shallow binding structure we often use, + /// would not be that useful.) + pub fn no_bound_vars<'tcx>(self) -> Option<T> + where + T: TypeFoldable<'tcx>, + { + if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) } + } + + /// Given two things that have the same binder level, + /// and an operation that wraps on their contents, executes the operation + /// and then wraps its result. + /// + /// `f` should consider bound regions at depth 1 to be free, and + /// anything it produces with bound regions at depth 1 will be + /// bound in the resulting return value. + pub fn fuse<U, F, R>(self, u: Binder<U>, f: F) -> Binder<R> + where + F: FnOnce(T, U) -> R, + { + Binder(f(self.0, u.0)) + } + + /// Splits the contents into two things that share the same binder + /// level as the original, returning two distinct binders. + /// + /// `f` should consider bound regions at depth 1 to be free, and + /// anything it produces with bound regions at depth 1 will be + /// bound in the resulting return values. + pub fn split<U, V, F>(self, f: F) -> (Binder<U>, Binder<V>) + where + F: FnOnce(T) -> (U, V), + { + let (u, v) = f(self.0); + (Binder(u), Binder(v)) + } +} + +impl<T> Binder<Option<T>> { + pub fn transpose(self) -> Option<Binder<T>> { + match self.0 { + Some(v) => Some(Binder(v)), + None => None, + } + } +} + +/// Represents the projection of an associated type. In explicit UFCS +/// form this would be written `<T as Trait<..>>::N`. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable)] +pub struct ProjectionTy<'tcx> { + /// The parameters of the associated item. + pub substs: SubstsRef<'tcx>, + + /// The `DefId` of the `TraitItem` for the associated type `N`. + /// + /// Note that this is not the `DefId` of the `TraitRef` containing this + /// associated type, which is in `tcx.associated_item(item_def_id).container`. + pub item_def_id: DefId, +} + +impl<'tcx> ProjectionTy<'tcx> { + /// Construct a `ProjectionTy` by searching the trait from `trait_ref` for the + /// associated item named `item_name`. + pub fn from_ref_and_name( + tcx: TyCtxt<'_>, + trait_ref: ty::TraitRef<'tcx>, + item_name: Ident, + ) -> ProjectionTy<'tcx> { + let item_def_id = tcx + .associated_items(trait_ref.def_id) + .find_by_name_and_kind(tcx, item_name, ty::AssocKind::Type, trait_ref.def_id) + .unwrap() + .def_id; + + ProjectionTy { substs: trait_ref.substs, item_def_id } + } + + /// Extracts the underlying trait reference from this projection. + /// For example, if this is a projection of `<T as Iterator>::Item`, + /// then this function would return a `T: Iterator` trait reference. + pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> { + let def_id = tcx.associated_item(self.item_def_id).container.id(); + ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, tcx.generics_of(def_id)) } + } + + pub fn self_ty(&self) -> Ty<'tcx> { + self.substs.type_at(0) + } +} + +#[derive(Copy, Clone, Debug, TypeFoldable)] +pub struct GenSig<'tcx> { + pub resume_ty: Ty<'tcx>, + pub yield_ty: Ty<'tcx>, + pub return_ty: Ty<'tcx>, +} + +pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>; + +impl<'tcx> PolyGenSig<'tcx> { + pub fn resume_ty(&self) -> ty::Binder<Ty<'tcx>> { + self.map_bound_ref(|sig| sig.resume_ty) + } + pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> { + self.map_bound_ref(|sig| sig.yield_ty) + } + pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> { + self.map_bound_ref(|sig| sig.return_ty) + } +} + +/// Signature of a function type, which we have arbitrarily +/// decided to use to refer to the input/output types. +/// +/// - `inputs`: is the list of arguments and their modes. +/// - `output`: is the return type. +/// - `c_variadic`: indicates whether this is a C-variadic function. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable)] +pub struct FnSig<'tcx> { + pub inputs_and_output: &'tcx List<Ty<'tcx>>, + pub c_variadic: bool, + pub unsafety: hir::Unsafety, + pub abi: abi::Abi, +} + +impl<'tcx> FnSig<'tcx> { + pub fn inputs(&self) -> &'tcx [Ty<'tcx>] { + &self.inputs_and_output[..self.inputs_and_output.len() - 1] + } + + pub fn output(&self) -> Ty<'tcx> { + self.inputs_and_output[self.inputs_and_output.len() - 1] + } + + // Creates a minimal `FnSig` to be used when encountering a `TyKind::Error` in a fallible + // method. + fn fake() -> FnSig<'tcx> { + FnSig { + inputs_and_output: List::empty(), + c_variadic: false, + unsafety: hir::Unsafety::Normal, + abi: abi::Abi::Rust, + } + } +} + +pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>; + +impl<'tcx> PolyFnSig<'tcx> { + #[inline] + pub fn inputs(&self) -> Binder<&'tcx [Ty<'tcx>]> { + self.map_bound_ref(|fn_sig| fn_sig.inputs()) + } + #[inline] + pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> { + self.map_bound_ref(|fn_sig| fn_sig.inputs()[index]) + } + pub fn inputs_and_output(&self) -> ty::Binder<&'tcx List<Ty<'tcx>>> { + self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output) + } + #[inline] + pub fn output(&self) -> ty::Binder<Ty<'tcx>> { + self.map_bound_ref(|fn_sig| fn_sig.output()) + } + pub fn c_variadic(&self) -> bool { + self.skip_binder().c_variadic + } + pub fn unsafety(&self) -> hir::Unsafety { + self.skip_binder().unsafety + } + pub fn abi(&self) -> abi::Abi { + self.skip_binder().abi + } +} + +pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>; + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable)] +pub struct ParamTy { + pub index: u32, + pub name: Symbol, +} + +impl<'tcx> ParamTy { + pub fn new(index: u32, name: Symbol) -> ParamTy { + ParamTy { index, name } + } + + pub fn for_self() -> ParamTy { + ParamTy::new(0, kw::SelfUpper) + } + + pub fn for_def(def: &ty::GenericParamDef) -> ParamTy { + ParamTy::new(def.index, def.name) + } + + pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + tcx.mk_ty_param(self.index, self.name) + } +} + +#[derive(Copy, Clone, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)] +#[derive(HashStable)] +pub struct ParamConst { + pub index: u32, + pub name: Symbol, +} + +impl<'tcx> ParamConst { + pub fn new(index: u32, name: Symbol) -> ParamConst { + ParamConst { index, name } + } + + pub fn for_def(def: &ty::GenericParamDef) -> ParamConst { + ParamConst::new(def.index, def.name) + } + + pub fn to_const(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> { + tcx.mk_const_param(self.index, self.name, ty) + } +} + +rustc_index::newtype_index! { + /// A [De Bruijn index][dbi] is a standard means of representing + /// regions (and perhaps later types) in a higher-ranked setting. In + /// particular, imagine a type like this: + /// + /// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char) + /// ^ ^ | | | + /// | | | | | + /// | +------------+ 0 | | + /// | | | + /// +--------------------------------+ 1 | + /// | | + /// +------------------------------------------+ 0 + /// + /// In this type, there are two binders (the outer fn and the inner + /// fn). We need to be able to determine, for any given region, which + /// fn type it is bound by, the inner or the outer one. There are + /// various ways you can do this, but a De Bruijn index is one of the + /// more convenient and has some nice properties. The basic idea is to + /// count the number of binders, inside out. Some examples should help + /// clarify what I mean. + /// + /// Let's start with the reference type `&'b isize` that is the first + /// argument to the inner function. This region `'b` is assigned a De + /// Bruijn index of 0, meaning "the innermost binder" (in this case, a + /// fn). The region `'a` that appears in the second argument type (`&'a + /// isize`) would then be assigned a De Bruijn index of 1, meaning "the + /// second-innermost binder". (These indices are written on the arrays + /// in the diagram). + /// + /// What is interesting is that De Bruijn index attached to a particular + /// variable will vary depending on where it appears. For example, + /// the final type `&'a char` also refers to the region `'a` declared on + /// the outermost fn. But this time, this reference is not nested within + /// any other binders (i.e., it is not an argument to the inner fn, but + /// rather the outer one). Therefore, in this case, it is assigned a + /// De Bruijn index of 0, because the innermost binder in that location + /// is the outer fn. + /// + /// [dbi]: https://en.wikipedia.org/wiki/De_Bruijn_index + #[derive(HashStable)] + pub struct DebruijnIndex { + DEBUG_FORMAT = "DebruijnIndex({})", + const INNERMOST = 0, + } +} + +pub type Region<'tcx> = &'tcx RegionKind; + +/// Representation of regions. Note that the NLL checker uses a distinct +/// representation of regions. For this reason, it internally replaces all the +/// regions with inference variables -- the index of the variable is then used +/// to index into internal NLL data structures. See `rustc_mir::borrow_check` +/// module for more information. +/// +/// ## The Region lattice within a given function +/// +/// In general, the region lattice looks like +/// +/// ``` +/// static ----------+-----...------+ (greatest) +/// | | | +/// early-bound and | | +/// free regions | | +/// | | | +/// | | | +/// empty(root) placeholder(U1) | +/// | / | +/// | / placeholder(Un) +/// empty(U1) -- / +/// | / +/// ... / +/// | / +/// empty(Un) -------- (smallest) +/// ``` +/// +/// Early-bound/free regions are the named lifetimes in scope from the +/// function declaration. They have relationships to one another +/// determined based on the declared relationships from the +/// function. +/// +/// Note that inference variables and bound regions are not included +/// in this diagram. In the case of inference variables, they should +/// be inferred to some other region from the diagram. In the case of +/// bound regions, they are excluded because they don't make sense to +/// include -- the diagram indicates the relationship between free +/// regions. +/// +/// ## Inference variables +/// +/// During region inference, we sometimes create inference variables, +/// represented as `ReVar`. These will be inferred by the code in +/// `infer::lexical_region_resolve` to some free region from the +/// lattice above (the minimal region that meets the +/// constraints). +/// +/// During NLL checking, where regions are defined differently, we +/// also use `ReVar` -- in that case, the index is used to index into +/// the NLL region checker's data structures. The variable may in fact +/// represent either a free region or an inference variable, in that +/// case. +/// +/// ## Bound Regions +/// +/// These are regions that are stored behind a binder and must be substituted +/// with some concrete region before being used. There are two kind of +/// bound regions: early-bound, which are bound in an item's `Generics`, +/// and are substituted by a `InternalSubsts`, and late-bound, which are part of +/// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by +/// the likes of `liberate_late_bound_regions`. The distinction exists +/// because higher-ranked lifetimes aren't supported in all places. See [1][2]. +/// +/// Unlike `Param`s, bound regions are not supposed to exist "in the wild" +/// outside their binder, e.g., in types passed to type inference, and +/// should first be substituted (by placeholder regions, free regions, +/// or region variables). +/// +/// ## Placeholder and Free Regions +/// +/// One often wants to work with bound regions without knowing their precise +/// identity. For example, when checking a function, the lifetime of a borrow +/// can end up being assigned to some region parameter. In these cases, +/// it must be ensured that bounds on the region can't be accidentally +/// assumed without being checked. +/// +/// To do this, we replace the bound regions with placeholder markers, +/// which don't satisfy any relation not explicitly provided. +/// +/// There are two kinds of placeholder regions in rustc: `ReFree` and +/// `RePlaceholder`. When checking an item's body, `ReFree` is supposed +/// to be used. These also support explicit bounds: both the internally-stored +/// *scope*, which the region is assumed to outlive, as well as other +/// relations stored in the `FreeRegionMap`. Note that these relations +/// aren't checked when you `make_subregion` (or `eq_types`), only by +/// `resolve_regions_and_report_errors`. +/// +/// When working with higher-ranked types, some region relations aren't +/// yet known, so you can't just call `resolve_regions_and_report_errors`. +/// `RePlaceholder` is designed for this purpose. In these contexts, +/// there's also the risk that some inference variable laying around will +/// get unified with your placeholder region: if you want to check whether +/// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a` +/// with a placeholder region `'%a`, the variable `'_` would just be +/// instantiated to the placeholder region `'%a`, which is wrong because +/// the inference variable is supposed to satisfy the relation +/// *for every value of the placeholder region*. To ensure that doesn't +/// happen, you can use `leak_check`. This is more clearly explained +/// by the [rustc dev guide]. +/// +/// [1]: http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/ +/// [2]: http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/ +/// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html +#[derive(Clone, PartialEq, Eq, Hash, Copy, TyEncodable, TyDecodable, PartialOrd, Ord)] +pub enum RegionKind { + /// Region bound in a type or fn declaration which will be + /// substituted 'early' -- that is, at the same time when type + /// parameters are substituted. + ReEarlyBound(EarlyBoundRegion), + + /// Region bound in a function scope, which will be substituted when the + /// function is called. + ReLateBound(DebruijnIndex, BoundRegion), + + /// When checking a function body, the types of all arguments and so forth + /// that refer to bound region parameters are modified to refer to free + /// region parameters. + ReFree(FreeRegion), + + /// Static data that has an "infinite" lifetime. Top in the region lattice. + ReStatic, + + /// A region variable. Should not exist after typeck. + ReVar(RegionVid), + + /// A placeholder region -- basically, the higher-ranked version of `ReFree`. + /// Should not exist after typeck. + RePlaceholder(ty::PlaceholderRegion), + + /// Empty lifetime is for data that is never accessed. We tag the + /// empty lifetime with a universe -- the idea is that we don't + /// want `exists<'a> { forall<'b> { 'b: 'a } }` to be satisfiable. + /// Therefore, the `'empty` in a universe `U` is less than all + /// regions visible from `U`, but not less than regions not visible + /// from `U`. + ReEmpty(ty::UniverseIndex), + + /// Erased region, used by trait selection, in MIR and during codegen. + ReErased, +} + +#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)] +pub struct EarlyBoundRegion { + pub def_id: DefId, + pub index: u32, + pub name: Symbol, +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +pub struct TyVid { + pub index: u32, +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +pub struct ConstVid<'tcx> { + pub index: u32, + pub phantom: PhantomData<&'tcx ()>, +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +pub struct IntVid { + pub index: u32, +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +pub struct FloatVid { + pub index: u32, +} + +rustc_index::newtype_index! { + pub struct RegionVid { + DEBUG_FORMAT = custom, + } +} + +impl Atom for RegionVid { + fn index(self) -> usize { + Idx::index(self) + } +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable)] +pub enum InferTy { + TyVar(TyVid), + IntVar(IntVid), + FloatVar(FloatVid), + + /// A `FreshTy` is one that is generated as a replacement for an + /// unbound type variable. This is convenient for caching etc. See + /// `infer::freshen` for more details. + FreshTy(u32), + FreshIntTy(u32), + FreshFloatTy(u32), +} + +rustc_index::newtype_index! { + pub struct BoundVar { .. } +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable)] +pub struct BoundTy { + pub var: BoundVar, + pub kind: BoundTyKind, +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable)] +pub enum BoundTyKind { + Anon, + Param(Symbol), +} + +impl From<BoundVar> for BoundTy { + fn from(var: BoundVar) -> Self { + BoundTy { var, kind: BoundTyKind::Anon } + } +} + +/// A `ProjectionPredicate` for an `ExistentialTraitRef`. +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable)] +pub struct ExistentialProjection<'tcx> { + pub item_def_id: DefId, + pub substs: SubstsRef<'tcx>, + pub ty: Ty<'tcx>, +} + +pub type PolyExistentialProjection<'tcx> = Binder<ExistentialProjection<'tcx>>; + +impl<'tcx> ExistentialProjection<'tcx> { + /// Extracts the underlying existential trait reference from this projection. + /// For example, if this is a projection of `exists T. <T as Iterator>::Item == X`, + /// then this function would return a `exists T. T: Iterator` existential trait + /// reference. + pub fn trait_ref(&self, tcx: TyCtxt<'_>) -> ty::ExistentialTraitRef<'tcx> { + let def_id = tcx.associated_item(self.item_def_id).container.id(); + ty::ExistentialTraitRef { def_id, substs: self.substs } + } + + pub fn with_self_ty( + &self, + tcx: TyCtxt<'tcx>, + self_ty: Ty<'tcx>, + ) -> ty::ProjectionPredicate<'tcx> { + // otherwise the escaping regions would be captured by the binders + debug_assert!(!self_ty.has_escaping_bound_vars()); + + ty::ProjectionPredicate { + projection_ty: ty::ProjectionTy { + item_def_id: self.item_def_id, + substs: tcx.mk_substs_trait(self_ty, self.substs), + }, + ty: self.ty, + } + } +} + +impl<'tcx> PolyExistentialProjection<'tcx> { + pub fn with_self_ty( + &self, + tcx: TyCtxt<'tcx>, + self_ty: Ty<'tcx>, + ) -> ty::PolyProjectionPredicate<'tcx> { + self.map_bound(|p| p.with_self_ty(tcx, self_ty)) + } + + pub fn item_def_id(&self) -> DefId { + self.skip_binder().item_def_id + } +} + +impl DebruijnIndex { + /// Returns the resulting index when this value is moved into + /// `amount` number of new binders. So, e.g., if you had + /// + /// for<'a> fn(&'a x) + /// + /// and you wanted to change it to + /// + /// for<'a> fn(for<'b> fn(&'a x)) + /// + /// you would need to shift the index for `'a` into a new binder. + #[must_use] + pub fn shifted_in(self, amount: u32) -> DebruijnIndex { + DebruijnIndex::from_u32(self.as_u32() + amount) + } + + /// Update this index in place by shifting it "in" through + /// `amount` number of binders. + pub fn shift_in(&mut self, amount: u32) { + *self = self.shifted_in(amount); + } + + /// Returns the resulting index when this value is moved out from + /// `amount` number of new binders. + #[must_use] + pub fn shifted_out(self, amount: u32) -> DebruijnIndex { + DebruijnIndex::from_u32(self.as_u32() - amount) + } + + /// Update in place by shifting out from `amount` binders. + pub fn shift_out(&mut self, amount: u32) { + *self = self.shifted_out(amount); + } + + /// Adjusts any De Bruijn indices so as to make `to_binder` the + /// innermost binder. That is, if we have something bound at `to_binder`, + /// it will now be bound at INNERMOST. This is an appropriate thing to do + /// when moving a region out from inside binders: + /// + /// ``` + /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _) + /// // Binder: D3 D2 D1 ^^ + /// ``` + /// + /// Here, the region `'a` would have the De Bruijn index D3, + /// because it is the bound 3 binders out. However, if we wanted + /// to refer to that region `'a` in the second argument (the `_`), + /// those two binders would not be in scope. In that case, we + /// might invoke `shift_out_to_binder(D3)`. This would adjust the + /// De Bruijn index of `'a` to D1 (the innermost binder). + /// + /// If we invoke `shift_out_to_binder` and the region is in fact + /// bound by one of the binders we are shifting out of, that is an + /// error (and should fail an assertion failure). + pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self { + self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32()) + } +} + +/// Region utilities +impl RegionKind { + /// Is this region named by the user? + pub fn has_name(&self) -> bool { + match *self { + RegionKind::ReEarlyBound(ebr) => ebr.has_name(), + RegionKind::ReLateBound(_, br) => br.is_named(), + RegionKind::ReFree(fr) => fr.bound_region.is_named(), + RegionKind::ReStatic => true, + RegionKind::ReVar(..) => false, + RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(), + RegionKind::ReEmpty(_) => false, + RegionKind::ReErased => false, + } + } + + pub fn is_late_bound(&self) -> bool { + match *self { + ty::ReLateBound(..) => true, + _ => false, + } + } + + pub fn is_placeholder(&self) -> bool { + match *self { + ty::RePlaceholder(..) => true, + _ => false, + } + } + + pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool { + match *self { + ty::ReLateBound(debruijn, _) => debruijn >= index, + _ => false, + } + } + + /// Adjusts any De Bruijn indices so as to make `to_binder` the + /// innermost binder. That is, if we have something bound at `to_binder`, + /// it will now be bound at INNERMOST. This is an appropriate thing to do + /// when moving a region out from inside binders: + /// + /// ``` + /// for<'a> fn(for<'b> for<'c> fn(&'a u32), _) + /// // Binder: D3 D2 D1 ^^ + /// ``` + /// + /// Here, the region `'a` would have the De Bruijn index D3, + /// because it is the bound 3 binders out. However, if we wanted + /// to refer to that region `'a` in the second argument (the `_`), + /// those two binders would not be in scope. In that case, we + /// might invoke `shift_out_to_binder(D3)`. This would adjust the + /// De Bruijn index of `'a` to D1 (the innermost binder). + /// + /// If we invoke `shift_out_to_binder` and the region is in fact + /// bound by one of the binders we are shifting out of, that is an + /// error (and should fail an assertion failure). + pub fn shifted_out_to_binder(&self, to_binder: ty::DebruijnIndex) -> RegionKind { + match *self { + ty::ReLateBound(debruijn, r) => { + ty::ReLateBound(debruijn.shifted_out_to_binder(to_binder), r) + } + r => r, + } + } + + pub fn type_flags(&self) -> TypeFlags { + let mut flags = TypeFlags::empty(); + + match *self { + ty::ReVar(..) => { + flags = flags | TypeFlags::HAS_FREE_REGIONS; + flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS; + flags = flags | TypeFlags::HAS_RE_INFER; + } + ty::RePlaceholder(..) => { + flags = flags | TypeFlags::HAS_FREE_REGIONS; + flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS; + flags = flags | TypeFlags::HAS_RE_PLACEHOLDER; + } + ty::ReEarlyBound(..) => { + flags = flags | TypeFlags::HAS_FREE_REGIONS; + flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS; + flags = flags | TypeFlags::HAS_RE_PARAM; + } + ty::ReFree { .. } => { + flags = flags | TypeFlags::HAS_FREE_REGIONS; + flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS; + } + ty::ReEmpty(_) | ty::ReStatic => { + flags = flags | TypeFlags::HAS_FREE_REGIONS; + } + ty::ReLateBound(..) => { + flags = flags | TypeFlags::HAS_RE_LATE_BOUND; + } + ty::ReErased => { + flags = flags | TypeFlags::HAS_RE_ERASED; + } + } + + debug!("type_flags({:?}) = {:?}", self, flags); + + flags + } + + /// Given an early-bound or free region, returns the `DefId` where it was bound. + /// For example, consider the regions in this snippet of code: + /// + /// ``` + /// impl<'a> Foo { + /// ^^ -- early bound, declared on an impl + /// + /// fn bar<'b, 'c>(x: &self, y: &'b u32, z: &'c u64) where 'static: 'c + /// ^^ ^^ ^ anonymous, late-bound + /// | early-bound, appears in where-clauses + /// late-bound, appears only in fn args + /// {..} + /// } + /// ``` + /// + /// Here, `free_region_binding_scope('a)` would return the `DefId` + /// of the impl, and for all the other highlighted regions, it + /// would return the `DefId` of the function. In other cases (not shown), this + /// function might return the `DefId` of a closure. + pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_>) -> DefId { + match self { + ty::ReEarlyBound(br) => tcx.parent(br.def_id).unwrap(), + ty::ReFree(fr) => fr.scope, + _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self), + } + } +} + +/// Type utilities +impl<'tcx> TyS<'tcx> { + #[inline] + pub fn is_unit(&self) -> bool { + match self.kind { + Tuple(ref tys) => tys.is_empty(), + _ => false, + } + } + + #[inline] + pub fn is_never(&self) -> bool { + match self.kind { + Never => true, + _ => false, + } + } + + /// Checks whether a type is definitely uninhabited. This is + /// conservative: for some types that are uninhabited we return `false`, + /// but we only return `true` for types that are definitely uninhabited. + /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty` + /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero + /// size, to account for partial initialisation. See #49298 for details.) + pub fn conservative_is_privately_uninhabited(&self, tcx: TyCtxt<'tcx>) -> bool { + // FIXME(varkor): we can make this less conversative by substituting concrete + // type arguments. + match self.kind { + ty::Never => true, + ty::Adt(def, _) if def.is_union() => { + // For now, `union`s are never considered uninhabited. + false + } + ty::Adt(def, _) => { + // Any ADT is uninhabited if either: + // (a) It has no variants (i.e. an empty `enum`); + // (b) Each of its variants (a single one in the case of a `struct`) has at least + // one uninhabited field. + def.variants.iter().all(|var| { + var.fields.iter().any(|field| { + tcx.type_of(field.did).conservative_is_privately_uninhabited(tcx) + }) + }) + } + ty::Tuple(..) => { + self.tuple_fields().any(|ty| ty.conservative_is_privately_uninhabited(tcx)) + } + ty::Array(ty, len) => { + match len.try_eval_usize(tcx, ParamEnv::empty()) { + // If the array is definitely non-empty, it's uninhabited if + // the type of its elements is uninhabited. + Some(n) if n != 0 => ty.conservative_is_privately_uninhabited(tcx), + _ => false, + } + } + ty::Ref(..) => { + // References to uninitialised memory is valid for any type, including + // uninhabited types, in unsafe code, so we treat all references as + // inhabited. + false + } + _ => false, + } + } + + #[inline] + pub fn is_primitive(&self) -> bool { + self.kind.is_primitive() + } + + #[inline] + pub fn is_ty_var(&self) -> bool { + match self.kind { + Infer(TyVar(_)) => true, + _ => false, + } + } + + #[inline] + pub fn is_ty_infer(&self) -> bool { + match self.kind { + Infer(_) => true, + _ => false, + } + } + + #[inline] + pub fn is_phantom_data(&self) -> bool { + if let Adt(def, _) = self.kind { def.is_phantom_data() } else { false } + } + + #[inline] + pub fn is_bool(&self) -> bool { + self.kind == Bool + } + + /// Returns `true` if this type is a `str`. + #[inline] + pub fn is_str(&self) -> bool { + self.kind == Str + } + + #[inline] + pub fn is_param(&self, index: u32) -> bool { + match self.kind { + ty::Param(ref data) => data.index == index, + _ => false, + } + } + + #[inline] + pub fn is_slice(&self) -> bool { + match self.kind { + RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => match ty.kind { + Slice(_) | Str => true, + _ => false, + }, + _ => false, + } + } + + #[inline] + pub fn is_simd(&self) -> bool { + match self.kind { + Adt(def, _) => def.repr.simd(), + _ => false, + } + } + + pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + match self.kind { + Array(ty, _) | Slice(ty) => ty, + Str => tcx.mk_mach_uint(ast::UintTy::U8), + _ => bug!("`sequence_element_type` called on non-sequence value: {}", self), + } + } + + pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + match self.kind { + Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs), + _ => bug!("`simd_type` called on invalid type"), + } + } + + pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 { + // Parameter currently unused, but probably needed in the future to + // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`. + match self.kind { + Adt(def, _) => def.non_enum_variant().fields.len() as u64, + _ => bug!("`simd_size` called on invalid type"), + } + } + + pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) { + match self.kind { + Adt(def, substs) => { + let variant = def.non_enum_variant(); + (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs)) + } + _ => bug!("`simd_size_and_type` called on invalid type"), + } + } + + #[inline] + pub fn is_region_ptr(&self) -> bool { + match self.kind { + Ref(..) => true, + _ => false, + } + } + + #[inline] + pub fn is_mutable_ptr(&self) -> bool { + match self.kind { + RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. }) + | Ref(_, _, hir::Mutability::Mut) => true, + _ => false, + } + } + + #[inline] + pub fn is_unsafe_ptr(&self) -> bool { + match self.kind { + RawPtr(_) => true, + _ => false, + } + } + + /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer). + #[inline] + pub fn is_any_ptr(&self) -> bool { + self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr() + } + + #[inline] + pub fn is_box(&self) -> bool { + match self.kind { + Adt(def, _) => def.is_box(), + _ => false, + } + } + + /// Panics if called on any type other than `Box<T>`. + pub fn boxed_ty(&self) -> Ty<'tcx> { + match self.kind { + Adt(def, substs) if def.is_box() => substs.type_at(0), + _ => bug!("`boxed_ty` is called on non-box type {:?}", self), + } + } + + /// A scalar type is one that denotes an atomic datum, with no sub-components. + /// (A RawPtr is scalar because it represents a non-managed pointer, so its + /// contents are abstract to rustc.) + #[inline] + pub fn is_scalar(&self) -> bool { + match self.kind { + Bool + | Char + | Int(_) + | Float(_) + | Uint(_) + | Infer(IntVar(_) | FloatVar(_)) + | FnDef(..) + | FnPtr(_) + | RawPtr(_) => true, + _ => false, + } + } + + /// Returns `true` if this type is a floating point type. + #[inline] + pub fn is_floating_point(&self) -> bool { + match self.kind { + Float(_) | Infer(FloatVar(_)) => true, + _ => false, + } + } + + #[inline] + pub fn is_trait(&self) -> bool { + match self.kind { + Dynamic(..) => true, + _ => false, + } + } + + #[inline] + pub fn is_enum(&self) -> bool { + match self.kind { + Adt(adt_def, _) => adt_def.is_enum(), + _ => false, + } + } + + #[inline] + pub fn is_closure(&self) -> bool { + match self.kind { + Closure(..) => true, + _ => false, + } + } + + #[inline] + pub fn is_generator(&self) -> bool { + match self.kind { + Generator(..) => true, + _ => false, + } + } + + #[inline] + pub fn is_integral(&self) -> bool { + match self.kind { + Infer(IntVar(_)) | Int(_) | Uint(_) => true, + _ => false, + } + } + + #[inline] + pub fn is_fresh_ty(&self) -> bool { + match self.kind { + Infer(FreshTy(_)) => true, + _ => false, + } + } + + #[inline] + pub fn is_fresh(&self) -> bool { + match self.kind { + Infer(FreshTy(_)) => true, + Infer(FreshIntTy(_)) => true, + Infer(FreshFloatTy(_)) => true, + _ => false, + } + } + + #[inline] + pub fn is_char(&self) -> bool { + match self.kind { + Char => true, + _ => false, + } + } + + #[inline] + pub fn is_numeric(&self) -> bool { + self.is_integral() || self.is_floating_point() + } + + #[inline] + pub fn is_signed(&self) -> bool { + match self.kind { + Int(_) => true, + _ => false, + } + } + + #[inline] + pub fn is_ptr_sized_integral(&self) -> bool { + match self.kind { + Int(ast::IntTy::Isize) | Uint(ast::UintTy::Usize) => true, + _ => false, + } + } + + #[inline] + pub fn is_machine(&self) -> bool { + match self.kind { + Int(..) | Uint(..) | Float(..) => true, + _ => false, + } + } + + #[inline] + pub fn has_concrete_skeleton(&self) -> bool { + match self.kind { + Param(_) | Infer(_) | Error(_) => false, + _ => true, + } + } + + /// Returns the type and mutability of `*ty`. + /// + /// The parameter `explicit` indicates if this is an *explicit* dereference. + /// Some types -- notably unsafe ptrs -- can only be dereferenced explicitly. + pub fn builtin_deref(&self, explicit: bool) -> Option<TypeAndMut<'tcx>> { + match self.kind { + Adt(def, _) if def.is_box() => { + Some(TypeAndMut { ty: self.boxed_ty(), mutbl: hir::Mutability::Not }) + } + Ref(_, ty, mutbl) => Some(TypeAndMut { ty, mutbl }), + RawPtr(mt) if explicit => Some(mt), + _ => None, + } + } + + /// Returns the type of `ty[i]`. + pub fn builtin_index(&self) -> Option<Ty<'tcx>> { + match self.kind { + Array(ty, _) | Slice(ty) => Some(ty), + _ => None, + } + } + + pub fn fn_sig(&self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> { + match self.kind { + FnDef(def_id, substs) => tcx.fn_sig(def_id).subst(tcx, substs), + FnPtr(f) => f, + Error(_) => { + // ignore errors (#54954) + ty::Binder::dummy(FnSig::fake()) + } + Closure(..) => bug!( + "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`", + ), + _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self), + } + } + + #[inline] + pub fn is_fn(&self) -> bool { + match self.kind { + FnDef(..) | FnPtr(_) => true, + _ => false, + } + } + + #[inline] + pub fn is_fn_ptr(&self) -> bool { + match self.kind { + FnPtr(_) => true, + _ => false, + } + } + + #[inline] + pub fn is_impl_trait(&self) -> bool { + match self.kind { + Opaque(..) => true, + _ => false, + } + } + + #[inline] + pub fn ty_adt_def(&self) -> Option<&'tcx AdtDef> { + match self.kind { + Adt(adt, _) => Some(adt), + _ => None, + } + } + + /// Iterates over tuple fields. + /// Panics when called on anything but a tuple. + pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> { + match self.kind { + Tuple(substs) => substs.iter().map(|field| field.expect_ty()), + _ => bug!("tuple_fields called on non-tuple"), + } + } + + /// If the type contains variants, returns the valid range of variant indices. + // + // FIXME: This requires the optimized MIR in the case of generators. + #[inline] + pub fn variant_range(&self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> { + match self.kind { + TyKind::Adt(adt, _) => Some(adt.variant_range()), + TyKind::Generator(def_id, substs, _) => { + Some(substs.as_generator().variant_range(def_id, tcx)) + } + _ => None, + } + } + + /// If the type contains variants, returns the variant for `variant_index`. + /// Panics if `variant_index` is out of range. + // + // FIXME: This requires the optimized MIR in the case of generators. + #[inline] + pub fn discriminant_for_variant( + &self, + tcx: TyCtxt<'tcx>, + variant_index: VariantIdx, + ) -> Option<Discr<'tcx>> { + match self.kind { + TyKind::Adt(adt, _) if adt.variants.is_empty() => { + bug!("discriminant_for_variant called on zero variant enum"); + } + TyKind::Adt(adt, _) if adt.is_enum() => { + Some(adt.discriminant_for_variant(tcx, variant_index)) + } + TyKind::Generator(def_id, substs, _) => { + Some(substs.as_generator().discriminant_for_variant(def_id, tcx, variant_index)) + } + _ => None, + } + } + + /// Returns the type of the discriminant of this type. + pub fn discriminant_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { + match self.kind { + ty::Adt(adt, _) if adt.is_enum() => adt.repr.discr_type().to_ty(tcx), + ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx), + _ => { + // This can only be `0`, for now, so `u8` will suffice. + tcx.types.u8 + } + } + } + + /// When we create a closure, we record its kind (i.e., what trait + /// it implements) into its `ClosureSubsts` using a type + /// parameter. This is kind of a phantom type, except that the + /// most convenient thing for us to are the integral types. This + /// function converts such a special type into the closure + /// kind. To go the other way, use + /// `tcx.closure_kind_ty(closure_kind)`. + /// + /// Note that during type checking, we use an inference variable + /// to represent the closure kind, because it has not yet been + /// inferred. Once upvar inference (in `src/librustc_typeck/check/upvar.rs`) + /// is complete, that type variable will be unified. + pub fn to_opt_closure_kind(&self) -> Option<ty::ClosureKind> { + match self.kind { + Int(int_ty) => match int_ty { + ast::IntTy::I8 => Some(ty::ClosureKind::Fn), + ast::IntTy::I16 => Some(ty::ClosureKind::FnMut), + ast::IntTy::I32 => Some(ty::ClosureKind::FnOnce), + _ => bug!("cannot convert type `{:?}` to a closure kind", self), + }, + + // "Bound" types appear in canonical queries when the + // closure type is not yet known + Bound(..) | Infer(_) => None, + + Error(_) => Some(ty::ClosureKind::Fn), + + _ => bug!("cannot convert type `{:?}` to a closure kind", self), + } + } + + /// Fast path helper for testing if a type is `Sized`. + /// + /// Returning true means the type is known to be sized. Returning + /// `false` means nothing -- could be sized, might not be. + pub fn is_trivially_sized(&self, tcx: TyCtxt<'tcx>) -> bool { + match self.kind { + ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) + | ty::Uint(_) + | ty::Int(_) + | ty::Bool + | ty::Float(_) + | ty::FnDef(..) + | ty::FnPtr(_) + | ty::RawPtr(..) + | ty::Char + | ty::Ref(..) + | ty::Generator(..) + | ty::GeneratorWitness(..) + | ty::Array(..) + | ty::Closure(..) + | ty::Never + | ty::Error(_) => true, + + ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false, + + ty::Tuple(tys) => tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx)), + + ty::Adt(def, _substs) => def.sized_constraint(tcx).is_empty(), + + ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => false, + + ty::Infer(ty::TyVar(_)) => false, + + ty::Bound(..) + | ty::Placeholder(..) + | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { + bug!("`is_trivially_sized` applied to unexpected type: {:?}", self) + } + } + } + + /// Is this a zero-sized type? + pub fn is_zst(&'tcx self, tcx: TyCtxt<'tcx>, did: DefId) -> bool { + tcx.layout_of(tcx.param_env(did).and(self)).map(|layout| layout.is_zst()).unwrap_or(false) + } +} |