+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This module contains TypeVariants and its major components
+
+use middle::def_id::DefId;
+use middle::region;
+use middle::subst::{self, Substs};
+use middle::traits;
+use middle::ty::{self, AdtDef, TypeFlags, Ty, TyS};
+use middle::ty::{RegionEscape, ToPredicate};
+use util::common::ErrorReported;
+
+use collections::enum_set::{self, EnumSet, CLike};
+use std::fmt;
+use std::ops;
+use std::mem;
+use syntax::abi;
+use syntax::ast::{Name, NodeId};
+
+use rustc_front::hir;
+
+use self::FnOutput::*;
+use self::InferTy::*;
+use self::TypeVariants::*;
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub struct TypeAndMut<'tcx> {
+ pub ty: Ty<'tcx>,
+ pub mutbl: hir::Mutability,
+}
+
+#[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash,
+ RustcEncodable, RustcDecodable, Copy)]
+/// A "free" region `fr` can be interpreted as "some region
+/// at least as big as the scope `fr.scope`".
+pub struct FreeRegion {
+ pub scope: region::CodeExtent,
+ pub bound_region: BoundRegion
+}
+
+#[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash,
+ RustcEncodable, RustcDecodable, Copy)]
+pub enum BoundRegion {
+ /// An anonymous region parameter for a given fn (&T)
+ BrAnon(u32),
+
+ /// Named region parameters for functions (a in &'a T)
+ ///
+ /// The def-id is needed to distinguish free regions in
+ /// the event of shadowing.
+ BrNamed(DefId, Name),
+
+ /// Fresh bound identifiers created during GLB computations.
+ BrFresh(u32),
+
+ // Anonymous region for the implicit env pointer parameter
+ // to a closure
+ BrEnv
+}
+
+// NB: If you change this, you'll probably want to change the corresponding
+// AST structure in libsyntax/ast.rs as well.
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum TypeVariants<'tcx> {
+ /// The primitive boolean type. Written as `bool`.
+ TyBool,
+
+ /// The primitive character type; holds a Unicode scalar value
+ /// (a non-surrogate code point). Written as `char`.
+ TyChar,
+
+ /// A primitive signed integer type. For example, `i32`.
+ TyInt(hir::IntTy),
+
+ /// A primitive unsigned integer type. For example, `u32`.
+ TyUint(hir::UintTy),
+
+ /// A primitive floating-point type. For example, `f64`.
+ TyFloat(hir::FloatTy),
+
+ /// An enumerated type, defined with `enum`.
+ ///
+ /// Substs here, possibly against intuition, *may* contain `TyParam`s.
+ /// That is, even after substitution it is possible that there are type
+ /// variables. This happens when the `TyEnum` corresponds to an enum
+ /// definition and not a concrete use of it. To get the correct `TyEnum`
+ /// from the tcx, use the `NodeId` from the `hir::Ty` and look it up in
+ /// the `ast_ty_to_ty_cache`. This is probably true for `TyStruct` as
+ /// well.
+ TyEnum(AdtDef<'tcx>, &'tcx Substs<'tcx>),
+
+ /// A structure type, defined with `struct`.
+ ///
+ /// See warning about substitutions for enumerated types.
+ TyStruct(AdtDef<'tcx>, &'tcx Substs<'tcx>),
+
+ /// `Box<T>`; this is nominally a struct in the documentation, but is
+ /// special-cased internally. For example, it is possible to implicitly
+ /// move the contents of a box out of that box, and methods of any type
+ /// can have type `Box<Self>`.
+ TyBox(Ty<'tcx>),
+
+ /// The pointee of a string slice. Written as `str`.
+ TyStr,
+
+ /// An array with the given length. Written as `[T; n]`.
+ TyArray(Ty<'tcx>, usize),
+
+ /// The pointee of an array slice. Written as `[T]`.
+ TySlice(Ty<'tcx>),
+
+ /// A raw pointer. Written as `*mut T` or `*const T`
+ TyRawPtr(TypeAndMut<'tcx>),
+
+ /// A reference; a pointer with an associated lifetime. Written as
+ /// `&a mut T` or `&'a T`.
+ TyRef(&'tcx Region, TypeAndMut<'tcx>),
+
+ /// If the def-id is Some(_), then this is the type of a specific
+ /// fn item. Otherwise, if None(_), it a fn pointer type.
+ ///
+ /// FIXME: Conflating function pointers and the type of a
+ /// function is probably a terrible idea; a function pointer is a
+ /// value with a specific type, but a function can be polymorphic
+ /// or dynamically dispatched.
+ TyBareFn(Option<DefId>, &'tcx BareFnTy<'tcx>),
+
+ /// A trait, defined with `trait`.
+ TyTrait(Box<TraitTy<'tcx>>),
+
+ /// The anonymous type of a closure. Used to represent the type of
+ /// `|a| a`.
+ TyClosure(DefId, Box<ClosureSubsts<'tcx>>),
+
+ /// A tuple type. For example, `(i32, bool)`.
+ TyTuple(Vec<Ty<'tcx>>),
+
+ /// The projection of an associated type. For example,
+ /// `<T as Trait<..>>::N`.
+ TyProjection(ProjectionTy<'tcx>),
+
+ /// A type parameter; for example, `T` in `fn f<T>(x: T) {}
+ TyParam(ParamTy),
+
+ /// A type variable used during type-checking.
+ TyInfer(InferTy),
+
+ /// A placeholder for a type which could not be computed; this is
+ /// propagated to avoid useless error messages.
+ TyError,
+}
+
+/// A closure can be modeled as a struct that looks like:
+///
+/// struct Closure<'l0...'li, T0...Tj, U0...Uk> {
+/// upvar0: U0,
+/// ...
+/// upvark: Uk
+/// }
+///
+/// where 'l0...'li and T0...Tj are the lifetime and type parameters
+/// in scope on the function that defined the closure, and U0...Uk are
+/// type parameters representing the types of its upvars (borrowed, if
+/// appropriate).
+///
+/// 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, U0> {
+/// data: U0
+/// }
+///
+/// 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
+/// as extra type parameters? 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 extent of the closure itself; this is some
+/// subset of `foo`, probably just the extent 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 trans 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
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct ClosureSubsts<'tcx> {
+ /// Lifetime and type parameters from the enclosing function.
+ /// These are separated out because trans wants to pass them around
+ /// when monomorphizing.
+ pub func_substs: &'tcx Substs<'tcx>,
+
+ /// The types of the upvars. The list parallels the freevars and
+ /// `upvar_borrows` lists. These are kept distinct so that we can
+ /// easily index into them.
+ pub upvar_tys: Vec<Ty<'tcx>>
+}
+
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct TraitTy<'tcx> {
+ pub principal: ty::PolyTraitRef<'tcx>,
+ pub bounds: ExistentialBounds<'tcx>,
+}
+
+impl<'tcx> TraitTy<'tcx> {
+ pub fn principal_def_id(&self) -> DefId {
+ self.principal.0.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 skolemized type.
+ pub fn principal_trait_ref_with_self_ty(&self,
+ tcx: &ty::ctxt<'tcx>,
+ self_ty: Ty<'tcx>)
+ -> ty::PolyTraitRef<'tcx>
+ {
+ // otherwise the escaping regions would be captured by the binder
+ assert!(!self_ty.has_escaping_regions());
+
+ ty::Binder(TraitRef {
+ def_id: self.principal.0.def_id,
+ substs: tcx.mk_substs(self.principal.0.substs.with_self_ty(self_ty)),
+ })
+ }
+
+ pub fn projection_bounds_with_self_ty(&self,
+ tcx: &ty::ctxt<'tcx>,
+ self_ty: Ty<'tcx>)
+ -> Vec<ty::PolyProjectionPredicate<'tcx>>
+ {
+ // otherwise the escaping regions would be captured by the binders
+ assert!(!self_ty.has_escaping_regions());
+
+ self.bounds.projection_bounds.iter()
+ .map(|in_poly_projection_predicate| {
+ let in_projection_ty = &in_poly_projection_predicate.0.projection_ty;
+ let substs = tcx.mk_substs(in_projection_ty.trait_ref.substs.with_self_ty(self_ty));
+ let trait_ref = ty::TraitRef::new(in_projection_ty.trait_ref.def_id,
+ substs);
+ let projection_ty = ty::ProjectionTy {
+ trait_ref: trait_ref,
+ item_name: in_projection_ty.item_name
+ };
+ ty::Binder(ty::ProjectionPredicate {
+ projection_ty: projection_ty,
+ ty: in_poly_projection_predicate.0.ty
+ })
+ })
+ .collect()
+ }
+}
+
+/// 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 def-id is the
+/// def-id for the trait `Foo` and the substs defines `T` as parameter 0 in the
+/// `SelfSpace` and `U` as parameter 0 in the `TypeSpace`.
+///
+/// Trait references also appear in object types like `Foo<U>`, but in
+/// that case the `Self` parameter is absent from the substitutions.
+///
+/// Note that a `TraitRef` introduces a level of region binding, to
+/// account for higher-ranked trait bounds like `T : for<'a> Foo<&'a
+/// U>` or higher-ranked object types.
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TraitRef<'tcx> {
+ pub def_id: DefId,
+ pub substs: &'tcx Substs<'tcx>,
+}
+
+pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
+
+impl<'tcx> PolyTraitRef<'tcx> {
+ pub fn self_ty(&self) -> Ty<'tcx> {
+ self.0.self_ty()
+ }
+
+ pub fn def_id(&self) -> DefId {
+ self.0.def_id
+ }
+
+ pub fn substs(&self) -> &'tcx Substs<'tcx> {
+ // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
+ self.0.substs
+ }
+
+ pub fn input_types(&self) -> &[Ty<'tcx>] {
+ // FIXME(#20664) every use of this fn is probably a bug, it should yield Binder<>
+ self.0.input_types()
+ }
+
+ pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
+ // Note that we preserve binding levels
+ Binder(ty::TraitPredicate { trait_ref: self.0.clone() })
+ }
+}
+
+/// Binder is a binder for higher-ranked lifetimes. 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 skolemize, instantiate,
+/// erase, or otherwise "discharge" these bound regions, we change the
+/// type from `Binder<T>` to just `T` (see
+/// e.g. `liberate_late_bound_regions`).
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct Binder<T>(pub T);
+
+impl<T> Binder<T> {
+ /// Skips the binder and returns the "bound" value. This is a
+ /// risky thing to do because it's easy to get confused about
+ /// debruijn indices and the like. It is usually better to
+ /// discharge the binder using `no_late_bound_regions` 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 regions, 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 def-id 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> {
+ ty::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
+ {
+ ty::Binder(f(self.0))
+ }
+}
+
+impl fmt::Debug for TypeFlags {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "{}", self.bits)
+ }
+}
+
+/// Represents the projection of an associated type. In explicit UFCS
+/// form this would be written `<T as Trait<..>>::N`.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct ProjectionTy<'tcx> {
+ /// The trait reference `T as Trait<..>`.
+ pub trait_ref: ty::TraitRef<'tcx>,
+
+ /// The name `N` of the associated type.
+ pub item_name: Name,
+}
+
+impl<'tcx> ProjectionTy<'tcx> {
+ pub fn sort_key(&self) -> (DefId, Name) {
+ (self.trait_ref.def_id, self.item_name)
+ }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct BareFnTy<'tcx> {
+ pub unsafety: hir::Unsafety,
+ pub abi: abi::Abi,
+ pub sig: PolyFnSig<'tcx>,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct ClosureTy<'tcx> {
+ pub unsafety: hir::Unsafety,
+ pub abi: abi::Abi,
+ pub sig: PolyFnSig<'tcx>,
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub enum FnOutput<'tcx> {
+ FnConverging(Ty<'tcx>),
+ FnDiverging
+}
+
+impl<'tcx> FnOutput<'tcx> {
+ pub fn diverges(&self) -> bool {
+ *self == FnDiverging
+ }
+
+ pub fn unwrap(self) -> Ty<'tcx> {
+ match self {
+ ty::FnConverging(t) => t,
+ ty::FnDiverging => unreachable!()
+ }
+ }
+
+ pub fn unwrap_or(self, def: Ty<'tcx>) -> Ty<'tcx> {
+ match self {
+ ty::FnConverging(t) => t,
+ ty::FnDiverging => def
+ }
+ }
+}
+
+pub type PolyFnOutput<'tcx> = Binder<FnOutput<'tcx>>;
+
+impl<'tcx> PolyFnOutput<'tcx> {
+ pub fn diverges(&self) -> bool {
+ self.0.diverges()
+ }
+}
+
+/// Signature of a function type, which I 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.
+/// - `variadic` indicates whether this is a variadic function. (only true for foreign fns)
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct FnSig<'tcx> {
+ pub inputs: Vec<Ty<'tcx>>,
+ pub output: FnOutput<'tcx>,
+ pub variadic: bool
+}
+
+pub type PolyFnSig<'tcx> = Binder<FnSig<'tcx>>;
+
+impl<'tcx> PolyFnSig<'tcx> {
+ pub fn inputs(&self) -> ty::Binder<Vec<Ty<'tcx>>> {
+ self.map_bound_ref(|fn_sig| fn_sig.inputs.clone())
+ }
+ pub fn input(&self, index: usize) -> ty::Binder<Ty<'tcx>> {
+ self.map_bound_ref(|fn_sig| fn_sig.inputs[index])
+ }
+ pub fn output(&self) -> ty::Binder<FnOutput<'tcx>> {
+ self.map_bound_ref(|fn_sig| fn_sig.output.clone())
+ }
+ pub fn variadic(&self) -> bool {
+ self.skip_binder().variadic
+ }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ParamTy {
+ pub space: subst::ParamSpace,
+ pub idx: u32,
+ pub name: Name,
+}
+
+/// 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)
+/// ^ ^ | | |
+/// | | | | |
+/// | +------------+ 1 | |
+/// | | |
+/// +--------------------------------+ 2 |
+/// | |
+/// +------------------------------------------+ 1
+///
+/// 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 1, 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 2, 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 1, because the innermost binder in that location
+/// is the outer fn.
+///
+/// [dbi]: http://en.wikipedia.org/wiki/De_Bruijn_index
+#[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, Copy)]
+pub struct DebruijnIndex {
+ // We maintain the invariant that this is never 0. So 1 indicates
+ // the innermost binder. To ensure this, create with `DebruijnIndex::new`.
+ pub depth: u32,
+}
+
+/// Representation of regions.
+///
+/// Unlike types, most region variants are "fictitious", not concrete,
+/// regions. Among these, `ReStatic`, `ReEmpty` and `ReScope` are the only
+/// ones representing concrete regions.
+///
+/// ## Bound Regions
+///
+/// These are regions that are stored behind a binder and must be substituted
+/// with some concrete region before being used. There are 2 kind of
+/// bound regions: early-bound, which are bound in a TypeScheme/TraitDef,
+/// and are substituted by a Substs, 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 TyParam-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 skolemized regions, free regions,
+/// or region variables).
+///
+/// ## Skolemized 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.
+///
+/// The process of doing that is called "skolemization". The bound regions
+/// are replaced by skolemized markers, which don't satisfy any relation
+/// not explicity provided.
+///
+/// There are 2 kinds of skolemized regions in rustc: `ReFree` and
+/// `ReSkolemized`. 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 `mk_eqty`), 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`.
+/// `ReSkolemized` is designed for this purpose. In these contexts,
+/// there's also the risk that some inference variable laying around will
+/// get unified with your skolemized region: if you want to check whether
+/// `for<'a> Foo<'_>: 'a`, and you substitute your bound region `'a`
+/// with a skolemized region `'%a`, the variable `'_` would just be
+/// instantiated to the skolemized region `'%a`, which is wrong because
+/// the inference variable is supposed to satisfy the relation
+/// *for every value of the skolemized region*. To ensure that doesn't
+/// happen, you can use `leak_check`. This is more clearly explained
+/// by infer/higher_ranked/README.md.
+///
+/// [1] http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
+/// [2] http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
+#[derive(Clone, PartialEq, Eq, Hash, Copy)]
+pub enum Region {
+ // 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),
+
+ /// A concrete region naming some statically determined extent
+ /// (e.g. an expression or sequence of statements) within the
+ /// current function.
+ ReScope(region::CodeExtent),
+
+ /// Static data that has an "infinite" lifetime. Top in the region lattice.
+ ReStatic,
+
+ /// A region variable. Should not exist after typeck.
+ ReVar(RegionVid),
+
+ /// A skolemized region - basically the higher-ranked version of ReFree.
+ /// Should not exist after typeck.
+ ReSkolemized(SkolemizedRegionVid, BoundRegion),
+
+ /// Empty lifetime is for data that is never accessed.
+ /// Bottom in the region lattice. We treat ReEmpty somewhat
+ /// specially; at least right now, we do not generate instances of
+ /// it during the GLB computations, but rather
+ /// generate an error instead. This is to improve error messages.
+ /// The only way to get an instance of ReEmpty is to have a region
+ /// variable with no constraints.
+ ReEmpty,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
+pub struct EarlyBoundRegion {
+ pub param_id: NodeId,
+ pub space: subst::ParamSpace,
+ pub index: u32,
+ pub name: Name,
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct TyVid {
+ pub index: u32
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct IntVid {
+ pub index: u32
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct FloatVid {
+ pub index: u32
+}
+
+#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
+pub struct RegionVid {
+ pub index: u32
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub struct SkolemizedRegionVid {
+ pub index: u32
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+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
+ /// `middle::infer::freshen` for more details.
+ FreshTy(u32),
+ FreshIntTy(u32),
+ FreshFloatTy(u32)
+}
+
+/// Bounds suitable for an existentially quantified type parameter
+/// such as those that appear in object types or closure types.
+#[derive(PartialEq, Eq, Hash, Clone)]
+pub struct ExistentialBounds<'tcx> {
+ pub region_bound: ty::Region,
+ pub builtin_bounds: BuiltinBounds,
+ pub projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
+}
+
+impl<'tcx> ExistentialBounds<'tcx> {
+ pub fn new(region_bound: ty::Region,
+ builtin_bounds: BuiltinBounds,
+ projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>)
+ -> Self {
+ let mut projection_bounds = projection_bounds;
+ projection_bounds.sort_by(|a, b| a.sort_key().cmp(&b.sort_key()));
+ ExistentialBounds {
+ region_bound: region_bound,
+ builtin_bounds: builtin_bounds,
+ projection_bounds: projection_bounds
+ }
+ }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub struct BuiltinBounds(EnumSet<BuiltinBound>);
+
+impl BuiltinBounds {
+ pub fn empty() -> BuiltinBounds {
+ BuiltinBounds(EnumSet::new())
+ }
+
+ pub fn iter(&self) -> enum_set::Iter<BuiltinBound> {
+ self.into_iter()
+ }
+
+ pub fn to_predicates<'tcx>(&self,
+ tcx: &ty::ctxt<'tcx>,
+ self_ty: Ty<'tcx>) -> Vec<ty::Predicate<'tcx>> {
+ self.iter().filter_map(|builtin_bound|
+ match traits::trait_ref_for_builtin_bound(tcx, builtin_bound, self_ty) {
+ Ok(trait_ref) => Some(trait_ref.to_predicate()),
+ Err(ErrorReported) => { None }
+ }
+ ).collect()
+ }
+}
+
+impl ops::Deref for BuiltinBounds {
+ type Target = EnumSet<BuiltinBound>;
+ fn deref(&self) -> &Self::Target { &self.0 }
+}
+
+impl ops::DerefMut for BuiltinBounds {
+ fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 }
+}
+
+impl<'a> IntoIterator for &'a BuiltinBounds {
+ type Item = BuiltinBound;
+ type IntoIter = enum_set::Iter<BuiltinBound>;
+ fn into_iter(self) -> Self::IntoIter {
+ (**self).into_iter()
+ }
+}
+
+#[derive(Clone, RustcEncodable, PartialEq, Eq, RustcDecodable, Hash,
+ Debug, Copy)]
+#[repr(usize)]
+pub enum BuiltinBound {
+ Send,
+ Sized,
+ Copy,
+ Sync,
+}
+
+impl CLike for BuiltinBound {
+ fn to_usize(&self) -> usize {
+ *self as usize
+ }
+ fn from_usize(v: usize) -> BuiltinBound {
+ unsafe { mem::transmute(v) }
+ }
+}
+
+impl<'tcx> ty::ctxt<'tcx> {
+ pub fn try_add_builtin_trait(&self,
+ trait_def_id: DefId,
+ builtin_bounds: &mut EnumSet<BuiltinBound>)
+ -> bool
+ {
+ //! Checks whether `trait_ref` refers to one of the builtin
+ //! traits, like `Send`, and adds the corresponding
+ //! bound to the set `builtin_bounds` if so. Returns true if `trait_ref`
+ //! is a builtin trait.
+
+ match self.lang_items.to_builtin_kind(trait_def_id) {
+ Some(bound) => { builtin_bounds.insert(bound); true }
+ None => false
+ }
+ }
+}
+
+impl DebruijnIndex {
+ pub fn new(depth: u32) -> DebruijnIndex {
+ assert!(depth > 0);
+ DebruijnIndex { depth: depth }
+ }
+
+ pub fn shifted(&self, amount: u32) -> DebruijnIndex {
+ DebruijnIndex { depth: self.depth + amount }
+ }
+}
+
+// Region utilities
+impl Region {
+ pub fn is_bound(&self) -> bool {
+ match *self {
+ ty::ReEarlyBound(..) => true,
+ ty::ReLateBound(..) => true,
+ _ => false
+ }
+ }
+
+ pub fn needs_infer(&self) -> bool {
+ match *self {
+ ty::ReVar(..) | ty::ReSkolemized(..) => true,
+ _ => false
+ }
+ }
+
+ pub fn escapes_depth(&self, depth: u32) -> bool {
+ match *self {
+ ty::ReLateBound(debruijn, _) => debruijn.depth > depth,
+ _ => false,
+ }
+ }
+
+ /// Returns the depth of `self` from the (1-based) binding level `depth`
+ pub fn from_depth(&self, depth: u32) -> Region {
+ match *self {
+ ty::ReLateBound(debruijn, r) => ty::ReLateBound(DebruijnIndex {
+ depth: debruijn.depth - (depth - 1)
+ }, r),
+ r => r
+ }
+ }
+}
+
+// Type utilities
+impl<'tcx> TyS<'tcx> {
+ pub fn is_nil(&self) -> bool {
+ match self.sty {
+ TyTuple(ref tys) => tys.is_empty(),
+ _ => false
+ }
+ }
+
+ pub fn is_empty(&self, _cx: &ty::ctxt) -> bool {
+ // FIXME(#24885): be smarter here
+ match self.sty {
+ TyEnum(def, _) | TyStruct(def, _) => def.is_empty(),
+ _ => false
+ }
+ }
+
+ pub fn is_ty_var(&self) -> bool {
+ match self.sty {
+ TyInfer(TyVar(_)) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_bool(&self) -> bool { self.sty == TyBool }
+
+ pub fn is_self(&self) -> bool {
+ match self.sty {
+ TyParam(ref p) => p.space == subst::SelfSpace,
+ _ => false
+ }
+ }
+
+ fn is_slice(&self) -> bool {
+ match self.sty {
+ TyRawPtr(mt) | TyRef(_, mt) => match mt.ty.sty {
+ TySlice(_) | TyStr => true,
+ _ => false,
+ },
+ _ => false
+ }
+ }
+
+ pub fn is_structural(&self) -> bool {
+ match self.sty {
+ TyStruct(..) | TyTuple(_) | TyEnum(..) |
+ TyArray(..) | TyClosure(..) => true,
+ _ => self.is_slice() | self.is_trait()
+ }
+ }
+
+ #[inline]
+ pub fn is_simd(&self) -> bool {
+ match self.sty {
+ TyStruct(def, _) => def.is_simd(),
+ _ => false
+ }
+ }
+
+ pub fn sequence_element_type(&self, cx: &ty::ctxt<'tcx>) -> Ty<'tcx> {
+ match self.sty {
+ TyArray(ty, _) | TySlice(ty) => ty,
+ TyStr => cx.mk_mach_uint(hir::TyU8),
+ _ => cx.sess.bug(&format!("sequence_element_type called on non-sequence value: {}",
+ self)),
+ }
+ }
+
+ pub fn simd_type(&self, cx: &ty::ctxt<'tcx>) -> Ty<'tcx> {
+ match self.sty {
+ TyStruct(def, substs) => {
+ def.struct_variant().fields[0].ty(cx, substs)
+ }
+ _ => panic!("simd_type called on invalid type")
+ }
+ }
+
+ pub fn simd_size(&self, _cx: &ty::ctxt) -> usize {
+ match self.sty {
+ TyStruct(def, _) => def.struct_variant().fields.len(),
+ _ => panic!("simd_size called on invalid type")
+ }
+ }
+
+ pub fn is_region_ptr(&self) -> bool {
+ match self.sty {
+ TyRef(..) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_unsafe_ptr(&self) -> bool {
+ match self.sty {
+ TyRawPtr(_) => return true,
+ _ => return false
+ }
+ }
+
+ pub fn is_unique(&self) -> bool {
+ match self.sty {
+ TyBox(_) => true,
+ _ => false
+ }
+ }
+
+ /*
+ A scalar type is one that denotes an atomic datum, with no sub-components.
+ (A TyRawPtr is scalar because it represents a non-managed pointer, so its
+ contents are abstract to rustc.)
+ */
+ pub fn is_scalar(&self) -> bool {
+ match self.sty {
+ TyBool | TyChar | TyInt(_) | TyFloat(_) | TyUint(_) |
+ TyInfer(IntVar(_)) | TyInfer(FloatVar(_)) |
+ TyBareFn(..) | TyRawPtr(_) => true,
+ _ => false
+ }
+ }
+
+ /// Returns true if this type is a floating point type and false otherwise.
+ pub fn is_floating_point(&self) -> bool {
+ match self.sty {
+ TyFloat(_) |
+ TyInfer(FloatVar(_)) => true,
+ _ => false,
+ }
+ }
+
+ pub fn is_trait(&self) -> bool {
+ match self.sty {
+ TyTrait(..) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_integral(&self) -> bool {
+ match self.sty {
+ TyInfer(IntVar(_)) | TyInt(_) | TyUint(_) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_fresh(&self) -> bool {
+ match self.sty {
+ TyInfer(FreshTy(_)) => true,
+ TyInfer(FreshIntTy(_)) => true,
+ TyInfer(FreshFloatTy(_)) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_uint(&self) -> bool {
+ match self.sty {
+ TyInfer(IntVar(_)) | TyUint(hir::TyUs) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_char(&self) -> bool {
+ match self.sty {
+ TyChar => true,
+ _ => false
+ }
+ }
+
+ pub fn is_bare_fn(&self) -> bool {
+ match self.sty {
+ TyBareFn(..) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_bare_fn_item(&self) -> bool {
+ match self.sty {
+ TyBareFn(Some(_), _) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_fp(&self) -> bool {
+ match self.sty {
+ TyInfer(FloatVar(_)) | TyFloat(_) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_numeric(&self) -> bool {
+ self.is_integral() || self.is_fp()
+ }
+
+ pub fn is_signed(&self) -> bool {
+ match self.sty {
+ TyInt(_) => true,
+ _ => false
+ }
+ }
+
+ pub fn is_machine(&self) -> bool {
+ match self.sty {
+ TyInt(hir::TyIs) | TyUint(hir::TyUs) => false,
+ TyInt(..) | TyUint(..) | TyFloat(..) => true,
+ _ => false
+ }
+ }
+
+ // 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, pref: ty::LvaluePreference)
+ -> Option<TypeAndMut<'tcx>>
+ {
+ match self.sty {
+ TyBox(ty) => {
+ Some(TypeAndMut {
+ ty: ty,
+ mutbl: if pref == ty::PreferMutLvalue {
+ hir::MutMutable
+ } else {
+ hir::MutImmutable
+ },
+ })
+ },
+ TyRef(_, mt) => Some(mt),
+ TyRawPtr(mt) if explicit => Some(mt),
+ _ => None
+ }
+ }
+
+ // Returns the type of ty[i]
+ pub fn builtin_index(&self) -> Option<Ty<'tcx>> {
+ match self.sty {
+ TyArray(ty, _) | TySlice(ty) => Some(ty),
+ _ => None
+ }
+ }
+
+ pub fn fn_sig(&self) -> &'tcx PolyFnSig<'tcx> {
+ match self.sty {
+ TyBareFn(_, ref f) => &f.sig,
+ _ => panic!("Ty::fn_sig() called on non-fn type: {:?}", self)
+ }
+ }
+
+ /// Returns the ABI of the given function.
+ pub fn fn_abi(&self) -> abi::Abi {
+ match self.sty {
+ TyBareFn(_, ref f) => f.abi,
+ _ => panic!("Ty::fn_abi() called on non-fn type"),
+ }
+ }
+
+ // Type accessors for substructures of types
+ pub fn fn_args(&self) -> ty::Binder<Vec<Ty<'tcx>>> {
+ self.fn_sig().inputs()
+ }
+
+ pub fn fn_ret(&self) -> Binder<FnOutput<'tcx>> {
+ self.fn_sig().output()
+ }
+
+ pub fn is_fn(&self) -> bool {
+ match self.sty {
+ TyBareFn(..) => true,
+ _ => false
+ }
+ }
+
+ pub fn ty_to_def_id(&self) -> Option<DefId> {
+ match self.sty {
+ TyTrait(ref tt) => Some(tt.principal_def_id()),
+ TyStruct(def, _) |
+ TyEnum(def, _) => Some(def.did),
+ TyClosure(id, _) => Some(id),
+ _ => None
+ }
+ }
+
+ pub fn ty_adt_def(&self) -> Option<AdtDef<'tcx>> {
+ match self.sty {
+ TyStruct(adt, _) | TyEnum(adt, _) => Some(adt),
+ _ => None
+ }
+ }
+}