diff options
Diffstat (limited to 'compiler/rustc_middle/src/ty/sty.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/sty.rs | 2295 |
1 files changed, 2295 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs new file mode 100644 index 000000000..52c3a3886 --- /dev/null +++ b/compiler/rustc_middle/src/ty/sty.rs @@ -0,0 +1,2295 @@ +//! This module contains `TyKind` and its major components. + +#![allow(rustc::usage_of_ty_tykind)] + +use crate::infer::canonical::Canonical; +use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef}; +use crate::ty::visit::ValidateBoundVars; +use crate::ty::InferTy::*; +use crate::ty::{ + self, AdtDef, DefIdTree, Discr, Term, Ty, TyCtxt, TypeFlags, TypeSuperVisitable, TypeVisitable, + TypeVisitor, +}; +use crate::ty::{List, ParamEnv}; +use polonius_engine::Atom; +use rustc_data_structures::captures::Captures; +use rustc_data_structures::intern::Interned; +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, Symbol}; +use rustc_target::abi::VariantIdx; +use rustc_target::spec::abi; +use std::borrow::Cow; +use std::cmp::Ordering; +use std::fmt; +use std::marker::PhantomData; +use std::ops::{ControlFlow, Deref, Range}; +use ty::util::IntTypeExt; + +use rustc_type_ir::sty::TyKind::*; +use rustc_type_ir::RegionKind as IrRegionKind; +use rustc_type_ir::TyKind as IrTyKind; + +// Re-export the `TyKind` from `rustc_type_ir` here for convenience +#[rustc_diagnostic_item = "TyKind"] +pub type TyKind<'tcx> = IrTyKind<TyCtxt<'tcx>>; +pub type RegionKind<'tcx> = IrRegionKind<TyCtxt<'tcx>>; + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable, 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: BoundRegionKind, +} + +#[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, TyEncodable, TyDecodable, Copy)] +#[derive(HashStable)] +pub enum BoundRegionKind { + /// 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, +} + +#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, PartialOrd, Ord)] +#[derive(HashStable)] +pub struct BoundRegion { + pub var: BoundVar, + pub kind: BoundRegionKind, +} + +impl BoundRegionKind { + pub fn is_named(&self) -> bool { + match *self { + BoundRegionKind::BrNamed(_, name) => name != kw::UnderscoreLifetime, + _ => false, + } + } +} + +pub trait Article { + fn article(&self) -> &'static str; +} + +impl<'tcx> Article for TyKind<'tcx> { + /// Get the article ("a" or "an") to use with this type. + fn article(&self) -> &'static str { + match self { + Int(_) | Float(_) | Array(_, _) => "an", + Adt(def, _) if def.is_enum() => "an", + // This should never happen, but ICEing and causing the user's code + // to not compile felt too harsh. + Error(_) => "a", + _ => "a", + } + } +} + +// `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger. +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +static_assert_size!(TyKind<'_>, 32); + +/// A closure can be modeled as a struct that looks like: +/// ```ignore (illustrative) +/// 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 +/// `Ty::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 a 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: +/// ```ignore (illustrative) +/// fn foo<'a, T>(data: &'a mut T) { +/// do(|| data.count += 1) +/// } +/// ``` +/// the type of the closure would be something like: +/// ```ignore (illustrative) +/// 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: +/// ```ignore (illustrative) +/// 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, TypeVisitable)] +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 + } + + /// Returns an iterator over the list of types of captured paths by the closure. + /// In case there was a type error in figuring out the types of the captured path, an + /// empty iterator is returned. + #[inline] + pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx { + match self.tupled_upvars_ty().kind() { + TyKind::Error(_) => None, + TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()), + TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"), + ty => bug!("Unexpected representation of upvar types tuple {:?}", ty), + } + .into_iter() + .flatten() + } + + /// 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, TypeVisitable)] +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() + } + + /// Returns an iterator over the list of types of captured paths by the generator. + /// In case there was a type error in figuring out the types of the captured path, an + /// empty iterator is returned. + #[inline] + pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx { + match self.tupled_upvars_ty().kind() { + TyKind::Error(_) => None, + TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()), + TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"), + ty => bug!("Unexpected representation of upvar types tuple {:?}", ty), + } + .into_iter() + .flatten() + } + + /// 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).unwrap().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).unwrap(); + layout.variant_fields.iter().map(move |variant| { + variant + .iter() + .map(move |field| EarlyBinder(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, HashStable)] +pub enum UpvarSubsts<'tcx> { + Closure(SubstsRef<'tcx>), + Generator(SubstsRef<'tcx>), +} + +impl<'tcx> UpvarSubsts<'tcx> { + /// Returns an iterator over the list of types of captured paths by the closure/generator. + /// In case there was a type error in figuring out the types of the captured path, an + /// empty iterator is returned. + #[inline] + pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx { + let tupled_tys = match self { + UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(), + UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(), + }; + + match tupled_tys.kind() { + TyKind::Error(_) => None, + TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()), + TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"), + ty => bug!("Unexpected representation of upvar types tuple {:?}", ty), + } + .into_iter() + .flatten() + } + + #[inline] + pub fn tupled_upvars_ty(self) -> Ty<'tcx> { + match self { + UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(), + UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(), + } + } +} + +/// An inline const is modeled like +/// ```ignore (illustrative) +/// const InlineConst<'l0...'li, T0...Tj, R>: R; +/// ``` +/// where: +/// +/// - 'l0...'li and T0...Tj are the generic parameters +/// inherited from the item that defined the inline const, +/// - R represents the type of the constant. +/// +/// When the inline const is instantiated, `R` is substituted as the actual inferred +/// type of the constant. The reason that `R` is represented as an extra type parameter +/// is the same reason that [`ClosureSubsts`] have `CS` and `U` as type parameters: +/// inline const can reference lifetimes that are internal to the creating function. +#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)] +pub struct InlineConstSubsts<'tcx> { + /// Generic parameters from the enclosing item, + /// concatenated with the inferred type of the constant. + pub substs: SubstsRef<'tcx>, +} + +/// Struct returned by `split()`. +pub struct InlineConstSubstsParts<'tcx, T> { + pub parent_substs: &'tcx [GenericArg<'tcx>], + pub ty: T, +} + +impl<'tcx> InlineConstSubsts<'tcx> { + /// Construct `InlineConstSubsts` from `InlineConstSubstsParts`. + pub fn new( + tcx: TyCtxt<'tcx>, + parts: InlineConstSubstsParts<'tcx, Ty<'tcx>>, + ) -> InlineConstSubsts<'tcx> { + InlineConstSubsts { + substs: tcx.mk_substs( + parts.parent_substs.iter().copied().chain(std::iter::once(parts.ty.into())), + ), + } + } + + /// Divides the inline const substs into their respective components. + /// The ordering assumed here must match that used by `InlineConstSubsts::new` above. + fn split(self) -> InlineConstSubstsParts<'tcx, GenericArg<'tcx>> { + match self.substs[..] { + [ref parent_substs @ .., ty] => InlineConstSubstsParts { parent_substs, ty }, + _ => bug!("inline const substs missing synthetics"), + } + } + + /// Returns the substitutions of the inline const's parent. + pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] { + self.split().parent_substs + } + + /// Returns the type of this inline const. + pub fn ty(self) -> Ty<'tcx> { + self.split().ty.expect_ty() + } +} + +#[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +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.def_path_hash(*a).cmp(&tcx.def_path_hash(*b)) + } + (Trait(_), _) => Ordering::Less, + (Projection(_), Trait(_)) => Ordering::Greater, + (Projection(_), _) => Ordering::Less, + (AutoTrait(_), _) => Ordering::Greater, + } + } +} + +impl<'tcx> Binder<'tcx, 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) => { + self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx) + } + ExistentialPredicate::Projection(p) => { + self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx) + } + ExistentialPredicate::AutoTrait(did) => { + let trait_ref = self.rebind(ty::TraitRef { + def_id: did, + substs: tcx.mk_substs_trait(self_ty, &[]), + }); + trait_ref.without_const().to_predicate(tcx) + } + } + } +} + +impl<'tcx> List<ty::Binder<'tcx, 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<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> { + self[0] + .map_bound(|this| match this { + ExistentialPredicate::Trait(tr) => Some(tr), + _ => None, + }) + .transpose() + } + + pub fn principal_def_id(&self) -> Option<DefId> { + self.principal().map(|trait_ref| trait_ref.skip_binder().def_id) + } + + #[inline] + pub fn projection_bounds<'a>( + &'a self, + ) -> impl Iterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> + 'a { + self.iter().filter_map(|predicate| { + predicate + .map_bound(|pred| match pred { + ExistentialPredicate::Projection(projection) => Some(projection), + _ => None, + }) + .transpose() + }) + } + + #[inline] + pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item = DefId> + Captures<'tcx> + 'a { + self.iter().filter_map(|predicate| match predicate.skip_binder() { + ExistentialPredicate::AutoTrait(did) => Some(did), + _ => None, + }) + } +} + +/// A complete reference to a trait. These take numerous guises in syntax, +/// but perhaps the most recognizable form is in a where-clause: +/// ```ignore (illustrative) +/// 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, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +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) -> Binder<'tcx, TraitRef<'tcx>> { + ty::Binder::dummy(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<'tcx, TraitRef<'tcx>>; + +impl<'tcx> PolyTraitRef<'tcx> { + pub fn self_ty(&self) -> Binder<'tcx, 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> { + self.map_bound(|trait_ref| ty::TraitPredicate { + trait_ref, + constness: ty::BoundConstness::NotConst, + polarity: ty::ImplPolarity::Positive, + }) + } + + /// Same as [`PolyTraitRef::to_poly_trait_predicate`] but sets a negative polarity instead. + pub fn to_poly_trait_predicate_negative_polarity(&self) -> ty::PolyTraitPredicate<'tcx> { + self.map_bound(|trait_ref| ty::TraitPredicate { + trait_ref, + constness: ty::BoundConstness::NotConst, + polarity: ty::ImplPolarity::Negative, + }) + } +} + +/// An existential reference to a trait, where `Self` is erased. +/// For example, the trait object `Trait<'a, 'b, X, Y>` is: +/// ```ignore (illustrative) +/// 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, TypeVisitable)] +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<'tcx, 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)) + } +} + +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] +#[derive(Encodable, Decodable, HashStable)] +pub struct EarlyBinder<T>(pub T); + +impl<T> EarlyBinder<T> { + pub fn as_ref(&self) -> EarlyBinder<&T> { + EarlyBinder(&self.0) + } + + pub fn map_bound_ref<F, U>(&self, f: F) -> EarlyBinder<U> + where + F: FnOnce(&T) -> U, + { + self.as_ref().map_bound(f) + } + + pub fn map_bound<F, U>(self, f: F) -> EarlyBinder<U> + where + F: FnOnce(T) -> U, + { + let value = f(self.0); + EarlyBinder(value) + } + + pub fn try_map_bound<F, U, E>(self, f: F) -> Result<EarlyBinder<U>, E> + where + F: FnOnce(T) -> Result<U, E>, + { + let value = f(self.0)?; + Ok(EarlyBinder(value)) + } + + pub fn rebind<U>(&self, value: U) -> EarlyBinder<U> { + EarlyBinder(value) + } +} + +impl<T> EarlyBinder<Option<T>> { + pub fn transpose(self) -> Option<EarlyBinder<T>> { + self.0.map(|v| EarlyBinder(v)) + } +} + +impl<T, U> EarlyBinder<(T, U)> { + pub fn transpose_tuple2(self) -> (EarlyBinder<T>, EarlyBinder<U>) { + (EarlyBinder(self.0.0), EarlyBinder(self.0.1)) + } +} + +pub struct EarlyBinderIter<T> { + t: T, +} + +impl<T: IntoIterator> EarlyBinder<T> { + pub fn transpose_iter(self) -> EarlyBinderIter<T::IntoIter> { + EarlyBinderIter { t: self.0.into_iter() } + } +} + +impl<T: Iterator> Iterator for EarlyBinderIter<T> { + type Item = EarlyBinder<T::Item>; + + fn next(&mut self) -> Option<Self::Item> { + self.t.next().map(|i| EarlyBinder(i)) + } +} + +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable)] +pub enum BoundVariableKind { + Ty(BoundTyKind), + Region(BoundRegionKind), + Const, +} + +impl BoundVariableKind { + pub fn expect_region(self) -> BoundRegionKind { + match self { + BoundVariableKind::Region(lt) => lt, + _ => bug!("expected a region, but found another kind"), + } + } + + pub fn expect_ty(self) -> BoundTyKind { + match self { + BoundVariableKind::Ty(ty) => ty, + _ => bug!("expected a type, but found another kind"), + } + } + + pub fn expect_const(self) { + match self { + BoundVariableKind::Const => (), + _ => bug!("expected a const, but found another kind"), + } + } +} + +/// 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<'tcx, TraitRef>`). Note that when we instantiate, +/// erase, or otherwise "discharge" these bound vars, we change the +/// type from `Binder<'tcx, T>` to just `T` (see +/// e.g., `liberate_late_bound_regions`). +/// +/// `Decodable` and `Encodable` are implemented for `Binder<T>` using the `impl_binder_encode_decode!` macro. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] +#[derive(HashStable)] +pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>); + +impl<'tcx, T> Binder<'tcx, T> +where + T: TypeVisitable<'tcx>, +{ + /// 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(value: T) -> Binder<'tcx, T> { + assert!(!value.has_escaping_bound_vars()); + Binder(value, ty::List::empty()) + } + + pub fn bind_with_vars(value: T, vars: &'tcx List<BoundVariableKind>) -> Binder<'tcx, T> { + if cfg!(debug_assertions) { + let mut validator = ValidateBoundVars::new(vars); + value.visit_with(&mut validator); + } + Binder(value, vars) + } +} + +impl<'tcx, T> Binder<'tcx, T> { + /// 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 bound_vars(&self) -> &'tcx List<BoundVariableKind> { + self.1 + } + + pub fn as_ref(&self) -> Binder<'tcx, &T> { + Binder(&self.0, self.1) + } + + pub fn as_deref(&self) -> Binder<'tcx, &T::Target> + where + T: Deref, + { + Binder(&self.0, self.1) + } + + pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U> + where + F: FnOnce(&T) -> U, + { + let value = f(&self.0); + Binder(value, self.1) + } + + pub fn map_bound_ref<F, U: TypeVisitable<'tcx>>(&self, f: F) -> Binder<'tcx, U> + where + F: FnOnce(&T) -> U, + { + self.as_ref().map_bound(f) + } + + pub fn map_bound<F, U: TypeVisitable<'tcx>>(self, f: F) -> Binder<'tcx, U> + where + F: FnOnce(T) -> U, + { + let value = f(self.0); + if cfg!(debug_assertions) { + let mut validator = ValidateBoundVars::new(self.1); + value.visit_with(&mut validator); + } + Binder(value, self.1) + } + + pub fn try_map_bound<F, U: TypeVisitable<'tcx>, E>(self, f: F) -> Result<Binder<'tcx, U>, E> + where + F: FnOnce(T) -> Result<U, E>, + { + let value = f(self.0)?; + if cfg!(debug_assertions) { + let mut validator = ValidateBoundVars::new(self.1); + value.visit_with(&mut validator); + } + Ok(Binder(value, self.1)) + } + + /// Wraps a `value` in a binder, using the same bound variables as the + /// current `Binder`. This should not be used if the new value *changes* + /// the bound variables. Note: the (old or new) value itself does not + /// necessarily need to *name* all the bound variables. + /// + /// This currently doesn't do anything different than `bind`, because we + /// don't actually track bound vars. However, semantically, it is different + /// because bound vars aren't allowed to change here, whereas they are + /// in `bind`. This may be (debug) asserted in the future. + pub fn rebind<U>(&self, value: U) -> Binder<'tcx, U> + where + U: TypeVisitable<'tcx>, + { + if cfg!(debug_assertions) { + let mut validator = ValidateBoundVars::new(self.bound_vars()); + value.visit_with(&mut validator); + } + Binder(value, self.1) + } + + /// 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(self) -> Option<T> + where + T: TypeVisitable<'tcx>, + { + if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) } + } + + /// 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<'tcx, U>, Binder<'tcx, V>) + where + F: FnOnce(T) -> (U, V), + { + let (u, v) = f(self.0); + (Binder(u, self.1), Binder(v, self.1)) + } +} + +impl<'tcx, T> Binder<'tcx, Option<T>> { + pub fn transpose(self) -> Option<Binder<'tcx, T>> { + let bound_vars = self.1; + self.0.map(|v| Binder(v, bound_vars)) + } +} + +/// 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, TypeVisitable)] +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`, + /// aka. `tcx.parent(item_def_id).unwrap()`. + pub item_def_id: DefId, +} + +impl<'tcx> ProjectionTy<'tcx> { + pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId { + tcx.parent(self.item_def_id) + } + + /// Extracts the underlying trait reference and own substs from this projection. + /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`, + /// then this function would return a `T: Iterator` trait reference and `['a]` as the own substs + pub fn trait_ref_and_own_substs( + &self, + tcx: TyCtxt<'tcx>, + ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) { + let def_id = tcx.parent(self.item_def_id); + let trait_generics = tcx.generics_of(def_id); + ( + ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, trait_generics) }, + &self.substs[trait_generics.count()..], + ) + } + + /// 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. + /// + /// WARNING: This will drop the substs for generic associated types + /// consider calling [Self::trait_ref_and_own_substs] to get those + /// as well. + pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> { + let def_id = self.trait_def_id(tcx); + 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, TypeVisitable)] +pub struct GenSig<'tcx> { + pub resume_ty: Ty<'tcx>, + pub yield_ty: Ty<'tcx>, + pub return_ty: Ty<'tcx>, +} + +pub type PolyGenSig<'tcx> = Binder<'tcx, GenSig<'tcx>>; + +/// 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, TypeVisitable)] +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<'tcx, FnSig<'tcx>>; + +impl<'tcx> PolyFnSig<'tcx> { + #[inline] + pub fn inputs(&self) -> Binder<'tcx, &'tcx [Ty<'tcx>]> { + self.map_bound_ref_unchecked(|fn_sig| fn_sig.inputs()) + } + #[inline] + pub fn input(&self, index: usize) -> ty::Binder<'tcx, Ty<'tcx>> { + self.map_bound_ref(|fn_sig| fn_sig.inputs()[index]) + } + pub fn inputs_and_output(&self) -> ty::Binder<'tcx, &'tcx List<Ty<'tcx>>> { + self.map_bound_ref(|fn_sig| fn_sig.inputs_and_output) + } + #[inline] + pub fn output(&self) -> ty::Binder<'tcx, 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<'tcx, 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_def(def: &ty::GenericParamDef) -> ParamTy { + ParamTy::new(def.index, def.name) + } + + #[inline] + 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 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) + } +} + +/// Use this rather than `RegionKind`, whenever possible. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)] +#[rustc_pass_by_value] +pub struct Region<'tcx>(pub Interned<'tcx, RegionKind<'tcx>>); + +impl<'tcx> Deref for Region<'tcx> { + type Target = RegionKind<'tcx>; + + #[inline] + fn deref(&self) -> &RegionKind<'tcx> { + &self.0.0 + } +} + +impl<'tcx> fmt::Debug for Region<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{:?}", self.kind()) + } +} + +#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, PartialOrd, Ord)] +#[derive(HashStable)] +pub struct EarlyBoundRegion { + pub def_id: DefId, + pub index: u32, + pub name: Symbol, +} + +impl fmt::Debug for EarlyBoundRegion { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{}, {}", self.index, self.name) + } +} + +/// A **`const`** **v**ariable **ID**. +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] +#[derive(HashStable, TyEncodable, TyDecodable)] +pub struct ConstVid<'tcx> { + pub index: u32, + pub phantom: PhantomData<&'tcx ()>, +} + +rustc_index::newtype_index! { + /// A **region** (lifetime) **v**ariable **ID**. + #[derive(HashStable)] + pub struct RegionVid { + DEBUG_FORMAT = custom, + } +} + +impl Atom for RegionVid { + fn index(self) -> usize { + Idx::index(self) + } +} + +rustc_index::newtype_index! { + #[derive(HashStable)] + 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, TypeVisitable)] +pub struct ExistentialProjection<'tcx> { + pub item_def_id: DefId, + pub substs: SubstsRef<'tcx>, + pub term: Term<'tcx>, +} + +pub type PolyExistentialProjection<'tcx> = Binder<'tcx, 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 an `exists T. T: Iterator` existential trait + /// reference. + pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> { + let def_id = tcx.parent(self.item_def_id); + let subst_count = tcx.generics_of(def_id).count() - 1; + let substs = tcx.intern_substs(&self.substs[..subst_count]); + ty::ExistentialTraitRef { def_id, 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), + }, + term: self.term, + } + } + + pub fn erase_self_ty( + tcx: TyCtxt<'tcx>, + projection_predicate: ty::ProjectionPredicate<'tcx>, + ) -> Self { + // Assert there is a Self. + projection_predicate.projection_ty.substs.type_at(0); + + Self { + item_def_id: projection_predicate.projection_ty.item_def_id, + substs: tcx.intern_substs(&projection_predicate.projection_ty.substs[1..]), + term: projection_predicate.term, + } + } +} + +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 + } +} + +/// Region utilities +impl<'tcx> Region<'tcx> { + pub fn kind(self) -> RegionKind<'tcx> { + *self.0.0 + } + + /// Is this region named by the user? + pub fn has_name(self) -> bool { + match *self { + ty::ReEarlyBound(ebr) => ebr.has_name(), + ty::ReLateBound(_, br) => br.kind.is_named(), + ty::ReFree(fr) => fr.bound_region.is_named(), + ty::ReStatic => true, + ty::ReVar(..) => false, + ty::RePlaceholder(placeholder) => placeholder.name.is_named(), + ty::ReEmpty(_) => false, + ty::ReErased => false, + } + } + + #[inline] + pub fn is_static(self) -> bool { + matches!(*self, ty::ReStatic) + } + + #[inline] + pub fn is_erased(self) -> bool { + matches!(*self, ty::ReErased) + } + + #[inline] + pub fn is_late_bound(self) -> bool { + matches!(*self, ty::ReLateBound(..)) + } + + #[inline] + pub fn is_placeholder(self) -> bool { + matches!(*self, ty::RePlaceholder(..)) + } + + #[inline] + pub fn is_empty(self) -> bool { + matches!(*self, ty::ReEmpty(..)) + } + + #[inline] + pub fn bound_at_or_above_binder(self, index: ty::DebruijnIndex) -> bool { + match *self { + ty::ReLateBound(debruijn, _) => debruijn >= index, + _ => false, + } + } + + 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: + /// + /// ```ignore (illustrative) + /// 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), + ty::ReFree(fr) => fr.scope, + _ => bug!("free_region_binding_scope invoked on inappropriate region: {:?}", self), + } + } + + /// True for free regions other than `'static`. + pub fn is_free(self) -> bool { + matches!(*self, ty::ReEarlyBound(_) | ty::ReFree(_)) + } + + /// True if `self` is a free region or static. + pub fn is_free_or_static(self) -> bool { + match *self { + ty::ReStatic => true, + _ => self.is_free(), + } + } +} + +/// Type utilities +impl<'tcx> Ty<'tcx> { + #[inline(always)] + pub fn kind(self) -> &'tcx TyKind<'tcx> { + &self.0.0.kind + } + + #[inline(always)] + pub fn flags(self) -> TypeFlags { + self.0.0.flags + } + + #[inline] + pub fn is_unit(self) -> bool { + match self.kind() { + Tuple(ref tys) => tys.is_empty(), + _ => false, + } + } + + #[inline] + pub fn is_never(self) -> bool { + matches!(self.kind(), Never) + } + + #[inline] + pub fn is_primitive(self) -> bool { + self.kind().is_primitive() + } + + #[inline] + pub fn is_adt(self) -> bool { + matches!(self.kind(), Adt(..)) + } + + #[inline] + pub fn is_ref(self) -> bool { + matches!(self.kind(), Ref(..)) + } + + #[inline] + pub fn is_ty_var(self) -> bool { + matches!(self.kind(), Infer(TyVar(_))) + } + + #[inline] + pub fn ty_vid(self) -> Option<ty::TyVid> { + match self.kind() { + &Infer(TyVar(vid)) => Some(vid), + _ => None, + } + } + + #[inline] + pub fn is_ty_infer(self) -> bool { + matches!(self.kind(), Infer(_)) + } + + #[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 { + matches!(self.kind(), Slice(_)) + } + + #[inline] + pub fn is_array_slice(self) -> bool { + match self.kind() { + Slice(_) => true, + RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_)), + _ => false, + } + } + + #[inline] + pub fn is_array(self) -> bool { + matches!(self.kind(), Array(..)) + } + + #[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.types.u8, + _ => bug!("`sequence_element_type` called on non-sequence value: {}", self), + } + } + + pub fn simd_size_and_type(self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) { + match self.kind() { + Adt(def, substs) => { + assert!(def.repr().simd(), "`simd_size_and_type` called on non-SIMD type"); + let variant = def.non_enum_variant(); + let f0_ty = variant.fields[0].ty(tcx, substs); + + match f0_ty.kind() { + // If the first field is an array, we assume it is the only field and its + // elements are the SIMD components. + Array(f0_elem_ty, f0_len) => { + // FIXME(repr_simd): https://github.com/rust-lang/rust/pull/78863#discussion_r522784112 + // The way we evaluate the `N` in `[T; N]` here only works since we use + // `simd_size_and_type` post-monomorphization. It will probably start to ICE + // if we use it in generic code. See the `simd-array-trait` ui test. + (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, *f0_elem_ty) + } + // Otherwise, the fields of this Adt are the SIMD components (and we assume they + // all have the same type). + _ => (variant.fields.len() as u64, f0_ty), + } + } + _ => bug!("`simd_size_and_type` called on invalid type"), + } + } + + #[inline] + pub fn is_region_ptr(self) -> bool { + matches!(self.kind(), Ref(..)) + } + + #[inline] + pub fn is_mutable_ptr(self) -> bool { + matches!( + self.kind(), + RawPtr(TypeAndMut { mutbl: hir::Mutability::Mut, .. }) + | Ref(_, _, hir::Mutability::Mut) + ) + } + + /// Get the mutability of the reference or `None` when not a reference + #[inline] + pub fn ref_mutability(self) -> Option<hir::Mutability> { + match self.kind() { + Ref(_, _, mutability) => Some(*mutability), + _ => None, + } + } + + #[inline] + pub fn is_unsafe_ptr(self) -> bool { + matches!(self.kind(), RawPtr(_)) + } + + /// 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 { + matches!( + self.kind(), + Bool | Char + | Int(_) + | Float(_) + | Uint(_) + | FnDef(..) + | FnPtr(_) + | RawPtr(_) + | Infer(IntVar(_) | FloatVar(_)) + ) + } + + /// Returns `true` if this type is a floating point type. + #[inline] + pub fn is_floating_point(self) -> bool { + matches!(self.kind(), Float(_) | Infer(FloatVar(_))) + } + + #[inline] + pub fn is_trait(self) -> bool { + matches!(self.kind(), Dynamic(..)) + } + + #[inline] + pub fn is_enum(self) -> bool { + matches!(self.kind(), Adt(adt_def, _) if adt_def.is_enum()) + } + + #[inline] + pub fn is_union(self) -> bool { + matches!(self.kind(), Adt(adt_def, _) if adt_def.is_union()) + } + + #[inline] + pub fn is_closure(self) -> bool { + matches!(self.kind(), Closure(..)) + } + + #[inline] + pub fn is_generator(self) -> bool { + matches!(self.kind(), Generator(..)) + } + + #[inline] + pub fn is_integral(self) -> bool { + matches!(self.kind(), Infer(IntVar(_)) | Int(_) | Uint(_)) + } + + #[inline] + pub fn is_fresh_ty(self) -> bool { + matches!(self.kind(), Infer(FreshTy(_))) + } + + #[inline] + pub fn is_fresh(self) -> bool { + matches!(self.kind(), Infer(FreshTy(_) | FreshIntTy(_) | FreshFloatTy(_))) + } + + #[inline] + pub fn is_char(self) -> bool { + matches!(self.kind(), Char) + } + + #[inline] + pub fn is_numeric(self) -> bool { + self.is_integral() || self.is_floating_point() + } + + #[inline] + pub fn is_signed(self) -> bool { + matches!(self.kind(), Int(_)) + } + + #[inline] + pub fn is_ptr_sized_integral(self) -> bool { + matches!(self.kind(), Int(ty::IntTy::Isize) | Uint(ty::UintTy::Usize)) + } + + #[inline] + pub fn has_concrete_skeleton(self) -> bool { + !matches!(self.kind(), Param(_) | Infer(_) | Error(_)) + } + + /// Checks whether a type recursively contains another type + /// + /// Example: `Option<()>` contains `()` + pub fn contains(self, other: Ty<'tcx>) -> bool { + struct ContainsTyVisitor<'tcx>(Ty<'tcx>); + + impl<'tcx> TypeVisitor<'tcx> for ContainsTyVisitor<'tcx> { + type BreakTy = (); + + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + if self.0 == t { ControlFlow::BREAK } else { t.super_visit_with(self) } + } + } + + let cf = self.visit_with(&mut ContainsTyVisitor(other)); + cf.is_break() + } + + /// 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: *ty, mutbl: *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.bound_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 { + matches!(self.kind(), FnDef(..) | FnPtr(_)) + } + + #[inline] + pub fn is_fn_ptr(self) -> bool { + matches!(self.kind(), FnPtr(_)) + } + + #[inline] + pub fn is_impl_trait(self) -> bool { + matches!(self.kind(), Opaque(..)) + } + + #[inline] + pub fn ty_adt_def(self) -> Option<AdtDef<'tcx>> { + match self.kind() { + Adt(adt, _) => Some(*adt), + _ => None, + } + } + + /// Iterates over tuple fields. + /// Panics when called on anything but a tuple. + #[inline] + pub fn tuple_fields(self) -> &'tcx List<Ty<'tcx>> { + match self.kind() { + Tuple(substs) => substs, + _ => 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() => { + // This can actually happen during CTFE, see + // https://github.com/rust-lang/rust/issues/89765. + None + } + 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), + + ty::Param(_) | ty::Projection(_) | ty::Opaque(..) | ty::Infer(ty::TyVar(_)) => { + let assoc_items = tcx.associated_item_def_ids( + tcx.require_lang_item(hir::LangItem::DiscriminantKind, None), + ); + tcx.mk_projection(assoc_items[0], tcx.intern_substs(&[self.into()])) + } + + ty::Bool + | ty::Char + | ty::Int(_) + | ty::Uint(_) + | ty::Float(_) + | ty::Adt(..) + | ty::Foreign(_) + | ty::Str + | ty::Array(..) + | ty::Slice(_) + | ty::RawPtr(_) + | ty::Ref(..) + | ty::FnDef(..) + | ty::FnPtr(..) + | ty::Dynamic(..) + | ty::Closure(..) + | ty::GeneratorWitness(..) + | ty::Never + | ty::Tuple(_) + | ty::Error(_) + | ty::Infer(IntVar(_) | FloatVar(_)) => tcx.types.u8, + + ty::Bound(..) + | ty::Placeholder(_) + | ty::Infer(FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { + bug!("`discriminant_ty` applied to unexpected type: {:?}", self) + } + } + } + + /// Returns the type of metadata for (potentially fat) pointers to this type, + /// and a boolean signifying if this is conditional on this type being `Sized`. + pub fn ptr_metadata_ty( + self, + tcx: TyCtxt<'tcx>, + normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>, + ) -> (Ty<'tcx>, bool) { + let tail = tcx.struct_tail_with_normalize(self, normalize, || {}); + match tail.kind() { + // Sized types + 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(_) + // Extern types have metadata = (). + | ty::Foreign(..) + // If returned by `struct_tail_without_normalization` this is a unit struct + // without any fields, or not a struct, and therefore is Sized. + | ty::Adt(..) + // If returned by `struct_tail_without_normalization` this is the empty tuple, + // a.k.a. unit type, which is Sized + | ty::Tuple(..) => (tcx.types.unit, false), + + ty::Str | ty::Slice(_) => (tcx.types.usize, false), + ty::Dynamic(..) => { + let dyn_metadata = tcx.lang_items().dyn_metadata().unwrap(); + (tcx.bound_type_of(dyn_metadata).subst(tcx, &[tail.into()]), false) + }, + + // type parameters only have unit metadata if they're sized, so return true + // to make sure we double check this during confirmation + ty::Param(_) | ty::Projection(_) | ty::Opaque(..) => (tcx.types.unit, true), + + ty::Infer(ty::TyVar(_)) + | ty::Bound(..) + | ty::Placeholder(..) + | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { + bug!("`ptr_metadata_ty` applied to unexpected type: {:?} (tail = {:?})", self, tail) + } + } + } + + /// 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 `rustc_typeck/src/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 { + ty::IntTy::I8 => Some(ty::ClosureKind::Fn), + ty::IntTy::I16 => Some(ty::ClosureKind::FnMut), + ty::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. + /// + /// Note that we could never rely on the fact that a type such as `[_]` is + /// trivially `!Sized` because we could be in a type environment with a + /// bound such as `[_]: Copy`. A function with such a bound obviously never + /// can be called, but that doesn't mean it shouldn't typecheck. This is why + /// this method doesn't return `Option<bool>`. + 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.is_trivially_sized(tcx)), + + ty::Adt(def, _substs) => def.sized_constraint(tcx).0.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) + } + } + } + + /// Fast path helper for primitives which are always `Copy` and which + /// have a side-effect-free `Clone` impl. + /// + /// Returning true means the type is known to be pure and `Copy+Clone`. + /// Returning `false` means nothing -- could be `Copy`, might not be. + /// + /// This is mostly useful for optimizations, as there are the types + /// on which we can replace cloning with dereferencing. + pub fn is_trivially_pure_clone_copy(self) -> bool { + match self.kind() { + ty::Bool | ty::Char | ty::Never => true, + + // These aren't even `Clone` + ty::Str | ty::Slice(..) | ty::Foreign(..) | ty::Dynamic(..) => false, + + ty::Int(..) | ty::Uint(..) | ty::Float(..) => true, + + // The voldemort ZSTs are fine. + ty::FnDef(..) => true, + + ty::Array(element_ty, _len) => element_ty.is_trivially_pure_clone_copy(), + + // A 100-tuple isn't "trivial", so doing this only for reasonable sizes. + ty::Tuple(field_tys) => { + field_tys.len() <= 3 && field_tys.iter().all(Self::is_trivially_pure_clone_copy) + } + + // Sometimes traits aren't implemented for every ABI or arity, + // because we can't be generic over everything yet. + ty::FnPtr(..) => false, + + // Definitely absolutely not copy. + ty::Ref(_, _, hir::Mutability::Mut) => false, + + // Thin pointers & thin shared references are pure-clone-copy, but for + // anything with custom metadata it might be more complicated. + ty::Ref(_, _, hir::Mutability::Not) | ty::RawPtr(..) => false, + + ty::Generator(..) | ty::GeneratorWitness(..) => false, + + // Might be, but not "trivial" so just giving the safe answer. + ty::Adt(..) | ty::Closure(..) | ty::Opaque(..) => false, + + ty::Projection(..) | ty::Param(..) | ty::Infer(..) | ty::Error(..) => false, + + ty::Bound(..) | ty::Placeholder(..) => { + bug!("`is_trivially_pure_clone_copy` applied to unexpected type: {:?}", self); + } + } + } +} + +/// Extra information about why we ended up with a particular variance. +/// This is only used to add more information to error messages, and +/// has no effect on soundness. While choosing the 'wrong' `VarianceDiagInfo` +/// may lead to confusing notes in error messages, it will never cause +/// a miscompilation or unsoundness. +/// +/// When in doubt, use `VarianceDiagInfo::default()` +#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)] +pub enum VarianceDiagInfo<'tcx> { + /// No additional information - this is the default. + /// We will not add any additional information to error messages. + #[default] + None, + /// We switched our variance because a generic argument occurs inside + /// the invariant generic argument of another type. + Invariant { + /// The generic type containing the generic parameter + /// that changes the variance (e.g. `*mut T`, `MyStruct<T>`) + ty: Ty<'tcx>, + /// The index of the generic parameter being used + /// (e.g. `0` for `*mut T`, `1` for `MyStruct<'CovariantParam, 'InvariantParam>`) + param_index: u32, + }, +} + +impl<'tcx> VarianceDiagInfo<'tcx> { + /// Mirrors `Variance::xform` - used to 'combine' the existing + /// and new `VarianceDiagInfo`s when our variance changes. + pub fn xform(self, other: VarianceDiagInfo<'tcx>) -> VarianceDiagInfo<'tcx> { + // For now, just use the first `VarianceDiagInfo::Invariant` that we see + match self { + VarianceDiagInfo::None => other, + VarianceDiagInfo::Invariant { .. } => self, + } + } +} |