| // Generic arguments. |
| |
| use crate::ty::codec::{TyDecoder, TyEncoder}; |
| use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable}; |
| use crate::ty::sty::{ClosureArgs, CoroutineArgs, InlineConstArgs}; |
| use crate::ty::visit::{TypeVisitable, TypeVisitableExt, TypeVisitor}; |
| use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt}; |
| |
| use rustc_data_structures::intern::Interned; |
| use rustc_errors::{DiagnosticArgValue, IntoDiagnosticArg}; |
| use rustc_hir::def_id::DefId; |
| use rustc_macros::HashStable; |
| use rustc_serialize::{self, Decodable, Encodable}; |
| use rustc_type_ir::WithCachedTypeInfo; |
| use smallvec::SmallVec; |
| |
| use core::intrinsics; |
| use std::cmp::Ordering; |
| use std::marker::PhantomData; |
| use std::mem; |
| use std::num::NonZeroUsize; |
| use std::ops::{ControlFlow, Deref}; |
| |
| /// An entity in the Rust type system, which can be one of |
| /// several kinds (types, lifetimes, and consts). |
| /// To reduce memory usage, a `GenericArg` is an interned pointer, |
| /// with the lowest 2 bits being reserved for a tag to |
| /// indicate the type (`Ty`, `Region`, or `Const`) it points to. |
| /// |
| /// Note: the `PartialEq`, `Eq` and `Hash` derives are only valid because `Ty`, |
| /// `Region` and `Const` are all interned. |
| #[derive(Copy, Clone, PartialEq, Eq, Hash)] |
| pub struct GenericArg<'tcx> { |
| ptr: NonZeroUsize, |
| marker: PhantomData<(Ty<'tcx>, ty::Region<'tcx>, ty::Const<'tcx>)>, |
| } |
| |
| impl<'tcx> IntoDiagnosticArg for GenericArg<'tcx> { |
| fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> { |
| self.to_string().into_diagnostic_arg() |
| } |
| } |
| |
| const TAG_MASK: usize = 0b11; |
| const TYPE_TAG: usize = 0b00; |
| const REGION_TAG: usize = 0b01; |
| const CONST_TAG: usize = 0b10; |
| |
| #[derive(Debug, TyEncodable, TyDecodable, PartialEq, Eq, PartialOrd, Ord, HashStable)] |
| pub enum GenericArgKind<'tcx> { |
| Lifetime(ty::Region<'tcx>), |
| Type(Ty<'tcx>), |
| Const(ty::Const<'tcx>), |
| } |
| |
| impl<'tcx> GenericArgKind<'tcx> { |
| #[inline] |
| fn pack(self) -> GenericArg<'tcx> { |
| let (tag, ptr) = match self { |
| GenericArgKind::Lifetime(lt) => { |
| // Ensure we can use the tag bits. |
| assert_eq!(mem::align_of_val(&*lt.0.0) & TAG_MASK, 0); |
| (REGION_TAG, lt.0.0 as *const ty::RegionKind<'tcx> as usize) |
| } |
| GenericArgKind::Type(ty) => { |
| // Ensure we can use the tag bits. |
| assert_eq!(mem::align_of_val(&*ty.0.0) & TAG_MASK, 0); |
| (TYPE_TAG, ty.0.0 as *const WithCachedTypeInfo<ty::TyKind<'tcx>> as usize) |
| } |
| GenericArgKind::Const(ct) => { |
| // Ensure we can use the tag bits. |
| assert_eq!(mem::align_of_val(&*ct.0.0) & TAG_MASK, 0); |
| (CONST_TAG, ct.0.0 as *const ty::ConstData<'tcx> as usize) |
| } |
| }; |
| |
| GenericArg { ptr: unsafe { NonZeroUsize::new_unchecked(ptr | tag) }, marker: PhantomData } |
| } |
| } |
| |
| impl<'tcx> Ord for GenericArg<'tcx> { |
| fn cmp(&self, other: &GenericArg<'tcx>) -> Ordering { |
| self.unpack().cmp(&other.unpack()) |
| } |
| } |
| |
| impl<'tcx> PartialOrd for GenericArg<'tcx> { |
| fn partial_cmp(&self, other: &GenericArg<'tcx>) -> Option<Ordering> { |
| Some(self.cmp(&other)) |
| } |
| } |
| |
| impl<'tcx> From<ty::Region<'tcx>> for GenericArg<'tcx> { |
| #[inline] |
| fn from(r: ty::Region<'tcx>) -> GenericArg<'tcx> { |
| GenericArgKind::Lifetime(r).pack() |
| } |
| } |
| |
| impl<'tcx> From<Ty<'tcx>> for GenericArg<'tcx> { |
| #[inline] |
| fn from(ty: Ty<'tcx>) -> GenericArg<'tcx> { |
| GenericArgKind::Type(ty).pack() |
| } |
| } |
| |
| impl<'tcx> From<ty::Const<'tcx>> for GenericArg<'tcx> { |
| #[inline] |
| fn from(c: ty::Const<'tcx>) -> GenericArg<'tcx> { |
| GenericArgKind::Const(c).pack() |
| } |
| } |
| |
| impl<'tcx> From<ty::Term<'tcx>> for GenericArg<'tcx> { |
| fn from(value: ty::Term<'tcx>) -> Self { |
| match value.unpack() { |
| ty::TermKind::Ty(t) => t.into(), |
| ty::TermKind::Const(c) => c.into(), |
| } |
| } |
| } |
| |
| impl<'tcx> GenericArg<'tcx> { |
| #[inline] |
| pub fn unpack(self) -> GenericArgKind<'tcx> { |
| let ptr = self.ptr.get(); |
| // SAFETY: use of `Interned::new_unchecked` here is ok because these |
| // pointers were originally created from `Interned` types in `pack()`, |
| // and this is just going in the other direction. |
| unsafe { |
| match ptr & TAG_MASK { |
| REGION_TAG => GenericArgKind::Lifetime(ty::Region(Interned::new_unchecked( |
| &*((ptr & !TAG_MASK) as *const ty::RegionKind<'tcx>), |
| ))), |
| TYPE_TAG => GenericArgKind::Type(Ty(Interned::new_unchecked( |
| &*((ptr & !TAG_MASK) as *const WithCachedTypeInfo<ty::TyKind<'tcx>>), |
| ))), |
| CONST_TAG => GenericArgKind::Const(ty::Const(Interned::new_unchecked( |
| &*((ptr & !TAG_MASK) as *const ty::ConstData<'tcx>), |
| ))), |
| _ => intrinsics::unreachable(), |
| } |
| } |
| } |
| |
| #[inline] |
| pub fn as_type(self) -> Option<Ty<'tcx>> { |
| match self.unpack() { |
| GenericArgKind::Type(ty) => Some(ty), |
| _ => None, |
| } |
| } |
| |
| #[inline] |
| pub fn as_region(self) -> Option<ty::Region<'tcx>> { |
| match self.unpack() { |
| GenericArgKind::Lifetime(re) => Some(re), |
| _ => None, |
| } |
| } |
| |
| #[inline] |
| pub fn as_const(self) -> Option<ty::Const<'tcx>> { |
| match self.unpack() { |
| GenericArgKind::Const(ct) => Some(ct), |
| _ => None, |
| } |
| } |
| |
| /// Unpack the `GenericArg` as a region when it is known certainly to be a region. |
| pub fn expect_region(self) -> ty::Region<'tcx> { |
| self.as_region().unwrap_or_else(|| bug!("expected a region, but found another kind")) |
| } |
| |
| /// Unpack the `GenericArg` as a type when it is known certainly to be a type. |
| /// This is true in cases where `GenericArgs` is used in places where the kinds are known |
| /// to be limited (e.g. in tuples, where the only parameters are type parameters). |
| pub fn expect_ty(self) -> Ty<'tcx> { |
| self.as_type().unwrap_or_else(|| bug!("expected a type, but found another kind")) |
| } |
| |
| /// Unpack the `GenericArg` as a const when it is known certainly to be a const. |
| pub fn expect_const(self) -> ty::Const<'tcx> { |
| self.as_const().unwrap_or_else(|| bug!("expected a const, but found another kind")) |
| } |
| |
| pub fn is_non_region_infer(self) -> bool { |
| match self.unpack() { |
| GenericArgKind::Lifetime(_) => false, |
| GenericArgKind::Type(ty) => ty.is_ty_or_numeric_infer(), |
| GenericArgKind::Const(ct) => ct.is_ct_infer(), |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> Lift<'tcx> for GenericArg<'a> { |
| type Lifted = GenericArg<'tcx>; |
| |
| fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> { |
| match self.unpack() { |
| GenericArgKind::Lifetime(lt) => tcx.lift(lt).map(|lt| lt.into()), |
| GenericArgKind::Type(ty) => tcx.lift(ty).map(|ty| ty.into()), |
| GenericArgKind::Const(ct) => tcx.lift(ct).map(|ct| ct.into()), |
| } |
| } |
| } |
| |
| impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for GenericArg<'tcx> { |
| fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>( |
| self, |
| folder: &mut F, |
| ) -> Result<Self, F::Error> { |
| match self.unpack() { |
| GenericArgKind::Lifetime(lt) => lt.try_fold_with(folder).map(Into::into), |
| GenericArgKind::Type(ty) => ty.try_fold_with(folder).map(Into::into), |
| GenericArgKind::Const(ct) => ct.try_fold_with(folder).map(Into::into), |
| } |
| } |
| } |
| |
| impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for GenericArg<'tcx> { |
| fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> { |
| match self.unpack() { |
| GenericArgKind::Lifetime(lt) => lt.visit_with(visitor), |
| GenericArgKind::Type(ty) => ty.visit_with(visitor), |
| GenericArgKind::Const(ct) => ct.visit_with(visitor), |
| } |
| } |
| } |
| |
| impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for GenericArg<'tcx> { |
| fn encode(&self, e: &mut E) { |
| self.unpack().encode(e) |
| } |
| } |
| |
| impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArg<'tcx> { |
| fn decode(d: &mut D) -> GenericArg<'tcx> { |
| GenericArgKind::decode(d).pack() |
| } |
| } |
| |
| /// List of generic arguments that are gonna be used to replace generic parameters. |
| pub type GenericArgs<'tcx> = List<GenericArg<'tcx>>; |
| |
| pub type GenericArgsRef<'tcx> = &'tcx GenericArgs<'tcx>; |
| |
| impl<'tcx> GenericArgs<'tcx> { |
| /// Converts generic args to a type list. |
| /// |
| /// # Panics |
| /// |
| /// If any of the generic arguments are not types. |
| pub fn into_type_list(&self, tcx: TyCtxt<'tcx>) -> &'tcx List<Ty<'tcx>> { |
| tcx.mk_type_list_from_iter(self.iter().map(|arg| match arg.unpack() { |
| GenericArgKind::Type(ty) => ty, |
| _ => bug!("`into_type_list` called on generic arg with non-types"), |
| })) |
| } |
| |
| /// Interpret these generic args as the args of a closure type. |
| /// Closure args have a particular structure controlled by the |
| /// compiler that encodes information like the signature and closure kind; |
| /// see `ty::ClosureArgs` struct for more comments. |
| pub fn as_closure(&'tcx self) -> ClosureArgs<'tcx> { |
| ClosureArgs { args: self } |
| } |
| |
| /// Interpret these generic args as the args of a coroutine type. |
| /// Coroutine args have a particular structure controlled by the |
| /// compiler that encodes information like the signature and coroutine kind; |
| /// see `ty::CoroutineArgs` struct for more comments. |
| pub fn as_coroutine(&'tcx self) -> CoroutineArgs<'tcx> { |
| CoroutineArgs { args: self } |
| } |
| |
| /// Interpret these generic args as the args of an inline const. |
| /// Inline const args have a particular structure controlled by the |
| /// compiler that encodes information like the inferred type; |
| /// see `ty::InlineConstArgs` struct for more comments. |
| pub fn as_inline_const(&'tcx self) -> InlineConstArgs<'tcx> { |
| InlineConstArgs { args: self } |
| } |
| |
| /// Creates an `GenericArgs` that maps each generic parameter to itself. |
| pub fn identity_for_item(tcx: TyCtxt<'tcx>, def_id: impl Into<DefId>) -> GenericArgsRef<'tcx> { |
| Self::for_item(tcx, def_id.into(), |param, _| tcx.mk_param_from_def(param)) |
| } |
| |
| /// Creates an `GenericArgs` for generic parameter definitions, |
| /// by calling closures to obtain each kind. |
| /// The closures get to observe the `GenericArgs` as they're |
| /// being built, which can be used to correctly |
| /// replace defaults of generic parameters. |
| pub fn for_item<F>(tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> GenericArgsRef<'tcx> |
| where |
| F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>, |
| { |
| let defs = tcx.generics_of(def_id); |
| let count = defs.count(); |
| let mut args = SmallVec::with_capacity(count); |
| Self::fill_item(&mut args, tcx, defs, &mut mk_kind); |
| tcx.mk_args(&args) |
| } |
| |
| pub fn extend_to<F>( |
| &self, |
| tcx: TyCtxt<'tcx>, |
| def_id: DefId, |
| mut mk_kind: F, |
| ) -> GenericArgsRef<'tcx> |
| where |
| F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>, |
| { |
| Self::for_item(tcx, def_id, |param, args| { |
| self.get(param.index as usize).cloned().unwrap_or_else(|| mk_kind(param, args)) |
| }) |
| } |
| |
| pub fn fill_item<F>( |
| args: &mut SmallVec<[GenericArg<'tcx>; 8]>, |
| tcx: TyCtxt<'tcx>, |
| defs: &ty::Generics, |
| mk_kind: &mut F, |
| ) where |
| F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>, |
| { |
| if let Some(def_id) = defs.parent { |
| let parent_defs = tcx.generics_of(def_id); |
| Self::fill_item(args, tcx, parent_defs, mk_kind); |
| } |
| Self::fill_single(args, defs, mk_kind) |
| } |
| |
| pub fn fill_single<F>( |
| args: &mut SmallVec<[GenericArg<'tcx>; 8]>, |
| defs: &ty::Generics, |
| mk_kind: &mut F, |
| ) where |
| F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>, |
| { |
| args.reserve(defs.params.len()); |
| for param in &defs.params { |
| let kind = mk_kind(param, args); |
| assert_eq!(param.index as usize, args.len(), "{args:#?}, {defs:#?}"); |
| args.push(kind); |
| } |
| } |
| |
| // Extend an `original_args` list to the full number of args expected by `def_id`, |
| // filling in the missing parameters with error ty/ct or 'static regions. |
| pub fn extend_with_error( |
| tcx: TyCtxt<'tcx>, |
| def_id: DefId, |
| original_args: &[GenericArg<'tcx>], |
| ) -> GenericArgsRef<'tcx> { |
| ty::GenericArgs::for_item(tcx, def_id, |def, args| { |
| if let Some(arg) = original_args.get(def.index as usize) { |
| *arg |
| } else { |
| def.to_error(tcx, args) |
| } |
| }) |
| } |
| |
| #[inline] |
| pub fn types(&'tcx self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> + 'tcx { |
| self.iter().filter_map(|k| k.as_type()) |
| } |
| |
| #[inline] |
| pub fn regions(&'tcx self) -> impl DoubleEndedIterator<Item = ty::Region<'tcx>> + 'tcx { |
| self.iter().filter_map(|k| k.as_region()) |
| } |
| |
| #[inline] |
| pub fn consts(&'tcx self) -> impl DoubleEndedIterator<Item = ty::Const<'tcx>> + 'tcx { |
| self.iter().filter_map(|k| k.as_const()) |
| } |
| |
| /// Returns generic arguments that are not lifetimes or host effect params. |
| #[inline] |
| pub fn non_erasable_generics( |
| &'tcx self, |
| tcx: TyCtxt<'tcx>, |
| def_id: DefId, |
| ) -> impl DoubleEndedIterator<Item = GenericArgKind<'tcx>> + 'tcx { |
| let generics = tcx.generics_of(def_id); |
| self.iter().enumerate().filter_map(|(i, k)| match k.unpack() { |
| _ if Some(i) == generics.host_effect_index => None, |
| ty::GenericArgKind::Lifetime(_) => None, |
| generic => Some(generic), |
| }) |
| } |
| |
| #[inline] |
| #[track_caller] |
| pub fn type_at(&self, i: usize) -> Ty<'tcx> { |
| self[i].as_type().unwrap_or_else(|| bug!("expected type for param #{} in {:?}", i, self)) |
| } |
| |
| #[inline] |
| #[track_caller] |
| pub fn region_at(&self, i: usize) -> ty::Region<'tcx> { |
| self[i] |
| .as_region() |
| .unwrap_or_else(|| bug!("expected region for param #{} in {:?}", i, self)) |
| } |
| |
| #[inline] |
| #[track_caller] |
| pub fn const_at(&self, i: usize) -> ty::Const<'tcx> { |
| self[i].as_const().unwrap_or_else(|| bug!("expected const for param #{} in {:?}", i, self)) |
| } |
| |
| #[inline] |
| #[track_caller] |
| pub fn type_for_def(&self, def: &ty::GenericParamDef) -> GenericArg<'tcx> { |
| self.type_at(def.index as usize).into() |
| } |
| |
| /// Transform from generic args for a child of `source_ancestor` |
| /// (e.g., a trait or impl) to args for the same child |
| /// in a different item, with `target_args` as the base for |
| /// the target impl/trait, with the source child-specific |
| /// parameters (e.g., method parameters) on top of that base. |
| /// |
| /// For example given: |
| /// |
| /// ```no_run |
| /// trait X<S> { fn f<T>(); } |
| /// impl<U> X<U> for U { fn f<V>() {} } |
| /// ``` |
| /// |
| /// * If `self` is `[Self, S, T]`: the identity args of `f` in the trait. |
| /// * If `source_ancestor` is the def_id of the trait. |
| /// * If `target_args` is `[U]`, the args for the impl. |
| /// * Then we will return `[U, T]`, the arg for `f` in the impl that |
| /// are needed for it to match the trait. |
| pub fn rebase_onto( |
| &self, |
| tcx: TyCtxt<'tcx>, |
| source_ancestor: DefId, |
| target_args: GenericArgsRef<'tcx>, |
| ) -> GenericArgsRef<'tcx> { |
| let defs = tcx.generics_of(source_ancestor); |
| tcx.mk_args_from_iter(target_args.iter().chain(self.iter().skip(defs.count()))) |
| } |
| |
| pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> GenericArgsRef<'tcx> { |
| tcx.mk_args_from_iter(self.iter().take(generics.count())) |
| } |
| |
| pub fn print_as_list(&self) -> String { |
| let v = self.iter().map(|arg| arg.to_string()).collect::<Vec<_>>(); |
| format!("[{}]", v.join(", ")) |
| } |
| } |
| |
| impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for GenericArgsRef<'tcx> { |
| fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>( |
| self, |
| folder: &mut F, |
| ) -> Result<Self, F::Error> { |
| // This code is hot enough that it's worth specializing for the most |
| // common length lists, to avoid the overhead of `SmallVec` creation. |
| // The match arms are in order of frequency. The 1, 2, and 0 cases are |
| // typically hit in 90--99.99% of cases. When folding doesn't change |
| // the args, it's faster to reuse the existing args rather than |
| // calling `mk_args`. |
| match self.len() { |
| 1 => { |
| let param0 = self[0].try_fold_with(folder)?; |
| if param0 == self[0] { Ok(self) } else { Ok(folder.interner().mk_args(&[param0])) } |
| } |
| 2 => { |
| let param0 = self[0].try_fold_with(folder)?; |
| let param1 = self[1].try_fold_with(folder)?; |
| if param0 == self[0] && param1 == self[1] { |
| Ok(self) |
| } else { |
| Ok(folder.interner().mk_args(&[param0, param1])) |
| } |
| } |
| 0 => Ok(self), |
| _ => ty::util::fold_list(self, folder, |tcx, v| tcx.mk_args(v)), |
| } |
| } |
| } |
| |
| impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<Ty<'tcx>> { |
| fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>( |
| self, |
| folder: &mut F, |
| ) -> Result<Self, F::Error> { |
| // This code is fairly hot, though not as hot as `GenericArgsRef`. |
| // |
| // When compiling stage 2, I get the following results: |
| // |
| // len | total | % |
| // --- | --------- | ----- |
| // 2 | 15083590 | 48.1 |
| // 3 | 7540067 | 24.0 |
| // 1 | 5300377 | 16.9 |
| // 4 | 1351897 | 4.3 |
| // 0 | 1256849 | 4.0 |
| // |
| // I've tried it with some private repositories and got |
| // close to the same result, with 4 and 0 swapping places |
| // sometimes. |
| match self.len() { |
| 2 => { |
| let param0 = self[0].try_fold_with(folder)?; |
| let param1 = self[1].try_fold_with(folder)?; |
| if param0 == self[0] && param1 == self[1] { |
| Ok(self) |
| } else { |
| Ok(folder.interner().mk_type_list(&[param0, param1])) |
| } |
| } |
| _ => ty::util::fold_list(self, folder, |tcx, v| tcx.mk_type_list(v)), |
| } |
| } |
| } |
| |
| impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitable<TyCtxt<'tcx>> for &'tcx ty::List<T> { |
| #[inline] |
| fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> { |
| self.iter().try_for_each(|t| t.visit_with(visitor)) |
| } |
| } |
| |
| /// Similar to [`super::Binder`] except that it tracks early bound generics, i.e. `struct Foo<T>(T)` |
| /// needs `T` instantiated immediately. This type primarily exists to avoid forgetting to call |
| /// `instantiate`. |
| /// |
| /// If you don't have anything to `instantiate`, you may be looking for |
| /// [`instantiate_identity`](EarlyBinder::instantiate_identity) or [`skip_binder`](EarlyBinder::skip_binder). |
| #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] |
| #[derive(Encodable, Decodable, HashStable)] |
| pub struct EarlyBinder<T> { |
| value: T, |
| } |
| |
| /// For early binders, you should first call `instantiate` before using any visitors. |
| impl<'tcx, T> !TypeFoldable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {} |
| impl<'tcx, T> !TypeVisitable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {} |
| |
| impl<T> EarlyBinder<T> { |
| pub fn bind(value: T) -> EarlyBinder<T> { |
| EarlyBinder { value } |
| } |
| |
| pub fn as_ref(&self) -> EarlyBinder<&T> { |
| EarlyBinder { value: &self.value } |
| } |
| |
| 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.value); |
| 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.value)?; |
| Ok(EarlyBinder { value }) |
| } |
| |
| pub fn rebind<U>(&self, value: U) -> EarlyBinder<U> { |
| EarlyBinder { value } |
| } |
| |
| /// Skips the binder and returns the "bound" value. |
| /// This can be used to extract data that does not depend on generic parameters |
| /// (e.g., getting the `DefId` of the inner value or getting the number of |
| /// arguments of an `FnSig`). Otherwise, consider using |
| /// [`instantiate_identity`](EarlyBinder::instantiate_identity). |
| /// |
| /// To skip the binder on `x: &EarlyBinder<T>` to obtain `&T`, leverage |
| /// [`EarlyBinder::as_ref`](EarlyBinder::as_ref): `x.as_ref().skip_binder()`. |
| /// |
| /// See also [`Binder::skip_binder`](super::Binder::skip_binder), which is |
| /// the analogous operation on [`super::Binder`]. |
| pub fn skip_binder(self) -> T { |
| self.value |
| } |
| } |
| |
| impl<T> EarlyBinder<Option<T>> { |
| pub fn transpose(self) -> Option<EarlyBinder<T>> { |
| self.value.map(|value| EarlyBinder { value }) |
| } |
| } |
| |
| impl<T, U> EarlyBinder<(T, U)> { |
| pub fn transpose_tuple2(self) -> (EarlyBinder<T>, EarlyBinder<U>) { |
| let EarlyBinder { value: (lhs, rhs) } = self; |
| (EarlyBinder { value: lhs }, EarlyBinder { value: rhs }) |
| } |
| } |
| |
| impl<'tcx, 's, I: IntoIterator> EarlyBinder<I> |
| where |
| I::Item: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| pub fn iter_instantiated( |
| self, |
| tcx: TyCtxt<'tcx>, |
| args: &'s [GenericArg<'tcx>], |
| ) -> IterInstantiated<'s, 'tcx, I> { |
| IterInstantiated { it: self.value.into_iter(), tcx, args } |
| } |
| |
| /// Similar to [`instantiate_identity`](EarlyBinder::instantiate_identity), |
| /// but on an iterator of `TypeFoldable` values. |
| pub fn instantiate_identity_iter(self) -> I::IntoIter { |
| self.value.into_iter() |
| } |
| } |
| |
| pub struct IterInstantiated<'s, 'tcx, I: IntoIterator> { |
| it: I::IntoIter, |
| tcx: TyCtxt<'tcx>, |
| args: &'s [GenericArg<'tcx>], |
| } |
| |
| impl<'tcx, I: IntoIterator> Iterator for IterInstantiated<'_, 'tcx, I> |
| where |
| I::Item: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| type Item = I::Item; |
| |
| fn next(&mut self) -> Option<Self::Item> { |
| Some(EarlyBinder { value: self.it.next()? }.instantiate(self.tcx, self.args)) |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.it.size_hint() |
| } |
| } |
| |
| impl<'tcx, I: IntoIterator> DoubleEndedIterator for IterInstantiated<'_, 'tcx, I> |
| where |
| I::IntoIter: DoubleEndedIterator, |
| I::Item: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| fn next_back(&mut self) -> Option<Self::Item> { |
| Some(EarlyBinder { value: self.it.next_back()? }.instantiate(self.tcx, self.args)) |
| } |
| } |
| |
| impl<'tcx, I: IntoIterator> ExactSizeIterator for IterInstantiated<'_, 'tcx, I> |
| where |
| I::IntoIter: ExactSizeIterator, |
| I::Item: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| } |
| |
| impl<'tcx, 's, I: IntoIterator> EarlyBinder<I> |
| where |
| I::Item: Deref, |
| <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>, |
| { |
| pub fn iter_instantiated_copied( |
| self, |
| tcx: TyCtxt<'tcx>, |
| args: &'s [GenericArg<'tcx>], |
| ) -> IterInstantiatedCopied<'s, 'tcx, I> { |
| IterInstantiatedCopied { it: self.value.into_iter(), tcx, args } |
| } |
| |
| /// Similar to [`instantiate_identity`](EarlyBinder::instantiate_identity), |
| /// but on an iterator of values that deref to a `TypeFoldable`. |
| pub fn instantiate_identity_iter_copied( |
| self, |
| ) -> impl Iterator<Item = <I::Item as Deref>::Target> { |
| self.value.into_iter().map(|v| *v) |
| } |
| } |
| |
| pub struct IterInstantiatedCopied<'a, 'tcx, I: IntoIterator> { |
| it: I::IntoIter, |
| tcx: TyCtxt<'tcx>, |
| args: &'a [GenericArg<'tcx>], |
| } |
| |
| impl<'tcx, I: IntoIterator> Iterator for IterInstantiatedCopied<'_, 'tcx, I> |
| where |
| I::Item: Deref, |
| <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>, |
| { |
| type Item = <I::Item as Deref>::Target; |
| |
| fn next(&mut self) -> Option<Self::Item> { |
| self.it.next().map(|value| EarlyBinder { value: *value }.instantiate(self.tcx, self.args)) |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.it.size_hint() |
| } |
| } |
| |
| impl<'tcx, I: IntoIterator> DoubleEndedIterator for IterInstantiatedCopied<'_, 'tcx, I> |
| where |
| I::IntoIter: DoubleEndedIterator, |
| I::Item: Deref, |
| <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>, |
| { |
| fn next_back(&mut self) -> Option<Self::Item> { |
| self.it |
| .next_back() |
| .map(|value| EarlyBinder { value: *value }.instantiate(self.tcx, self.args)) |
| } |
| } |
| |
| impl<'tcx, I: IntoIterator> ExactSizeIterator for IterInstantiatedCopied<'_, 'tcx, I> |
| where |
| I::IntoIter: ExactSizeIterator, |
| I::Item: Deref, |
| <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>, |
| { |
| } |
| |
| pub struct EarlyBinderIter<T> { |
| t: T, |
| } |
| |
| impl<T: IntoIterator> EarlyBinder<T> { |
| pub fn transpose_iter(self) -> EarlyBinderIter<T::IntoIter> { |
| EarlyBinderIter { t: self.value.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(|value| EarlyBinder { value }) |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.t.size_hint() |
| } |
| } |
| |
| impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> ty::EarlyBinder<T> { |
| pub fn instantiate(self, tcx: TyCtxt<'tcx>, args: &[GenericArg<'tcx>]) -> T { |
| let mut folder = ArgFolder { tcx, args, binders_passed: 0 }; |
| self.value.fold_with(&mut folder) |
| } |
| |
| /// Makes the identity replacement `T0 => T0, ..., TN => TN`. |
| /// Conceptually, this converts universally bound variables into placeholders |
| /// when inside of a given item. |
| /// |
| /// For example, consider `for<T> fn foo<T>(){ .. }`: |
| /// - Outside of `foo`, `T` is bound (represented by the presence of `EarlyBinder`). |
| /// - Inside of the body of `foo`, we treat `T` as a placeholder by calling |
| /// `instantiate_identity` to discharge the `EarlyBinder`. |
| pub fn instantiate_identity(self) -> T { |
| self.value |
| } |
| |
| /// Returns the inner value, but only if it contains no bound vars. |
| pub fn no_bound_vars(self) -> Option<T> { |
| if !self.value.has_param() { Some(self.value) } else { None } |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // The actual substitution engine itself is a type folder. |
| |
| struct ArgFolder<'a, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| args: &'a [GenericArg<'tcx>], |
| |
| /// Number of region binders we have passed through while doing the substitution |
| binders_passed: u32, |
| } |
| |
| impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ArgFolder<'a, 'tcx> { |
| #[inline] |
| fn interner(&self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>( |
| &mut self, |
| t: ty::Binder<'tcx, T>, |
| ) -> ty::Binder<'tcx, T> { |
| self.binders_passed += 1; |
| let t = t.super_fold_with(self); |
| self.binders_passed -= 1; |
| t |
| } |
| |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| #[cold] |
| #[inline(never)] |
| fn region_param_out_of_range(data: ty::EarlyBoundRegion, args: &[GenericArg<'_>]) -> ! { |
| bug!( |
| "Region parameter out of range when substituting in region {} (index={}, args = {:?})", |
| data.name, |
| data.index, |
| args, |
| ) |
| } |
| |
| #[cold] |
| #[inline(never)] |
| fn region_param_invalid(data: ty::EarlyBoundRegion, other: GenericArgKind<'_>) -> ! { |
| bug!( |
| "Unexpected parameter {:?} when substituting in region {} (index={})", |
| other, |
| data.name, |
| data.index |
| ) |
| } |
| |
| // Note: This routine only handles regions that are bound on |
| // type declarations and other outer declarations, not those |
| // bound in *fn types*. Region substitution of the bound |
| // regions that appear in a function signature is done using |
| // the specialized routine `ty::replace_late_regions()`. |
| match *r { |
| ty::ReEarlyBound(data) => { |
| let rk = self.args.get(data.index as usize).map(|k| k.unpack()); |
| match rk { |
| Some(GenericArgKind::Lifetime(lt)) => self.shift_region_through_binders(lt), |
| Some(other) => region_param_invalid(data, other), |
| None => region_param_out_of_range(data, self.args), |
| } |
| } |
| ty::ReLateBound(..) |
| | ty::ReFree(_) |
| | ty::ReStatic |
| | ty::RePlaceholder(_) |
| | ty::ReErased |
| | ty::ReError(_) => r, |
| ty::ReVar(_) => bug!("unexpected region: {r:?}"), |
| } |
| } |
| |
| fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { |
| if !t.has_param() { |
| return t; |
| } |
| |
| match *t.kind() { |
| ty::Param(p) => self.ty_for_param(p, t), |
| _ => t.super_fold_with(self), |
| } |
| } |
| |
| fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> { |
| if let ty::ConstKind::Param(p) = c.kind() { |
| self.const_for_param(p, c) |
| } else { |
| c.super_fold_with(self) |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> ArgFolder<'a, 'tcx> { |
| fn ty_for_param(&self, p: ty::ParamTy, source_ty: Ty<'tcx>) -> Ty<'tcx> { |
| // Look up the type in the args. It really should be in there. |
| let opt_ty = self.args.get(p.index as usize).map(|k| k.unpack()); |
| let ty = match opt_ty { |
| Some(GenericArgKind::Type(ty)) => ty, |
| Some(kind) => self.type_param_expected(p, source_ty, kind), |
| None => self.type_param_out_of_range(p, source_ty), |
| }; |
| |
| self.shift_vars_through_binders(ty) |
| } |
| |
| #[cold] |
| #[inline(never)] |
| fn type_param_expected(&self, p: ty::ParamTy, ty: Ty<'tcx>, kind: GenericArgKind<'tcx>) -> ! { |
| bug!( |
| "expected type for `{:?}` ({:?}/{}) but found {:?} when substituting, args={:?}", |
| p, |
| ty, |
| p.index, |
| kind, |
| self.args, |
| ) |
| } |
| |
| #[cold] |
| #[inline(never)] |
| fn type_param_out_of_range(&self, p: ty::ParamTy, ty: Ty<'tcx>) -> ! { |
| bug!( |
| "type parameter `{:?}` ({:?}/{}) out of range when substituting, args={:?}", |
| p, |
| ty, |
| p.index, |
| self.args, |
| ) |
| } |
| |
| fn const_for_param(&self, p: ParamConst, source_ct: ty::Const<'tcx>) -> ty::Const<'tcx> { |
| // Look up the const in the args. It really should be in there. |
| let opt_ct = self.args.get(p.index as usize).map(|k| k.unpack()); |
| let ct = match opt_ct { |
| Some(GenericArgKind::Const(ct)) => ct, |
| Some(kind) => self.const_param_expected(p, source_ct, kind), |
| None => self.const_param_out_of_range(p, source_ct), |
| }; |
| |
| self.shift_vars_through_binders(ct) |
| } |
| |
| #[cold] |
| #[inline(never)] |
| fn const_param_expected( |
| &self, |
| p: ty::ParamConst, |
| ct: ty::Const<'tcx>, |
| kind: GenericArgKind<'tcx>, |
| ) -> ! { |
| bug!( |
| "expected const for `{:?}` ({:?}/{}) but found {:?} when substituting args={:?}", |
| p, |
| ct, |
| p.index, |
| kind, |
| self.args, |
| ) |
| } |
| |
| #[cold] |
| #[inline(never)] |
| fn const_param_out_of_range(&self, p: ty::ParamConst, ct: ty::Const<'tcx>) -> ! { |
| bug!( |
| "const parameter `{:?}` ({:?}/{}) out of range when substituting args={:?}", |
| p, |
| ct, |
| p.index, |
| self.args, |
| ) |
| } |
| |
| /// It is sometimes necessary to adjust the De Bruijn indices during substitution. This occurs |
| /// when we are substituting a type with escaping bound vars into a context where we have |
| /// passed through binders. That's quite a mouthful. Let's see an example: |
| /// |
| /// ``` |
| /// type Func<A> = fn(A); |
| /// type MetaFunc = for<'a> fn(Func<&'a i32>); |
| /// ``` |
| /// |
| /// The type `MetaFunc`, when fully expanded, will be |
| /// ```ignore (illustrative) |
| /// for<'a> fn(fn(&'a i32)) |
| /// // ^~ ^~ ^~~ |
| /// // | | | |
| /// // | | DebruijnIndex of 2 |
| /// // Binders |
| /// ``` |
| /// Here the `'a` lifetime is bound in the outer function, but appears as an argument of the |
| /// inner one. Therefore, that appearance will have a DebruijnIndex of 2, because we must skip |
| /// over the inner binder (remember that we count De Bruijn indices from 1). However, in the |
| /// definition of `MetaFunc`, the binder is not visible, so the type `&'a i32` will have a |
| /// De Bruijn index of 1. It's only during the substitution that we can see we must increase the |
| /// depth by 1 to account for the binder that we passed through. |
| /// |
| /// As a second example, consider this twist: |
| /// |
| /// ``` |
| /// type FuncTuple<A> = (A,fn(A)); |
| /// type MetaFuncTuple = for<'a> fn(FuncTuple<&'a i32>); |
| /// ``` |
| /// |
| /// Here the final type will be: |
| /// ```ignore (illustrative) |
| /// for<'a> fn((&'a i32, fn(&'a i32))) |
| /// // ^~~ ^~~ |
| /// // | | |
| /// // DebruijnIndex of 1 | |
| /// // DebruijnIndex of 2 |
| /// ``` |
| /// As indicated in the diagram, here the same type `&'a i32` is substituted once, but in the |
| /// first case we do not increase the De Bruijn index and in the second case we do. The reason |
| /// is that only in the second case have we passed through a fn binder. |
| fn shift_vars_through_binders<T: TypeFoldable<TyCtxt<'tcx>>>(&self, val: T) -> T { |
| debug!( |
| "shift_vars(val={:?}, binders_passed={:?}, has_escaping_bound_vars={:?})", |
| val, |
| self.binders_passed, |
| val.has_escaping_bound_vars() |
| ); |
| |
| if self.binders_passed == 0 || !val.has_escaping_bound_vars() { |
| return val; |
| } |
| |
| let result = ty::fold::shift_vars(TypeFolder::interner(self), val, self.binders_passed); |
| debug!("shift_vars: shifted result = {:?}", result); |
| |
| result |
| } |
| |
| fn shift_region_through_binders(&self, region: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| if self.binders_passed == 0 || !region.has_escaping_bound_vars() { |
| return region; |
| } |
| ty::fold::shift_region(self.tcx, region, self.binders_passed) |
| } |
| } |
| |
| /// Stores the user-given args to reach some fully qualified path |
| /// (e.g., `<T>::Item` or `<T as Trait>::Item`). |
| #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable)] |
| #[derive(HashStable, TypeFoldable, TypeVisitable)] |
| pub struct UserArgs<'tcx> { |
| /// The args for the item as given by the user. |
| pub args: GenericArgsRef<'tcx>, |
| |
| /// The self type, in the case of a `<T>::Item` path (when applied |
| /// to an inherent impl). See `UserSelfTy` below. |
| pub user_self_ty: Option<UserSelfTy<'tcx>>, |
| } |
| |
| /// Specifies the user-given self type. In the case of a path that |
| /// refers to a member in an inherent impl, this self type is |
| /// sometimes needed to constrain the type parameters on the impl. For |
| /// example, in this code: |
| /// |
| /// ```ignore (illustrative) |
| /// struct Foo<T> { } |
| /// impl<A> Foo<A> { fn method() { } } |
| /// ``` |
| /// |
| /// when you then have a path like `<Foo<&'static u32>>::method`, |
| /// this struct would carry the `DefId` of the impl along with the |
| /// self type `Foo<u32>`. Then we can instantiate the parameters of |
| /// the impl (with the args from `UserArgs`) and apply those to |
| /// the self type, giving `Foo<?A>`. Finally, we unify that with |
| /// the self type here, which contains `?A` to be `&'static u32` |
| #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable)] |
| #[derive(HashStable, TypeFoldable, TypeVisitable)] |
| pub struct UserSelfTy<'tcx> { |
| pub impl_def_id: DefId, |
| pub self_ty: Ty<'tcx>, |
| } |