980 lines
33 KiB
Rust
980 lines
33 KiB
Rust
// Type substitutions.
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use crate::ty::codec::{TyDecoder, TyEncoder};
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use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
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use crate::ty::sty::{ClosureSubsts, GeneratorSubsts, InlineConstSubsts};
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use crate::ty::visit::{TypeVisitable, TypeVisitor};
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use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt};
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use rustc_data_structures::intern::Interned;
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use rustc_hir::def_id::DefId;
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use rustc_macros::HashStable;
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use rustc_serialize::{self, Decodable, Encodable};
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use rustc_type_ir::WithCachedTypeInfo;
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use smallvec::SmallVec;
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use core::intrinsics;
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use std::cmp::Ordering;
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use std::fmt;
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use std::marker::PhantomData;
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use std::mem;
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use std::num::NonZeroUsize;
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use std::ops::{ControlFlow, Deref};
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use std::slice;
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/// An entity in the Rust type system, which can be one of
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/// several kinds (types, lifetimes, and consts).
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/// To reduce memory usage, a `GenericArg` is an interned pointer,
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/// with the lowest 2 bits being reserved for a tag to
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/// indicate the type (`Ty`, `Region`, or `Const`) it points to.
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///
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/// Note: the `PartialEq`, `Eq` and `Hash` derives are only valid because `Ty`,
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/// `Region` and `Const` are all interned.
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#[derive(Copy, Clone, PartialEq, Eq, Hash)]
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pub struct GenericArg<'tcx> {
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ptr: NonZeroUsize,
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marker: PhantomData<(Ty<'tcx>, ty::Region<'tcx>, ty::Const<'tcx>)>,
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}
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const TAG_MASK: usize = 0b11;
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const TYPE_TAG: usize = 0b00;
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const REGION_TAG: usize = 0b01;
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const CONST_TAG: usize = 0b10;
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#[derive(Debug, TyEncodable, TyDecodable, PartialEq, Eq, PartialOrd, Ord)]
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pub enum GenericArgKind<'tcx> {
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Lifetime(ty::Region<'tcx>),
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Type(Ty<'tcx>),
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Const(ty::Const<'tcx>),
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}
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/// This function goes from `&'a [Ty<'tcx>]` to `&'a [GenericArg<'tcx>]`
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///
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/// This is sound as, for types, `GenericArg` is just
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/// `NonZeroUsize::new_unchecked(ty as *const _ as usize)` as
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/// long as we use `0` for the `TYPE_TAG`.
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pub fn ty_slice_as_generic_args<'a, 'tcx>(ts: &'a [Ty<'tcx>]) -> &'a [GenericArg<'tcx>] {
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assert_eq!(TYPE_TAG, 0);
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// SAFETY: the whole slice is valid and immutable.
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// `Ty` and `GenericArg` is explained above.
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unsafe { slice::from_raw_parts(ts.as_ptr().cast(), ts.len()) }
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}
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impl<'tcx> List<Ty<'tcx>> {
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/// Allows to freely switch between `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>`.
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///
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/// As lists are interned, `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>` have
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/// be interned together, see `intern_type_list` for more details.
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#[inline]
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pub fn as_substs(&'tcx self) -> SubstsRef<'tcx> {
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assert_eq!(TYPE_TAG, 0);
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// SAFETY: `List<T>` is `#[repr(C)]`. `Ty` and `GenericArg` is explained above.
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unsafe { &*(self as *const List<Ty<'tcx>> as *const List<GenericArg<'tcx>>) }
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}
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}
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impl<'tcx> GenericArgKind<'tcx> {
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#[inline]
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fn pack(self) -> GenericArg<'tcx> {
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let (tag, ptr) = match self {
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GenericArgKind::Lifetime(lt) => {
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// Ensure we can use the tag bits.
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assert_eq!(mem::align_of_val(&*lt.0.0) & TAG_MASK, 0);
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(REGION_TAG, lt.0.0 as *const ty::RegionKind<'tcx> as usize)
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}
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GenericArgKind::Type(ty) => {
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// Ensure we can use the tag bits.
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assert_eq!(mem::align_of_val(&*ty.0.0) & TAG_MASK, 0);
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(TYPE_TAG, ty.0.0 as *const WithCachedTypeInfo<ty::TyKind<'tcx>> as usize)
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}
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GenericArgKind::Const(ct) => {
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// Ensure we can use the tag bits.
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assert_eq!(mem::align_of_val(&*ct.0.0) & TAG_MASK, 0);
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(CONST_TAG, ct.0.0 as *const ty::ConstS<'tcx> as usize)
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}
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};
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GenericArg { ptr: unsafe { NonZeroUsize::new_unchecked(ptr | tag) }, marker: PhantomData }
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}
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}
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impl<'tcx> fmt::Debug for GenericArg<'tcx> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self.unpack() {
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GenericArgKind::Lifetime(lt) => lt.fmt(f),
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GenericArgKind::Type(ty) => ty.fmt(f),
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GenericArgKind::Const(ct) => ct.fmt(f),
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}
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}
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}
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impl<'tcx> Ord for GenericArg<'tcx> {
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fn cmp(&self, other: &GenericArg<'tcx>) -> Ordering {
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self.unpack().cmp(&other.unpack())
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}
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}
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impl<'tcx> PartialOrd for GenericArg<'tcx> {
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fn partial_cmp(&self, other: &GenericArg<'tcx>) -> Option<Ordering> {
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Some(self.cmp(&other))
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}
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}
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impl<'tcx> From<ty::Region<'tcx>> for GenericArg<'tcx> {
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#[inline]
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fn from(r: ty::Region<'tcx>) -> GenericArg<'tcx> {
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GenericArgKind::Lifetime(r).pack()
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}
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}
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impl<'tcx> From<Ty<'tcx>> for GenericArg<'tcx> {
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#[inline]
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fn from(ty: Ty<'tcx>) -> GenericArg<'tcx> {
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GenericArgKind::Type(ty).pack()
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}
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}
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impl<'tcx> From<ty::Const<'tcx>> for GenericArg<'tcx> {
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#[inline]
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fn from(c: ty::Const<'tcx>) -> GenericArg<'tcx> {
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GenericArgKind::Const(c).pack()
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}
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}
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impl<'tcx> From<ty::Term<'tcx>> for GenericArg<'tcx> {
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fn from(value: ty::Term<'tcx>) -> Self {
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match value.unpack() {
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ty::TermKind::Ty(t) => t.into(),
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ty::TermKind::Const(c) => c.into(),
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}
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}
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}
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impl<'tcx> GenericArg<'tcx> {
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#[inline]
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pub fn unpack(self) -> GenericArgKind<'tcx> {
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let ptr = self.ptr.get();
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// SAFETY: use of `Interned::new_unchecked` here is ok because these
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// pointers were originally created from `Interned` types in `pack()`,
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// and this is just going in the other direction.
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unsafe {
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match ptr & TAG_MASK {
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REGION_TAG => GenericArgKind::Lifetime(ty::Region(Interned::new_unchecked(
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&*((ptr & !TAG_MASK) as *const ty::RegionKind<'tcx>),
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))),
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TYPE_TAG => GenericArgKind::Type(Ty(Interned::new_unchecked(
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&*((ptr & !TAG_MASK) as *const WithCachedTypeInfo<ty::TyKind<'tcx>>),
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))),
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CONST_TAG => GenericArgKind::Const(ty::Const(Interned::new_unchecked(
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&*((ptr & !TAG_MASK) as *const ty::ConstS<'tcx>),
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))),
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_ => intrinsics::unreachable(),
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}
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}
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}
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/// Unpack the `GenericArg` as a region when it is known certainly to be a region.
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pub fn expect_region(self) -> ty::Region<'tcx> {
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match self.unpack() {
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GenericArgKind::Lifetime(lt) => lt,
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_ => bug!("expected a region, but found another kind"),
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}
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}
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/// Unpack the `GenericArg` as a type when it is known certainly to be a type.
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/// This is true in cases where `Substs` is used in places where the kinds are known
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/// to be limited (e.g. in tuples, where the only parameters are type parameters).
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pub fn expect_ty(self) -> Ty<'tcx> {
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match self.unpack() {
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GenericArgKind::Type(ty) => ty,
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_ => bug!("expected a type, but found another kind"),
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}
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}
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/// Unpack the `GenericArg` as a const when it is known certainly to be a const.
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pub fn expect_const(self) -> ty::Const<'tcx> {
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match self.unpack() {
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GenericArgKind::Const(c) => c,
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_ => bug!("expected a const, but found another kind"),
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}
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}
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pub fn is_non_region_infer(self) -> bool {
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match self.unpack() {
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GenericArgKind::Lifetime(_) => false,
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GenericArgKind::Type(ty) => ty.is_ty_infer(),
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GenericArgKind::Const(ct) => ct.is_ct_infer(),
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}
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}
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}
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impl<'a, 'tcx> Lift<'tcx> for GenericArg<'a> {
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type Lifted = GenericArg<'tcx>;
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fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
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match self.unpack() {
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GenericArgKind::Lifetime(lt) => tcx.lift(lt).map(|lt| lt.into()),
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GenericArgKind::Type(ty) => tcx.lift(ty).map(|ty| ty.into()),
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GenericArgKind::Const(ct) => tcx.lift(ct).map(|ct| ct.into()),
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}
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}
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}
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impl<'tcx> TypeFoldable<'tcx> for GenericArg<'tcx> {
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fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
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match self.unpack() {
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GenericArgKind::Lifetime(lt) => lt.try_fold_with(folder).map(Into::into),
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GenericArgKind::Type(ty) => ty.try_fold_with(folder).map(Into::into),
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GenericArgKind::Const(ct) => ct.try_fold_with(folder).map(Into::into),
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}
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}
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}
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impl<'tcx> TypeVisitable<'tcx> for GenericArg<'tcx> {
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fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
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match self.unpack() {
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GenericArgKind::Lifetime(lt) => lt.visit_with(visitor),
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GenericArgKind::Type(ty) => ty.visit_with(visitor),
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GenericArgKind::Const(ct) => ct.visit_with(visitor),
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}
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}
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}
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impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for GenericArg<'tcx> {
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fn encode(&self, e: &mut E) {
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self.unpack().encode(e)
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}
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}
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impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArg<'tcx> {
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fn decode(d: &mut D) -> GenericArg<'tcx> {
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GenericArgKind::decode(d).pack()
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}
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}
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/// List of generic arguments that are gonna be used to substitute generic parameters.
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pub type InternalSubsts<'tcx> = List<GenericArg<'tcx>>;
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pub type SubstsRef<'tcx> = &'tcx InternalSubsts<'tcx>;
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impl<'tcx> InternalSubsts<'tcx> {
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/// Checks whether all elements of this list are types, if so, transmute.
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pub fn try_as_type_list(&'tcx self) -> Option<&'tcx List<Ty<'tcx>>> {
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if self.iter().all(|arg| matches!(arg.unpack(), GenericArgKind::Type(_))) {
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assert_eq!(TYPE_TAG, 0);
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// SAFETY: All elements are types, see `List<Ty<'tcx>>::as_substs`.
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Some(unsafe { &*(self as *const List<GenericArg<'tcx>> as *const List<Ty<'tcx>>) })
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} else {
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None
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}
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}
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/// Interpret these substitutions as the substitutions of a closure type.
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/// Closure substitutions have a particular structure controlled by the
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/// compiler that encodes information like the signature and closure kind;
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/// see `ty::ClosureSubsts` struct for more comments.
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pub fn as_closure(&'tcx self) -> ClosureSubsts<'tcx> {
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ClosureSubsts { substs: self }
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}
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/// Interpret these substitutions as the substitutions of a generator type.
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/// Generator substitutions have a particular structure controlled by the
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/// compiler that encodes information like the signature and generator kind;
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/// see `ty::GeneratorSubsts` struct for more comments.
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pub fn as_generator(&'tcx self) -> GeneratorSubsts<'tcx> {
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GeneratorSubsts { substs: self }
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}
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/// Interpret these substitutions as the substitutions of an inline const.
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/// Inline const substitutions have a particular structure controlled by the
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/// compiler that encodes information like the inferred type;
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/// see `ty::InlineConstSubsts` struct for more comments.
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pub fn as_inline_const(&'tcx self) -> InlineConstSubsts<'tcx> {
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InlineConstSubsts { substs: self }
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}
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/// Creates an `InternalSubsts` that maps each generic parameter to itself.
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pub fn identity_for_item(tcx: TyCtxt<'tcx>, def_id: DefId) -> SubstsRef<'tcx> {
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Self::for_item(tcx, def_id, |param, _| tcx.mk_param_from_def(param))
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}
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/// Creates an `InternalSubsts` for generic parameter definitions,
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/// by calling closures to obtain each kind.
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/// The closures get to observe the `InternalSubsts` as they're
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/// being built, which can be used to correctly
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/// substitute defaults of generic parameters.
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pub fn for_item<F>(tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> SubstsRef<'tcx>
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where
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F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
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{
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let defs = tcx.generics_of(def_id);
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let count = defs.count();
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let mut substs = SmallVec::with_capacity(count);
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Self::fill_item(&mut substs, tcx, defs, &mut mk_kind);
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tcx.intern_substs(&substs)
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}
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pub fn extend_to<F>(&self, tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> SubstsRef<'tcx>
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where
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F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
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{
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Self::for_item(tcx, def_id, |param, substs| {
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self.get(param.index as usize).cloned().unwrap_or_else(|| mk_kind(param, substs))
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})
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}
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pub fn fill_item<F>(
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substs: &mut SmallVec<[GenericArg<'tcx>; 8]>,
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tcx: TyCtxt<'tcx>,
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defs: &ty::Generics,
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mk_kind: &mut F,
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) where
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F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
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{
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if let Some(def_id) = defs.parent {
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let parent_defs = tcx.generics_of(def_id);
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Self::fill_item(substs, tcx, parent_defs, mk_kind);
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}
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Self::fill_single(substs, defs, mk_kind)
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}
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pub fn fill_single<F>(
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substs: &mut SmallVec<[GenericArg<'tcx>; 8]>,
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defs: &ty::Generics,
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mk_kind: &mut F,
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) where
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F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
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{
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substs.reserve(defs.params.len());
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for param in &defs.params {
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let kind = mk_kind(param, substs);
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assert_eq!(param.index as usize, substs.len());
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substs.push(kind);
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}
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}
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// Extend an `original_substs` list to the full number of substs expected by `def_id`,
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// filling in the missing parameters with error ty/ct or 'static regions.
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pub fn extend_with_error(
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tcx: TyCtxt<'tcx>,
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def_id: DefId,
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original_substs: &[GenericArg<'tcx>],
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) -> SubstsRef<'tcx> {
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ty::InternalSubsts::for_item(tcx, def_id, |def, substs| {
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if let Some(subst) = original_substs.get(def.index as usize) {
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*subst
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} else {
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def.to_error(tcx, substs)
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}
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})
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}
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#[inline]
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pub fn types(&'tcx self) -> impl DoubleEndedIterator<Item = Ty<'tcx>> + 'tcx {
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self.iter()
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.filter_map(|k| if let GenericArgKind::Type(ty) = k.unpack() { Some(ty) } else { None })
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}
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#[inline]
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pub fn regions(&'tcx self) -> impl DoubleEndedIterator<Item = ty::Region<'tcx>> + 'tcx {
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self.iter().filter_map(|k| {
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if let GenericArgKind::Lifetime(lt) = k.unpack() { Some(lt) } else { None }
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})
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}
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#[inline]
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pub fn consts(&'tcx self) -> impl DoubleEndedIterator<Item = ty::Const<'tcx>> + 'tcx {
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self.iter().filter_map(|k| {
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if let GenericArgKind::Const(ct) = k.unpack() { Some(ct) } else { None }
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})
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}
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#[inline]
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pub fn non_erasable_generics(
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&'tcx self,
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) -> impl DoubleEndedIterator<Item = GenericArgKind<'tcx>> + 'tcx {
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self.iter().filter_map(|k| match k.unpack() {
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GenericArgKind::Lifetime(_) => None,
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generic => Some(generic),
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})
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}
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#[inline]
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pub fn type_at(&self, i: usize) -> Ty<'tcx> {
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if let GenericArgKind::Type(ty) = self[i].unpack() {
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ty
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} else {
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bug!("expected type for param #{} in {:?}", i, self);
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}
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}
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#[inline]
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pub fn region_at(&self, i: usize) -> ty::Region<'tcx> {
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if let GenericArgKind::Lifetime(lt) = self[i].unpack() {
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lt
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} else {
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bug!("expected region for param #{} in {:?}", i, self);
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}
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}
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#[inline]
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pub fn const_at(&self, i: usize) -> ty::Const<'tcx> {
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if let GenericArgKind::Const(ct) = self[i].unpack() {
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ct
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} else {
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bug!("expected const for param #{} in {:?}", i, self);
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}
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}
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#[inline]
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pub fn type_for_def(&self, def: &ty::GenericParamDef) -> GenericArg<'tcx> {
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self.type_at(def.index as usize).into()
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}
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/// Transform from substitutions for a child of `source_ancestor`
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/// (e.g., a trait or impl) to substitutions for the same child
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/// in a different item, with `target_substs` 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 substs of `f` in the trait.
|
|
/// * If `source_ancestor` is the def_id of the trait.
|
|
/// * If `target_substs` is `[U]`, the substs for the impl.
|
|
/// * Then we will return `[U, T]`, the subst 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_substs: SubstsRef<'tcx>,
|
|
) -> SubstsRef<'tcx> {
|
|
let defs = tcx.generics_of(source_ancestor);
|
|
tcx.mk_substs(target_substs.iter().chain(self.iter().skip(defs.params.len())))
|
|
}
|
|
|
|
pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> SubstsRef<'tcx> {
|
|
tcx.mk_substs(self.iter().take(generics.count()))
|
|
}
|
|
}
|
|
|
|
impl<'tcx> TypeFoldable<'tcx> for SubstsRef<'tcx> {
|
|
fn try_fold_with<F: FallibleTypeFolder<'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 substs, it's faster to reuse the existing substs rather than
|
|
// calling `intern_substs`.
|
|
match self.len() {
|
|
1 => {
|
|
let param0 = self[0].try_fold_with(folder)?;
|
|
if param0 == self[0] { Ok(self) } else { Ok(folder.tcx().intern_substs(&[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.tcx().intern_substs(&[param0, param1]))
|
|
}
|
|
}
|
|
0 => Ok(self),
|
|
_ => ty::util::fold_list(self, folder, |tcx, v| tcx.intern_substs(v)),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
|
|
fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
|
|
// This code is fairly hot, though not as hot as `SubstsRef`.
|
|
//
|
|
// 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.tcx().intern_type_list(&[param0, param1]))
|
|
}
|
|
}
|
|
_ => ty::util::fold_list(self, folder, |tcx, v| tcx.intern_type_list(v)),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &'tcx ty::List<T> {
|
|
#[inline]
|
|
fn visit_with<V: TypeVisitor<'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` substituted immediately. This type primarily exists to avoid forgetting to call
|
|
/// `subst`.
|
|
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
|
|
#[derive(Encodable, Decodable, HashStable)]
|
|
pub struct EarlyBinder<T>(pub T);
|
|
|
|
/// For early binders, you should first call `subst` before using any visitors.
|
|
impl<'tcx, T> !TypeFoldable<'tcx> for ty::EarlyBinder<T> {}
|
|
impl<'tcx, T> !TypeVisitable<'tcx> for ty::EarlyBinder<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))
|
|
}
|
|
}
|
|
|
|
impl<'tcx, 's, I: IntoIterator> EarlyBinder<I>
|
|
where
|
|
I::Item: TypeFoldable<'tcx>,
|
|
{
|
|
pub fn subst_iter(
|
|
self,
|
|
tcx: TyCtxt<'tcx>,
|
|
substs: &'s [GenericArg<'tcx>],
|
|
) -> SubstIter<'s, 'tcx, I> {
|
|
SubstIter { it: self.0.into_iter(), tcx, substs }
|
|
}
|
|
}
|
|
|
|
pub struct SubstIter<'s, 'tcx, I: IntoIterator> {
|
|
it: I::IntoIter,
|
|
tcx: TyCtxt<'tcx>,
|
|
substs: &'s [GenericArg<'tcx>],
|
|
}
|
|
|
|
impl<'tcx, I: IntoIterator> Iterator for SubstIter<'_, 'tcx, I>
|
|
where
|
|
I::Item: TypeFoldable<'tcx>,
|
|
{
|
|
type Item = I::Item;
|
|
|
|
fn next(&mut self) -> Option<Self::Item> {
|
|
Some(EarlyBinder(self.it.next()?).subst(self.tcx, self.substs))
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
self.it.size_hint()
|
|
}
|
|
}
|
|
|
|
impl<'tcx, I: IntoIterator> DoubleEndedIterator for SubstIter<'_, 'tcx, I>
|
|
where
|
|
I::IntoIter: DoubleEndedIterator,
|
|
I::Item: TypeFoldable<'tcx>,
|
|
{
|
|
fn next_back(&mut self) -> Option<Self::Item> {
|
|
Some(EarlyBinder(self.it.next_back()?).subst(self.tcx, self.substs))
|
|
}
|
|
}
|
|
|
|
impl<'tcx, 's, I: IntoIterator> EarlyBinder<I>
|
|
where
|
|
I::Item: Deref,
|
|
<I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
|
|
{
|
|
pub fn subst_iter_copied(
|
|
self,
|
|
tcx: TyCtxt<'tcx>,
|
|
substs: &'s [GenericArg<'tcx>],
|
|
) -> SubstIterCopied<'s, 'tcx, I> {
|
|
SubstIterCopied { it: self.0.into_iter(), tcx, substs }
|
|
}
|
|
}
|
|
|
|
pub struct SubstIterCopied<'a, 'tcx, I: IntoIterator> {
|
|
it: I::IntoIter,
|
|
tcx: TyCtxt<'tcx>,
|
|
substs: &'a [GenericArg<'tcx>],
|
|
}
|
|
|
|
impl<'tcx, I: IntoIterator> Iterator for SubstIterCopied<'_, 'tcx, I>
|
|
where
|
|
I::Item: Deref,
|
|
<I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
|
|
{
|
|
type Item = <I::Item as Deref>::Target;
|
|
|
|
fn next(&mut self) -> Option<Self::Item> {
|
|
Some(EarlyBinder(*self.it.next()?).subst(self.tcx, self.substs))
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
self.it.size_hint()
|
|
}
|
|
}
|
|
|
|
impl<'tcx, I: IntoIterator> DoubleEndedIterator for SubstIterCopied<'_, 'tcx, I>
|
|
where
|
|
I::IntoIter: DoubleEndedIterator,
|
|
I::Item: Deref,
|
|
<I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
|
|
{
|
|
fn next_back(&mut self) -> Option<Self::Item> {
|
|
Some(EarlyBinder(*self.it.next_back()?).subst(self.tcx, self.substs))
|
|
}
|
|
}
|
|
|
|
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))
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
self.t.size_hint()
|
|
}
|
|
}
|
|
|
|
impl<'tcx, T: TypeFoldable<'tcx>> ty::EarlyBinder<T> {
|
|
pub fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> T {
|
|
let mut folder = SubstFolder { tcx, substs, binders_passed: 0 };
|
|
self.0.fold_with(&mut folder)
|
|
}
|
|
}
|
|
|
|
///////////////////////////////////////////////////////////////////////////
|
|
// The actual substitution engine itself is a type folder.
|
|
|
|
struct SubstFolder<'a, 'tcx> {
|
|
tcx: TyCtxt<'tcx>,
|
|
substs: &'a [GenericArg<'tcx>],
|
|
|
|
/// Number of region binders we have passed through while doing the substitution
|
|
binders_passed: u32,
|
|
}
|
|
|
|
impl<'a, 'tcx> TypeFolder<'tcx> for SubstFolder<'a, 'tcx> {
|
|
#[inline]
|
|
fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
|
|
self.tcx
|
|
}
|
|
|
|
fn fold_binder<T: TypeFoldable<'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, substs: &[GenericArg<'_>]) -> ! {
|
|
bug!(
|
|
"Region parameter out of range when substituting in region {} (index={}, substs = {:?})",
|
|
data.name,
|
|
data.index,
|
|
substs,
|
|
)
|
|
}
|
|
|
|
#[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.substs.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.substs),
|
|
}
|
|
}
|
|
_ => r,
|
|
}
|
|
}
|
|
|
|
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
|
|
if !t.needs_subst() {
|
|
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> SubstFolder<'a, 'tcx> {
|
|
fn ty_for_param(&self, p: ty::ParamTy, source_ty: Ty<'tcx>) -> Ty<'tcx> {
|
|
// Look up the type in the substitutions. It really should be in there.
|
|
let opt_ty = self.substs.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, substs={:?}",
|
|
p,
|
|
ty,
|
|
p.index,
|
|
kind,
|
|
self.substs,
|
|
)
|
|
}
|
|
|
|
#[cold]
|
|
#[inline(never)]
|
|
fn type_param_out_of_range(&self, p: ty::ParamTy, ty: Ty<'tcx>) -> ! {
|
|
bug!(
|
|
"type parameter `{:?}` ({:?}/{}) out of range when substituting, substs={:?}",
|
|
p,
|
|
ty,
|
|
p.index,
|
|
self.substs,
|
|
)
|
|
}
|
|
|
|
fn const_for_param(&self, p: ParamConst, source_ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
|
|
// Look up the const in the substitutions. It really should be in there.
|
|
let opt_ct = self.substs.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 substs={:?}",
|
|
p,
|
|
ct,
|
|
p.index,
|
|
kind,
|
|
self.substs,
|
|
)
|
|
}
|
|
|
|
#[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 substs={:?}",
|
|
p,
|
|
ct,
|
|
p.index,
|
|
self.substs,
|
|
)
|
|
}
|
|
|
|
/// 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<'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::tcx(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 substs 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, Lift)]
|
|
pub struct UserSubsts<'tcx> {
|
|
/// The substitutions for the item as given by the user.
|
|
pub substs: SubstsRef<'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 substs from `UserSubsts`) 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, Lift)]
|
|
pub struct UserSelfTy<'tcx> {
|
|
pub impl_def_id: DefId,
|
|
pub self_ty: Ty<'tcx>,
|
|
}
|