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Auto merge of #79169 - LeSeulArtichaut:ty-lib, r=nikomatsakis
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Create `rustc_type_ir`

Decided to start small 😄

This PR creates a `rustc_type_ir` crate as part of the WG-Traits plan to create a shared type library.
~~There already exists a `rustc_ty` crate, so I named the new crate `rustc_ty_library`. However I think it would make sense to rename the current `rustc_ty` to something else (e.g. `rustc_ty_passes`) to free the name for this new crate.~~

r? `@jackh726`
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bors committed Dec 12, 2020
2 parents c3ed668 + 0cf5a8a commit 3f2088a
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11 changes: 11 additions & 0 deletions Cargo.lock
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Expand Up @@ -3932,6 +3932,7 @@ dependencies = [
"rustc_session",
"rustc_span",
"rustc_target",
"rustc_type_ir",
"smallvec 1.4.2",
"tracing",
]
Expand Down Expand Up @@ -4266,6 +4267,16 @@ dependencies = [
"tracing",
]

[[package]]
name = "rustc_type_ir"
version = "0.0.0"
dependencies = [
"bitflags",
"rustc_data_structures",
"rustc_index",
"rustc_serialize",
]

[[package]]
name = "rustc_typeck"
version = "0.0.0"
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1 change: 1 addition & 0 deletions compiler/rustc_middle/Cargo.toml
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Expand Up @@ -30,3 +30,4 @@ chalk-ir = "0.36.0"
smallvec = { version = "1.0", features = ["union", "may_dangle"] }
measureme = "9.0.0"
rustc_session = { path = "../rustc_session" }
rustc_type_ir = { path = "../rustc_type_ir" }
88 changes: 2 additions & 86 deletions compiler/rustc_middle/src/ty/mod.rs
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Expand Up @@ -56,7 +56,7 @@ pub use self::sty::InferTy::*;
pub use self::sty::RegionKind;
pub use self::sty::RegionKind::*;
pub use self::sty::TyKind::*;
pub use self::sty::{Binder, BoundTy, BoundTyKind, BoundVar, DebruijnIndex, INNERMOST};
pub use self::sty::{Binder, BoundTy, BoundTyKind, BoundVar};
pub use self::sty::{BoundRegion, EarlyBoundRegion, FreeRegion, Region};
pub use self::sty::{CanonicalPolyFnSig, FnSig, GenSig, PolyFnSig, PolyGenSig};
pub use self::sty::{ClosureSubsts, GeneratorSubsts, TypeAndMut, UpvarSubsts};
Expand All @@ -67,6 +67,7 @@ pub use self::sty::{ExistentialProjection, PolyExistentialProjection};
pub use self::sty::{ExistentialTraitRef, PolyExistentialTraitRef};
pub use self::sty::{PolyTraitRef, TraitRef, TyKind};
pub use crate::ty::diagnostics::*;
pub use rustc_type_ir::{DebruijnIndex, TypeFlags, INNERMOST};

pub use self::binding::BindingMode;
pub use self::binding::BindingMode::*;
Expand Down Expand Up @@ -497,91 +498,6 @@ pub struct CReaderCacheKey {
pub pos: usize,
}

bitflags! {
/// Flags that we track on types. These flags are propagated upwards
/// through the type during type construction, so that we can quickly check
/// whether the type has various kinds of types in it without recursing
/// over the type itself.
pub struct TypeFlags: u32 {
// Does this have parameters? Used to determine whether substitution is
// required.
/// Does this have [Param]?
const HAS_TY_PARAM = 1 << 0;
/// Does this have [ReEarlyBound]?
const HAS_RE_PARAM = 1 << 1;
/// Does this have [ConstKind::Param]?
const HAS_CT_PARAM = 1 << 2;

const NEEDS_SUBST = TypeFlags::HAS_TY_PARAM.bits
| TypeFlags::HAS_RE_PARAM.bits
| TypeFlags::HAS_CT_PARAM.bits;

/// Does this have [Infer]?
const HAS_TY_INFER = 1 << 3;
/// Does this have [ReVar]?
const HAS_RE_INFER = 1 << 4;
/// Does this have [ConstKind::Infer]?
const HAS_CT_INFER = 1 << 5;

/// Does this have inference variables? Used to determine whether
/// inference is required.
const NEEDS_INFER = TypeFlags::HAS_TY_INFER.bits
| TypeFlags::HAS_RE_INFER.bits
| TypeFlags::HAS_CT_INFER.bits;

/// Does this have [Placeholder]?
const HAS_TY_PLACEHOLDER = 1 << 6;
/// Does this have [RePlaceholder]?
const HAS_RE_PLACEHOLDER = 1 << 7;
/// Does this have [ConstKind::Placeholder]?
const HAS_CT_PLACEHOLDER = 1 << 8;

/// `true` if there are "names" of regions and so forth
/// that are local to a particular fn/inferctxt
const HAS_FREE_LOCAL_REGIONS = 1 << 9;

/// `true` if there are "names" of types and regions and so forth
/// that are local to a particular fn
const HAS_FREE_LOCAL_NAMES = TypeFlags::HAS_TY_PARAM.bits
| TypeFlags::HAS_CT_PARAM.bits
| TypeFlags::HAS_TY_INFER.bits
| TypeFlags::HAS_CT_INFER.bits
| TypeFlags::HAS_TY_PLACEHOLDER.bits
| TypeFlags::HAS_CT_PLACEHOLDER.bits
| TypeFlags::HAS_FREE_LOCAL_REGIONS.bits;

/// Does this have [Projection]?
const HAS_TY_PROJECTION = 1 << 10;
/// Does this have [Opaque]?
const HAS_TY_OPAQUE = 1 << 11;
/// Does this have [ConstKind::Unevaluated]?
const HAS_CT_PROJECTION = 1 << 12;

/// Could this type be normalized further?
const HAS_PROJECTION = TypeFlags::HAS_TY_PROJECTION.bits
| TypeFlags::HAS_TY_OPAQUE.bits
| TypeFlags::HAS_CT_PROJECTION.bits;

/// Is an error type/const reachable?
const HAS_ERROR = 1 << 13;

/// Does this have any region that "appears free" in the type?
/// Basically anything but [ReLateBound] and [ReErased].
const HAS_FREE_REGIONS = 1 << 14;

/// Does this have any [ReLateBound] regions? Used to check
/// if a global bound is safe to evaluate.
const HAS_RE_LATE_BOUND = 1 << 15;

/// Does this have any [ReErased] regions?
const HAS_RE_ERASED = 1 << 16;

/// Does this value have parameters/placeholders/inference variables which could be
/// replaced later, in a way that would change the results of `impl` specialization?
const STILL_FURTHER_SPECIALIZABLE = 1 << 17;
}
}

#[allow(rustc::usage_of_ty_tykind)]
pub struct TyS<'tcx> {
/// This field shouldn't be used directly and may be removed in the future.
Expand Down
110 changes: 2 additions & 108 deletions compiler/rustc_middle/src/ty/sty.rs
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Expand Up @@ -1289,53 +1289,6 @@ impl<'tcx> ParamConst {
}
}

rustc_index::newtype_index! {
/// A [De Bruijn index][dbi] is a standard means of representing
/// regions (and perhaps later types) in a higher-ranked setting. In
/// particular, imagine a type like this:
///
/// for<'a> fn(for<'b> fn(&'b isize, &'a isize), &'a char)
/// ^ ^ | | |
/// | | | | |
/// | +------------+ 0 | |
/// | | |
/// +----------------------------------+ 1 |
/// | |
/// +----------------------------------------------+ 0
///
/// In this type, there are two binders (the outer fn and the inner
/// fn). We need to be able to determine, for any given region, which
/// fn type it is bound by, the inner or the outer one. There are
/// various ways you can do this, but a De Bruijn index is one of the
/// more convenient and has some nice properties. The basic idea is to
/// count the number of binders, inside out. Some examples should help
/// clarify what I mean.
///
/// Let's start with the reference type `&'b isize` that is the first
/// argument to the inner function. This region `'b` is assigned a De
/// Bruijn index of 0, meaning "the innermost binder" (in this case, a
/// fn). The region `'a` that appears in the second argument type (`&'a
/// isize`) would then be assigned a De Bruijn index of 1, meaning "the
/// second-innermost binder". (These indices are written on the arrays
/// in the diagram).
///
/// What is interesting is that De Bruijn index attached to a particular
/// variable will vary depending on where it appears. For example,
/// the final type `&'a char` also refers to the region `'a` declared on
/// the outermost fn. But this time, this reference is not nested within
/// any other binders (i.e., it is not an argument to the inner fn, but
/// rather the outer one). Therefore, in this case, it is assigned a
/// De Bruijn index of 0, because the innermost binder in that location
/// is the outer fn.
///
/// [dbi]: https://en.wikipedia.org/wiki/De_Bruijn_index
#[derive(HashStable)]
pub struct DebruijnIndex {
DEBUG_FORMAT = "DebruijnIndex({})",
const INNERMOST = 0,
}
}

pub type Region<'tcx> = &'tcx RegionKind;

/// Representation of regions. Note that the NLL checker uses a distinct
Expand Down Expand Up @@ -1450,7 +1403,7 @@ pub enum RegionKind {

/// Region bound in a function scope, which will be substituted when the
/// function is called.
ReLateBound(DebruijnIndex, BoundRegion),
ReLateBound(ty::DebruijnIndex, BoundRegion),

/// When checking a function body, the types of all arguments and so forth
/// that refer to bound region parameters are modified to refer to free
Expand Down Expand Up @@ -1614,65 +1567,6 @@ impl<'tcx> PolyExistentialProjection<'tcx> {
}
}

impl DebruijnIndex {
/// Returns the resulting index when this value is moved into
/// `amount` number of new binders. So, e.g., if you had
///
/// for<'a> fn(&'a x)
///
/// and you wanted to change it to
///
/// for<'a> fn(for<'b> fn(&'a x))
///
/// you would need to shift the index for `'a` into a new binder.
#[must_use]
pub fn shifted_in(self, amount: u32) -> DebruijnIndex {
DebruijnIndex::from_u32(self.as_u32() + amount)
}

/// Update this index in place by shifting it "in" through
/// `amount` number of binders.
pub fn shift_in(&mut self, amount: u32) {
*self = self.shifted_in(amount);
}

/// Returns the resulting index when this value is moved out from
/// `amount` number of new binders.
#[must_use]
pub fn shifted_out(self, amount: u32) -> DebruijnIndex {
DebruijnIndex::from_u32(self.as_u32() - amount)
}

/// Update in place by shifting out from `amount` binders.
pub fn shift_out(&mut self, amount: u32) {
*self = self.shifted_out(amount);
}

/// Adjusts any De Bruijn indices so as to make `to_binder` the
/// innermost binder. That is, if we have something bound at `to_binder`,
/// it will now be bound at INNERMOST. This is an appropriate thing to do
/// when moving a region out from inside binders:
///
/// ```
/// for<'a> fn(for<'b> for<'c> fn(&'a u32), _)
/// // Binder: D3 D2 D1 ^^
/// ```
///
/// Here, the region `'a` would have the De Bruijn index D3,
/// because it is the bound 3 binders out. However, if we wanted
/// to refer to that region `'a` in the second argument (the `_`),
/// those two binders would not be in scope. In that case, we
/// might invoke `shift_out_to_binder(D3)`. This would adjust the
/// De Bruijn index of `'a` to D1 (the innermost binder).
///
/// If we invoke `shift_out_to_binder` and the region is in fact
/// bound by one of the binders we are shifting out of, that is an
/// error (and should fail an assertion failure).
pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Self {
self.shifted_out(to_binder.as_u32() - INNERMOST.as_u32())
}
}

/// Region utilities
impl RegionKind {
/// Is this region named by the user?
Expand Down Expand Up @@ -1703,7 +1597,7 @@ impl RegionKind {
}
}

pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {
pub fn bound_at_or_above_binder(&self, index: ty::DebruijnIndex) -> bool {
match *self {
ty::ReLateBound(debruijn, _) => debruijn >= index,
_ => false,
Expand Down
14 changes: 14 additions & 0 deletions compiler/rustc_type_ir/Cargo.toml
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@@ -0,0 +1,14 @@
[package]
name = "rustc_type_ir"
version = "0.0.0"
authors = ["The Rust Project Developers"]
edition = "2018"

[lib]
doctest = false

[dependencies]
bitflags = "1.2.1"
rustc_index = { path = "../rustc_index" }
rustc_serialize = { path = "../rustc_serialize" }
rustc_data_structures = { path = "../rustc_data_structures" }
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