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Move datatypes definitions in specific modules inside rustc::{traits, infer} #68461

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merged 11 commits into from
Feb 6, 2020
Merged

Move datatypes definitions in specific modules inside rustc::{traits, infer} #68461

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369f360
Move rustc::traits datatypes to module traits::types.
cjgillot Jan 22, 2020
a2cd071
Move traits::Reveal to traits::types.
cjgillot Jan 22, 2020
a77da35
Move traits::select datatypes to traits::types.
cjgillot Jan 22, 2020
4e42f38
Move traits::query datatypes to traits::types.
cjgillot Jan 22, 2020
9c07dad
Move infer::region_constraints::MemberConstraint to infer::types module.
cjgillot Jan 22, 2020
005f14d
Move infer::canonical datatypes to infer::types.
cjgillot Jan 22, 2020
b3f13b0
Move implementation of UnifyKey to unify_key.rs.
cjgillot Jan 22, 2020
9444975
Split traits::structural_impls in two.
cjgillot Jan 22, 2020
c851db9
Move specialization_graph definition in traits::types.
cjgillot Jan 22, 2020
551cc5e
Move ExpectedFound::new to ty::error.
cjgillot Jan 22, 2020
735d664
Move EvaluationCache::clear.
cjgillot Jan 22, 2020
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339 changes: 5 additions & 334 deletions src/librustc/infer/canonical/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,284 +21,22 @@
//!
//! [c]: https://rust-lang.github.io/rustc-guide/traits/canonicalization.html

use crate::infer::region_constraints::MemberConstraint;
use crate::infer::{ConstVariableOrigin, ConstVariableOriginKind};
use crate::infer::{InferCtxt, RegionVariableOrigin, TypeVariableOrigin, TypeVariableOriginKind};
use crate::ty::fold::TypeFoldable;
use crate::ty::subst::GenericArg;
use crate::ty::{self, BoundVar, List, Region, TyCtxt};
use rustc::ty::fold::TypeFoldable;
use rustc::ty::subst::GenericArg;
use rustc::ty::{self, BoundVar, List};
use rustc_index::vec::IndexVec;
use rustc_macros::HashStable;
use rustc_serialize::UseSpecializedDecodable;
use rustc_span::source_map::Span;
use smallvec::SmallVec;
use std::ops::Index;

pub use rustc::infer::types::canonical::*;

mod canonicalizer;

pub mod query_response;

mod substitute;

/// A "canonicalized" type `V` is one where all free inference
/// variables have been rewritten to "canonical vars". These are
/// numbered starting from 0 in order of first appearance.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcDecodable, RustcEncodable)]
#[derive(HashStable, TypeFoldable, Lift)]
pub struct Canonical<'tcx, V> {
pub max_universe: ty::UniverseIndex,
pub variables: CanonicalVarInfos<'tcx>,
pub value: V,
}

pub type CanonicalVarInfos<'tcx> = &'tcx List<CanonicalVarInfo>;

impl<'tcx> UseSpecializedDecodable for CanonicalVarInfos<'tcx> {}

/// A set of values corresponding to the canonical variables from some
/// `Canonical`. You can give these values to
/// `canonical_value.substitute` to substitute them into the canonical
/// value at the right places.
///
/// When you canonicalize a value `V`, you get back one of these
/// vectors with the original values that were replaced by canonical
/// variables. You will need to supply it later to instantiate the
/// canonicalized query response.
#[derive(Clone, Debug, PartialEq, Eq, Hash, RustcDecodable, RustcEncodable)]
#[derive(HashStable, TypeFoldable, Lift)]
pub struct CanonicalVarValues<'tcx> {
pub var_values: IndexVec<BoundVar, GenericArg<'tcx>>,
}

/// When we canonicalize a value to form a query, we wind up replacing
/// various parts of it with canonical variables. This struct stores
/// those replaced bits to remember for when we process the query
/// result.
#[derive(Clone, Debug)]
pub struct OriginalQueryValues<'tcx> {
/// Map from the universes that appear in the query to the
/// universes in the caller context. For the time being, we only
/// ever put ROOT values into the query, so this map is very
/// simple.
pub universe_map: SmallVec<[ty::UniverseIndex; 4]>,

/// This is equivalent to `CanonicalVarValues`, but using a
/// `SmallVec` yields a significant performance win.
pub var_values: SmallVec<[GenericArg<'tcx>; 8]>,
}

impl Default for OriginalQueryValues<'tcx> {
fn default() -> Self {
let mut universe_map = SmallVec::default();
universe_map.push(ty::UniverseIndex::ROOT);

Self { universe_map, var_values: SmallVec::default() }
}
}

/// Information about a canonical variable that is included with the
/// canonical value. This is sufficient information for code to create
/// a copy of the canonical value in some other inference context,
/// with fresh inference variables replacing the canonical values.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcDecodable, RustcEncodable, HashStable)]
pub struct CanonicalVarInfo {
pub kind: CanonicalVarKind,
}

impl CanonicalVarInfo {
pub fn universe(&self) -> ty::UniverseIndex {
self.kind.universe()
}

pub fn is_existential(&self) -> bool {
match self.kind {
CanonicalVarKind::Ty(_) => true,
CanonicalVarKind::PlaceholderTy(_) => false,
CanonicalVarKind::Region(_) => true,
CanonicalVarKind::PlaceholderRegion(..) => false,
CanonicalVarKind::Const(_) => true,
CanonicalVarKind::PlaceholderConst(_) => false,
}
}
}

/// Describes the "kind" of the canonical variable. This is a "kind"
/// in the type-theory sense of the term -- i.e., a "meta" type system
/// that analyzes type-like values.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcDecodable, RustcEncodable, HashStable)]
pub enum CanonicalVarKind {
/// Some kind of type inference variable.
Ty(CanonicalTyVarKind),

/// A "placeholder" that represents "any type".
PlaceholderTy(ty::PlaceholderType),

/// Region variable `'?R`.
Region(ty::UniverseIndex),

/// A "placeholder" that represents "any region". Created when you
/// are solving a goal like `for<'a> T: Foo<'a>` to represent the
/// bound region `'a`.
PlaceholderRegion(ty::PlaceholderRegion),

/// Some kind of const inference variable.
Const(ty::UniverseIndex),

/// A "placeholder" that represents "any const".
PlaceholderConst(ty::PlaceholderConst),
}

impl CanonicalVarKind {
pub fn universe(self) -> ty::UniverseIndex {
match self {
CanonicalVarKind::Ty(kind) => match kind {
CanonicalTyVarKind::General(ui) => ui,
CanonicalTyVarKind::Float | CanonicalTyVarKind::Int => ty::UniverseIndex::ROOT,
},

CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.universe,
CanonicalVarKind::Region(ui) => ui,
CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.universe,
CanonicalVarKind::Const(ui) => ui,
CanonicalVarKind::PlaceholderConst(placeholder) => placeholder.universe,
}
}
}

/// Rust actually has more than one category of type variables;
/// notably, the type variables we create for literals (e.g., 22 or
/// 22.) can only be instantiated with integral/float types (e.g.,
/// usize or f32). In order to faithfully reproduce a type, we need to
/// know what set of types a given type variable can be unified with.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcDecodable, RustcEncodable, HashStable)]
pub enum CanonicalTyVarKind {
/// General type variable `?T` that can be unified with arbitrary types.
General(ty::UniverseIndex),

/// Integral type variable `?I` (that can only be unified with integral types).
Int,

/// Floating-point type variable `?F` (that can only be unified with float types).
Float,
}

/// After we execute a query with a canonicalized key, we get back a
/// `Canonical<QueryResponse<..>>`. You can use
/// `instantiate_query_result` to access the data in this result.
#[derive(Clone, Debug, HashStable, TypeFoldable, Lift)]
pub struct QueryResponse<'tcx, R> {
pub var_values: CanonicalVarValues<'tcx>,
pub region_constraints: QueryRegionConstraints<'tcx>,
pub certainty: Certainty,
pub value: R,
}

#[derive(Clone, Debug, Default, HashStable, TypeFoldable, Lift)]
pub struct QueryRegionConstraints<'tcx> {
pub outlives: Vec<QueryOutlivesConstraint<'tcx>>,
pub member_constraints: Vec<MemberConstraint<'tcx>>,
}

impl QueryRegionConstraints<'_> {
/// Represents an empty (trivially true) set of region
/// constraints.
pub fn is_empty(&self) -> bool {
self.outlives.is_empty() && self.member_constraints.is_empty()
}
}

pub type Canonicalized<'tcx, V> = Canonical<'tcx, V>;

pub type CanonicalizedQueryResponse<'tcx, T> = &'tcx Canonical<'tcx, QueryResponse<'tcx, T>>;

/// Indicates whether or not we were able to prove the query to be
/// true.
#[derive(Copy, Clone, Debug, HashStable)]
pub enum Certainty {
/// The query is known to be true, presuming that you apply the
/// given `var_values` and the region-constraints are satisfied.
Proven,

/// The query is not known to be true, but also not known to be
/// false. The `var_values` represent *either* values that must
/// hold in order for the query to be true, or helpful tips that
/// *might* make it true. Currently rustc's trait solver cannot
/// distinguish the two (e.g., due to our preference for where
/// clauses over impls).
///
/// After some unifiations and things have been done, it makes
/// sense to try and prove again -- of course, at that point, the
/// canonical form will be different, making this a distinct
/// query.
Ambiguous,
}

impl Certainty {
pub fn is_proven(&self) -> bool {
match self {
Certainty::Proven => true,
Certainty::Ambiguous => false,
}
}

pub fn is_ambiguous(&self) -> bool {
!self.is_proven()
}
}

impl<'tcx, R> QueryResponse<'tcx, R> {
pub fn is_proven(&self) -> bool {
self.certainty.is_proven()
}

pub fn is_ambiguous(&self) -> bool {
!self.is_proven()
}
}

impl<'tcx, R> Canonical<'tcx, QueryResponse<'tcx, R>> {
pub fn is_proven(&self) -> bool {
self.value.is_proven()
}

pub fn is_ambiguous(&self) -> bool {
!self.is_proven()
}
}

impl<'tcx, V> Canonical<'tcx, V> {
/// Allows you to map the `value` of a canonical while keeping the
/// same set of bound variables.
///
/// **WARNING:** This function is very easy to mis-use, hence the
/// name! In particular, the new value `W` must use all **the
/// same type/region variables** in **precisely the same order**
/// as the original! (The ordering is defined by the
/// `TypeFoldable` implementation of the type in question.)
///
/// An example of a **correct** use of this:
///
/// ```rust,ignore (not real code)
/// let a: Canonical<'_, T> = ...;
/// let b: Canonical<'_, (T,)> = a.unchecked_map(|v| (v, ));
/// ```
///
/// An example of an **incorrect** use of this:
///
/// ```rust,ignore (not real code)
/// let a: Canonical<'tcx, T> = ...;
/// let ty: Ty<'tcx> = ...;
/// let b: Canonical<'tcx, (T, Ty<'tcx>)> = a.unchecked_map(|v| (v, ty));
/// ```
pub fn unchecked_map<W>(self, map_op: impl FnOnce(V) -> W) -> Canonical<'tcx, W> {
let Canonical { max_universe, variables, value } = self;
Canonical { max_universe, variables, value: map_op(value) }
}
}

pub type QueryOutlivesConstraint<'tcx> =
ty::Binder<ty::OutlivesPredicate<GenericArg<'tcx>, Region<'tcx>>>;

impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
/// Creates a substitution S for the canonical value with fresh
/// inference variables and applies it to the canonical value.
Expand Down Expand Up @@ -424,70 +162,3 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
}
}
}

CloneTypeFoldableAndLiftImpls! {
crate::infer::canonical::Certainty,
crate::infer::canonical::CanonicalVarInfo,
crate::infer::canonical::CanonicalVarKind,
}

CloneTypeFoldableImpls! {
for <'tcx> {
crate::infer::canonical::CanonicalVarInfos<'tcx>,
}
}

impl<'tcx> CanonicalVarValues<'tcx> {
pub fn len(&self) -> usize {
self.var_values.len()
}

/// Makes an identity substitution from this one: each bound var
/// is matched to the same bound var, preserving the original kinds.
/// For example, if we have:
/// `self.var_values == [Type(u32), Lifetime('a), Type(u64)]`
/// we'll return a substitution `subst` with:
/// `subst.var_values == [Type(^0), Lifetime(^1), Type(^2)]`.
pub fn make_identity(&self, tcx: TyCtxt<'tcx>) -> Self {
use crate::ty::subst::GenericArgKind;

CanonicalVarValues {
var_values: self
.var_values
.iter()
.zip(0..)
.map(|(kind, i)| match kind.unpack() {
GenericArgKind::Type(..) => {
tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_u32(i).into())).into()
}
GenericArgKind::Lifetime(..) => tcx
.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BoundRegion::BrAnon(i)))
.into(),
GenericArgKind::Const(ct) => tcx
.mk_const(ty::Const {
ty: ct.ty,
val: ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_u32(i)),
})
.into(),
})
.collect(),
}
}
}

impl<'a, 'tcx> IntoIterator for &'a CanonicalVarValues<'tcx> {
type Item = GenericArg<'tcx>;
type IntoIter = ::std::iter::Cloned<::std::slice::Iter<'a, GenericArg<'tcx>>>;

fn into_iter(self) -> Self::IntoIter {
self.var_values.iter().cloned()
}
}

impl<'tcx> Index<BoundVar> for CanonicalVarValues<'tcx> {
type Output = GenericArg<'tcx>;

fn index(&self, value: BoundVar) -> &GenericArg<'tcx> {
&self.var_values[value]
}
}
11 changes: 1 addition & 10 deletions src/librustc/infer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@ pub mod region_constraints;
pub mod resolve;
mod sub;
pub mod type_variable;
mod types;
pub mod unify_key;

#[must_use]
Expand Down Expand Up @@ -556,16 +557,6 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
}
}

impl<T> ExpectedFound<T> {
pub fn new(a_is_expected: bool, a: T, b: T) -> Self {
if a_is_expected {
ExpectedFound { expected: a, found: b }
} else {
ExpectedFound { expected: b, found: a }
}
}
}

impl<'tcx, T> InferOk<'tcx, T> {
pub fn unit(self) -> InferOk<'tcx, ()> {
InferOk { value: (), obligations: self.obligations }
Expand Down
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