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android / toolchain / rustc / 983137f038c4d4b95a0cd86b7c42d0313b50de67 / . / vendor / chalk-ir / src / lib.rs
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//! Defines the IR for types and logical predicates.
#![deny(rust_2018_idioms)]
#![warn(missing_docs)]
// Allows macros to refer to this crate as `::chalk_ir`
extern crate self as chalk_ir;
use crate::cast::{Cast, CastTo};
use crate::fold::shift::Shift;
use crate::fold::{Fold, Folder, Subst, SuperFold};
use crate::visit::{SuperVisit, Visit, VisitExt, VisitResult, Visitor};
use chalk_derive::{Fold, HasInterner, SuperVisit, Visit, Zip};
use std::iter;
use std::marker::PhantomData;
pub use crate::debug::SeparatorTraitRef;
/// Uninhabited (empty) type, used in combination with `PhantomData`.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Void {}
/// Many of our internal operations (e.g., unification) are an attempt
/// to perform some operation which may not complete.
pub type Fallible<T> = Result<T, NoSolution>;
/// Indicates that the attempted operation has "no solution" -- i.e.,
/// cannot be performed.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct NoSolution;
/// Error type for the `UnificationOps::program_clauses` method --
/// indicates that the complete set of program clauses for this goal
/// cannot be enumerated.
pub struct Floundered;
macro_rules! impl_debugs {
($($id:ident), *) => {
$(
impl<I: Interner> std::fmt::Debug for $id<I> {
fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
write!(fmt, "{}({:?})", stringify!($id), self.0)
}
}
)*
};
}
#[macro_use]
pub mod zip;
#[macro_use]
pub mod fold;
#[macro_use]
pub mod visit;
pub mod cast;
pub mod interner;
use interner::{HasInterner, Interner};
pub mod could_match;
pub mod debug;
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner)]
/// The set of assumptions we've made so far, and the current number of
/// universal (forall) quantifiers we're within.
pub struct Environment<I: Interner> {
/// The clauses in the environment.
pub clauses: ProgramClauses<I>,
}
impl<I: Interner> Copy for Environment<I> where I::InternedProgramClauses: Copy {}
impl<I: Interner> Environment<I> {
/// Creates a new environment.
pub fn new(interner: &I) -> Self {
Environment {
clauses: ProgramClauses::new(interner),
}
}
/// Adds (an iterator of) clauses to the environment.
pub fn add_clauses<II>(&self, interner: &I, clauses: II) -> Self
where
II: IntoIterator<Item = ProgramClause<I>>,
{
let mut env = self.clone();
env.clauses =
ProgramClauses::from(interner, env.clauses.iter(interner).cloned().chain(clauses));
env
}
}
/// A goal with an environment to solve it in.
#[derive(Clone, Debug, PartialEq, Eq, Hash, Fold, Visit)]
#[allow(missing_docs)]
pub struct InEnvironment<G: HasInterner> {
pub environment: Environment<G::Interner>,
pub goal: G,
}
impl<G: HasInterner<Interner = I> + Copy, I: Interner> Copy for InEnvironment<G> where
I::InternedProgramClauses: Copy
{
}
impl<G: HasInterner> InEnvironment<G> {
/// Creates a new environment/goal pair.
pub fn new(environment: &Environment<G::Interner>, goal: G) -> Self {
InEnvironment {
environment: environment.clone(),
goal,
}
}
/// Maps the goal without touching the environment.
pub fn map<OP, H>(self, op: OP) -> InEnvironment<H>
where
OP: FnOnce(G) -> H,
H: HasInterner<Interner = G::Interner>,
{
InEnvironment {
environment: self.environment,
goal: op(self.goal),
}
}
}
impl<G: HasInterner> HasInterner for InEnvironment<G> {
type Interner = G::Interner;
}
/// Different signed int types.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[allow(missing_docs)]
pub enum IntTy {
Isize,
I8,
I16,
I32,
I64,
I128,
}
/// Different unsigned int types.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[allow(missing_docs)]
pub enum UintTy {
Usize,
U8,
U16,
U32,
U64,
U128,
}
/// Different kinds of float types.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[allow(missing_docs)]
pub enum FloatTy {
F32,
F64,
}
/// Types of scalar values.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[allow(missing_docs)]
pub enum Scalar {
Bool,
Char,
Int(IntTy),
Uint(UintTy),
Float(FloatTy),
}
/// Whether a type is mutable or not.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Mutability {
/// Mutable
Mut,
/// Immutable
Not,
}
/// Different kinds of Rust types.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Fold, Visit)]
pub enum TypeName<I: Interner> {
/// Abstract data types, i.e., structs, unions, or enumerations.
/// For example, a type like `Vec<T>`.
Adt(AdtId<I>),
/// an associated type like `Iterator::Item`; see `AssociatedType` for details
AssociatedType(AssocTypeId<I>),
/// a scalar type like `bool` or `u32`
Scalar(Scalar),
/// a tuple of the given arity
Tuple(usize),
/// an array type like `[T; N]`
Array,
/// a slice type like `[T]`
Slice,
/// a raw pointer type like `*const T` or `*mut T`
Raw(Mutability),
/// a reference type like `&T` or `&mut T`
Ref(Mutability),
/// a placeholder for opaque types like `impl Trait`
OpaqueType(OpaqueTyId<I>),
/// a function definition
FnDef(FnDefId<I>),
/// the string primitive type
Str,
/// the never type `!`
Never,
/// A closure.
Closure(ClosureId<I>),
/// This can be used to represent an error, e.g. during name resolution of a type.
/// Chalk itself will not produce this, just pass it through when given.
Error,
}
impl<I: Interner> HasInterner for TypeName<I> {
type Interner = I;
}
/// An universe index is how a universally quantified parameter is
/// represented when it's binder is moved into the environment.
/// An example chain of transformations would be:
/// `forall<T> { Goal(T) }` (syntactical representation)
/// `forall { Goal(?0) }` (used a DeBruijn index)
/// `Goal(!U1)` (the quantifier was moved to the environment and replaced with a universe index)
/// See https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference.html#placeholders-and-universes for more.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct UniverseIndex {
/// The counter for the universe index, starts with 0.
pub counter: usize,
}
impl UniverseIndex {
/// Root universe index (0).
pub const ROOT: UniverseIndex = UniverseIndex { counter: 0 };
/// Root universe index (0).
pub fn root() -> UniverseIndex {
Self::ROOT
}
/// Whether one universe can "see" another.
pub fn can_see(self, ui: UniverseIndex) -> bool {
self.counter >= ui.counter
}
/// Increases the index counter.
pub fn next(self) -> UniverseIndex {
UniverseIndex {
counter: self.counter + 1,
}
}
}
/// Maps the universes found in the `u_canonicalize` result (the
/// "canonical" universes) to the universes found in the original
/// value (and vice versa). When used as a folder -- i.e., from
/// outside this module -- converts from "canonical" universes to the
/// original (but see the `UMapToCanonical` folder).
#[derive(Clone, Debug)]
pub struct UniverseMap {
/// A reverse map -- for each universe Ux that appears in
/// `quantified`, the corresponding universe in the original was
/// `universes[x]`.
pub universes: Vec<UniverseIndex>,
}
impl UniverseMap {
/// Creates a new universe map.
pub fn new() -> Self {
UniverseMap {
universes: vec![UniverseIndex::root()],
}
}
/// Number of canonical universes.
pub fn num_canonical_universes(&self) -> usize {
self.universes.len()
}
}
/// The id for an Abstract Data Type (i.e. structs, unions and enums).
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct AdtId<I: Interner>(pub I::InternedAdtId);
/// The id of a trait definition; could be used to load the trait datum by
/// invoking the [`trait_datum`] method.
///
/// [`trait_datum`]: ../chalk_solve/trait.RustIrDatabase.html#tymethod.trait_datum
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct TraitId<I: Interner>(pub I::DefId);
/// The id for an impl.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ImplId<I: Interner>(pub I::DefId);
/// Id for a specific clause.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ClauseId<I: Interner>(pub I::DefId);
/// The id for the associated type member of a trait. The details of the type
/// can be found by invoking the [`associated_ty_data`] method.
///
/// [`associated_ty_data`]: ../chalk_solve/trait.RustIrDatabase.html#tymethod.associated_ty_data
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct AssocTypeId<I: Interner>(pub I::DefId);
/// Id for an opaque type.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct OpaqueTyId<I: Interner>(pub I::DefId);
/// Function definition id.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct FnDefId<I: Interner>(pub I::DefId);
/// Id for Rust closures.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ClosureId<I: Interner>(pub I::DefId);
impl_debugs!(ImplId, ClauseId);
/// A Rust type. The actual type data is stored in `TyData`.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct Ty<I: Interner> {
interned: I::InternedType,
}
impl<I: Interner> Ty<I> {
/// Creates a type from `TyData`.
pub fn new(interner: &I, data: impl CastTo<TyData<I>>) -> Self {
Ty {
interned: I::intern_ty(interner, data.cast(interner)),
}
}
/// Gets the interned type.
pub fn interned(&self) -> &I::InternedType {
&self.interned
}
/// Gets the underlying type data.
pub fn data(&self, interner: &I) -> &TyData<I> {
I::ty_data(interner, &self.interned)
}
/// Creates a `FromEnv` constraint using this type.
pub fn from_env(&self) -> FromEnv<I> {
FromEnv::Ty(self.clone())
}
/// Creates a WF-constraint for this type.
pub fn well_formed(&self) -> WellFormed<I> {
WellFormed::Ty(self.clone())
}
/// Creates a domain goal `FromEnv(T)` where `T` is this type.
pub fn into_from_env_goal(self, interner: &I) -> DomainGoal<I> {
self.from_env().cast(interner)
}
/// If this is a `TyData::BoundVar(d)`, returns `Some(d)` else `None`.
pub fn bound_var(&self, interner: &I) -> Option<BoundVar> {
if let TyData::BoundVar(bv) = self.data(interner) {
Some(*bv)
} else {
None
}
}
/// If this is a `TyData::InferenceVar(d)`, returns `Some(d)` else `None`.
pub fn inference_var(&self, interner: &I) -> Option<InferenceVar> {
if let TyData::InferenceVar(depth, _) = self.data(interner) {
Some(*depth)
} else {
None
}
}
/// Returns true if this is a `BoundVar` or `InferenceVar`.
pub fn is_var(&self, interner: &I) -> bool {
match self.data(interner) {
TyData::BoundVar(_) | TyData::InferenceVar(_, _) => true,
_ => false,
}
}
/// Returns true if this is an `Alias`.
pub fn is_alias(&self, interner: &I) -> bool {
match self.data(interner) {
TyData::Alias(..) => true,
_ => false,
}
}
/// Returns true if this is an `IntTy` or `UintTy`.
pub fn is_integer(&self, interner: &I) -> bool {
match self.data(interner) {
TyData::Apply(ApplicationTy {
name: TypeName::Scalar(Scalar::Int(_)),
..
})
| TyData::Apply(ApplicationTy {
name: TypeName::Scalar(Scalar::Uint(_)),
..
}) => true,
_ => false,
}
}
/// Returns true if this is a `FloatTy`.
pub fn is_float(&self, interner: &I) -> bool {
match self.data(interner) {
TyData::Apply(ApplicationTy {
name: TypeName::Scalar(Scalar::Float(_)),
..
}) => true,
_ => false,
}
}
/// True if this type contains "bound" types/lifetimes, and hence
/// needs to be shifted across binders. This is a very inefficient
/// check, intended only for debug assertions, because I am lazy.
pub fn needs_shift(&self, interner: &I) -> bool {
self.has_free_vars(interner)
}
}
/// Type data, which holds the actual type information.
#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
pub enum TyData<I: Interner> {
/// An "application" type is one that applies the set of type
/// arguments to some base type. For example, `Vec<u32>` would be
/// "applying" the parameters `[u32]` to the code type `Vec`.
/// This type is also used for base types like `u32` (which just apply
/// an empty list).
Apply(ApplicationTy<I>),
/// instantiated form a universally quantified type, e.g., from
/// `forall<T> { .. }`. Stands in as a representative of "some
/// unknown type".
Placeholder(PlaceholderIndex),
/// A "dyn" type is a trait object type created via the "dyn Trait" syntax.
/// In the chalk parser, the traits that the object represents is parsed as
/// a QuantifiedInlineBound, and is then changed to a list of where clauses
/// during lowering.
///
/// See the `Opaque` variant for a discussion about the use of
/// binders here.
Dyn(DynTy<I>),
/// An "alias" type represents some form of type alias, such as:
/// - An associated type projection like `<T as Iterator>::Item`
/// - `impl Trait` types
/// - Named type aliases like `type Foo<X> = Vec<X>`
Alias(AliasTy<I>),
/// A function type such as `for<'a> fn(&'a u32)`.
/// Note that "higher-ranked" types (starting with `for<>`) are either
/// function types or dyn types, and do not appear otherwise in Rust
/// surface syntax.
Function(Fn<I>),
/// References the binding at the given depth. The index is a [de
/// Bruijn index], so it counts back through the in-scope binders.
BoundVar(BoundVar),
/// Inference variable defined in the current inference context.
InferenceVar(InferenceVar, TyKind),
}
impl<I: Interner> Copy for TyData<I>
where
I::InternedLifetime: Copy,
I::InternedSubstitution: Copy,
I::InternedVariableKinds: Copy,
I::InternedQuantifiedWhereClauses: Copy,
{
}
impl<I: Interner> TyData<I> {
/// Casts the type data to a type.
pub fn intern(self, interner: &I) -> Ty<I> {
Ty::new(interner, self)
}
}
/// Identifies a particular bound variable within a binder.
/// Variables are identified by the combination of a [`DebruijnIndex`],
/// which identifies the *binder*, and an index within that binder.
///
/// Consider this case:
///
/// ```ignore
/// forall<'a, 'b> { forall<'c, 'd> { ... } }
/// ```
///
/// Within the `...` term:
///
/// * the variable `'a` have a debruijn index of 1 and index 0
/// * the variable `'b` have a debruijn index of 1 and index 1
/// * the variable `'c` have a debruijn index of 0 and index 0
/// * the variable `'d` have a debruijn index of 0 and index 1
///
/// The variables `'a` and `'b` both have debruijn index of 1 because,
/// counting out, they are the 2nd binder enclosing `...`. The indices
/// identify the location *within* that binder.
///
/// The variables `'c` and `'d` both have debruijn index of 0 because
/// they appear in the *innermost* binder enclosing the `...`. The
/// indices identify the location *within* that binder.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct BoundVar {
/// Debruijn index, which identifies the binder.
pub debruijn: DebruijnIndex,
/// Index within the binder.
pub index: usize,
}
impl BoundVar {
/// Creates a new bound variable.
pub fn new(debruijn: DebruijnIndex, index: usize) -> Self {
Self { debruijn, index }
}
/// Casts the bound variable to a type.
pub fn to_ty<I: Interner>(self, interner: &I) -> Ty<I> {
TyData::<I>::BoundVar(self).intern(interner)
}
/// Wrap the bound variable in a lifetime.
pub fn to_lifetime<I: Interner>(self, interner: &I) -> Lifetime<I> {
LifetimeData::<I>::BoundVar(self).intern(interner)
}
/// Wraps the bound variable in a constant.
pub fn to_const<I: Interner>(self, interner: &I, ty: Ty<I>) -> Const<I> {
ConstData {
ty,
value: ConstValue::<I>::BoundVar(self),
}
.intern(interner)
}
/// True if this variable is bound within the `amount` innermost binders.
pub fn bound_within(self, outer_binder: DebruijnIndex) -> bool {
self.debruijn.within(outer_binder)
}
/// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
#[must_use]
pub fn shifted_in(self) -> Self {
BoundVar::new(self.debruijn.shifted_in(), self.index)
}
/// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
#[must_use]
pub fn shifted_in_from(self, outer_binder: DebruijnIndex) -> Self {
BoundVar::new(self.debruijn.shifted_in_from(outer_binder), self.index)
}
/// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
#[must_use]
pub fn shifted_out(self) -> Option<Self> {
self.debruijn
.shifted_out()
.map(|db| BoundVar::new(db, self.index))
}
/// Adjusts the debruijn index (see [`DebruijnIndex::shifted_in`]).
#[must_use]
pub fn shifted_out_to(self, outer_binder: DebruijnIndex) -> Option<Self> {
self.debruijn
.shifted_out_to(outer_binder)
.map(|db| BoundVar::new(db, self.index))
}
/// Return the index of the bound variable, but only if it is bound
/// at the innermost binder. Otherwise, returns `None`.
pub fn index_if_innermost(self) -> Option<usize> {
self.index_if_bound_at(DebruijnIndex::INNERMOST)
}
/// Return the index of the bound variable, but only if it is bound
/// at the innermost binder. Otherwise, returns `None`.
pub fn index_if_bound_at(self, debruijn: DebruijnIndex) -> Option<usize> {
if self.debruijn == debruijn {
Some(self.index)
} else {
None
}
}
}
/// References the binder at the given depth. The index is a [de
/// Bruijn index], so it counts back through the in-scope binders,
/// with 0 being the innermost binder. This is used in impls and
/// the like. For example, if we had a rule like `for<T> { (T:
/// Clone) :- (T: Copy) }`, then `T` would be represented as a
/// `BoundVar(0)` (as the `for` is the innermost binder).
///
/// [de Bruijn index]: https://en.wikipedia.org/wiki/De_Bruijn_index
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct DebruijnIndex {
depth: u32,
}
impl DebruijnIndex {
/// Innermost index.
pub const INNERMOST: DebruijnIndex = DebruijnIndex { depth: 0 };
/// One level higher than the innermost index.
pub const ONE: DebruijnIndex = DebruijnIndex { depth: 1 };
/// Creates a new de Bruijn index with a given depth.
pub fn new(depth: u32) -> Self {
DebruijnIndex { depth }
}
/// Depth of the De Bruijn index, counting from 0 starting with
/// the innermost binder.
pub fn depth(self) -> u32 {
self.depth
}
/// True if the binder identified by this index is within the
/// binder identified by the index `outer_binder`.
///
/// # Example
///
/// Imagine you have the following binders in scope
///
/// ```ignore
/// forall<a> forall<b> forall<c>
/// ```
///
/// then the Debruijn index for `c` would be `0`, the index for
/// `b` would be 1, and so on. Now consider the following calls:
///
/// * `c.within(a) = true`
/// * `b.within(a) = true`
/// * `a.within(a) = false`
/// * `a.within(c) = false`
pub fn within(self, outer_binder: DebruijnIndex) -> bool {
self < outer_binder
}
/// Returns the resulting index when this value is moved into
/// through one binder.
#[must_use]
pub fn shifted_in(self) -> DebruijnIndex {
self.shifted_in_from(DebruijnIndex::ONE)
}
/// Update this index in place by shifting it "in" through
/// `amount` number of binders.
pub fn shift_in(&mut self) {
*self = self.shifted_in();
}
/// Adds `outer_binder` levels to the `self` index. Intuitively, this
/// shifts the `self` index, which was valid at the outer binder,
/// so that it is valid at the innermost binder.
///
/// Example: Assume that the following binders are in scope:
///
/// ```ignore
/// for<A> for<B> for<C> for<D>
/// ^ outer binder
/// ```
///
/// Assume further that the `outer_binder` argument is 2,
/// which means that it is referring to the `for<B>` binder
/// (since `D` would be the innermost binder).
///
/// This means that `self` is relative to the binder `B` -- so
/// if `self` is 0 (`INNERMOST`), then it refers to `B`,
/// and if `self` is 1, then it refers to `A`.
///
/// We will return as follows:
///
/// * `0.shifted_in_from(2) = 2` -- i.e., `B`, when shifted in to the binding level `D`, has index 2
/// * `1.shifted_in_from(2) = 3` -- i.e., `A`, when shifted in to the binding level `D`, has index 3
/// * `2.shifted_in_from(1) = 3` -- here, we changed the `outer_binder` to refer to `C`.
/// Therefore `2` (relative to `C`) refers to `A`, so the result is still 3 (since `A`, relative to the
/// innermost binder, has index 3).
#[must_use]
pub fn shifted_in_from(self, outer_binder: DebruijnIndex) -> DebruijnIndex {
DebruijnIndex::new(self.depth() + outer_binder.depth())
}
/// Returns the resulting index when this value is moved out from
/// `amount` number of new binders.
#[must_use]
pub fn shifted_out(self) -> Option<DebruijnIndex> {
self.shifted_out_to(DebruijnIndex::ONE)
}
/// Update in place by shifting out from `amount` binders.
pub fn shift_out(&mut self) {
*self = self.shifted_out().unwrap();
}
/// Subtracts `outer_binder` levels from the `self` index. Intuitively, this
/// shifts the `self` index, which was valid at the innermost
/// binder, to one that is valid at the binder `outer_binder`.
///
/// This will return `None` if the `self` index is internal to the
/// outer binder (i.e., if `self < outer_binder`).
///
/// Example: Assume that the following binders are in scope:
///
/// ```ignore
/// for<A> for<B> for<C> for<D>
/// ^ outer binder
/// ```
///
/// Assume further that the `outer_binder` argument is 2,
/// which means that it is referring to the `for<B>` binder
/// (since `D` would be the innermost binder).
///
/// This means that the result is relative to the binder `B` -- so
/// if `self` is 0 (`INNERMOST`), then it refers to `B`,
/// and if `self` is 1, then it refers to `A`.
///
/// We will return as follows:
///
/// * `1.shifted_out_to(2) = None` -- i.e., the binder for `C` can't be named from the binding level `B`
/// * `3.shifted_out_to(2) = Some(1)` -- i.e., `A`, when shifted out to the binding level `B`, has index 1
pub fn shifted_out_to(self, outer_binder: DebruijnIndex) -> Option<DebruijnIndex> {
if self.within(outer_binder) {
None
} else {
Some(DebruijnIndex::new(self.depth() - outer_binder.depth()))
}
}
}
/// A "DynTy" represents a trait object (`dyn Trait`). Trait objects
/// are conceptually very related to an "existential type" of the form
/// `exists<T> { T: Trait }` (another example of such type is `impl Trait`).
/// `DynTy` represents the bounds on that type.
///
/// The "bounds" here represents the unknown self type. So, a type like
/// `dyn for<'a> Fn(&'a u32)` would be represented with two-levels of
/// binder, as "depicted" here:
///
/// ```notrust
/// exists<type> {
/// vec![
/// // A QuantifiedWhereClause:
/// forall<region> { ^1.0: Fn(&^0.0 u32) }
/// ]
/// }
/// ```
///
/// The outer `exists<type>` binder indicates that there exists
/// some type that meets the criteria within, but that type is not
/// known. It is referenced within the type using `^1.0`, indicating
/// a bound type with debruijn index 1 (i.e., skipping through one
/// level of binder).
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub struct DynTy<I: Interner> {
/// The unknown self type.
pub bounds: Binders<QuantifiedWhereClauses<I>>,
/// Lifetime of the `DynTy`.
pub lifetime: Lifetime<I>,
}
impl<I: Interner> Copy for DynTy<I>
where
I::InternedLifetime: Copy,
I::InternedQuantifiedWhereClauses: Copy,
I::InternedVariableKinds: Copy,
{
}
/// A type, lifetime or constant whose value is being inferred.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct InferenceVar {
index: u32,
}
impl From<u32> for InferenceVar {
fn from(index: u32) -> InferenceVar {
InferenceVar { index }
}
}
impl InferenceVar {
/// Gets the underlying index value.
pub fn index(self) -> u32 {
self.index
}
/// Wraps the inference variable in a type.
pub fn to_ty<I: Interner>(self, interner: &I, kind: TyKind) -> Ty<I> {
TyData::<I>::InferenceVar(self, kind).intern(interner)
}
/// Wraps the inference variable in a lifetime.
pub fn to_lifetime<I: Interner>(self, interner: &I) -> Lifetime<I> {
LifetimeData::<I>::InferenceVar(self).intern(interner)
}
/// Wraps the inference variable in a constant.
pub fn to_const<I: Interner>(self, interner: &I, ty: Ty<I>) -> Const<I> {
ConstData {
ty,
value: ConstValue::<I>::InferenceVar(self),
}
.intern(interner)
}
}
/// for<'a...'z> X -- all binders are instantiated at once,
/// and we use deBruijn indices within `self.ty`
#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
#[allow(missing_docs)]
pub struct Fn<I: Interner> {
pub num_binders: usize,
pub substitution: Substitution<I>,
}
impl<I: Interner> Copy for Fn<I> where I::InternedSubstitution: Copy {}
/// Constants.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct Const<I: Interner> {
interned: I::InternedConst,
}
impl<I: Interner> Const<I> {
/// Create a `Const` using something that can be cast to const data.
pub fn new(interner: &I, data: impl CastTo<ConstData<I>>) -> Self {
Const {
interned: I::intern_const(interner, data.cast(interner)),
}
}
/// Gets the interned constant.
pub fn interned(&self) -> &I::InternedConst {
&self.interned
}
/// Gets the constant data from the interner.
pub fn data(&self, interner: &I) -> &ConstData<I> {
I::const_data(interner, &self.interned)
}
/// If this is a `ConstData::BoundVar(d)`, returns `Some(d)` else `None`.
pub fn bound_var(&self, interner: &I) -> Option<BoundVar> {
if let ConstValue::BoundVar(bv) = &self.data(interner).value {
Some(*bv)
} else {
None
}
}
/// If this is a `ConstData::InferenceVar(d)`, returns `Some(d)` else `None`.
pub fn inference_var(&self, interner: &I) -> Option<InferenceVar> {
if let ConstValue::InferenceVar(iv) = &self.data(interner).value {
Some(*iv)
} else {
None
}
}
/// True if this const is a "bound" const, and hence
/// needs to be shifted across binders. Meant for debug assertions.
pub fn needs_shift(&self, interner: &I) -> bool {
match &self.data(interner).value {
ConstValue::BoundVar(_) => true,
ConstValue::InferenceVar(_) => false,
ConstValue::Placeholder(_) => false,
ConstValue::Concrete(_) => false,
}
}
}
/// Constant data, containing the constant's type and value.
#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
pub struct ConstData<I: Interner> {
/// Type that holds the constant.
pub ty: Ty<I>,
/// The value of the constant.
pub value: ConstValue<I>,
}
/// A constant value, not necessarily concrete.
#[derive(Clone, PartialEq, Eq, Hash, HasInterner)]
pub enum ConstValue<I: Interner> {
/// Bound var (e.g. a parameter).
BoundVar(BoundVar),
/// Constant whose value is being inferred.
InferenceVar(InferenceVar),
/// Lifetime on some yet-unknown placeholder.
Placeholder(PlaceholderIndex),
/// Concrete constant value.
Concrete(ConcreteConst<I>),
}
impl<I: Interner> Copy for ConstValue<I> where I::InternedConcreteConst: Copy {}
impl<I: Interner> ConstData<I> {
/// Wraps the constant data in a `Const`.
pub fn intern(self, interner: &I) -> Const<I> {
Const::new(interner, self)
}
}
/// Concrete constant, whose value is known (as opposed to
/// inferred constants and placeholders).
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct ConcreteConst<I: Interner> {
/// The interned constant.
pub interned: I::InternedConcreteConst,
}
impl<I: Interner> ConcreteConst<I> {
/// Checks whether two concrete constants are equal.
pub fn const_eq(&self, ty: &Ty<I>, other: &ConcreteConst<I>, interner: &I) -> bool {
interner.const_eq(&ty.interned, &self.interned, &other.interned)
}
}
/// A Rust lifetime.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct Lifetime<I: Interner> {
interned: I::InternedLifetime,
}
impl<I: Interner> Lifetime<I> {
/// Create a lifetime from lifetime data
/// (or something that can be cast to lifetime data).
pub fn new(interner: &I, data: impl CastTo<LifetimeData<I>>) -> Self {
Lifetime {
interned: I::intern_lifetime(interner, data.cast(interner)),
}
}
/// Gets the interned value.
pub fn interned(&self) -> &I::InternedLifetime {
&self.interned
}
/// Gets the lifetime data.
pub fn data(&self, interner: &I) -> &LifetimeData<I> {
I::lifetime_data(interner, &self.interned)
}
/// If this is a `Lifetime::BoundVar(d)`, returns `Some(d)` else `None`.
pub fn bound_var(&self, interner: &I) -> Option<BoundVar> {
if let LifetimeData::BoundVar(bv) = self.data(interner) {
Some(*bv)
} else {
None
}
}
/// If this is a `Lifetime::InferenceVar(d)`, returns `Some(d)` else `None`.
pub fn inference_var(&self, interner: &I) -> Option<InferenceVar> {
if let LifetimeData::InferenceVar(depth) = self.data(interner) {
Some(*depth)
} else {
None
}
}
/// True if this lifetime is a "bound" lifetime, and hence
/// needs to be shifted across binders. Meant for debug assertions.
pub fn needs_shift(&self, interner: &I) -> bool {
match self.data(interner) {
LifetimeData::BoundVar(_) => true,
LifetimeData::InferenceVar(_) => false,
LifetimeData::Placeholder(_) => false,
LifetimeData::Phantom(..) => unreachable!(),
}
}
}
/// Lifetime data, including what kind of lifetime it is and what it points to.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub enum LifetimeData<I: Interner> {
/// See TyData::BoundVar.
BoundVar(BoundVar),
/// Lifetime whose value is being inferred.
InferenceVar(InferenceVar),
/// Lifetime on some yet-unknown placeholder.
Placeholder(PlaceholderIndex),
/// Lifetime on phantom data.
Phantom(Void, PhantomData<I>),
}
impl<I: Interner> LifetimeData<I> {
/// Wrap the lifetime data in a lifetime.
pub fn intern(self, interner: &I) -> Lifetime<I> {
Lifetime::new(interner, self)
}
}
/// Index of an universally quantified parameter in the environment.
/// Two indexes are required, the one of the universe itself
/// and the relative index inside the universe.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct PlaceholderIndex {
/// Index *of* the universe.
pub ui: UniverseIndex,
/// Index *in* the universe.
pub idx: usize,
}
impl PlaceholderIndex {
/// Wrap the placeholder instance in a lifetime.
pub fn to_lifetime<I: Interner>(self, interner: &I) -> Lifetime<I> {
LifetimeData::<I>::Placeholder(self).intern(interner)
}
/// Create an interned type.
pub fn to_ty<I: Interner>(self, interner: &I) -> Ty<I> {
TyData::Placeholder(self).intern(interner)
}
/// Wrap the placeholder index in a constant.
pub fn to_const<I: Interner>(self, interner: &I, ty: Ty<I>) -> Const<I> {
ConstData {
ty,
value: ConstValue::Placeholder(self),
}
.intern(interner)
}
}
/// Normal Rust types, containing the type name and zero or more generic arguments.
/// For example, in `Vec<u32>` those would be `Vec` and `[u32]` respectively.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub struct ApplicationTy<I: Interner> {
/// The type name.
pub name: TypeName<I>,
/// The substitution containing the generic arguments.
pub substitution: Substitution<I>,
}
impl<I: Interner> Copy for ApplicationTy<I> where I::InternedSubstitution: Copy {}
impl<I: Interner> ApplicationTy<I> {
/// Create an interned type from this application type.
pub fn intern(self, interner: &I) -> Ty<I> {
Ty::new(interner, self)
}
/// Gets an iterator of all type parameters.
pub fn type_parameters<'a>(&'a self, interner: &'a I) -> impl Iterator<Item = Ty<I>> + 'a {
self.substitution
.iter(interner)
.filter_map(move |p| p.ty(interner))
.cloned()
}
/// Gets the first type parameter.
pub fn first_type_parameter(&self, interner: &I) -> Option<Ty<I>> {
self.type_parameters(interner).next()
}
/// Gets the number of type parameters.
pub fn len_type_parameters(&self, interner: &I) -> usize {
self.type_parameters(interner).count()
}
}
/// Represents some extra knowledge we may have about the type variable.
/// ```ignore
/// let x: &[u32];
/// let i = 1;
/// x[i]
/// ```
/// In this example, `i` is known to be some type of integer. We can infer that
/// it is `usize` because that is the only integer type that slices have an
/// `Index` impl for. `i` would have a `TyKind` of `Integer` to guide the
/// inference process.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
#[allow(missing_docs)]
pub enum TyKind {
General,
Integer,
Float,
}
/// The "kind" of variable. Type, lifetime or constant.
#[derive(Clone, PartialEq, Eq, Hash)]
#[allow(missing_docs)]
pub enum VariableKind<I: Interner> {
Ty(TyKind),
Lifetime,
Const(Ty<I>),
}
impl<I: Interner> Copy for VariableKind<I> where I::InternedType: Copy {}
impl<I: Interner> VariableKind<I> {
fn to_bound_variable(&self, interner: &I, bound_var: BoundVar) -> GenericArg<I> {
match self {
VariableKind::Ty(_) => {
GenericArgData::Ty(TyData::BoundVar(bound_var).intern(interner)).intern(interner)
}
VariableKind::Lifetime => {
GenericArgData::Lifetime(LifetimeData::BoundVar(bound_var).intern(interner))
.intern(interner)
}
VariableKind::Const(ty) => GenericArgData::Const(
ConstData {
ty: ty.clone(),
value: ConstValue::BoundVar(bound_var),
}
.intern(interner),
)
.intern(interner),
}
}
}
/// A generic argument, see `GenericArgData` for more information.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct GenericArg<I: Interner> {
interned: I::InternedGenericArg,
}
impl<I: Interner> GenericArg<I> {
/// Constructs a generic argument using `GenericArgData`.
pub fn new(interner: &I, data: GenericArgData<I>) -> Self {
let interned = I::intern_generic_arg(interner, data);
GenericArg { interned }
}
/// Gets the interned value.
pub fn interned(&self) -> &I::InternedGenericArg {
&self.interned
}
/// Gets the underlying data.
pub fn data(&self, interner: &I) -> &GenericArgData<I> {
I::generic_arg_data(interner, &self.interned)
}
/// Asserts that this is a type argument.
pub fn assert_ty_ref(&self, interner: &I) -> &Ty<I> {
self.ty(interner).unwrap()
}
/// Asserts that this is a lifetime argument.
pub fn assert_lifetime_ref(&self, interner: &I) -> &Lifetime<I> {
self.lifetime(interner).unwrap()
}
/// Asserts that this is a constant argument.
pub fn assert_const_ref(&self, interner: &I) -> &Const<I> {
self.constant(interner).unwrap()
}
/// Checks whether the generic argument is a type.
pub fn is_ty(&self, interner: &I) -> bool {
match self.data(interner) {
GenericArgData::Ty(_) => true,
GenericArgData::Lifetime(_) => false,
GenericArgData::Const(_) => false,
}
}
/// Returns the type if it is one, `None` otherwise.
pub fn ty(&self, interner: &I) -> Option<&Ty<I>> {
match self.data(interner) {
GenericArgData::Ty(t) => Some(t),
_ => None,
}
}
/// Returns the lifetime if it is one, `None` otherwise.
pub fn lifetime(&self, interner: &I) -> Option<&Lifetime<I>> {
match self.data(interner) {
GenericArgData::Lifetime(t) => Some(t),
_ => None,
}
}
/// Returns the constant if it is one, `None` otherwise.
pub fn constant(&self, interner: &I) -> Option<&Const<I>> {
match self.data(interner) {
GenericArgData::Const(c) => Some(c),
_ => None,
}
}
}
/// Generic arguments data.
#[derive(Clone, PartialEq, Eq, Hash, Visit, Fold, Zip)]
pub enum GenericArgData<I: Interner> {
/// Type argument
Ty(Ty<I>),
/// Lifetime argument
Lifetime(Lifetime<I>),
/// Constant argument
Const(Const<I>),
}
impl<I: Interner> Copy for GenericArgData<I>
where
I::InternedType: Copy,
I::InternedLifetime: Copy,
I::InternedConst: Copy,
{
}
impl<I: Interner> GenericArgData<I> {
/// Create an interned type.
pub fn intern(self, interner: &I) -> GenericArg<I> {
GenericArg::new(interner, self)
}
}
/// A value with an associated variable kind.
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct WithKind<I: Interner, T> {
/// The associated variable kind.
pub kind: VariableKind<I>,
/// The wrapped value.
value: T,
}
impl<I: Interner, T: Copy> Copy for WithKind<I, T> where I::InternedType: Copy {}
impl<I: Interner, T> HasInterner for WithKind<I, T> {
type Interner = I;
}
impl<I: Interner, T> From<WithKind<I, T>> for (VariableKind<I>, T) {
fn from(with_kind: WithKind<I, T>) -> Self {
(with_kind.kind, with_kind.value)
}
}
impl<I: Interner, T> WithKind<I, T> {
/// Creates a `WithKind` from a variable kind and a value.
pub fn new(kind: VariableKind<I>, value: T) -> Self {
Self { kind, value }
}
/// Maps the value in `WithKind`.
pub fn map<U, OP>(self, op: OP) -> WithKind<I, U>
where
OP: FnOnce(T) -> U,
{
WithKind {
kind: self.kind,
value: op(self.value),
}
}
/// Maps a function taking `WithKind<I, &T>` over `&WithKind<I, T>`.
pub fn map_ref<U, OP>(&self, op: OP) -> WithKind<I, U>
where
OP: FnOnce(&T) -> U,
{
WithKind {
kind: self.kind.clone(),
value: op(&self.value),
}
}
/// Extract the value, ignoring the variable kind.
pub fn skip_kind(&self) -> &T {
&self.value
}
}
/// A variable kind with universe index.
#[allow(type_alias_bounds)]
pub type CanonicalVarKind<I: Interner> = WithKind<I, UniverseIndex>;
/// An alias, which is a trait indirection such as a projection or opaque type.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub enum AliasTy<I: Interner> {
/// An associated type projection.
Projection(ProjectionTy<I>),
/// An opaque type.
Opaque(OpaqueTy<I>),
}
impl<I: Interner> Copy for AliasTy<I> where I::InternedSubstitution: Copy {}
impl<I: Interner> AliasTy<I> {
/// Create an interned type for this alias.
pub fn intern(self, interner: &I) -> Ty<I> {
Ty::new(interner, self)
}
/// Gets the type parameters of the `Self` type in this alias type.
pub fn self_type_parameter(&self, interner: &I) -> Ty<I> {
match self {
AliasTy::Projection(projection_ty) => projection_ty
.substitution
.iter(interner)
.find_map(move |p| p.ty(interner))
.unwrap()
.clone(),
_ => todo!(),
}
}
}
/// A projection `<P0 as TraitName<P1..Pn>>::AssocItem<Pn+1..Pm>`.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub struct ProjectionTy<I: Interner> {
/// The id for the associated type member.
pub associated_ty_id: AssocTypeId<I>,
/// The substitution for the projection.
pub substitution: Substitution<I>,
}
impl<I: Interner> Copy for ProjectionTy<I> where I::InternedSubstitution: Copy {}
/// An opaque type `opaque type T<..>: Trait = HiddenTy`.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub struct OpaqueTy<I: Interner> {
/// The id for the opaque type.
pub opaque_ty_id: OpaqueTyId<I>,
/// The substitution for the opaque type.
pub substitution: Substitution<I>,
}
impl<I: Interner> Copy for OpaqueTy<I> where I::InternedSubstitution: Copy {}
/// A trait reference describes the relationship between a type and a trait.
/// This can be used in two forms:
/// - `P0: Trait<P1..Pn>` (e.g. `i32: Copy`), which mentions that the type
/// implements the trait.
/// - `<P0 as Trait<P1..Pn>>` (e.g. `i32 as Copy`), which casts the type to
/// that specific trait.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub struct TraitRef<I: Interner> {
/// The trait id.
pub trait_id: TraitId<I>,
/// The substitution, containing both the `Self` type and the parameters.
pub substitution: Substitution<I>,
}
impl<I: Interner> Copy for TraitRef<I> where I::InternedSubstitution: Copy {}
impl<I: Interner> TraitRef<I> {
/// Gets all type parameters in this trait ref, including `Self`.
pub fn type_parameters<'a>(&'a self, interner: &'a I) -> impl Iterator<Item = Ty<I>> + 'a {
self.substitution
.iter(interner)
.filter_map(move |p| p.ty(interner))
.cloned()
}
/// Gets the type parameters of the `Self` type in this trait ref.
pub fn self_type_parameter(&self, interner: &I) -> Ty<I> {
self.type_parameters(interner).next().unwrap()
}
/// Construct a `FromEnv` using this trait ref.
pub fn from_env(self) -> FromEnv<I> {
FromEnv::Trait(self)
}
/// Construct a `WellFormed` using this trait ref.
pub fn well_formed(self) -> WellFormed<I> {
WellFormed::Trait(self)
}
}
/// Lifetime outlives, which for `'a: 'b`` checks that the lifetime `'a`
/// is a superset of the value of `'b`.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
#[allow(missing_docs)]
pub struct LifetimeOutlives<I: Interner> {
pub a: Lifetime<I>,
pub b: Lifetime<I>,
}
impl<I: Interner> Copy for LifetimeOutlives<I> where I::InternedLifetime: Copy {}
/// Where clauses that can be written by a Rust programmer.
#[derive(Clone, PartialEq, Eq, Hash, Fold, SuperVisit, HasInterner, Zip)]
pub enum WhereClause<I: Interner> {
/// Type implements a trait.
Implemented(TraitRef<I>),
/// Type is equal to an alias.
AliasEq(AliasEq<I>),
/// One lifetime outlives another.
LifetimeOutlives(LifetimeOutlives<I>),
}
impl<I: Interner> Copy for WhereClause<I>
where
I::InternedSubstitution: Copy,
I::InternedLifetime: Copy,
I::InternedType: Copy,
{
}
/// Checks whether a type or trait ref is well-formed.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub enum WellFormed<I: Interner> {
/// A predicate which is true when some trait ref is well-formed.
/// For example, given the following trait definitions:
///
/// ```notrust
/// trait Clone { ... }
/// trait Copy where Self: Clone { ... }
/// ```
///
/// then we have the following rule:
///
/// ```notrust
/// WellFormed(?Self: Copy) :- ?Self: Copy, WellFormed(?Self: Clone)
/// ```
Trait(TraitRef<I>),
/// A predicate which is true when some type is well-formed.
/// For example, given the following type definition:
///
/// ```notrust
/// struct Set<K> where K: Hash {
/// ...
/// }
/// ```
///
/// then we have the following rule: `WellFormedTy(Set<K>) :- Implemented(K: Hash)`.
Ty(Ty<I>),
}
impl<I: Interner> Copy for WellFormed<I>
where
I::InternedType: Copy,
I::InternedSubstitution: Copy,
{
}
/// Checks whether a type or trait ref can be derived from the contents of the environment.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub enum FromEnv<I: Interner> {
/// A predicate which enables deriving everything which should be true if we *know* that
/// some trait ref is well-formed. For example given the above trait definitions, we can use
/// `FromEnv(T: Copy)` to derive that `T: Clone`, like in:
///
/// ```notrust
/// forall<T> {
/// if (FromEnv(T: Copy)) {
/// T: Clone
/// }
/// }
/// ```
Trait(TraitRef<I>),
/// A predicate which enables deriving everything which should be true if we *know* that
/// some type is well-formed. For example given the above type definition, we can use
/// `FromEnv(Set<K>)` to derive that `K: Hash`, like in:
///
/// ```notrust
/// forall<K> {
/// if (FromEnv(Set<K>)) {
/// K: Hash
/// }
/// }
/// ```
Ty(Ty<I>),
}
impl<I: Interner> Copy for FromEnv<I>
where
I::InternedType: Copy,
I::InternedSubstitution: Copy,
{
}
/// A "domain goal" is a goal that is directly about Rust, rather than a pure
/// logical statement. As much as possible, the Chalk solver should avoid
/// decomposing this enum, and instead treat its values opaquely.
#[derive(Clone, PartialEq, Eq, Hash, Fold, SuperVisit, HasInterner, Zip)]
pub enum DomainGoal<I: Interner> {
/// Simple goal that is true if the where clause is true.
Holds(WhereClause<I>),
/// True if the type or trait ref is well-formed.
WellFormed(WellFormed<I>),
/// True if the trait ref can be derived from in-scope where clauses.
FromEnv(FromEnv<I>),
/// True if the alias type can be normalized to some other type
Normalize(Normalize<I>),
/// True if a type is considered to have been "defined" by the current crate. This is true for
/// a `struct Foo { }` but false for a `#[upstream] struct Foo { }`. However, for fundamental types
/// like `Box<T>`, it is true if `T` is local.
IsLocal(Ty<I>),
/// True if a type is *not* considered to have been "defined" by the current crate. This is
/// false for a `struct Foo { }` but true for a `#[upstream] struct Foo { }`. However, for
/// fundamental types like `Box<T>`, it is true if `T` is upstream.
IsUpstream(Ty<I>),
/// True if a type and its input types are fully visible, known types. That is, there are no
/// unknown type parameters anywhere in this type.
///
/// More formally, for each struct S<P0..Pn>:
/// forall<P0..Pn> {
/// IsFullyVisible(S<P0...Pn>) :-
/// IsFullyVisible(P0),
/// ...
/// IsFullyVisible(Pn)
/// }
///
/// Note that any of these types can have lifetimes in their parameters too, but we only
/// consider type parameters.
IsFullyVisible(Ty<I>),
/// Used to dictate when trait impls are allowed in the current (local) crate based on the
/// orphan rules.
///
/// `LocalImplAllowed(T: Trait)` is true if the type T is allowed to impl trait Trait in
/// the current crate. Under the current rules, this is unconditionally true for all types if
/// the Trait is considered to be "defined" in the current crate. If that is not the case, then
/// `LocalImplAllowed(T: Trait)` can still be true if `IsLocal(T)` is true.
LocalImplAllowed(TraitRef<I>),
/// Used to activate the "compatible modality" rules. Rules that introduce predicates that have
/// to do with "all compatible universes" should depend on this clause so that they only apply
/// if this is present.
///
/// (HACK: Having `()` makes some of our macros work better.)
Compatible(()),
/// Used to indicate that a given type is in a downstream crate. Downstream crates contain the
/// current crate at some level of their dependencies.
///
/// Since chalk does not actually see downstream types, this is usually introduced with
/// implication on a fresh, universally quantified type.
///
/// forall<T> { if (DownstreamType(T)) { /* ... */ } }
///
/// This makes a new type `T` available and makes `DownstreamType(T)` provable for that type.
DownstreamType(Ty<I>),
/// Used to activate the "reveal mode", in which opaque (`impl Trait`) types can be equated
/// to their actual type.
Reveal(()),
/// Used to indicate that a trait is object safe.
ObjectSafe(TraitId<I>),
}
impl<I: Interner> Copy for DomainGoal<I>
where
I::InternedSubstitution: Copy,
I::InternedLifetime: Copy,
I::InternedType: Copy,
{
}
/// A where clause that can contain `forall<>` or `exists<>` quantifiers.
pub type QuantifiedWhereClause<I> = Binders<WhereClause<I>>;
impl<I: Interner> WhereClause<I> {
/// Turn a where clause into the WF version of it i.e.:
/// * `Implemented(T: Trait)` maps to `WellFormed(T: Trait)`
/// * `ProjectionEq(<T as Trait>::Item = Foo)` maps to `WellFormed(<T as Trait>::Item = Foo)`
/// * any other clause maps to itself
pub fn into_well_formed_goal(self, interner: &I) -> DomainGoal<I> {
match self {
WhereClause::Implemented(trait_ref) => WellFormed::Trait(trait_ref).cast(interner),
wc => wc.cast(interner),
}
}
/// Same as `into_well_formed_goal` but with the `FromEnv` predicate instead of `WellFormed`.
pub fn into_from_env_goal(self, interner: &I) -> DomainGoal<I> {
match self {
WhereClause::Implemented(trait_ref) => FromEnv::Trait(trait_ref).cast(interner),
wc => wc.cast(interner),
}
}
/// If where clause is a `TraitRef`, returns its trait id.
pub fn trait_id(&self) -> Option<TraitId<I>> {
match self {
WhereClause::Implemented(trait_ref) => Some(trait_ref.trait_id),
WhereClause::AliasEq(_) => None,
WhereClause::LifetimeOutlives(_) => None,
}
}
}
impl<I: Interner> QuantifiedWhereClause<I> {
/// As with `WhereClause::into_well_formed_goal`, but for a
/// quantified where clause. For example, `forall<T> {
/// Implemented(T: Trait)}` would map to `forall<T> {
/// WellFormed(T: Trait) }`.
pub fn into_well_formed_goal(self, interner: &I) -> Binders<DomainGoal<I>> {
self.map(|wc| wc.into_well_formed_goal(interner))
}
/// As with `WhereClause::into_from_env_goal`, but mapped over any
/// binders. For example, `forall<T> {
/// Implemented(T: Trait)}` would map to `forall<T> {
/// FromEnv(T: Trait) }`.
pub fn into_from_env_goal(self, interner: &I) -> Binders<DomainGoal<I>> {
self.map(|wc| wc.into_from_env_goal(interner))
}
/// If the underlying where clause is a `TraitRef`, returns its trait id.
pub fn trait_id(&self) -> Option<TraitId<I>> {
self.skip_binders().trait_id()
}
}
/// List of quantified (forall/exists) where clauses.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct QuantifiedWhereClauses<I: Interner> {
interned: I::InternedQuantifiedWhereClauses,
}
impl<I: Interner> QuantifiedWhereClauses<I> {
/// Creates an empty list of quantified where clauses.
pub fn new(interner: &I) -> Self {
Self::from(interner, None::<QuantifiedWhereClause<I>>)
}
/// Get the interned quantified where clauses.
pub fn interned(&self) -> &I::InternedQuantifiedWhereClauses {
&self.interned
}
/// Creates a list of quantified where clauses from an iterator.
pub fn from(
interner: &I,
clauses: impl IntoIterator<Item = impl CastTo<QuantifiedWhereClause<I>>>,
) -> Self {
Self::from_fallible(
interner,
clauses
.into_iter()
.map(|p| -> Result<QuantifiedWhereClause<I>, ()> { Ok(p.cast(interner)) }),
)
.unwrap()
}
/// Tries to create a list of quantified where clauses from an iterator.
pub fn from_fallible<E>(
interner: &I,
clauses: impl IntoIterator<Item = Result<impl CastTo<QuantifiedWhereClause<I>>, E>>,
) -> Result<Self, E> {
use crate::cast::Caster;
Ok(QuantifiedWhereClauses {
interned: I::intern_quantified_where_clauses(
interner,
clauses.into_iter().casted(interner),
)?,
})
}
/// Get an iterator over the list of quantified where clauses.
pub fn iter(&self, interner: &I) -> std::slice::Iter<'_, QuantifiedWhereClause<I>> {
self.as_slice(interner).iter()
}
/// Checks whether the list of quantified where clauses is empty.
pub fn is_empty(&self, interner: &I) -> bool {
self.as_slice(interner).is_empty()
}
/// Returns the number of quantified where clauses.
pub fn len(&self, interner: &I) -> usize {
self.as_slice(interner).len()
}
/// Returns a slice containing the quantified where clauses.
pub fn as_slice(&self, interner: &I) -> &[QuantifiedWhereClause<I>] {
interner.quantified_where_clauses_data(&self.interned)
}
}
impl<I: Interner> DomainGoal<I> {
/// Convert `Implemented(...)` into `FromEnv(...)`, but leave other
/// goals unchanged.
pub fn into_from_env_goal(self, interner: &I) -> DomainGoal<I> {
match self {
DomainGoal::Holds(wc) => wc.into_from_env_goal(interner),
goal => goal,
}
}
/// Lists generic arguments that are inputs to this domain goal.
pub fn inputs(&self, interner: &I) -> Vec<GenericArg<I>> {
match self {
DomainGoal::Holds(WhereClause::AliasEq(alias_eq)) => {
vec![GenericArgData::Ty(alias_eq.alias.clone().intern(interner)).intern(interner)]
}
_ => Vec::new(),
}
}
}
/// Equality goal: tries to prove that two values are equal.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, Zip)]
#[allow(missing_docs)]
pub struct EqGoal<I: Interner> {
pub a: GenericArg<I>,
pub b: GenericArg<I>,
}
impl<I: Interner> Copy for EqGoal<I> where I::InternedGenericArg: Copy {}
/// Proves that the given type alias **normalizes** to the given
/// type. A projection `T::Foo` normalizes to the type `U` if we can
/// **match it to an impl** and that impl has a `type Foo = V` where
/// `U = V`.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, Zip)]
#[allow(missing_docs)]
pub struct Normalize<I: Interner> {
pub alias: AliasTy<I>,
pub ty: Ty<I>,
}
impl<I: Interner> Copy for Normalize<I>
where
I::InternedSubstitution: Copy,
I::InternedType: Copy,
{
}
/// Proves **equality** between an alias and a type.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, Zip)]
#[allow(missing_docs)]
pub struct AliasEq<I: Interner> {
pub alias: AliasTy<I>,
pub ty: Ty<I>,
}
impl<I: Interner> Copy for AliasEq<I>
where
I::InternedSubstitution: Copy,
I::InternedType: Copy,
{
}
impl<I: Interner> HasInterner for AliasEq<I> {
type Interner = I;
}
/// Indicates that the `value` is universally quantified over `N`
/// parameters of the given kinds, where `N == self.binders.len()`. A
/// variable with depth `i < N` refers to the value at
/// `self.binders[i]`. Variables with depth `>= N` are free.
///
/// (IOW, we use deBruijn indices, where binders are introduced in reverse order
/// of `self.binders`.)
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct Binders<T: HasInterner> {
/// The binders that quantify over the value.
pub binders: VariableKinds<T::Interner>,
/// The value being quantified over.
value: T,
}
impl<T: HasInterner + Copy> Copy for Binders<T> where
<T::Interner as Interner>::InternedVariableKinds: Copy
{
}
impl<T: HasInterner> HasInterner for Binders<T> {
type Interner = T::Interner;
}
impl<T: HasInterner> Binders<T> {
/// Create new binders.
pub fn new(binders: VariableKinds<T::Interner>, value: T) -> Self {
Self { binders, value }
}
/// Wraps the given value in a binder without variables, i.e. `for<>
/// (value)`. Since our deBruijn indices count binders, not variables, this
/// is sometimes useful.
pub fn empty(interner: &T::Interner, value: T) -> Self {
let binders = VariableKinds::new(interner);
Self { binders, value }
}
/// Skips the binder and returns the "bound" value. This is a
/// risky thing to do because it's easy to get confused about
/// De Bruijn indices and the like. `skip_binder` is only valid
/// when you are either extracting data that has nothing to
/// do with bound vars, or you are being very careful about
/// your depth accounting.
///
/// Some examples where `skip_binder` is reasonable:
///
/// - extracting the `TraitId` from a TraitRef;
/// - checking if there are any fields in a StructDatum
pub fn skip_binders(&self) -> &T {
&self.value
}
/// Converts `&Binders<T>` to `Binders<&T>`. Produces new `Binders`
/// with cloned quantifiers containing a reference to the original
/// value, leaving the original in place.
pub fn as_ref(&self) -> Binders<&T> {
Binders {
binders: self.binders.clone(),
value: &self.value,
}
}
/// Maps the binders by applying a function.
pub fn map<U, OP>(self, op: OP) -> Binders<U>
where
OP: FnOnce(T) -> U,
U: HasInterner<Interner = T::Interner>,
{
let value = op(self.value);
Binders {
binders: self.binders,
value,
}
}
/// Transforms the inner value according to the given function; returns
/// `None` if the function returns `None`.
pub fn filter_map<U, OP>(self, op: OP) -> Option<Binders<U>>
where
OP: FnOnce(T) -> Option<U>,
U: HasInterner<Interner = T::Interner>,
{
let value = op(self.value)?;
Some(Binders {
binders: self.binders,
value,
})
}
/// Maps a function taking `Binders<&T>` over `&Binders<T>`.
pub fn map_ref<'a, U, OP>(&'a self, op: OP) -> Binders<U>
where
OP: FnOnce(&'a T) -> U,
U: HasInterner<Interner = T::Interner>,
{
self.as_ref().map(op)
}
/// Creates a `Substitution` containing bound vars such that applying this
/// substitution will not change the value, i.e. `^0.0, ^0.1, ^0.2` and so
/// on.
pub fn identity_substitution(&self, interner: &T::Interner) -> Substitution<T::Interner> {
Substitution::from(
interner,
self.binders
.iter(interner)
.enumerate()
.map(|p| p.to_generic_arg(interner)),
)
}
/// Creates a fresh binders that contains a single type
/// variable. The result of the closure will be embedded in this
/// binder. Note that you should be careful with what you return
/// from the closure to account for the binder that will be added.
///
/// XXX FIXME -- this is potentially a pretty footgun-y function.
pub fn with_fresh_type_var(
interner: &T::Interner,
op: impl FnOnce(Ty<T::Interner>) -> T,
) -> Binders<T> {
// The new variable is at the front and everything afterwards is shifted up by 1
let new_var = TyData::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(interner);
let value = op(new_var);
let binders = VariableKinds::from(interner, iter::once(VariableKind::Ty(TyKind::General)));
Binders { binders, value }
}
/// Returns the number of binders.
pub fn len(&self, interner: &T::Interner) -> usize {
self.binders.len(interner)
}
}
impl<T, I> Binders<Binders<T>>
where
T: Fold<I, I> + HasInterner<Interner = I>,
T::Result: HasInterner<Interner = I>,
I: Interner,
{
/// This turns two levels of binders (`for<A> for<B>`) into one level (`for<A, B>`).
pub fn fuse_binders(self, interner: &T::Interner) -> Binders<T::Result> {
let num_binders = self.len(interner);
// generate a substitution to shift the indexes of the inner binder:
let subst = Substitution::from(
interner,
self.value
.binders
.iter(interner)
.enumerate()
.map(|(i, pk)| (i + num_binders, pk).to_generic_arg(interner)),
);
let value = self.value.substitute(interner, &subst);
let binders = VariableKinds::from(
interner,
self.binders
.iter(interner)
.chain(self.value.binders.iter(interner))
.cloned(),
);
Binders { binders, value }
}
}
impl<T: HasInterner> From<Binders<T>> for (VariableKinds<T::Interner>, T) {
fn from(binders: Binders<T>) -> Self {
(binders.binders, binders.value)
}
}
impl<T, I> Binders<T>
where
T: Fold<I, I> + HasInterner<Interner = I>,
I: Interner,
{
/// Substitute `parameters` for the variables introduced by these
/// binders. So if the binders represent (e.g.) `<X, Y> { T }` and
/// parameters is the slice `[A, B]`, then returns `[X => A, Y =>
/// B] T`.
pub fn substitute(
&self,
interner: &I,
parameters: &(impl AsParameters<I> + ?Sized),
) -> T::Result {
let parameters = parameters.as_parameters(interner);
assert_eq!(self.binders.len(interner), parameters.len());
Subst::apply(interner, parameters, &self.value)
}
}
/// Allows iterating over a Binders<Vec<T>>, for instance.
/// Each element will include the same set of parameter bounds.
impl<V, U> IntoIterator for Binders<V>
where
V: HasInterner + IntoIterator<Item = U>,
U: HasInterner<Interner = V::Interner>,
{
type Item = Binders<U>;
type IntoIter = BindersIntoIterator<V>;
fn into_iter(self) -> Self::IntoIter {
BindersIntoIterator {
iter: self.value.into_iter(),
binders: self.binders,
}
}
}
/// `IntoIterator` for binders.
pub struct BindersIntoIterator<V: HasInterner + IntoIterator> {
iter: <V as IntoIterator>::IntoIter,
binders: VariableKinds<V::Interner>,
}
impl<V> Iterator for BindersIntoIterator<V>
where
V: HasInterner + IntoIterator,
<V as IntoIterator>::Item: HasInterner<Interner = V::Interner>,
{
type Item = Binders<<V as IntoIterator>::Item>;
fn next(&mut self) -> Option<Self::Item> {
self.iter
.next()
.map(|v| Binders::new(self.binders.clone(), v))
}
}
/// Represents one clause of the form `consequence :- conditions` where
/// `conditions = cond_1 && cond_2 && ...` is the conjunction of the individual
/// conditions.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
pub struct ProgramClauseImplication<I: Interner> {
/// The consequence of the clause, which holds if the conditions holds.
pub consequence: DomainGoal<I>,
/// The condition goals that should hold.
pub conditions: Goals<I>,
/// The relative priority of the implication.
pub priority: ClausePriority,
}
/// Specifies how important an implication is.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub enum ClausePriority {
/// High priority, the solver should prioritize this.
High,
/// Low priority, this implication has lower chance to be relevant to the goal.
Low,
}
impl std::ops::BitAnd for ClausePriority {
type Output = ClausePriority;
fn bitand(self, rhs: ClausePriority) -> Self::Output {
match (self, rhs) {
(ClausePriority::High, ClausePriority::High) => ClausePriority::High,
_ => ClausePriority::Low,
}
}
}
/// Contains the data for a program clause.
#[derive(Clone, PartialEq, Eq, Hash, Fold, HasInterner, Zip)]
pub struct ProgramClauseData<I: Interner>(pub Binders<ProgramClauseImplication<I>>);
impl<I: Interner> ProgramClauseImplication<I> {
/// Change the implication into an application holding a `FromEnv` goal.
pub fn into_from_env_clause(self, interner: &I) -> ProgramClauseImplication<I> {
if self.conditions.is_empty(interner) {
ProgramClauseImplication {
consequence: self.consequence.into_from_env_goal(interner),
conditions: self.conditions.clone(),
priority: self.priority,
}
} else {
self
}
}
}
impl<I: Interner> ProgramClauseData<I> {
/// Change the program clause data into a `FromEnv` program clause.
pub fn into_from_env_clause(self, interner: &I) -> ProgramClauseData<I> {
ProgramClauseData(self.0.map(|i| i.into_from_env_clause(interner)))
}
/// Intern the program clause data.
pub fn intern(self, interner: &I) -> ProgramClause<I> {
ProgramClause {
interned: interner.intern_program_clause(self),
}
}
}
/// A program clause is a logic expression used to describe a part of the program.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct ProgramClause<I: Interner> {
interned: I::InternedProgramClause,
}
impl<I: Interner> ProgramClause<I> {
/// Create a new program clause using `ProgramClauseData`.
pub fn new(interner: &I, clause: ProgramClauseData<I>) -> Self {
let interned = interner.intern_program_clause(clause);
Self { interned }
}
/// Change the clause into a `FromEnv` clause.
pub fn into_from_env_clause(self, interner: &I) -> ProgramClause<I> {
let program_clause_data = self.data(interner);
let new_clause = program_clause_data.clone().into_from_env_clause(interner);
Self::new(interner, new_clause)
}
/// Get the interned program clause.
pub fn interned(&self) -> &I::InternedProgramClause {
&self.interned
}
/// Get the program clause data.
pub fn data(&self, interner: &I) -> &ProgramClauseData<I> {
interner.program_clause_data(&self.interned)
}
}
/// List of program clauses.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct ProgramClauses<I: Interner> {
interned: I::InternedProgramClauses,
}
impl<I: Interner> ProgramClauses<I> {
/// Creates an empty list of program clauses.
pub fn new(interner: &I) -> Self {
Self::from(interner, None::<ProgramClause<I>>)
}
/// Get the interned program clauses.
pub fn interned(&self) -> &I::InternedProgramClauses {
&self.interned
}
/// Creates a list of program clauses from an iterator.
pub fn from(
interner: &I,
clauses: impl IntoIterator<Item = impl CastTo<ProgramClause<I>>>,
) -> Self {
Self::from_fallible(
interner,
clauses
.into_iter()
.map(|p| -> Result<ProgramClause<I>, ()> { Ok(p.cast(interner)) }),
)
.unwrap()
}
/// Tries to create a list of program clauses from an iterator.
pub fn from_fallible<E>(
interner: &I,
clauses: impl IntoIterator<Item = Result<impl CastTo<ProgramClause<I>>, E>>,
) -> Result<Self, E> {
use crate::cast::Caster;
Ok(ProgramClauses {
interned: I::intern_program_clauses(interner, clauses.into_iter().casted(interner))?,
})
}
/// Get an iterator over the list of program clauses.
pub fn iter(&self, interner: &I) -> std::slice::Iter<'_, ProgramClause<I>> {
self.as_slice(interner).iter()
}
/// Checks whether the list of program clauses is empty.
pub fn is_empty(&self, interner: &I) -> bool {
self.as_slice(interner).is_empty()
}
/// Returns the number of program clauses.
pub fn len(&self, interner: &I) -> usize {
self.as_slice(interner).len()
}
/// Returns a slice containing the program clauses.
pub fn as_slice(&self, interner: &I) -> &[ProgramClause<I>] {
interner.program_clauses_data(&self.interned)
}
}
/// List of variable kinds.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct VariableKinds<I: Interner> {
interned: I::InternedVariableKinds,
}
impl<I: Interner> VariableKinds<I> {
/// Creates an empty list of canonical variable kinds.
pub fn new(interner: &I) -> Self {
Self::from(interner, None::<VariableKind<I>>)
}
/// Get the interned variable kinds.
pub fn interned(&self) -> &I::InternedVariableKinds {
&self.interned
}
/// Creates a list of variable kinds using an iterator.
pub fn from(interner: &I, variable_kinds: impl IntoIterator<Item = VariableKind<I>>) -> Self {
Self::from_fallible(
interner,
variable_kinds
.into_iter()
.map(|p| -> Result<VariableKind<I>, ()> { Ok(p) }),
)
.unwrap()
}
/// Tries to create a list of variable kinds using an iterator.
pub fn from_fallible<E>(
interner: &I,
variable_kinds: impl IntoIterator<Item = Result<VariableKind<I>, E>>,
) -> Result<Self, E> {
Ok(VariableKinds {
interned: I::intern_generic_arg_kinds(interner, variable_kinds.into_iter())?,
})
}
/// Get an iterator over the list of variable kinds.
pub fn iter(&self, interner: &I) -> std::slice::Iter<'_, VariableKind<I>> {
self.as_slice(interner).iter()
}
/// Checks whether the list of variable kinds is empty.
pub fn is_empty(&self, interner: &I) -> bool {
self.as_slice(interner).is_empty()
}
/// Returns the number of variable kinds.
pub fn len(&self, interner: &I) -> usize {
self.as_slice(interner).len()
}
/// Returns a slice containing the list of variable kinds.
pub fn as_slice(&self, interner: &I) -> &[VariableKind<I>] {
interner.variable_kinds_data(&self.interned)
}
}
/// List of variable kinds with universe index. Wraps `InternedCanonicalVarKinds`.
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
pub struct CanonicalVarKinds<I: Interner> {
interned: I::InternedCanonicalVarKinds,
}
impl<I: Interner> CanonicalVarKinds<I> {
/// Creates an empty list of canonical variable kinds.
pub fn new(interner: &I) -> Self {
Self::from(interner, None::<CanonicalVarKind<I>>)
}
/// Get the interned canonical variable kinds.
pub fn interned(&self) -> &I::InternedCanonicalVarKinds {
&self.interned
}
/// Creates a list of canonical variable kinds using an iterator.
pub fn from(
interner: &I,
variable_kinds: impl IntoIterator<Item = CanonicalVarKind<I>>,
) -> Self {
Self::from_fallible(
interner,
variable_kinds
.into_iter()
.map(|p| -> Result<CanonicalVarKind<I>, ()> { Ok(p) }),
)
.unwrap()
}
/// Tries to create a list of canonical variable kinds using an iterator.
pub fn from_fallible<E>(
interner: &I,
variable_kinds: impl IntoIterator<Item = Result<CanonicalVarKind<I>, E>>,
) -> Result<Self, E> {
Ok(CanonicalVarKinds {
interned: I::intern_canonical_var_kinds(interner, variable_kinds.into_iter())?,
})
}
/// Get an iterator over the list of canonical variable kinds.
pub fn iter(&self, interner: &I) -> std::slice::Iter<'_, CanonicalVarKind<I>> {
self.as_slice(interner).iter()
}
/// Checks whether the list of canonical variable kinds is empty.
pub fn is_empty(&self, interner: &I) -> bool {
self.as_slice(interner).is_empty()
}
/// Returns the number of canonical variable kinds.
pub fn len(&self, interner: &I) -> usize {
self.as_slice(interner).len()
}
/// Returns a slice containing the canonical variable kinds.
pub fn as_slice(&self, interner: &I) -> &[CanonicalVarKind<I>] {
interner.canonical_var_kinds_data(&self.interned)
}
}
/// Wraps a "canonicalized item". Items are canonicalized as follows:
///
/// All unresolved existential variables are "renumbered" according to their
/// first appearance; the kind/universe of the variable is recorded in the
/// `binders` field.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct Canonical<T: HasInterner> {
/// The item that is canonicalized.
pub value: T,
/// The kind/universe of the variable.
pub binders: CanonicalVarKinds<T::Interner>,
}
impl<T: HasInterner> HasInterner for Canonical<T> {
type Interner = T::Interner;
}
/// A "universe canonical" value. This is a wrapper around a
/// `Canonical`, indicating that the universes within have been
/// "renumbered" to start from 0 and collapse unimportant
/// distinctions.
///
/// To produce one of these values, use the `u_canonicalize` method.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct UCanonical<T: HasInterner> {
/// The wrapped `Canonical`.
pub canonical: Canonical<T>,
/// The number of universes that have been collapsed.
pub universes: usize,
}
impl<T: HasInterner> UCanonical<T> {
/// Checks whether the universe canonical value is a trivial
/// substitution (e.g. an identity substitution).
pub fn is_trivial_substitution(
&self,
interner: &T::Interner,
canonical_subst: &Canonical<AnswerSubst<T::Interner>>,
) -> bool {
let subst = &canonical_subst.value.subst;
assert_eq!(
self.canonical.binders.len(interner),
subst.parameters(interner).len()
);
subst.is_identity_subst(interner)
}
/// Creates an identity substitution.
pub fn trivial_substitution(&self, interner: &T::Interner) -> Substitution<T::Interner> {
let binders = &self.canonical.binders;
Substitution::from(
interner,
binders
.iter(interner)
.enumerate()
.map(|(index, pk)| {
let bound_var = BoundVar::new(DebruijnIndex::INNERMOST, index);
match &pk.kind {
VariableKind::Ty(_) => {
GenericArgData::Ty(TyData::BoundVar(bound_var).intern(interner))
.intern(interner)
}
VariableKind::Lifetime => GenericArgData::Lifetime(
LifetimeData::BoundVar(bound_var).intern(interner),
)
.intern(interner),
VariableKind::Const(ty) => GenericArgData::Const(
ConstData {
ty: ty.clone(),
value: ConstValue::BoundVar(bound_var),
}
.intern(interner),
)
.intern(interner),
}
})
.collect::<Vec<_>>(),
)
}
}
#[derive(Copy, Clone, PartialEq, Eq, Hash, HasInterner)]
/// A list of goals.
pub struct Goals<I: Interner> {
interned: I::InternedGoals,
}
impl<I: Interner> Goals<I> {
/// Creates an empty list of goals.
pub fn new(interner: &I) -> Self {
Self::from(interner, None::<Goal<I>>)
}
/// Get the interned list of goals.
pub fn interned(&self) -> &I::InternedGoals {
&self.interned
}
/// Creates `Goals` using an iterator of goal-like things.
pub fn from(interner: &I, goals: impl IntoIterator<Item = impl CastTo<Goal<I>>>) -> Self {
Self::from_fallible(
interner,
goals
.into_iter()
.map(|p| -> Result<Goal<I>, ()> { Ok(p.cast(interner)) }),
)
.unwrap()
}
/// Tries to create a `Goals` using an iterator of goal-like things.
pub fn from_fallible<E>(
interner: &I,
goals: impl IntoIterator<Item = Result<impl CastTo<Goal<I>>, E>>,
) -> Result<Self, E> {
use crate::cast::Caster;
Ok(Goals {
interned: I::intern_goals(interner, goals.into_iter().casted(interner))?,
})
}
/// Get an iterator over the list of goals.
pub fn iter(&self, interner: &I) -> std::slice::Iter<'_, Goal<I>> {
self.as_slice(interner).iter()
}
/// Checks whether the list of goals is empty.
pub fn is_empty(&self, interner: &I) -> bool {
self.as_slice(interner).is_empty()
}
/// Returns the number of goals.
pub fn len(&self, interner: &I) -> usize {
self.as_slice(interner).len()
}
/// Returns a slice containing the list of goals.
pub fn as_slice(&self, interner: &I) -> &[Goal<I>] {
interner.goals_data(&self.interned)
}
}
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, HasInterner)]
/// A general goal; this is the full range of questions you can pose to Chalk.
pub struct Goal<I: Interner> {
interned: I::InternedGoal,
}
impl<I: Interner> Goal<I> {
/// Create a new goal using `GoalData`.
pub fn new(interner: &I, interned: GoalData<I>) -> Self {
let interned = I::intern_goal(interner, interned);
Self { interned }
}
/// Gets the interned goal.
pub fn interned(&self) -> &I::InternedGoal {
&self.interned
}
/// Gets the interned goal data.
pub fn data(&self, interner: &I) -> &GoalData<I> {
interner.goal_data(&self.interned)
}
/// Create a goal using a `forall` or `exists` quantifier.
pub fn quantify(
self,
interner: &I,
kind: QuantifierKind,
binders: VariableKinds<I>,
) -> Goal<I> {
GoalData::Quantified(kind, Binders::new(binders, self)).intern(interner)
}
/// Takes a goal `G` and turns it into `not { G }`.
pub fn negate(self, interner: &I) -> Self {
GoalData::Not(self).intern(interner)
}
/// Takes a goal `G` and turns it into `compatible { G }`.
pub fn compatible(self, interner: &I) -> Self {
// compatible { G } desugars into: forall<T> { if (Compatible, DownstreamType(T)) { G } }
// This activates the compatible modality rules and introduces an anonymous downstream type
GoalData::Quantified(
QuantifierKind::ForAll,
Binders::with_fresh_type_var(interner, |ty| {
GoalData::Implies(
ProgramClauses::from(
interner,
vec![DomainGoal::Compatible(()), DomainGoal::DownstreamType(ty)],
),
self.shifted_in(interner),
)
.intern(interner)
}),
)
.intern(interner)
}
/// Create an implication goal that holds if the predicates are true.
pub fn implied_by(self, interner: &I, predicates: ProgramClauses<I>) -> Goal<I> {
GoalData::Implies(predicates, self).intern(interner)
}
/// True if this goal is "trivially true" -- i.e., no work is
/// required to prove it.
pub fn is_trivially_true(&self, interner: &I) -> bool {
match self.data(interner) {
GoalData::All(goals) => goals.is_empty(interner),
_ => false,
}
}
}
impl<I> Goal<I>
where
I: Interner,
{
/// Creates a single goal that only holds if a list of goals holds.
pub fn all<II>(interner: &I, iter: II) -> Self
where
II: IntoIterator<Item = Goal<I>>,
{
let mut iter = iter.into_iter();
if let Some(goal0) = iter.next() {
if let Some(goal1) = iter.next() {
// More than one goal to prove
let goals = Goals::from(
interner,
Some(goal0).into_iter().chain(Some(goal1)).chain(iter),
);
GoalData::All(goals).intern(interner)
} else {
// One goal to prove
goal0
}
} else {
// No goals to prove, always true
GoalData::All(Goals::new(interner)).intern(interner)
}
}
}
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner, Zip)]
/// A general goal; this is the full range of questions you can pose to Chalk.
pub enum GoalData<I: Interner> {
/// Introduces a binding at depth 0, shifting other bindings up
/// (deBruijn index).
Quantified(QuantifierKind, Binders<Goal<I>>),
/// A goal that holds given some clauses (like an if-statement).
Implies(ProgramClauses<I>, Goal<I>),
/// List of goals that all should hold.
All(Goals<I>),
/// Negation: the inner goal should not hold.
Not(Goal<I>),
/// Make two things equal; the rules for doing so are well known to the logic
EqGoal(EqGoal<I>),
/// A "domain goal" indicates some base sort of goal that can be
/// proven via program clauses
DomainGoal(DomainGoal<I>),
/// Adds a region constraint requiring `'a : 'b`, given two lifetimes `'a, 'b`
AddRegionConstraint(Lifetime<I>, Lifetime<I>),
/// Indicates something that cannot be proven to be true or false
/// definitively. This can occur with overflow but also with
/// unifications of skolemized variables like `forall<X,Y> { X = Y
/// }`. Of course, that statement is false, as there exist types
/// X, Y where `X = Y` is not true. But we treat it as "cannot
/// prove" so that `forall<X,Y> { not { X = Y } }` also winds up
/// as cannot prove.
///
/// (TOTAL HACK: Having a unit result makes some of our macros work better.)
CannotProve(()),
}
impl<I: Interner> Copy for GoalData<I>
where
I::InternedType: Copy,
I::InternedLifetime: Copy,
I::InternedGenericArg: Copy,
I::InternedSubstitution: Copy,
I::InternedGoal: Copy,
I::InternedGoals: Copy,
I::InternedProgramClauses: Copy,
I::InternedVariableKinds: Copy,
{
}
impl<I: Interner> GoalData<I> {
/// Create an interned goal.
pub fn intern(self, interner: &I) -> Goal<I> {
Goal::new(interner, self)
}
}
/// Kinds of quantifiers in the logic, such as `forall` and `exists`.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum QuantifierKind {
/// Universal quantifier `ForAll`.
///
/// A formula with the universal quantifier `forall(x). P(x)` is satisfiable
/// if and only if the subformula `P(x)` is true for all possible values for x.
ForAll,
/// Existential quantifier `Exists`.
///
/// A formula with the existential quantifier `exists(x). P(x)` is satisfiable
/// if and only if there exists at least one value for all possible values of x
/// which satisfies the subformula `P(x)`.
/// In the context of chalk, the existential quantifier usually demands the
/// existence of exactly one instance (i.e. type) that satisfies the formula
/// (i.e. type constraints). More than one instance means that the result is ambiguous.
Exists,
}
/// A constraint on lifetimes.
///
/// When we search for solutions within the trait system, we essentially ignore
/// lifetime constraints, instead gathering them up to return with our solution
/// for later checking. This allows for decoupling between type and region
/// checking in the compiler.
#[derive(Clone, PartialEq, Eq, Hash, Fold, Visit, HasInterner)]
pub enum Constraint<I: Interner> {
/// Outlives constraint `'a: 'b`, indicating that the value of `'a` must be
/// a superset of the value of `'b`.
Outlives(Lifetime<I>, Lifetime<I>),
}
impl<I: Interner> Copy for Constraint<I> where I::InternedLifetime: Copy {}
/// A mapping of inference variables to instantiations thereof.
#[derive(Copy, Clone, PartialEq, Eq, Hash, HasInterner)]
pub struct Substitution<I: Interner> {
/// Map free variable with given index to the value with the same
/// index. Naturally, the kind of the variable must agree with
/// the kind of the value.
interned: I::InternedSubstitution,
}
impl<I: Interner> Substitution<I> {
/// Create a substitution from parameters.
pub fn from(
interner: &I,
parameters: impl IntoIterator<Item = impl CastTo<GenericArg<I>>>,
) -> Self {
Self::from_fallible(
interner,
parameters
.into_iter()
.map(|p| -> Result<GenericArg<I>, ()> { Ok(p.cast(interner)) }),
)
.unwrap()
}
/// Try to create a substitution from parameters.
pub fn from_fallible<E>(
interner: &I,
parameters: impl IntoIterator<Item = Result<impl CastTo<GenericArg<I>>, E>>,
) -> Result<Self, E> {
use crate::cast::Caster;
Ok(Substitution {
interned: I::intern_substitution(interner, parameters.into_iter().casted(interner))?,
})
}
/// Get the interned representation of the substitution.
pub fn interned(&self) -> &I::InternedSubstitution {
&self.interned
}
/// Index into the list of parameters.
pub fn at(&self, interner: &I, index: usize) -> &GenericArg<I> {
&self.parameters(interner)[index]
}
/// Create a substitution from a single parameter.
pub fn from1(interner: &I, parameter: impl CastTo<GenericArg<I>>) -> Self {
Self::from(interner, Some(parameter))
}
/// Create an empty substitution.
pub fn empty(interner: &I) -> Self {
Self::from(interner, None::<GenericArg<I>>)
}
/// Check whether this is an empty substitution.
pub fn is_empty(&self, interner: &I) -> bool {
self.parameters(interner).is_empty()
}
/// Get an iterator over the parameters of the substitution.
pub fn iter(&self, interner: &I) -> std::slice::Iter<'_, GenericArg<I>> {
self.parameters(interner).iter()
}
/// Get the parameters associated with a substitution.
pub fn parameters(&self, interner: &I) -> &[GenericArg<I>] {
interner.substitution_data(&self.interned)
}
/// Get the length of the substitution (number of parameters).
pub fn len(&self, interner: &I) -> usize {
self.parameters(interner).len()
}
/// A substitution is an **identity substitution** if it looks
/// like this
///
/// ```text
/// ?0 := ?0
/// ?1 := ?1
/// ?2 := ?2
/// ...
/// ```
///
/// Basically, each value is mapped to a type or lifetime with its
/// same index.
pub fn is_identity_subst(&self, interner: &I) -> bool {
self.iter(interner).zip(0..).all(|(generic_arg, index)| {
let index_db = BoundVar::new(DebruijnIndex::INNERMOST, index);
match generic_arg.data(interner) {
GenericArgData::Ty(ty) => match ty.data(interner) {
TyData::BoundVar(depth) => index_db == *depth,
_ => false,
},
GenericArgData::Lifetime(lifetime) => match lifetime.data(interner) {
LifetimeData::BoundVar(depth) => index_db == *depth,
_ => false,
},
GenericArgData::Const(constant) => match &constant.data(interner).value {
ConstValue::BoundVar(depth) => index_db == *depth,
_ => false,
},
}
})
}
/// Apply the substitution to a value.
pub fn apply<T>(&self, value: &T, interner: &I) -> T::Result
where
T: Fold<I, I>,
{
value
.fold_with(
&mut &SubstFolder {
interner,
subst: self,
},
DebruijnIndex::INNERMOST,
)
.unwrap()
}
}
struct SubstFolder<'i, I: Interner> {
interner: &'i I,
subst: &'i Substitution<I>,
}
impl<I: Interner> SubstFolder<'_, I> {
/// Index into the list of parameters.
pub fn at(&self, index: usize) -> &GenericArg<I> {
let interner = self.interner;
&self.subst.parameters(interner)[index]
}
}
/// Convert a value to a list of parameters.
pub trait AsParameters<I: Interner> {
/// Convert the current value to parameters.
fn as_parameters(&self, interner: &I) -> &[GenericArg<I>];
}
impl<I: Interner> AsParameters<I> for Substitution<I> {
#[allow(unreachable_code, unused_variables)]
fn as_parameters(&self, interner: &I) -> &[GenericArg<I>] {
self.parameters(interner)
}
}
impl<I: Interner> AsParameters<I> for [GenericArg<I>] {
fn as_parameters(&self, _interner: &I) -> &[GenericArg<I>] {
self
}
}
impl<I: Interner> AsParameters<I> for [GenericArg<I>; 1] {
fn as_parameters(&self, _interner: &I) -> &[GenericArg<I>] {
self
}
}
impl<I: Interner> AsParameters<I> for Vec<GenericArg<I>> {
fn as_parameters(&self, _interner: &I) -> &[GenericArg<I>] {
self
}
}
impl<T, I: Interner> AsParameters<I> for &T
where
T: ?Sized + AsParameters<I>,
{
fn as_parameters(&self, interner: &I) -> &[GenericArg<I>] {
T::as_parameters(self, interner)
}
}
/// Utility for converting a list of all the binders into scope
/// into references to those binders. Simply pair the binders with
/// the indices, and invoke `to_generic_arg()` on the `(binder,
/// index)` pair. The result will be a reference to a bound
/// variable of appropriate kind at the corresponding index.
pub trait ToGenericArg<I: Interner> {
/// Converts the binders in scope to references to those binders.
fn to_generic_arg(&self, interner: &I) -> GenericArg<I> {
self.to_generic_arg_at_depth(interner, DebruijnIndex::INNERMOST)
}
/// Converts the binders at the specified depth to references to those binders.
fn to_generic_arg_at_depth(&self, interner: &I, debruijn: DebruijnIndex) -> GenericArg<I>;
}
impl<'a, I: Interner> ToGenericArg<I> for (usize, &'a VariableKind<I>) {
fn to_generic_arg_at_depth(&self, interner: &I, debruijn: DebruijnIndex) -> GenericArg<I> {
let &(index, binder) = self;
let bound_var = BoundVar::new(debruijn, index);
binder.to_bound_variable(interner, bound_var)
}
}
impl<'i, I: Interner> Folder<'i, I> for &SubstFolder<'i, I> {
fn as_dyn(&mut self) -> &mut dyn Folder<'i, I> {
self
}
fn fold_free_var_ty(
&mut self,
bound_var: BoundVar,
outer_binder: DebruijnIndex,
) -> Fallible<Ty<I>> {
assert_eq!(bound_var.debruijn, DebruijnIndex::INNERMOST);
let ty = self.at(bound_var.index);
let ty = ty.assert_ty_ref(self.interner());
Ok(ty.shifted_in_from(self.interner(), outer_binder))
}
fn fold_free_var_lifetime(
&mut self,
bound_var: BoundVar,
outer_binder: DebruijnIndex,
) -> Fallible<Lifetime<I>> {
assert_eq!(bound_var.debruijn, DebruijnIndex::INNERMOST);
let l = self.at(bound_var.index);
let l = l.assert_lifetime_ref(self.interner());
Ok(l.shifted_in_from(self.interner(), outer_binder))
}
fn fold_free_var_const(
&mut self,
_ty: &Ty<I>,
bound_var: BoundVar,
outer_binder: DebruijnIndex,
) -> Fallible<Const<I>> {
assert_eq!(bound_var.debruijn, DebruijnIndex::INNERMOST);
let c = self.at(bound_var.index);
let c = c.assert_const_ref(self.interner());
Ok(c.shifted_in_from(self.interner(), outer_binder))
}
fn interner(&self) -> &'i I {
self.interner
}
fn target_interner(&self) -> &'i I {
self.interner()
}
}
/// Combines a substitution (`subst`) with a set of region constraints
/// (`constraints`). This represents the result of a query; the
/// substitution stores the values for the query's unknown variables,
/// and the constraints represents any region constraints that must
/// additionally be solved.
#[derive(Clone, Debug, PartialEq, Eq, Hash, Fold, Visit, HasInterner)]
pub struct ConstrainedSubst<I: Interner> {
/// The substitution that is being constrained.
///
/// NB: The `is_trivial` routine relies on the fact that `subst` is folded first.
pub subst: Substitution<I>,
/// Region constraints that constrain the substitution.
pub constraints: Vec<InEnvironment<Constraint<I>>>,
}
/// The resulting substitution after solving a goal.
#[derive(Clone, Debug, PartialEq, Eq, Hash, Fold, Visit, HasInterner)]
pub struct AnswerSubst<I: Interner> {
/// The substitution result.
///
/// NB: The `is_trivial` routine relies on the fact that `subst` is folded first.
pub subst: Substitution<I>,
/// List of constraints that are part of the answer.
pub constraints: Vec<InEnvironment<Constraint<I>>>,
/// Delayed subgoals, used when the solver answered with an (incomplete) `Answer` (instead of a `CompleteAnswer`).
pub delayed_subgoals: Vec<InEnvironment<Goal<I>>>,
}