rustc_type_ir/predicate_kind.rs
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use std::fmt;
use derive_where::derive_where;
#[cfg(feature = "nightly")]
use rustc_macros::{Decodable, Encodable, HashStable_NoContext, TyDecodable, TyEncodable};
use rustc_type_ir_macros::{TypeFoldable_Generic, TypeVisitable_Generic};
use crate::{self as ty, Interner};
/// A clause is something that can appear in where bounds or be inferred
/// by implied bounds.
#[derive_where(Clone, Copy, Hash, PartialEq, Eq; I: Interner)]
#[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
#[cfg_attr(feature = "nightly", derive(TyEncodable, TyDecodable, HashStable_NoContext))]
pub enum ClauseKind<I: Interner> {
/// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
/// the `Self` type of the trait reference and `A`, `B`, and `C`
/// would be the type parameters.
Trait(ty::TraitPredicate<I>),
/// `where 'a: 'r`
RegionOutlives(ty::OutlivesPredicate<I, I::Region>),
/// `where T: 'r`
TypeOutlives(ty::OutlivesPredicate<I, I::Ty>),
/// `where <T as TraitRef>::Name == X`, approximately.
/// See the `ProjectionPredicate` struct for details.
Projection(ty::ProjectionPredicate<I>),
/// Ensures that a const generic argument to a parameter `const N: u8`
/// is of type `u8`.
ConstArgHasType(I::Const, I::Ty),
/// No syntax: `T` well-formed.
WellFormed(I::GenericArg),
/// Constant initializer must evaluate successfully.
ConstEvaluatable(I::Const),
}
#[derive_where(Clone, Copy, Hash, PartialEq, Eq; I: Interner)]
#[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
#[cfg_attr(feature = "nightly", derive(TyEncodable, TyDecodable, HashStable_NoContext))]
pub enum PredicateKind<I: Interner> {
/// Prove a clause
Clause(ClauseKind<I>),
/// Trait must be dyn-compatible.
DynCompatible(I::DefId),
/// `T1 <: T2`
///
/// This obligation is created most often when we have two
/// unresolved type variables and hence don't have enough
/// information to process the subtyping obligation yet.
Subtype(ty::SubtypePredicate<I>),
/// `T1` coerced to `T2`
///
/// Like a subtyping obligation, this is created most often
/// when we have two unresolved type variables and hence
/// don't have enough information to process the coercion
/// obligation yet. At the moment, we actually process coercions
/// very much like subtyping and don't handle the full coercion
/// logic.
Coerce(ty::CoercePredicate<I>),
/// Constants must be equal. The first component is the const that is expected.
ConstEquate(I::Const, I::Const),
/// A marker predicate that is always ambiguous.
/// Used for coherence to mark opaque types as possibly equal to each other but ambiguous.
Ambiguous,
/// This should only be used inside of the new solver for `AliasRelate` and expects
/// the `term` to be always be an unconstrained inference variable. It is used to
/// normalize `alias` as much as possible. In case the alias is rigid - i.e. it cannot
/// be normalized in the current environment - this constrains `term` to be equal to
/// the alias itself.
///
/// It is likely more useful to think of this as a function `normalizes_to(alias)`,
/// whose return value is written into `term`.
NormalizesTo(ty::NormalizesTo<I>),
/// Separate from `ClauseKind::Projection` which is used for normalization in new solver.
/// This predicate requires two terms to be equal to eachother.
///
/// Only used for new solver.
AliasRelate(I::Term, I::Term, AliasRelationDirection),
}
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Copy)]
#[cfg_attr(feature = "nightly", derive(HashStable_NoContext, Encodable, Decodable))]
pub enum AliasRelationDirection {
Equate,
Subtype,
}
impl std::fmt::Display for AliasRelationDirection {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
AliasRelationDirection::Equate => write!(f, "=="),
AliasRelationDirection::Subtype => write!(f, "<:"),
}
}
}
impl<I: Interner> fmt::Debug for ClauseKind<I> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
ClauseKind::ConstArgHasType(ct, ty) => write!(f, "ConstArgHasType({ct:?}, {ty:?})"),
ClauseKind::Trait(a) => a.fmt(f),
ClauseKind::RegionOutlives(pair) => pair.fmt(f),
ClauseKind::TypeOutlives(pair) => pair.fmt(f),
ClauseKind::Projection(pair) => pair.fmt(f),
ClauseKind::WellFormed(data) => write!(f, "WellFormed({data:?})"),
ClauseKind::ConstEvaluatable(ct) => {
write!(f, "ConstEvaluatable({ct:?})")
}
}
}
}
impl<I: Interner> fmt::Debug for PredicateKind<I> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
PredicateKind::Clause(a) => a.fmt(f),
PredicateKind::Subtype(pair) => pair.fmt(f),
PredicateKind::Coerce(pair) => pair.fmt(f),
PredicateKind::DynCompatible(trait_def_id) => {
write!(f, "DynCompatible({trait_def_id:?})")
}
PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({c1:?}, {c2:?})"),
PredicateKind::Ambiguous => write!(f, "Ambiguous"),
PredicateKind::NormalizesTo(p) => p.fmt(f),
PredicateKind::AliasRelate(t1, t2, dir) => {
write!(f, "AliasRelate({t1:?}, {dir:?}, {t2:?})")
}
}
}
}