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use crate::ty::{self, Ty, TyCtxt};
use rustc_data_structures::unify::{NoError, UnifyKey, UnifyValue};
use rustc_span::def_id::DefId;
use rustc_span::symbol::Symbol;
use rustc_span::Span;
use std::cmp;
use std::marker::PhantomData;
pub trait ToType {
fn to_type<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
}
#[derive(PartialEq, Copy, Clone, Debug)]
pub struct UnifiedRegion<'tcx>(pub Option<ty::Region<'tcx>>);
#[derive(PartialEq, Copy, Clone, Debug)]
pub struct RegionVidKey<'tcx> {
pub vid: ty::RegionVid,
pub phantom: PhantomData<UnifiedRegion<'tcx>>,
}
impl<'tcx> From<ty::RegionVid> for RegionVidKey<'tcx> {
fn from(vid: ty::RegionVid) -> Self {
RegionVidKey { vid, phantom: PhantomData }
}
}
impl<'tcx> UnifyKey for RegionVidKey<'tcx> {
type Value = UnifiedRegion<'tcx>;
#[inline]
fn index(&self) -> u32 {
self.vid.as_u32()
}
#[inline]
fn from_index(i: u32) -> Self {
RegionVidKey::from(ty::RegionVid::from_u32(i))
}
fn tag() -> &'static str {
"RegionVidKey"
}
}
impl<'tcx> UnifyValue for UnifiedRegion<'tcx> {
type Error = NoError;
fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
Ok(match (value1.0, value2.0) {
// Here we can just pick one value, because the full constraints graph
// will be handled later. Ideally, we might want a `MultipleValues`
// variant or something. For now though, this is fine.
(Some(_), Some(_)) => *value1,
(Some(_), _) => *value1,
(_, Some(_)) => *value2,
(None, None) => *value1,
})
}
}
impl ToType for ty::IntVarValue {
fn to_type<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
match *self {
ty::IntType(i) => tcx.mk_mach_int(i),
ty::UintType(i) => tcx.mk_mach_uint(i),
}
}
}
impl ToType for ty::FloatVarValue {
fn to_type<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
tcx.mk_mach_float(self.0)
}
}
// Generic consts.
#[derive(Copy, Clone, Debug)]
pub struct ConstVariableOrigin {
pub kind: ConstVariableOriginKind,
pub span: Span,
}
/// Reasons to create a const inference variable
#[derive(Copy, Clone, Debug)]
pub enum ConstVariableOriginKind {
MiscVariable,
ConstInference,
ConstParameterDefinition(Symbol, DefId),
SubstitutionPlaceholder,
}
#[derive(Copy, Clone, Debug)]
pub enum ConstVariableValue<'tcx> {
Known { value: ty::Const<'tcx> },
Unknown { universe: ty::UniverseIndex },
}
impl<'tcx> ConstVariableValue<'tcx> {
/// If this value is known, returns the const it is known to be.
/// Otherwise, `None`.
pub fn known(&self) -> Option<ty::Const<'tcx>> {
match *self {
ConstVariableValue::Unknown { .. } => None,
ConstVariableValue::Known { value } => Some(value),
}
}
}
#[derive(Copy, Clone, Debug)]
pub struct ConstVarValue<'tcx> {
pub origin: ConstVariableOrigin,
pub val: ConstVariableValue<'tcx>,
}
impl<'tcx> UnifyKey for ty::ConstVid<'tcx> {
type Value = ConstVarValue<'tcx>;
#[inline]
fn index(&self) -> u32 {
self.index
}
#[inline]
fn from_index(i: u32) -> Self {
ty::ConstVid { index: i, phantom: PhantomData }
}
fn tag() -> &'static str {
"ConstVid"
}
}
impl<'tcx> UnifyValue for ConstVarValue<'tcx> {
type Error = (ty::Const<'tcx>, ty::Const<'tcx>);
fn unify_values(&value1: &Self, &value2: &Self) -> Result<Self, Self::Error> {
Ok(match (value1.val, value2.val) {
(ConstVariableValue::Known { .. }, ConstVariableValue::Known { .. }) => {
bug!("equating two const variables, both of which have known values")
}
// If one side is known, prefer that one.
(ConstVariableValue::Known { .. }, ConstVariableValue::Unknown { .. }) => value1,
(ConstVariableValue::Unknown { .. }, ConstVariableValue::Known { .. }) => value2,
// If both sides are *unknown*, it hardly matters, does it?
(
ConstVariableValue::Unknown { universe: universe1 },
ConstVariableValue::Unknown { universe: universe2 },
) => {
// If we unify two unbound variables, ?T and ?U, then whatever
// value they wind up taking (which must be the same value) must
// be nameable by both universes. Therefore, the resulting
// universe is the minimum of the two universes, because that is
// the one which contains the fewest names in scope.
let universe = cmp::min(universe1, universe2);
ConstVarValue {
val: ConstVariableValue::Unknown { universe },
origin: value1.origin,
}
}
})
}
}
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