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use infer::canonical::{Canonical, CanonicalVarValues};
use ty::fold::{TypeFoldable, TypeFolder};
use ty::subst::UnpackedKind;
use ty::{self, Ty, TyCtxt, TypeFlags};
impl<'tcx, V> Canonical<'tcx, V> {
pub fn substitute(&self, tcx: TyCtxt<'_, '_, 'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V
where
V: TypeFoldable<'tcx>,
{
self.substitute_projected(tcx, var_values, |value| value)
}
pub fn substitute_projected<T>(
&self,
tcx: TyCtxt<'_, '_, 'tcx>,
var_values: &CanonicalVarValues<'tcx>,
projection_fn: impl FnOnce(&V) -> &T,
) -> T
where
T: TypeFoldable<'tcx>,
{
assert_eq!(self.variables.len(), var_values.len());
let value = projection_fn(&self.value);
substitute_value(tcx, var_values, value)
}
}
pub(super) fn substitute_value<'a, 'tcx, T>(
tcx: TyCtxt<'_, '_, 'tcx>,
var_values: &CanonicalVarValues<'tcx>,
value: &'a T,
) -> T
where
T: TypeFoldable<'tcx>,
{
if var_values.var_values.is_empty() {
debug_assert!(!value.has_type_flags(TypeFlags::HAS_CANONICAL_VARS));
value.clone()
} else if !value.has_type_flags(TypeFlags::HAS_CANONICAL_VARS) {
value.clone()
} else {
value.fold_with(&mut CanonicalVarValuesSubst { tcx, var_values })
}
}
struct CanonicalVarValuesSubst<'cx, 'gcx: 'tcx, 'tcx: 'cx> {
tcx: TyCtxt<'cx, 'gcx, 'tcx>,
var_values: &'cx CanonicalVarValues<'tcx>,
}
impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for CanonicalVarValuesSubst<'cx, 'gcx, 'tcx> {
fn tcx(&self) -> TyCtxt<'_, 'gcx, 'tcx> {
self.tcx
}
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
match t.sty {
ty::TyInfer(ty::InferTy::CanonicalTy(c)) => {
match self.var_values.var_values[c].unpack() {
UnpackedKind::Type(ty) => ty,
r => bug!("{:?} is a type but value is {:?}", c, r),
}
}
_ => {
if !t.has_type_flags(TypeFlags::HAS_CANONICAL_VARS) {
t
} else {
t.super_fold_with(self)
}
}
}
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match r {
ty::RegionKind::ReCanonical(c) => match self.var_values.var_values[*c].unpack() {
UnpackedKind::Lifetime(l) => l,
r => bug!("{:?} is a region but value is {:?}", c, r),
},
_ => r.super_fold_with(self),
}
}
}