use crate::infer::canonical::{Canonical, CanonicalVarValues};
use rustc_middle::ty::fold::{FnMutDelegate, TypeFoldable};
use rustc_middle::ty::GenericArgKind;
use rustc_middle::ty::{self, TyCtxt};
pub trait CanonicalExt<'tcx, V> {
fn substitute(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V
where
V: TypeFoldable<TyCtxt<'tcx>>;
fn substitute_projected<T>(
&self,
tcx: TyCtxt<'tcx>,
var_values: &CanonicalVarValues<'tcx>,
projection_fn: impl FnOnce(&V) -> T,
) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>;
}
impl<'tcx, V> CanonicalExt<'tcx, V> for Canonical<'tcx, V> {
fn substitute(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
self.substitute_projected(tcx, var_values, |value| value.clone())
}
fn substitute_projected<T>(
&self,
tcx: TyCtxt<'tcx>,
var_values: &CanonicalVarValues<'tcx>,
projection_fn: impl FnOnce(&V) -> T,
) -> T
where
T: TypeFoldable<TyCtxt<'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<'tcx, T>(
tcx: TyCtxt<'tcx>,
var_values: &CanonicalVarValues<'tcx>,
value: T,
) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if var_values.var_values.is_empty() {
value
} else {
let delegate = FnMutDelegate {
regions: &mut |br: ty::BoundRegion| match var_values[br.var].unpack() {
GenericArgKind::Lifetime(l) => l,
r => bug!("{:?} is a region but value is {:?}", br, r),
},
types: &mut |bound_ty: ty::BoundTy| match var_values[bound_ty.var].unpack() {
GenericArgKind::Type(ty) => ty,
r => bug!("{:?} is a type but value is {:?}", bound_ty, r),
},
consts: &mut |bound_ct: ty::BoundVar, _| match var_values[bound_ct].unpack() {
GenericArgKind::Const(ct) => ct,
c => bug!("{:?} is a const but value is {:?}", bound_ct, c),
},
};
tcx.replace_escaping_bound_vars_uncached(value, delegate)
}
}