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use super::*;
use crate::fold::shift::Shift;
pub struct Subst<'s, 'i, I: Interner> {
parameters: &'s [GenericArg<I>],
interner: &'i I,
}
impl<I: Interner> Subst<'_, '_, I> {
pub fn apply<T: Fold<I, I>>(
interner: &I,
parameters: &[GenericArg<I>],
value: &T,
) -> T::Result {
value
.fold_with(
&mut Subst {
parameters,
interner,
},
DebruijnIndex::INNERMOST,
)
.unwrap()
}
}
impl<'i, I: Interner> Folder<'i, I> for Subst<'_, '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>> {
if let Some(index) = bound_var.index_if_innermost() {
match self.parameters[index].data(self.interner()) {
GenericArgData::Ty(t) => Ok(t.shifted_in_from(self.interner(), outer_binder)),
_ => panic!("mismatched kinds in substitution"),
}
} else {
Ok(bound_var
.shifted_out()
.expect("cannot fail because this is not the innermost")
.shifted_in_from(outer_binder)
.to_ty(self.interner()))
}
}
fn fold_free_var_lifetime(
&mut self,
bound_var: BoundVar,
outer_binder: DebruijnIndex,
) -> Fallible<Lifetime<I>> {
if let Some(index) = bound_var.index_if_innermost() {
match self.parameters[index].data(self.interner()) {
GenericArgData::Lifetime(l) => Ok(l.shifted_in_from(self.interner(), outer_binder)),
_ => panic!("mismatched kinds in substitution"),
}
} else {
Ok(bound_var
.shifted_out()
.unwrap()
.shifted_in_from(outer_binder)
.to_lifetime(self.interner()))
}
}
fn fold_free_var_const(
&mut self,
ty: &Ty<I>,
bound_var: BoundVar,
outer_binder: DebruijnIndex,
) -> Fallible<Const<I>> {
if let Some(index) = bound_var.index_if_innermost() {
match self.parameters[index].data(self.interner()) {
GenericArgData::Const(c) => Ok(c.shifted_in_from(self.interner(), outer_binder)),
_ => panic!("mismatched kinds in substitution"),
}
} else {
Ok(bound_var
.shifted_out()
.unwrap()
.shifted_in_from(outer_binder)
.to_const(self.interner(), ty.clone()))
}
}
fn interner(&self) -> &'i I {
self.interner
}
fn target_interner(&self) -> &'i I {
self.interner()
}
}