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use super::*;
#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
pub struct SubstVec<T = ()> {
substs: Vec<TermOrShift>,
no_subst: u32,
base: u32,
ctx: T,
}
impl<T: TyCtxMut> SubstVec<T> {
#[inline]
pub fn new(ctx: T) -> SubstVec<T> {
SubstVec {
substs: Vec::new(),
no_subst: 0,
base: 0,
ctx,
}
}
}
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
enum TermOrShift {
Term(TermId),
Shift(u32),
}
impl<T: TyCtxMut> SubstCtx for SubstVec<T> {
type Ctx = T::MaxDeref;
fn subst_var(&mut self, ix: u32, annot: Option<&TermId>) -> Result<Option<TermId>, Error> {
if let Some(subst_ix) = ix.checked_sub(self.base) {
let subst = if (subst_ix as usize) < self.substs.len() {
self.substs[self.substs.len() - 1 - subst_ix as usize].clone()
} else {
TermOrShift::Shift(0)
};
match subst {
TermOrShift::Term(term) => {
Ok(Some(term))
}
TermOrShift::Shift(shift) => {
let ty = annot.subst_rec(self)?;
let new_ix = subst_ix + shift - self.no_subst;
if ty.is_none() && new_ix == subst_ix {
return Ok(None);
}
let ty = ty
.unwrap_or_else(|| annot.consed(self.ctx.cons_ctx()))
.map(|ty| ty.into_shallow_cons(self.ctx.cons_ctx()));
let term = Var::new_unchecked(new_ix, ty).into_id_with(self.ctx.cons_ctx());
Ok(Some(term))
}
}
} else {
Ok(None)
}
}
#[inline]
fn push_param(&mut self, param_ty: Option<&TermId>) -> Result<Option<TermId>, Error> {
let subst = if let Some(param_ty) = param_ty {
param_ty.subst_rec(self)?
} else {
None
};
self.ctx.push_param(subst.as_ref().or(param_ty))?;
self.base += 1;
Ok(subst)
}
#[inline]
fn intersects(&self, filter: VarFilter, _code: Code, _form: Form) -> bool {
filter.fvb() >= self.base
}
#[inline]
fn ctx(&mut self) -> &mut Self::Ctx {
self.ctx.ctx()
}
#[inline]
fn pop_param(&mut self) -> Result<(), Error> {
self.ctx.pop_param()?;
match self.substs.last() {
Some(TermOrShift::Shift(_)) => {
self.substs.pop();
}
_ if self.base == 0 => return Err(Error::ParameterUnderflow),
_ => self.base -= 1,
}
Ok(())
}
#[inline]
fn is_var_null(&self) -> bool {
self.substs.is_empty()
}
}
impl<T: TyCtxMut> EvalCtx for SubstVec<T> {
fn push_subst(&mut self, subst: TermId) -> Result<(), Error> {
self.substs.reserve(self.base as usize + 1);
while self.base > 0 {
self.substs.push(TermOrShift::Shift(self.no_subst));
self.base -= 1;
}
self.substs.push(TermOrShift::Term(subst));
self.no_subst += 1;
Ok(())
}
fn pop_subst(&mut self) -> Result<(), Error> {
if self.base != 0 {
return Err(Error::ParameterUnderflow);
}
match self.substs.last() {
Some(TermOrShift::Term(_)) => {
self.substs.pop();
self.no_subst -= 1;
}
_ => {
return Err(Error::ParameterUnderflow);
}
}
while let Some(TermOrShift::Shift(s)) = self.substs.last() {
if *s == self.no_subst {
self.substs.pop();
self.base += 1;
} else {
break;
}
}
Ok(())
}
}