1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
use super::*;
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Shift<T> {
pub shift: i32,
pub base: u32,
ctx: T,
}
impl<T: TyCtxMut> Shift<T> {
#[inline]
pub fn new(shift: i32, base: u32, ctx: T) -> Shift<T> {
Shift { shift, base, ctx }
}
}
impl<T: TyCtxMut> SubstCtx for Shift<T> {
type Ctx = T;
#[inline]
fn subst_var(&mut self, ix: u32, annot: Option<&TermId>) -> Result<Option<TermId>, Error> {
if self.shift == 0 {
return Ok(None);
}
let new_ix = if ix >= self.base {
let shifted = if self.shift < 0 {
ix.checked_sub(-self.shift as u32)
.ok_or(Error::ParameterUnderflow)?
} else {
ix.checked_add(self.shift as u32)
.ok_or(Error::ParameterOverflow)?
};
if shifted < self.base {
return Err(Error::HasDependency);
};
shifted
} else {
ix
};
let new_annot = annot.subst_rec(self)?;
if new_ix == ix && new_annot.is_none() {
return Ok(None);
}
let var = Var::new_unchecked(
new_ix,
new_annot.unwrap_or_else(|| annot.consed(self.ctx.cons_ctx())),
)
.into_id_with(self.ctx.cons_ctx());
Ok(Some(var))
}
#[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_id(self)?
} else {
None
};
self.base = self.base.checked_add(1).ok_or(Error::ParameterOverflow)?;
Ok(subst)
}
#[inline]
fn intersects(&self, filter: VarFilter, _code: Code, _form: Form) -> bool {
self.shift != 0 && filter.fvb() >= self.base
}
#[inline]
fn ctx(&mut self) -> &mut Self::Ctx {
&mut self.ctx
}
#[inline]
fn pop_param(&mut self) -> Result<(), Error> {
self.base = self.base.checked_sub(1).ok_or(Error::ParameterUnderflow)?;
Ok(())
}
#[inline]
fn is_var_null(&self) -> bool {
true
}
}