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-rw-r--r--dhall/src/syntax/ast/expr.rs33
1 files changed, 29 insertions, 4 deletions
diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 04b5adc..2372b0a 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
use crate::syntax::map::{DupTreeMap, DupTreeSet};
use crate::syntax::visitor::{self, ExprKindMutVisitor, ExprKindVisitor};
use crate::syntax::*;
@@ -302,7 +304,7 @@ impl<E> Expr<E> {
}
impl<Label: PartialEq + Clone> V<Label> {
- pub fn shift(&self, delta: isize, var: &V<Label>) -> Option<Self> {
+ pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Option<Self> {
let V(x, n) = var;
let V(y, m) = self;
Some(if x == y && n <= m {
@@ -312,11 +314,35 @@ impl<Label: PartialEq + Clone> V<Label> {
})
}
- pub fn over_binder(&self, x: &Label) -> Option<Self> {
+ pub(crate) fn over_binder(&self, x: &Label) -> Option<Self> {
self.shift(-1, &V(x.clone(), 0))
}
}
+impl V<Label> {
+ pub(crate) fn under_multiple_binders(
+ &self,
+ shift_map: &HashMap<Label, usize>,
+ ) -> Self {
+ let name = &self.0;
+ let idx = self.1 + shift_map.get(name).unwrap_or(&0);
+ V(name.clone(), idx)
+ }
+}
+
+impl V<()> {
+ pub(crate) fn under_multiple_binders(
+ &self,
+ shift_map: &HashMap<Label, usize>,
+ ) -> Self {
+ let mut idx = self.1;
+ for (_, n) in shift_map {
+ idx += n;
+ }
+ V((), idx)
+ }
+}
+
pub fn trivial_result<T>(x: Result<T, !>) -> T {
match x {
Ok(x) => x,
@@ -363,8 +389,7 @@ impl From<NaiveDouble> for f64 {
}
}
-/// This is only for the specific `Label` type, not generic
-impl From<Label> for V<Label> {
+impl<Label> From<Label> for V<Label> {
fn from(x: Label) -> V<Label> {
V(x, 0)
}