From 17ab417aeb5aea6cd21240a491607b9017194737 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Thu, 2 May 2019 17:18:52 +0200
Subject: Remove shift0

---
 dhall/src/normalize.rs | 39 +++++++++++++++++++++------------------
 dhall/src/typecheck.rs | 19 +++++--------------
 dhall_core/src/core.rs | 40 +++++++++++++++++-----------------------
 3 files changed, 43 insertions(+), 55 deletions(-)

diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index a023d38..f991a2e 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -38,10 +38,6 @@ impl<'a> Typed<'a> {
         Normalized(internal, self.1)
     }
 
-    pub(crate) fn shift0(&self, delta: isize, x: &Label) -> Self {
-        self.shift(delta, &V(x.clone(), 0))
-    }
-
     pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Self {
         Typed(self.0.shift(delta, var), self.1)
     }
@@ -257,10 +253,6 @@ enum EnvItem {
 }
 
 impl EnvItem {
-    fn shift0(&self, delta: isize, x: &Label) -> Self {
-        self.shift(delta, &V(x.clone(), 0))
-    }
-
     fn shift(&self, delta: isize, var: &V<Label>) -> Self {
         use EnvItem::*;
         match self {
@@ -297,8 +289,8 @@ impl NormalizationContext {
     fn skip(&self, x: &Label) -> Self {
         NormalizationContext(Rc::new(
             self.0
-                .map(|_, e| e.shift0(1, x))
-                .insert(x.clone(), EnvItem::Skip(V(x.clone(), 0))),
+                .map(|_, e| e.shift(1, &x.into()))
+                .insert(x.clone(), EnvItem::Skip(x.into())),
         ))
     }
     fn lookup(&self, var: &V<Label>) -> Value {
@@ -402,14 +394,14 @@ impl Value {
             Value::ListConsClosure(n, None) => {
                 let a = n.normalize_to_expr();
                 // Avoid accidental capture of the new `x` variable
-                let a1 = a.shift0(1, &"x".into());
+                let a1 = a.shift(1, &Label::from("x").into());
                 dhall::subexpr!(λ(x : a) -> λ(xs : List a1) -> [ x ] # xs)
             }
             Value::ListConsClosure(n, Some(v)) => {
                 let v = v.normalize_to_expr();
                 let a = n.normalize_to_expr();
                 // Avoid accidental capture of the new `xs` variable
-                let v = v.shift0(1, &"xs".into());
+                let v = v.shift(1, &Label::from("xs").into());
                 dhall::subexpr!(λ(xs : List a) -> [ v ] # xs)
             }
             Value::NaturalSuccClosure => {
@@ -746,7 +738,7 @@ impl Value {
             Value::Lam(x, t, e) => Value::Lam(
                 x.clone(),
                 t.shift(delta, var),
-                e.shift(delta, &var.shift0(1, x)),
+                e.shift(delta, &var.shift(1, &x.into())),
             ),
             Value::AppliedBuiltin(b, args) => Value::AppliedBuiltin(
                 *b,
@@ -763,7 +755,7 @@ impl Value {
             Value::Pi(x, t, e) => Value::Pi(
                 x.clone(),
                 t.shift(delta, var),
-                e.shift(delta, &var.shift0(1, x)),
+                e.shift(delta, &var.shift(1, &x.into())),
             ),
             Value::Var(v) => Value::Var(v.shift(delta, var)),
             Value::Const(c) => Value::Const(*c),
@@ -830,7 +822,7 @@ impl Value {
             Value::PartialExpr(e) => Value::PartialExpr(Box::new(
                 e.map_ref_with_special_handling_of_binders(
                     |v| v.shift(delta, var),
-                    |x, v| v.shift(delta, &var.shift0(1, x)),
+                    |x, v| v.shift(delta, &var.shift(1, &x.into())),
                     X::clone,
                     X::clone,
                     Label::clone,
@@ -849,7 +841,10 @@ impl Value {
             Value::Lam(x, t, e) => Value::Lam(
                 x.clone(),
                 t.subst_shift(var, val),
-                e.subst_shift(&var.shift0(1, x), &val.shift0(1, x)),
+                e.subst_shift(
+                    &var.shift(1, &x.into()),
+                    &val.shift(1, &x.into()),
+                ),
             ),
             Value::AppliedBuiltin(b, args) => Value::AppliedBuiltin(
                 *b,
@@ -866,7 +861,10 @@ impl Value {
             Value::Pi(x, t, e) => Value::Pi(
                 x.clone(),
                 t.subst_shift(var, val),
-                e.subst_shift(&var.shift0(1, x), &val.shift0(1, x)),
+                e.subst_shift(
+                    &var.shift(1, &x.into()),
+                    &val.shift(1, &x.into()),
+                ),
             ),
             Value::Var(v) if v == var => val.to_value().clone(),
             Value::Var(v) => Value::Var(v.shift(-1, var)),
@@ -934,7 +932,12 @@ impl Value {
             Value::PartialExpr(e) => Value::PartialExpr(Box::new(
                 e.map_ref_with_special_handling_of_binders(
                     |v| v.subst_shift(var, val),
-                    |x, v| v.subst_shift(&var.shift0(1, x), &val.shift0(1, x)),
+                    |x, v| {
+                        v.subst_shift(
+                            &var.shift(1, &x.into()),
+                            &val.shift(1, &x.into()),
+                        )
+                    },
                     X::clone,
                     X::clone,
                     Label::clone,
diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index 582930b..78538aa 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -46,9 +46,6 @@ impl<'a> Typed<'a> {
 }
 
 impl<'a> Normalized<'a> {
-    fn shift0(&self, delta: isize, label: &Label) -> Self {
-        self.shift(delta, &V(label.clone(), 0))
-    }
     fn shift(&self, delta: isize, var: &V<Label>) -> Self {
         Normalized(self.0.shift(delta, var), self.1)
     }
@@ -79,9 +76,6 @@ impl<'a> Type<'a> {
     fn internal_whnf(&self) -> Option<Value> {
         self.0.whnf()
     }
-    pub(crate) fn shift0(&self, delta: isize, label: &Label) -> Self {
-        Type(self.0.shift0(delta, label))
-    }
     pub(crate) fn shift(&self, delta: isize, var: &V<Label>) -> Self {
         Type(self.0.shift(delta, var))
     }
@@ -164,9 +158,6 @@ impl<'a> TypeInternal<'a> {
             _ => None,
         }
     }
-    fn shift0(&self, delta: isize, label: &Label) -> Self {
-        self.shift(delta, &V(label.clone(), 0))
-    }
     fn shift(&self, delta: isize, var: &V<Label>) -> Self {
         use TypeInternal::*;
         match self {
@@ -197,11 +188,11 @@ pub(crate) enum EnvItem {
 }
 
 impl EnvItem {
-    fn shift0(&self, delta: isize, x: &Label) -> Self {
+    fn shift(&self, delta: isize, var: &V<Label>) -> Self {
         use EnvItem::*;
         match self {
-            Type(v, e) => Type(v.shift0(delta, x), e.shift0(delta, x)),
-            Value(e) => Value(e.shift0(delta, x)),
+            Type(v, e) => Type(v.shift(delta, var), e.shift(delta, var)),
+            Value(e) => Value(e.shift(delta, var)),
         }
     }
 }
@@ -215,9 +206,9 @@ impl TypecheckContext {
     }
     pub(crate) fn insert_type(&self, x: &Label, t: Type<'static>) -> Self {
         TypecheckContext(
-            self.0.map(|_, e| e.shift0(1, x)).insert(
+            self.0.map(|_, e| e.shift(1, &x.into())).insert(
                 x.clone(),
-                EnvItem::Type(V(x.clone(), 0), t.shift0(1, x)),
+                EnvItem::Type(x.into(), t.shift(1, &x.into())),
             ),
         )
     }
diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index ebd95e7..3db07dd 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -62,6 +62,18 @@ pub enum Const {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct V<Label>(pub Label, pub usize);
 
+// This is only for the specific `Label` type, not generic
+impl From<Label> for V<Label> {
+    fn from(x: Label) -> V<Label> {
+        V(x, 0)
+    }
+}
+impl<'a> From<&'a Label> for V<Label> {
+    fn from(x: &'a Label) -> V<Label> {
+        V(x.clone(), 0)
+    }
+}
+
 // Definition order must match precedence order for
 // pretty-printing to work correctly
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
@@ -443,15 +455,11 @@ impl<N, E> SubExpr<N, E> {
             ExprF::Var(v) => rc(ExprF::Var(v.shift(delta, var))),
             _ => self.map_subexprs_with_special_handling_of_binders(
                 |e| e.shift(delta, var),
-                |x: &Label, e| e.shift(delta, &var.shift0(1, x)),
+                |x: &Label, e| e.shift(delta, &var.shift(1, &x.into())),
             ),
         }
     }
 
-    pub fn shift0(&self, delta: isize, label: &Label) -> Self {
-        self.shift(delta, &V(label.clone(), 0))
-    }
-
     pub fn subst_shift(&self, var: &V<Label>, val: &Self) -> Self {
         match self.as_ref() {
             ExprF::Var(v) if v == var => val.clone(),
@@ -459,7 +467,10 @@ impl<N, E> SubExpr<N, E> {
             _ => self.map_subexprs_with_special_handling_of_binders(
                 |e| e.subst_shift(var, val),
                 |x: &Label, e| {
-                    e.subst_shift(&var.shift0(1, x), &val.shift0(1, x))
+                    e.subst_shift(
+                        &var.shift(1, &x.into()),
+                        &val.shift(1, &x.into()),
+                    )
                 },
             ),
         }
@@ -509,15 +520,6 @@ impl<Label: PartialEq + Clone> V<Label> {
             V(y.clone(), *m)
         }
     }
-
-    pub fn shift0(&self, delta: isize, x: &Label) -> Self {
-        let V(y, m) = self;
-        if x == y {
-            V(y.clone(), add_ui(*m, delta))
-        } else {
-            V(y.clone(), *m)
-        }
-    }
 }
 
 /// `shift` is used by both normalization and type-checking to avoid variable
@@ -533,14 +535,6 @@ pub fn shift<N, E>(
     in_expr.shift(delta, var)
 }
 
-pub fn shift0<N, E>(
-    delta: isize,
-    label: &Label,
-    in_expr: &SubExpr<N, E>,
-) -> SubExpr<N, E> {
-    shift(delta, &V(label.clone(), 0), in_expr)
-}
-
 pub fn shift0_multiple<N, E>(
     deltas: &HashMap<Label, isize>,
     in_expr: &SubExpr<N, E>,
-- 
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