From cc0c6cc420ca8019665e745797758c997cc35358 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 16 Aug 2019 22:33:16 +0200
Subject: Use generic Shift/Subst impls

---
 dhall/src/core/thunk.rs | 35 ++++++++---------------------------
 1 file changed, 8 insertions(+), 27 deletions(-)

(limited to 'dhall/src/core/thunk.rs')

diff --git a/dhall/src/core/thunk.rs b/dhall/src/core/thunk.rs
index e315a90..b6358ef 100644
--- a/dhall/src/core/thunk.rs
+++ b/dhall/src/core/thunk.rs
@@ -266,24 +266,16 @@ impl TypedThunk {
 
 impl Shift for Thunk {
     fn shift(&self, delta: isize, var: &AlphaVar) -> Option<Self> {
-        Some(
-            self.0
-                .borrow()
-                .shift(delta, var)?
-                .into_thunk(self.1.shift(delta, var)?),
-        )
+        Some(Thunk(self.0.shift(delta, var)?, self.1.shift(delta, var)?))
     }
 }
 
 impl Shift for ThunkInternal {
     fn shift(&self, delta: isize, var: &AlphaVar) -> Option<Self> {
         Some(match self {
-            ThunkInternal::PartialExpr(e) => ThunkInternal::PartialExpr(
-                e.traverse_ref_with_special_handling_of_binders(
-                    |v| Ok(v.shift(delta, var)?),
-                    |x, v| Ok(v.shift(delta, &var.under_binder(x))?),
-                )?,
-            ),
+            ThunkInternal::PartialExpr(e) => {
+                ThunkInternal::PartialExpr(e.shift(delta, var)?)
+            }
             ThunkInternal::ValueF(m, v) => {
                 ThunkInternal::ValueF(*m, v.shift(delta, var)?)
             }
@@ -301,27 +293,16 @@ impl Shift for TypedThunk {
 
 impl Subst<Typed> for Thunk {
     fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
-        self.0
-            .borrow()
-            .subst_shift(var, val)
-            .into_thunk(self.1.subst_shift(var, val))
+        Thunk(self.0.subst_shift(var, val), self.1.subst_shift(var, val))
     }
 }
 
 impl Subst<Typed> for ThunkInternal {
     fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
         match self {
-            ThunkInternal::PartialExpr(e) => ThunkInternal::PartialExpr(
-                e.map_ref_with_special_handling_of_binders(
-                    |v| v.subst_shift(var, val),
-                    |x, v| {
-                        v.subst_shift(
-                            &var.under_binder(x),
-                            &val.under_binder(x),
-                        )
-                    },
-                ),
-            ),
+            ThunkInternal::PartialExpr(e) => {
+                ThunkInternal::PartialExpr(e.subst_shift(var, val))
+            }
             ThunkInternal::ValueF(_, v) => {
                 // The resulting value may not stay in normal form after substitution
                 ThunkInternal::ValueF(WHNF, v.subst_shift(var, val))
-- 
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