From 9e38d92bf481da8e34081c81c813acd802efa016 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Thu, 15 Aug 2019 22:03:41 +0200
Subject: Fix variable substitution

I have no idea how this didn't get caught before
---
 dhall/src/core/value.rs | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/dhall/src/core/value.rs b/dhall/src/core/value.rs
index 036a20c..75ef5a5 100644
--- a/dhall/src/core/value.rs
+++ b/dhall/src/core/value.rs
@@ -436,10 +436,8 @@ impl Subst<Typed> for Value {
                 t.subst_shift(var, val),
                 e.subst_shift(&var.under_binder(x), &val.under_binder(x)),
             ),
-            Value::Var(v) => match v.shift(-1, var) {
-                None => val.to_value().clone(),
-                Some(newvar) => Value::Var(newvar),
-            },
+            Value::Var(v) if v == var => val.to_value(),
+            Value::Var(v) => Value::Var(v.shift(-1, var).unwrap()),
             Value::Const(c) => Value::Const(*c),
             Value::BoolLit(b) => Value::BoolLit(*b),
             Value::NaturalLit(n) => Value::NaturalLit(*n),
-- 
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