From 9e8ae42b2742e27a70a7fb8ea79ae21060d43fc1 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 2 Nov 2020 03:47:15 +0000
Subject: Normalize `with` by mutation.

This is Cow-style mutation: we clone only what's shared and then mutate
it. This it more legible and more efficient than the immutable version.
---
 dhall/src/semantics/nze/lazy.rs | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

(limited to 'dhall/src/semantics/nze/lazy.rs')

diff --git a/dhall/src/semantics/nze/lazy.rs b/dhall/src/semantics/nze/lazy.rs
index d361313..550f69a 100644
--- a/dhall/src/semantics/nze/lazy.rs
+++ b/dhall/src/semantics/nze/lazy.rs
@@ -35,6 +35,22 @@ where
         let _ = lazy.tgt.set(tgt);
         lazy
     }
+
+    pub fn force(&self) -> &Tgt {
+        self.tgt.get_or_init(|| {
+            let src = self.src.take().unwrap();
+            src.eval()
+        })
+    }
+
+    pub fn get_mut(&mut self) -> &mut Tgt {
+        self.force();
+        self.tgt.get_mut().unwrap()
+    }
+    pub fn into_inner(self) -> Tgt {
+        self.force();
+        self.tgt.into_inner().unwrap()
+    }
 }
 
 impl<Src, Tgt> Deref for Lazy<Src, Tgt>
@@ -43,10 +59,7 @@ where
 {
     type Target = Tgt;
     fn deref(&self) -> &Self::Target {
-        self.tgt.get_or_init(|| {
-            let src = self.src.take().unwrap();
-            src.eval()
-        })
+        self.force()
     }
 }
 
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