From 2036663ed25b5885a87eb3a80caec3fa2e258d77 Mon Sep 17 00:00:00 2001
From: Laurenz <laurmaedje@gmail.com>
Date: Wed, 27 Jan 2021 15:05:18 +0100
Subject: =?UTF-8?q?Capture=20variables=20in=20templates=20=F0=9F=94=8D?=
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---
 src/eval/scope.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

(limited to 'src/eval/scope.rs')

diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index 1ed34f86..9c966a24 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -5,19 +5,19 @@ use std::iter;
 use super::Value;
 
 /// A stack of scopes.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Default, Clone, PartialEq)]
 pub struct Scopes<'a> {
     /// The active scope.
     top: Scope,
     /// The stack of lower scopes.
     scopes: Vec<Scope>,
     /// The base scope.
-    base: &'a Scope,
+    base: Option<&'a Scope>,
 }
 
 impl<'a> Scopes<'a> {
     /// Create a new hierarchy of scopes.
-    pub fn new(base: &'a Scope) -> Self {
+    pub fn new(base: Option<&'a Scope>) -> Self {
         Self { top: Scope::new(), scopes: vec![], base }
     }
 
@@ -43,7 +43,7 @@ impl<'a> Scopes<'a> {
     pub fn get(&self, var: &str) -> Option<&Value> {
         iter::once(&self.top)
             .chain(self.scopes.iter().rev())
-            .chain(iter::once(self.base))
+            .chain(self.base.into_iter())
             .find_map(|scope| scope.get(var))
     }
 
@@ -58,7 +58,7 @@ impl<'a> Scopes<'a> {
     ///
     /// Defaults to `false` if the variable does not exist.
     pub fn is_const(&self, var: &str) -> bool {
-        self.base.get(var).is_some()
+        self.base.map_or(false, |base| base.get(var).is_some())
     }
 }
 
-- 
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