From 4aa647ddc5791f9ac5c2a7877de483e9ae8dd187 Mon Sep 17 00:00:00 2001
From: Richard Newman <rnewman@twinql.com>
Date: Fri, 30 Jun 2017 09:14:29 -0700
Subject: [PATCH] Newtype VariableIterator.

---
 query-algebrizer/src/clauses/mod.rs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/query-algebrizer/src/clauses/mod.rs b/query-algebrizer/src/clauses/mod.rs
index b066be62..050b3400 100644
--- a/query-algebrizer/src/clauses/mod.rs
+++ b/query-algebrizer/src/clauses/mod.rs
@@ -264,6 +264,18 @@ impl Default for ConjoiningClauses {
     }
 }
 
+pub struct VariableIterator<'a>(
+    ::std::collections::btree_map::Keys<'a, Variable, TypedValue>,
+);
+
+impl<'a> Iterator for VariableIterator<'a> {
+    type Item = &'a Variable;
+
+    fn next(&mut self) -> Option<&'a Variable> {
+        self.0.next()
+    }
+}
+
 impl ConjoiningClauses {
     /// Construct a new `ConjoiningClauses` with the provided alias counter. This allows a caller
     /// to share a counter with an enclosing scope, and to start counting at a particular offset
@@ -370,8 +382,8 @@ impl ConjoiningClauses {
     }
 
     /// Return an interator over the variables externally bound to values.
-    pub fn value_bound_variables(&self) -> ::std::collections::btree_map::Keys<Variable, TypedValue> {
-        self.value_bindings.keys()
+    pub fn value_bound_variables(&self) -> VariableIterator {
+        VariableIterator(self.value_bindings.keys())
     }
 
     /// Return a set of the variables externally bound to values.