Add Debug for dictionary

src/util/dictionary/immutable.rs

@@ -1,4 +1,5 @@
 use std::ffi::{CStr, CString};
+use std::fmt;
 use std::marker::PhantomData;
 use std::ptr;
 use std::str::from_utf8_unchecked;
@@ -58,3 +59,9 @@ impl<'a> IntoIterator for &'a Ref<'a> {
         self.iter()
     }
 }
+
+impl<'a> fmt::Debug for Ref<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_map().entries(self.iter()).finish()
+    }
+}

src/util/dictionary/mutable.rs

@@ -1,4 +1,5 @@
 use std::ffi::CString;
+use std::fmt;
 use std::marker::PhantomData;
 use std::ops::Deref;
 
@@ -50,3 +51,9 @@ impl<'a> Deref for Ref<'a> {
         &self.imm
     }
 }
+
+impl<'a> fmt::Debug for Ref<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        self.imm.fmt(fmt)
+    }
+}

src/util/dictionary/owned.rs

@@ -1,3 +1,4 @@
+use std::fmt;
 use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
 use std::ptr;
@@ -126,3 +127,9 @@ impl<'a> Drop for Owned<'a> {
         }
     }
 }
+
+impl<'a> fmt::Debug for Owned<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        self.inner.fmt(fmt)
+    }
+}