Get the Editor crate compiling

crates/buffer/src/anchor.rs

@@ -185,6 +185,16 @@ impl<T: Debug> Debug for AnchorRangeMap<T> {
     }
 }
 
+impl Debug for AnchorRangeSet {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        let mut f = f.debug_set();
+        for (range, _) in &self.0.entries {
+            f.entry(range);
+        }
+        f.finish()
+    }
+}
+
 impl AnchorRangeSet {
     pub fn len(&self) -> usize {
         self.0.len()

crates/buffer/src/selection.rs

@@ -37,6 +37,10 @@ pub struct SelectionState {
 }
 
 impl<T: ToOffset + ToPoint + Copy + Ord> Selection<T> {
+    pub fn is_empty(&self) -> bool {
+        self.start == self.end
+    }
+
     pub fn head(&self) -> T {
         if self.reversed {
             self.start