Remove ExactSizeIterator requirement on Transaction::change

Size hint is enough.

helix-core/src/diff.rs

@@ -1,6 +1,4 @@
-use ropey::Rope;
-
-use crate::{Change, Transaction};
+use crate::{Rope, Transaction};
 
 /// Compares `old` and `new` to generate a [`Transaction`] describing
 /// the steps required to get from `old` to `new`.
@@ -25,8 +23,9 @@ pub fn compare_ropes(old: &Rope, new: &Rope) -> Transaction {
     // The current position of the change needs to be tracked to
     // construct the `Change`s.
     let mut pos = 0;
-    let changes: Vec<Change> = diff
-        .ops()
+    Transaction::change(
+        old,
+        diff.ops()
             .iter()
             .map(|op| op.as_tag_tuple())
             .filter_map(|(tag, old_range, new_range)| {
@@ -50,9 +49,8 @@ pub fn compare_ropes(old: &Rope, new: &Rope) -> Transaction {
                     similar::DiffTag::Delete => Some((old_pos, pos, None)),
                     similar::DiffTag::Equal => None,
                 }
-        })
-        .collect();
-    Transaction::change(old, changes.into_iter())
+            }),
+    )
 }
 
 #[cfg(test)]

helix-core/src/transaction.rs

@@ -473,11 +473,13 @@ impl Transaction {
     /// Generate a transaction from a set of changes.
     pub fn change<I>(doc: &Rope, changes: I) -> Self
     where
-        I: IntoIterator<Item = Change> + ExactSizeIterator,
+        I: IntoIterator<Item = Change> + Iterator,
     {
         let len = doc.len_chars();
 
-        let mut changeset = ChangeSet::with_capacity(2 * changes.len() + 1); // rough estimate
+        let (lower, upper) = changes.size_hint();
+        let size = upper.unwrap_or(lower);
+        let mut changeset = ChangeSet::with_capacity(2 * size + 1); // rough estimate
 
         // TODO: verify ranges are ordered and not overlapping or change will panic.