Fix surround cursor position calculation (#1183)

Fixes #1077. This was caused by the assumption that a block
cursor is represented as zero width internally and simply
rendered to be a single width selection, where as in reality
a block cursor is an actual single width selection in form and
function.

Behavioural changes:

1. Surround selection no longer works when cursor is _on_ a
    surround character that has matching pairs (like `'`
    or `"`). This was the intended behaviour from the start
    but worked till now because of the cursor position
    calculation mismatch.

1 files changed, 3 insertions, 3 deletions

diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index b4d1dffa..116a1c7c 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -308,10 +308,10 @@ impl Range {
 }
 
 impl From<(usize, usize)> for Range {
-    fn from(tuple: (usize, usize)) -> Self {
+    fn from((anchor, head): (usize, usize)) -> Self {
         Self {
-            anchor: tuple.0,
-            head: tuple.1,
+            anchor,
+            head,
             horiz: None,
         }
     }