use ??= (1/?)

Summary: Generated with {D10356459}

Reviewed By: viratyosin

Differential Revision: D10325207

fbshipit-source-id: d057835200bdbcc0035ccff6d8ca42b95b385b7c

Author: periodic1236

src/StringDiff.php

@@ -58,7 +58,7 @@ public function getUnifiedDiff(int $context = 3): string {
       $run_start = null;
       for ($i = $context; $i < $count; ++$i) {
         if ($remaining[$i] instanceof DiffKeepOp) {
-          $run_start = $run_start ?? $i;
+          $run_start ??= $i;
           continue;
         }
 
@@ -99,25 +99,25 @@ private function getUnifiedDiffHunk(
     foreach ($hunk as $op) {
       if ($op instanceof DiffKeepOp) {
         $lines[] = ' '.$op->getContent();
-        $old_start = $old_start ?? $op->getOldPos();
-        $new_start = $new_start ?? $op->getNewPos();
+        $old_start ??= $op->getOldPos();
+        $new_start ??= $op->getNewPos();
         ++$old_lines;
         ++$new_lines;
         continue;
       }
 
       if ($op instanceof DiffDeleteOp) {
         $lines[] = '-'.$op->getContent();
-        $old_start = $old_start ?? $op->getOldPos();
-        $new_start = $new_start ?? $op->getOldPos();
+        $old_start ??= $op->getOldPos();
+        $new_start ??= $op->getOldPos();
         ++$old_lines;
         continue;
       }
 
       if ($op instanceof DiffInsertOp) {
         $lines[] = '+'.$op->getContent();
-        $old_start = $old_start ?? $op->getNewPos();
-        $new_start = $new_start ?? $op->getNewPos();
+        $old_start ??= $op->getNewPos();
+        $new_start ??= $op->getNewPos();
         ++$new_lines;
         continue;
       }