Add a (public) utility method to clean-up code

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index b1dd15b34945ce0538407f3997c26a02d23852cf..a00e980d332a239b70224e93c91cfff50f0abb4c 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -2145,10 +2145,7 @@ class FixProcessor {
       if (n is MethodInvocation &&
           n.offset == errorOffset &&
           n.length == errorLength) {
-        Expression target = n.target;
-        while (target is ParenthesizedExpression) {
-          target = (target as ParenthesizedExpression).expression;
-        }
+        Expression target = n.target.unParenthesized;
         // replace "/" with "~/"
         BinaryExpression binary = target as BinaryExpression;
         _addReplaceEdit(rf.rangeToken(binary.operator), '~/');