fix: do not remove parens for optional params

CLoses #348

Author: dsherret

Cargo.lock

@@ -1587,7 +1587,7 @@ fn gen_arrow_func_expr<'a>(node: &'a ArrowExpr, context: &mut Context<'a>) -> Pr
 
     fn is_first_param_not_identifier_or_has_type_annotation(params: &[Pat]) -> bool {
       match params.get(0) {
-        Some(Pat::Ident(node)) => node.type_ann.is_some(),
+        Some(Pat::Ident(node)) => node.type_ann.is_some() || node.id.optional(),
         _ => true,
       }
     }

src/generation/generate.rs

@@ -34,3 +34,9 @@ const t = (...a) => 5;
 
 [expect]
 const t = (...a) => 5;
+
+== should not remove when optional ==
+const t = (a?) => 5;
+
+[expect]
+const t = (a?) => 5;