fix(es/minifier): Preserve function length (#9389)

**Related issue:**

 - Closes https://github.com/swc-project/swc/issues/9356

crates/swc_ecma_minifier/tests/exec.rs

@@ -11345,3 +11345,8 @@ fn issue_9184_2() {
 "#,
     );
 }
+
+#[test]
+fn issue_9356() {
+    run_default_exec_test("console.log((function ({ } = 42) { }).length)");
+}

crates/swc_ecma_transforms_optimization/src/simplify/branch/mod.rs

@@ -314,15 +314,6 @@ impl VisitMut for Remover {
                 *p = *assign.left.take();
             }
 
-            Pat::Assign(assign)
-                if match *assign.left {
-                    Pat::Object(ref o) => o.props.is_empty(),
-                    _ => false,
-                } && assign.right.is_number() =>
-            {
-                *p = *assign.left.take();
-            }
-
             _ => {}
         }
     }

crates/swc_ecma_transforms_optimization/src/simplify/branch/tests.rs

@@ -1452,16 +1452,6 @@ fn test_empty_key_in_object_pattern_removed() {
     test_same("const {[foo()]: {}} = {};");
 }
 
-#[test]
-fn test_empty_key_in_object_pattern_with_default_value_maybe_removed() {
-    test("const {f: {} = 0} = {};", "");
-    // In theory the following case could be reduced to `foo()`, but that gets more
-    // complicated to implement for object patterns with multiple keys with side
-    // effects. Instead the pass backs off for any default with a possible side
-    // effect
-    test_same("const {f: {} = foo()} = {};");
-}
-
 #[test]
 fn test_empty_key_in_object_pattern_not_removed_with_object_rest() {
     test_same("const {f: {}, ...g} = foo()");