test(ecmascript): add comments and tests for cases where ToPropertyKey throws an error (#9429)

crates/oxc_ecmascript/src/side_effects/may_have_side_effects.rs

@@ -340,6 +340,8 @@ impl MayHaveSideEffects for PropertyKey<'_> {
         match self {
             PropertyKey::StaticIdentifier(_) | PropertyKey::PrivateIdentifier(_) => false,
             match_expression!(PropertyKey) => {
+                // ToPropertyKey(key) throws an error when ToPrimitive(key) throws an Error
+                // But we can ignore that by using the assumption.
                 self.to_expression().may_have_side_effects(is_global_reference)
             }
         }

crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs

@@ -560,6 +560,11 @@ fn test_object_expression() {
     test("({[1]: 1})", false);
     test("({[1n]: 1})", false);
     test("({['1']: 1})", false);
+    // These actually have a side effect, but this treated as side-effect free.
+    test("({[{ toString() { console.log('sideeffect') } }]: 1})", false);
+    test("({[{ valueOf() { console.log('sideeffect') } }]: 1})", false);
+    test("({[{ [s]() { console.log('sideeffect') } }]: 1})", false); // assuming s is Symbol.toPrimitive
+    test("({[foo]: 1})", false);
     test("({[foo()]: 1 })", true);
     test("({a: foo()})", true);
     test("({...a})", true);