equals method
Implementation
@override
FutureOr<bool> equals(Object other) async {
if (identical(this, other)) return true;
if (other is ASTValueNum) {
return value == other.value;
} else if (other is ASTValue) {
var context = VMContext.getCurrent();
var v2 = await _getValue(context, other);
return value == v2;
}
return false;
}