Optional Parameter Default Value Must Be Constant: Explanation

This means that the default value of an optional parameter must be a constant, which implies it needs to be determined at compile time. It cannot be a variable or an expression. The reason lies in how default values are handled: they're resolved and assigned during compilation, not runtime. If the default value isn't constant, the compiler can't determine its value, leading to issues with memory allocation. To avoid this, the default value for optional parameters must always be a constant.