Consider this code:
struct Struct { public int Num; }
class Program
{
public void A(ref readonly Struct s) { }
public void B(ref readonly Struct s) => A(ref s);
}
I get a compilation error on this A(ref s), telling me:
CS8329: Cannot use variable as a ref or out value because it is a readonly variable
But the whole point of ref readonly is that you can guarantee it will not be changed. So why can't it be transitive?
Couldn't find helpful info in MSDN.
You should use the in modifier
class Program {
public void A(ref readonly Struct s) { }
public void B(ref readonly Struct s) => A(in s);
}
this is per the docs:
The
ref readonlymodifier isn't valid at the call site. Which modifier you use at the call site can help describe characteristics of the argument. You can only userefif the argument is a variable, and is writable. You can only useinwhen the argument is a variable. It might be writable, orreadonly.
