Type inference for flag enum contains (`in`) expression
Similarly to how it is now possible to specify an unqualified flag value when using it in a function/method call, it would also be great to be able to do same in an in
expression.
E.g.:
[Flags] enum EnumName { A, B; }
void test(EnumName value) { }
// inference in method calls compiles fine
test(A);
test(A|B);
// contains checks does not
EnumName value = A;
A in value; // Fails with compiler error: The name `A' does not exist in the context of...