The diagnostic when a user attempts to pass an argument requiring an implicit conversion (e.g. declared as a subclass, type conforming to protocol, etc.) to an inout parameter seems to be confusing for users—see e.g. SR-8155, SR-8148. This change replaces it with a more specific diagnostic which clearly suggests a solution. It also includes a fix-it suggesting the user change the type of the original variable if it’s a local with a simple type signature.