Andrés Sicard-Ramírez writes:

Dear all,

In GHC 8 RC 1, the `-Wmissed-specialisations` and `-Wall-missed-specialisations` options generate a warning instead of an error when using `-Werror`. Is it the expected behaviour?

I would say this can be considered correct. This warning is really intended to let the user know that a specialization hasn't occurred; fixing this may require changes in code which they have little control over (e.g. adding an inline pragma to an upstream library). Regardless, this behavior probably ought to be a bit better documented. I've opened D1829 fixing this. Cheers, - Ben