HEADS-UP: diagrams does not compile with HEAD (regressions)

Devs, as of recently GHC HEAD stopped building the diagrams library. Several prerequisite libs also fail to compile. A specific error message appears in an attoparsec issue https://github.com/bos/attoparsec/issues/67, for which I have submitted a workaround. But as Herbert cautiously points out, this could be a recent GHC bug surfacing. The symptoms of the bug seem to be that GHC complains about the usage of (~) type equality operation, but there is no reference to that type operator in the source code. To work around the problem it suffices to add -XGADTs or -XTypeFamilies. Does this ring any bells? Can automatized tests catch such things in the future? Cheers, Gabor