Ticket #5220 (closed bug: fixed)
GHC internal error when missing -XFlexibleContexts with generics
See test case GEq2 (currently on the ghc-generics branch, soon to be merged). When missing -XFlexibleContexts, the compiler panics with
GHC internal error: `Main.$gdmgeq' is not in scope during type checking, but it passed the renamer
When -XFlexibleContexts is added, the error disappears.