8.4.1 ghci findings

[Evan Laforge]

I just filed this bug:

#14963: ghci -fdefer-type-errors can't run IO action from another module

https://ghc.haskell.org/trac/ghc/ticket/14963

It seems like -fdefer-type-errors and ghci just don't get along at all now.


But on the good news side, ghci reloading a changed module in 8.4.1 is
much much faster than 8.0.2.  I don't know who did that, but good
work!  Reload being instant instead of having to wait a second or so
makes a big difference.