The impossible happened

ghc: panic! (the 'impossible' happened)
  (GHC version 6.12.1 for i386-apple-darwin):
	thread blocked indefinitely in an MVar operation

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Edited Mar 09, 2019 by Ian Lynagh -

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information