T7050 failing

Hi Simon, Your recent "unpack datacons" patch (https://phabricator.haskell.org/rGHC9187d5fb1d3d38a4e607b0d61784c21447c8195b https://phabricator.haskell.org/rGHC9187d5fb1d3d38a4e607b0d61784c21447c8195b) causes typecheck/should_compile/T7050 to loop. This was harder to discover because I had broken validation previously... Richard