GRHS with empty wherebinds gets wrong SrcSpan
GRHS with empty wherebinds gets wrong SrcSpan

Summary:
When parsing a rhs, the GRHS is constructed via unguardedRHS which is
given a SrcSpan which only takes account of the '=' and wherebinds, so
does not include the exp when wherebinds are empty.

Test Plan: ./validate

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D643

urbanslug/ghc,mfine/ghc,oldmanmike/ghc,TomMD/ghc,vTurbine/ghc,elieux/ghc,olsner/ghc,gcampax/ghc,ml9951/ghc,ghc-android/ghc,tjakway/ghcjvm,TomMD/ghc,urbanslug/ghc,vikraman/ghc,nushio3/ghc,mcschroeder/ghc,acowley/ghc,AlexanderPankiv/ghc,mcschroeder/ghc,TomMD/ghc,siddhanathan/ghc,ml9951/ghc,ghc-android/ghc,tjakway/ghcjvm,christiaanb/ghc,mfine/ghc,shlevy/ghc,mcschroeder/ghc,ezyang/ghc,gcampax/ghc,TomMD/ghc,vTurbine/ghc,AlexanderPankiv/ghc,nkaretnikov/ghc,olsner/ghc,oldmanmike/ghc,tjakway/ghcjvm,gridaphobe/ghc,elieux/ghc,GaloisInc/halvm-ghc,mcschroeder/ghc,wxwxwwxxx/ghc,oldmanmike/ghc,TomMD/ghc,tjakway/ghcjvm,ghc-android/ghc,mfine/ghc,ezyang/ghc,oldmanmike/ghc,wxwxwwxxx/ghc,AlexanderPankiv/ghc,gcampax/ghc,wxwxwwxxx/ghc,vikraman/ghc,anton-dessiatov/ghc,acowley/ghc,wxwxwwxxx/ghc,sgillespie/ghc,oldmanmike/ghc,gcampax/ghc,nkaretnikov/ghc,nkaretnikov/ghc,mcschroeder/ghc,acowley/ghc,shlevy/ghc,sdiehl/ghc,olsner/ghc,TomMD/ghc,vikraman/ghc,GaloisInc/halvm-ghc,mfine/ghc,GaloisInc/halvm-ghc,elieux/ghc,anton-dessiatov/ghc,snoyberg/ghc,fmthoma/ghc,vikraman/ghc,shlevy/ghc,sdiehl/ghc,urbanslug/ghc,oldmanmike/ghc,elieux/ghc,oldmanmike/ghc,urbanslug/ghc,ghc-android/ghc,fmthoma/ghc,fmthoma/ghc,elieux/ghc,tjakway/ghcjvm,snoyberg/ghc,wxwxwwxxx/ghc,wxwxwwxxx/ghc,vikraman/ghc,da-x/ghc,vTurbine/ghc,acowley/ghc,nkaretnikov/ghc,ml9951/ghc,vTurbine/ghc,nushio3/ghc,nkaretnikov/ghc,shlevy/ghc,TomMD/ghc,GaloisInc/halvm-ghc,christiaanb/ghc,mfine/ghc,mettekou/ghc,urbanslug/ghc,sdiehl/ghc,nushio3/ghc,AlexanderPankiv/ghc,AlexanderPankiv/ghc,fmthoma/ghc,gcampax/ghc,ezyang/ghc,da-x/ghc,urbanslug/ghc,mettekou/ghc,siddhanathan/ghc,gridaphobe/ghc,mettekou/ghc,gcampax/ghc,mfine/ghc,ghc-android/ghc,ezyang/ghc,sgillespie/ghc,ghc-android/ghc,gridaphobe/ghc,nushio3/ghc,ezyang/ghc,da-x/ghc,sgillespie/ghc,GaloisInc/halvm-ghc,olsner/ghc,christiaanb/ghc,sdiehl/ghc,vTurbine/ghc,nkaretnikov/ghc,mcschroeder/ghc,ezyang/ghc,GaloisInc/halvm-ghc,snoyberg/ghc,fmthoma/ghc,vTurbine/ghc,snoyberg/ghc,siddhanathan/ghc,ml9951/ghc,da-x/ghc,snoyberg/ghc,mcschroeder/ghc,olsner/ghc,anton-dessiatov/ghc,ezyang/ghc,siddhanathan/ghc,sdiehl/ghc,siddhanathan/ghc,vTurbine/ghc,elieux/ghc,da-x/ghc,urbanslug/ghc,anton-dessiatov/ghc,AlexanderPankiv/ghc,gridaphobe/ghc,wxwxwwxxx/ghc,olsner/ghc,nushio3/ghc,ml9951/ghc,AlexanderPankiv/ghc,gridaphobe/ghc,siddhanathan/ghc,GaloisInc/halvm-ghc,acowley/ghc,ml9951/ghc,acowley/ghc,shlevy/ghc,gridaphobe/ghc,fmthoma/ghc,anton-dessiatov/ghc,mettekou/ghc,da-x/ghc,anton-dessiatov/ghc,nkaretnikov/ghc,siddhanathan/ghc,acowley/ghc,sgillespie/ghc,mettekou/ghc,tjakway/ghcjvm,gridaphobe/ghc,fmthoma/ghc,sgillespie/ghc,vikraman/ghc,nushio3/ghc,snoyberg/ghc,shlevy/ghc,sgillespie/ghc,ml9951/ghc,shlevy/ghc,sdiehl/ghc,ghc-android/ghc,christiaanb/ghc,tjakway/ghcjvm,ml9951/ghc,snoyberg/ghc,mettekou/ghc,mettekou/ghc,elieux/ghc,christiaanb/ghc,christiaanb/ghc,gcampax/ghc,nushio3/ghc,da-x/ghc,vikraman/ghc,sdiehl/ghc,olsner/ghc,sgillespie/ghc,mfine/ghc,anton-dessiatov/ghc,christiaanb/ghc