valref.rst: Nullable sugar.
valref.rst: Nullable sugar.

Propose a syntax that lets us express ref (T?) and (ref T)? without requiring parens. Also add a note about how 'val' and 'ref' affect the type system up front.

Swift SVN r4450

johnno1962d/swift,glessard/swift,allevato/swift,arvedviehweger/swift,JaSpa/swift,allevato/swift,airspeedswift/swift,amraboelela/swift,atrick/swift,cbrentharris/swift,djwbrown/swift,bitjammer/swift,jmgc/swift,deyton/swift,sdulal/swift,adrfer/swift,sdulal/swift,gregomni/swift,stephentyrone/swift,manavgabhawala/swift,calebd/swift,russbishop/swift,frootloops/swift,roambotics/swift,practicalswift/swift,manavgabhawala/swift,swiftix/swift,gottesmm/swift,adrfer/swift,Ivacker/swift,sschiau/swift,alblue/swift,jckarter/swift,ben-ng/swift,deyton/swift,ken0nek/swift,shajrawi/swift,russbishop/swift,zisko/swift,codestergit/swift,jmgc/swift,stephentyrone/swift,stephentyrone/swift,benlangmuir/swift,LeoShimonaka/swift,djwbrown/swift,deyton/swift,xwu/swift,gmilos/swift,parkera/swift,shajrawi/swift,roambotics/swift,hughbe/swift,jmgc/swift,return/swift,sschiau/swift,natecook1000/swift,apple/swift,gmilos/swift,johnno1962d/swift,hughbe/swift,jopamer/swift,apple/swift,allevato/swift,parkera/swift,manavgabhawala/swift,kentya6/swift,jmgc/swift,JGiola/swift,milseman/swift,khizkhiz/swift,kstaring/swift,ahoppen/swift,frootloops/swift,brentdax/swift,OscarSwanros/swift,lorentey/swift,jopamer/swift,benlangmuir/swift,tjw/swift,LeoShimonaka/swift,atrick/swift,shahmishal/swift,JaSpa/swift,tardieu/swift,khizkhiz/swift,lorentey/swift,dduan/swift,xedin/swift,ken0nek/swift,benlangmuir/swift,nathawes/swift,danielmartin/swift,dduan/swift,emilstahl/swift,parkera/swift,swiftix/swift,karwa/swift,devincoughlin/swift,xwu/swift,djwbrown/swift,practicalswift/swift,SwiftAndroid/swift,OscarSwanros/swift,gmilos/swift,devincoughlin/swift,karwa/swift,ahoppen/swift,xedin/swift,harlanhaskins/swift,shahmishal/swift,deyton/swift,Jnosh/swift,deyton/swift,kstaring/swift,xedin/swift,atrick/swift,swiftix/swift,benlangmuir/swift,alblue/swift,devincoughlin/swift,gregomni/swift,lorentey/swift,KrishMunot/swift,huonw/swift,sschiau/swift,harlanhaskins/swift,slavapestov/swift,glessard/swift,JaSpa/swift,MukeshKumarS/Swift,sdulal/swift,apple/swift,manavgabhawala/swift,swiftix/swift.old,manavgabhawala/swift,atrick/swift,dduan/swift,frootloops/swift,nathawes/swift,Jnosh/swift,therealbnut/swift,gottesmm/swift,Ivacker/swift,aschwaighofer/swift,Ivacker/swift,JGiola/swift,JaSpa/swift,JGiola/swift,codestergit/swift,hughbe/swift,tkremenek/swift,gmilos/swift,kperryua/swift,apple/swift,adrfer/swift,hughbe/swift,mightydeveloper/swift,JGiola/swift,mightydeveloper/swift,jckarter/swift,ben-ng/swift,felix91gr/swift,nathawes/swift,hooman/swift,bitjammer/swift,LeoShimonaka/swift,amraboelela/swift,austinzheng/swift,hughbe/swift,milseman/swift,roambotics/swift,jckarter/swift,jckarter/swift,therealbnut/swift,modocache/swift,jopamer/swift,OscarSwanros/swift,kperryua/swift,therealbnut/swift,tardieu/swift,khizkhiz/swift,stephentyrone/swift,austinzheng/swift,milseman/swift,Ivacker/swift,kusl/swift,tinysun212/swift-windows,CodaFi/swift,tjw/swift,gottesmm/swift,aschwaighofer/swift,parkera/swift,sdulal/swift,CodaFi/swift,practicalswift/swift,KrishMunot/swift,LeoShimonaka/swift,dduan/swift,emilstahl/swift,shajrawi/swift,swiftix/swift.old,swiftix/swift,kperryua/swift,tkremenek/swift,LeoShimonaka/swift,hughbe/swift,bitjammer/swift,dreamsxin/swift,roambotics/swift,calebd/swift,IngmarStein/swift,allevato/swift,slavapestov/swift,rudkx/swift,felix91gr/swift,sschiau/swift,KrishMunot/swift,CodaFi/swift,ben-ng/swift,swiftix/swift.old,modocache/swift,hooman/swift,mightydeveloper/swift,shajrawi/swift,bitjammer/swift,arvedviehweger/swift,tjw/swift,felix91gr/swift,slavapestov/swift,tkremenek/swift,codestergit/swift,deyton/swift,shahmishal/swift,dduan/swift,uasys/swift,ben-ng/swift,cbrentharris/swift,airspeedswift/swift,ken0nek/swift,huonw/swift,dduan/swift,alblue/swift,devincoughlin/swift,kperryua/swift,aschwaighofer/swift,Jnosh/swift,austinzheng/swift,karwa/swift,nathawes/swift,uasys/swift,codestergit/swift,brentdax/swift,gregomni/swift,shajrawi/swift,kentya6/swift,airspeedswift/swift,milseman/swift,amraboelela/swift,aschwaighofer/swift,gottesmm/swift,kentya6/swift,CodaFi/swift,tardieu/swift,glessard/swift,IngmarStein/swift,brentdax/swift,kstaring/swift,IngmarStein/swift,huonw/swift,Jnosh/swift,kusl/swift,jmgc/swift,xedin/swift,johnno1962d/swift,allevato/swift,kperryua/swift,manavgabhawala/swift,SwiftAndroid/swift,CodaFi/swift,karwa/swift,therealbnut/swift,russbishop/swift,gmilos/swift,OscarSwanros/swift,codestergit/swift,jtbandes/swift,ahoppen/swift,kperryua/swift,emilstahl/swift,amraboelela/swift,austinzheng/swift,jmgc/swift,khizkhiz/swift,felix91gr/swift,zisko/swift,IngmarStein/swift,calebd/swift,emilstahl/swift,ken0nek/swift,IngmarStein/swift,SwiftAndroid/swift,KrishMunot/swift,kstaring/swift,devincoughlin/swift,kusl/swift,lorentey/swift,johnno1962d/swift,tkremenek/swift,tardieu/swift,danielmartin/swift,gottesmm/swift,zisko/swift,LeoShimonaka/swift,xedin/swift,kentya6/swift,gribozavr/swift,kusl/swift,tjw/swift,xwu/swift,deyton/swift,OscarSwanros/swift,slavapestov/swift,jopamer/swift,frootloops/swift,nathawes/swift,danielmartin/swift,kusl/swift,frootloops/swift,lorentey/swift,therealbnut/swift,modocache/swift,MukeshKumarS/Swift,practicalswift/swift,jopamer/swift,manavgabhawala/swift,parkera/swift,OscarSwanros/swift,aschwaighofer/swift,kentya6/swift,rudkx/swift,brentdax/swift,stephentyrone/swift,airspeedswift/swift,tinysun212/swift-windows,mightydeveloper/swift,return/swift,gregomni/swift,jtbandes/swift,harlanhaskins/swift,alblue/swift,aschwaighofer/swift,dduan/swift,huonw/swift,bitjammer/swift,Ivacker/swift,emilstahl/swift,tjw/swift,gribozavr/swift,harlanhaskins/swift,tardieu/swift,swiftix/swift.old,Jnosh/swift,MukeshKumarS/Swift,djwbrown/swift,swiftix/swift,SwiftAndroid/swift,rudkx/swift,khizkhiz/swift,danielmartin/swift,SwiftAndroid/swift,jmgc/swift,arvedviehweger/swift,uasys/swift,LeoShimonaka/swift,natecook1000/swift,johnno1962d/swift,arvedviehweger/swift,gribozavr/swift,KrishMunot/swift,benlangmuir/swift,shajrawi/swift,JaSpa/swift,huonw/swift,karwa/swift,rudkx/swift,alblue/swift,ken0nek/swift,LeoShimonaka/swift,austinzheng/swift,harlanhaskins/swift,hooman/swift,austinzheng/swift,tinysun212/swift-windows,lorentey/swift,milseman/swift,SwiftAndroid/swift,modocache/swift,zisko/swift,hooman/swift,adrfer/swift,jtbandes/swift,stephentyrone/swift,johnno1962d/swift,natecook1000/swift,modocache/swift,gmilos/swift,gribozavr/swift,cbrentharris/swift,brentdax/swift,lorentey/swift,hughbe/swift,sschiau/swift,aschwaighofer/swift,russbishop/swift,zisko/swift,return/swift,karwa/swift,sdulal/swift,roambotics/swift,mightydeveloper/swift,kusl/swift,jtbandes/swift,CodaFi/swift,therealbnut/swift,allevato/swift,ken0nek/swift,danielmartin/swift,atrick/swift,mightydeveloper/swift,shahmishal/swift,tkremenek/swift,uasys/swift,xedin/swift,cbrentharris/swift,russbishop/swift,arvedviehweger/swift,calebd/swift,natecook1000/swift,apple/swift,natecook1000/swift,jtbandes/swift,kentya6/swift,roambotics/swift,mightydeveloper/swift,tinysun212/swift-windows,glessard/swift,airspeedswift/swift,atrick/swift,ben-ng/swift,jtbandes/swift,harlanhaskins/swift,Ivacker/swift,Jnosh/swift,MukeshKumarS/Swift,nathawes/swift,hooman/swift,brentdax/swift,gmilos/swift,shahmishal/swift,natecook1000/swift,bitjammer/swift,frootloops/swift,huonw/swift,swiftix/swift,hooman/swift,practicalswift/swift,IngmarStein/swift,JGiola/swift,djwbrown/swift,xedin/swift,glessard/swift,practicalswift/swift,SwiftAndroid/swift,MukeshKumarS/Swift,calebd/swift,xwu/swift,JGiola/swift,harlanhaskins/swift,kentya6/swift,emilstahl/swift,devincoughlin/swift,russbishop/swift,MukeshKumarS/Swift,kstaring/swift,uasys/swift,ahoppen/swift,glessard/swift,xwu/swift,stephentyrone/swift,jtbandes/swift,devincoughlin/swift,tardieu/swift,return/swift,emilstahl/swift,rudkx/swift,tkremenek/swift,slavapestov/swift,johnno1962d/swift,shahmishal/swift,arvedviehweger/swift,therealbnut/swift,swiftix/swift.old,kperryua/swift,codestergit/swift,karwa/swift,gribozavr/swift,amraboelela/swift,kstaring/swift,parkera/swift,CodaFi/swift,return/swift,benlangmuir/swift,gregomni/swift,Jnosh/swift,gribozavr/swift,ben-ng/swift,amraboelela/swift,sdulal/swift,frootloops/swift,sdulal/swift,felix91gr/swift,alblue/swift,kusl/swift,KrishMunot/swift,gribozavr/swift,swiftix/swift,jckarter/swift,return/swift,danielmartin/swift,tjw/swift,uasys/swift,ken0nek/swift,djwbrown/swift,xwu/swift,adrfer/swift,shajrawi/swift,emilstahl/swift,tinysun212/swift-windows,IngmarStein/swift,parkera/swift,gribozavr/swift,gottesmm/swift,MukeshKumarS/Swift,slavapestov/swift,milseman/swift,ben-ng/swift,cbrentharris/swift,shahmishal/swift,modocache/swift,brentdax/swift,swiftix/swift.old,calebd/swift,russbishop/swift,tardieu/swift,calebd/swift,adrfer/swift,modocache/swift,alblue/swift,airspeedswift/swift,apple/swift,milseman/swift,danielmartin/swift,kentya6/swift,zisko/swift,slavapestov/swift,OscarSwanros/swift,ahoppen/swift,jckarter/swift,codestergit/swift,devincoughlin/swift,sschiau/swift,ahoppen/swift,allevato/swift,uasys/swift,sschiau/swift,JaSpa/swift,practicalswift/swift,shahmishal/swift,khizkhiz/swift,bitjammer/swift,dreamsxin/swift,gregomni/swift,JaSpa/swift,hooman/swift,kusl/swift,natecook1000/swift,djwbrown/swift,shajrawi/swift,tinysun212/swift-windows,adrfer/swift,xedin/swift,KrishMunot/swift,arvedviehweger/swift,felix91gr/swift,lorentey/swift,austinzheng/swift,cbrentharris/swift,zisko/swift,huonw/swift,karwa/swift,rudkx/swift,cbrentharris/swift,amraboelela/swift,parkera/swift,sschiau/swift,return/swift,khizkhiz/swift,sdulal/swift,kstaring/swift,tkremenek/swift,airspeedswift/swift,mightydeveloper/swift,practicalswift/swift,xwu/swift,Ivacker/swift,gottesmm/swift,jopamer/swift,felix91gr/swift,cbrentharris/swift,Ivacker/swift,swiftix/swift.old,tjw/swift,jopamer/swift,swiftix/swift.old,nathawes/swift,tinysun212/swift-windows,jckarter/swift