Prune a non-solution when one of its peers led to a solution.
Prune a non-solution when one of its peers led to a solution.

This cuts peak memory use while type-checking swift.swift by about
200MB (down to ~650MB).


Swift SVN r3119

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