When adding constraints for a ForEach expression, search for generator/element witnesses before creating fresh type variables to represent them.
When adding constraints for a ForEach expression, search for generator/element witnesses before creating fresh type variables to represent them.

Swift SVN r24517

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