[Typechecker] Return nullptr if base class is not present
[Typechecker] Return nullptr if base class is not present

CodaFi/swift,stephentyrone/swift,karwa/swift,roambotics/swift,lorentey/swift,nathawes/swift,CodaFi/swift,CodaFi/swift,karwa/swift,devincoughlin/swift,airspeedswift/swift,nathawes/swift,harlanhaskins/swift,harlanhaskins/swift,rudkx/swift,parkera/swift,gribozavr/swift,JGiola/swift,hooman/swift,hooman/swift,JGiola/swift,apple/swift,atrick/swift,lorentey/swift,shahmishal/swift,lorentey/swift,allevato/swift,shahmishal/swift,aschwaighofer/swift,tkremenek/swift,devincoughlin/swift,glessard/swift,CodaFi/swift,gribozavr/swift,hooman/swift,lorentey/swift,JGiola/swift,devincoughlin/swift,hooman/swift,xwu/swift,aschwaighofer/swift,aschwaighofer/swift,jckarter/swift,atrick/swift,rudkx/swift,nathawes/swift,stephentyrone/swift,glessard/swift,shahmishal/swift,apple/swift,lorentey/swift,gregomni/swift,stephentyrone/swift,parkera/swift,tkremenek/swift,CodaFi/swift,CodaFi/swift,harlanhaskins/swift,allevato/swift,ahoppen/swift,benlangmuir/swift,benlangmuir/swift,rudkx/swift,sschiau/swift,JGiola/swift,sschiau/swift,gregomni/swift,shahmishal/swift,roambotics/swift,apple/swift,harlanhaskins/swift,aschwaighofer/swift,atrick/swift,aschwaighofer/swift,shahmishal/swift,gribozavr/swift,sschiau/swift,xwu/swift,parkera/swift,karwa/swift,airspeedswift/swift,jmgc/swift,ahoppen/swift,jckarter/swift,jckarter/swift,devincoughlin/swift,ahoppen/swift,ahoppen/swift,jckarter/swift,allevato/swift,sschiau/swift,airspeedswift/swift,tkremenek/swift,tkremenek/swift,apple/swift,harlanhaskins/swift,benlangmuir/swift,allevato/swift,devincoughlin/swift,ahoppen/swift,atrick/swift,karwa/swift,ahoppen/swift,JGiola/swift,harlanhaskins/swift,gribozavr/swift,hooman/swift,allevato/swift,jmgc/swift,sschiau/swift,xwu/swift,jmgc/swift,aschwaighofer/swift,stephentyrone/swift,jmgc/swift,parkera/swift,lorentey/swift,tkremenek/swift,karwa/swift,glessard/swift,gregomni/swift,gribozavr/swift,glessard/swift,rudkx/swift,parkera/swift,devincoughlin/swift,nathawes/swift,devincoughlin/swift,parkera/swift,allevato/swift,tkremenek/swift,hooman/swift,allevato/swift,gregomni/swift,atrick/swift,benlangmuir/swift,sschiau/swift,gribozavr/swift,parkera/swift,jckarter/swift,lorentey/swift,xwu/swift,gribozavr/swift,shahmishal/swift,shahmishal/swift,gregomni/swift,apple/swift,rudkx/swift,jmgc/swift,harlanhaskins/swift,CodaFi/swift,jmgc/swift,jckarter/swift,roambotics/swift,glessard/swift,JGiola/swift,xwu/swift,atrick/swift,benlangmuir/swift,parkera/swift,devincoughlin/swift,jmgc/swift,jckarter/swift,nathawes/swift,karwa/swift,glessard/swift,gregomni/swift,xwu/swift,roambotics/swift,aschwaighofer/swift,airspeedswift/swift,benlangmuir/swift,roambotics/swift,karwa/swift,shahmishal/swift,stephentyrone/swift,sschiau/swift,lorentey/swift,rudkx/swift,tkremenek/swift,nathawes/swift,gribozavr/swift,sschiau/swift,hooman/swift,stephentyrone/swift,airspeedswift/swift,xwu/swift,nathawes/swift,airspeedswift/swift,karwa/swift,apple/swift,stephentyrone/swift,airspeedswift/swift,roambotics/swift