Add check that vector element type can be imported ... (#23885)
Add check that vector element type can be imported ... (#23885)

... before attempting to import the vector type.
(<rdar://problem/49677353>)
karwa/swift,jmgc/swift,stephentyrone/swift,tkremenek/swift,shahmishal/swift,nathawes/swift,apple/swift,shajrawi/swift,jmgc/swift,glessard/swift,benlangmuir/swift,gregomni/swift,nathawes/swift,lorentey/swift,xwu/swift,gribozavr/swift,karwa/swift,stephentyrone/swift,shahmishal/swift,aschwaighofer/swift,xedin/swift,jckarter/swift,allevato/swift,jmgc/swift,xwu/swift,stephentyrone/swift,parkera/swift,tkremenek/swift,lorentey/swift,CodaFi/swift,harlanhaskins/swift,nathawes/swift,xedin/swift,karwa/swift,benlangmuir/swift,benlangmuir/swift,xwu/swift,glessard/swift,sschiau/swift,atrick/swift,tkremenek/swift,gribozavr/swift,rudkx/swift,roambotics/swift,lorentey/swift,harlanhaskins/swift,jmgc/swift,jmgc/swift,hooman/swift,roambotics/swift,aschwaighofer/swift,gregomni/swift,devincoughlin/swift,CodaFi/swift,karwa/swift,jckarter/swift,devincoughlin/swift,gribozavr/swift,shahmishal/swift,xedin/swift,devincoughlin/swift,airspeedswift/swift,apple/swift,shajrawi/swift,jckarter/swift,allevato/swift,parkera/swift,devincoughlin/swift,sschiau/swift,roambotics/swift,xedin/swift,sschiau/swift,roambotics/swift,apple/swift,xwu/swift,parkera/swift,shajrawi/swift,gribozavr/swift,atrick/swift,airspeedswift/swift,tkremenek/swift,jckarter/swift,airspeedswift/swift,roambotics/swift,ahoppen/swift,xedin/swift,jmgc/swift,shajrawi/swift,rudkx/swift,sschiau/swift,xwu/swift,JGiola/swift,xwu/swift,airspeedswift/swift,gribozavr/swift,karwa/swift,airspeedswift/swift,gregomni/swift,CodaFi/swift,shahmishal/swift,apple/swift,tkremenek/swift,glessard/swift,parkera/swift,shahmishal/swift,hooman/swift,JGiola/swift,parkera/swift,apple/swift,stephentyrone/swift,lorentey/swift,allevato/swift,aschwaighofer/swift,atrick/swift,hooman/swift,hooman/swift,ahoppen/swift,devincoughlin/swift,ahoppen/swift,shajrawi/swift,ahoppen/swift,shahmishal/swift,xedin/swift,nathawes/swift,lorentey/swift,apple/swift,gribozavr/swift,shahmishal/swift,jckarter/swift,ahoppen/swift,JGiola/swift,rudkx/swift,tkremenek/swift,karwa/swift,gregomni/swift,sschiau/swift,allevato/swift,devincoughlin/swift,airspeedswift/swift,glessard/swift,benlangmuir/swift,jckarter/swift,aschwaighofer/swift,xwu/swift,gregomni/swift,parkera/swift,xedin/swift,allevato/swift,nathawes/swift,stephentyrone/swift,lorentey/swift,gregomni/swift,ahoppen/swift,hooman/swift,JGiola/swift,parkera/swift,karwa/swift,JGiola/swift,gribozavr/swift,sschiau/swift,sschiau/swift,harlanhaskins/swift,atrick/swift,allevato/swift,shajrawi/swift,harlanhaskins/swift,rudkx/swift,hooman/swift,lorentey/swift,harlanhaskins/swift,atrick/swift,rudkx/swift,jckarter/swift,CodaFi/swift,CodaFi/swift,CodaFi/swift,gribozavr/swift,atrick/swift,sschiau/swift,shajrawi/swift,nathawes/swift,benlangmuir/swift,stephentyrone/swift,hooman/swift,nathawes/swift,aschwaighofer/swift,glessard/swift,jmgc/swift,karwa/swift,harlanhaskins/swift,glessard/swift,xedin/swift,aschwaighofer/swift,CodaFi/swift,rudkx/swift,stephentyrone/swift,aschwaighofer/swift,devincoughlin/swift,shahmishal/swift,parkera/swift,tkremenek/swift,lorentey/swift,roambotics/swift,benlangmuir/swift,allevato/swift,JGiola/swift,airspeedswift/swift,shajrawi/swift,harlanhaskins/swift,devincoughlin/swift