[Sema] Fix SR-1681: spurious "unused result" warning in Swift 3
[Sema] Fix SR-1681: spurious "unused result" warning in Swift 3

An OptionalEvaluationExpr can have a CallExpr directly as its SubExpr,
if the CallExpr already has optional type.

extends ea52d4fbc7093582eef84c57b3906e9d7e274fe8

shahmishal/swift,gottesmm/swift,jtbandes/swift,gribozavr/swift,JGiola/swift,jmgc/swift,apple/swift,IngmarStein/swift,calebd/swift,xedin/swift,therealbnut/swift,zisko/swift,shahmishal/swift,deyton/swift,amraboelela/swift,allevato/swift,ben-ng/swift,parkera/swift,xedin/swift,tardieu/swift,return/swift,JGiola/swift,OscarSwanros/swift,karwa/swift,felix91gr/swift,gribozavr/swift,austinzheng/swift,ahoppen/swift,devincoughlin/swift,hughbe/swift,natecook1000/swift,harlanhaskins/swift,austinzheng/swift,deyton/swift,gribozavr/swift,tjw/swift,zisko/swift,modocache/swift,xedin/swift,sschiau/swift,parkera/swift,devincoughlin/swift,tardieu/swift,nathawes/swift,milseman/swift,ahoppen/swift,aschwaighofer/swift,uasys/swift,arvedviehweger/swift,aschwaighofer/swift,bitjammer/swift,airspeedswift/swift,gottesmm/swift,airspeedswift/swift,amraboelela/swift,brentdax/swift,return/swift,benlangmuir/swift,rudkx/swift,parkera/swift,milseman/swift,gribozavr/swift,shajrawi/swift,gottesmm/swift,JaSpa/swift,rudkx/swift,natecook1000/swift,airspeedswift/swift,sschiau/swift,jopamer/swift,OscarSwanros/swift,xedin/swift,JGiola/swift,djwbrown/swift,allevato/swift,stephentyrone/swift,austinzheng/swift,tardieu/swift,tardieu/swift,jtbandes/swift,Jnosh/swift,jmgc/swift,roambotics/swift,codestergit/swift,roambotics/swift,IngmarStein/swift,lorentey/swift,frootloops/swift,kstaring/swift,kperryua/swift,tkremenek/swift,JaSpa/swift,modocache/swift,kperryua/swift,alblue/swift,kstaring/swift,Jnosh/swift,CodaFi/swift,lorentey/swift,airspeedswift/swift,huonw/swift,apple/swift,tinysun212/swift-windows,hughbe/swift,jckarter/swift,codestergit/swift,shahmishal/swift,xedin/swift,natecook1000/swift,zisko/swift,IngmarStein/swift,milseman/swift,lorentey/swift,codestergit/swift,hooman/swift,uasys/swift,tinysun212/swift-windows,tkremenek/swift,tinysun212/swift-windows,modocache/swift,ahoppen/swift,natecook1000/swift,lorentey/swift,devincoughlin/swift,therealbnut/swift,airspeedswift/swift,benlangmuir/swift,jopamer/swift,aschwaighofer/swift,brentdax/swift,gottesmm/swift,sschiau/swift,zisko/swift,therealbnut/swift,benlangmuir/swift,shajrawi/swift,tinysun212/swift-windows,jopamer/swift,alblue/swift,xwu/swift,bitjammer/swift,milseman/swift,parkera/swift,hooman/swift,amraboelela/swift,glessard/swift,tjw/swift,airspeedswift/swift,danielmartin/swift,gribozavr/swift,huonw/swift,xedin/swift,JaSpa/swift,karwa/swift,djwbrown/swift,jtbandes/swift,OscarSwanros/swift,ben-ng/swift,kstaring/swift,jmgc/swift,tjw/swift,uasys/swift,manavgabhawala/swift,gribozavr/swift,roambotics/swift,tkremenek/swift,swiftix/swift,frootloops/swift,deyton/swift,arvedviehweger/swift,OscarSwanros/swift,gregomni/swift,return/swift,JGiola/swift,calebd/swift,apple/swift,aschwaighofer/swift,austinzheng/swift,swiftix/swift,uasys/swift,parkera/swift,kperryua/swift,swiftix/swift,frootloops/swift,shahmishal/swift,gregomni/swift,tinysun212/swift-windows,tkremenek/swift,ahoppen/swift,jtbandes/swift,Jnosh/swift,calebd/swift,danielmartin/swift,stephentyrone/swift,CodaFi/swift,gmilos/swift,aschwaighofer/swift,sschiau/swift,ben-ng/swift,natecook1000/swift,djwbrown/swift,brentdax/swift,parkera/swift,huonw/swift,kstaring/swift,IngmarStein/swift,therealbnut/swift,alblue/swift,danielmartin/swift,karwa/swift,alblue/swift,gregomni/swift,arvedviehweger/swift,karwa/swift,tjw/swift,CodaFi/swift,bitjammer/swift,jckarter/swift,tkremenek/swift,hooman/swift,kstaring/swift,djwbrown/swift,roambotics/swift,arvedviehweger/swift,jopamer/swift,benlangmuir/swift,glessard/swift,devincoughlin/swift,zisko/swift,return/swift,gottesmm/swift,milseman/swift,arvedviehweger/swift,devincoughlin/swift,jckarter/swift,huonw/swift,kperryua/swift,apple/swift,parkera/swift,devincoughlin/swift,tjw/swift,danielmartin/swift,devincoughlin/swift,allevato/swift,ben-ng/swift,bitjammer/swift,brentdax/swift,allevato/swift,austinzheng/swift,alblue/swift,Jnosh/swift,jmgc/swift,shajrawi/swift,calebd/swift,benlangmuir/swift,amraboelela/swift,ben-ng/swift,glessard/swift,hooman/swift,sschiau/swift,modocache/swift,shajrawi/swift,gribozavr/swift,hughbe/swift,roambotics/swift,OscarSwanros/swift,bitjammer/swift,jmgc/swift,jopamer/swift,airspeedswift/swift,gribozavr/swift,frootloops/swift,tkremenek/swift,practicalswift/swift,nathawes/swift,karwa/swift,therealbnut/swift,stephentyrone/swift,manavgabhawala/swift,manavgabhawala/swift,xwu/swift,CodaFi/swift,aschwaighofer/swift,kstaring/swift,deyton/swift,danielmartin/swift,gmilos/swift,roambotics/swift,harlanhaskins/swift,allevato/swift,sschiau/swift,codestergit/swift,jckarter/swift,tjw/swift,amraboelela/swift,sschiau/swift,practicalswift/swift,gottesmm/swift,huonw/swift,felix91gr/swift,rudkx/swift,gregomni/swift,OscarSwanros/swift,ben-ng/swift,return/swift,shahmishal/swift,manavgabhawala/swift,lorentey/swift,tinysun212/swift-windows,practicalswift/swift,stephentyrone/swift,atrick/swift,hughbe/swift,tjw/swift,swiftix/swift,apple/swift,calebd/swift,austinzheng/swift,xedin/swift,harlanhaskins/swift,swiftix/swift,harlanhaskins/swift,allevato/swift,gregomni/swift,brentdax/swift,tardieu/swift,alblue/swift,Jnosh/swift,jopamer/swift,amraboelela/swift,ahoppen/swift,uasys/swift,hooman/swift,hooman/swift,atrick/swift,deyton/swift,atrick/swift,alblue/swift,shajrawi/swift,huonw/swift,bitjammer/swift,CodaFi/swift,gregomni/swift,return/swift,harlanhaskins/swift,felix91gr/swift,huonw/swift,JaSpa/swift,felix91gr/swift,hughbe/swift,harlanhaskins/swift,ahoppen/swift,lorentey/swift,karwa/swift,uasys/swift,austinzheng/swift,brentdax/swift,milseman/swift,glessard/swift,kperryua/swift,manavgabhawala/swift,deyton/swift,jckarter/swift,uasys/swift,Jnosh/swift,danielmartin/swift,CodaFi/swift,hughbe/swift,allevato/swift,lorentey/swift,gottesmm/swift,benlangmuir/swift,deyton/swift,xwu/swift,gmilos/swift,shajrawi/swift,tinysun212/swift-windows,stephentyrone/swift,glessard/swift,natecook1000/swift,harlanhaskins/swift,JaSpa/swift,therealbnut/swift,djwbrown/swift,djwbrown/swift,felix91gr/swift,tardieu/swift,glessard/swift,xwu/swift,therealbnut/swift,shahmishal/swift,xwu/swift,atrick/swift,arvedviehweger/swift,codestergit/swift,karwa/swift,danielmartin/swift,jopamer/swift,karwa/swift,aschwaighofer/swift,gmilos/swift,parkera/swift,atrick/swift,jtbandes/swift,jtbandes/swift,lorentey/swift,xedin/swift,gmilos/swift,nathawes/swift,IngmarStein/swift,brentdax/swift,jtbandes/swift,nathawes/swift,jckarter/swift,shahmishal/swift,IngmarStein/swift,tkremenek/swift,calebd/swift,zisko/swift,practicalswift/swift,practicalswift/swift,shajrawi/swift,shahmishal/swift,OscarSwanros/swift,zisko/swift,frootloops/swift,frootloops/swift,calebd/swift,rudkx/swift,Jnosh/swift,gmilos/swift,rudkx/swift,xwu/swift,return/swift,xwu/swift,hooman/swift,modocache/swift,milseman/swift,bitjammer/swift,kstaring/swift,practicalswift/swift,stephentyrone/swift,swiftix/swift,amraboelela/swift,JGiola/swift,gmilos/swift,nathawes/swift,kperryua/swift,felix91gr/swift,JaSpa/swift,arvedviehweger/swift,hughbe/swift,apple/swift,codestergit/swift,modocache/swift,rudkx/swift,frootloops/swift,jckarter/swift,codestergit/swift,ben-ng/swift,manavgabhawala/swift,sschiau/swift,djwbrown/swift,JGiola/swift,swiftix/swift,practicalswift/swift,jmgc/swift,kperryua/swift,nathawes/swift,IngmarStein/swift,natecook1000/swift,modocache/swift,manavgabhawala/swift,jmgc/swift,tardieu/swift,nathawes/swift,CodaFi/swift,shajrawi/swift,devincoughlin/swift,practicalswift/swift,stephentyrone/swift,JaSpa/swift,atrick/swift,felix91gr/swift