[Lexer] Micro optimization for getTokenAt()
[Lexer] Micro optimization for getTokenAt()

lex() invokes lexImpl(). It doesn't need to lex next token.

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