Fix inference when source and target both have rest parameters
Fix inference when source and target both have rest parameters

nojvek/TypeScript,weswigham/TypeScript,basarat/TypeScript,kitsonk/TypeScript,basarat/TypeScript,SaschaNaz/TypeScript,kitsonk/TypeScript,basarat/TypeScript,kpreisser/TypeScript,RyanCavanaugh/TypeScript,nojvek/TypeScript,nojvek/TypeScript,minestarks/TypeScript,nojvek/TypeScript,donaldpipowitch/TypeScript,donaldpipowitch/TypeScript,alexeagle/TypeScript,basarat/TypeScript,microsoft/TypeScript,minestarks/TypeScript,weswigham/TypeScript,SaschaNaz/TypeScript,kitsonk/TypeScript,microsoft/TypeScript,alexeagle/TypeScript,Microsoft/TypeScript,SaschaNaz/TypeScript,donaldpipowitch/TypeScript,weswigham/TypeScript,SaschaNaz/TypeScript,RyanCavanaugh/TypeScript,kpreisser/TypeScript,microsoft/TypeScript,kpreisser/TypeScript,minestarks/TypeScript,RyanCavanaugh/TypeScript,donaldpipowitch/TypeScript,Microsoft/TypeScript,alexeagle/TypeScript,Microsoft/TypeScript