Check callback return values bi-variantly
Check callback return values bi-variantly

minestarks/TypeScript,weswigham/TypeScript,Eyas/TypeScript,Eyas/TypeScript,nojvek/TypeScript,nojvek/TypeScript,microsoft/TypeScript,weswigham/TypeScript,basarat/TypeScript,donaldpipowitch/TypeScript,alexeagle/TypeScript,Microsoft/TypeScript,kitsonk/TypeScript,mihailik/TypeScript,basarat/TypeScript,synaptek/TypeScript,TukekeSoft/TypeScript,SaschaNaz/TypeScript,TukekeSoft/TypeScript,chuckjaz/TypeScript,synaptek/TypeScript,synaptek/TypeScript,RyanCavanaugh/TypeScript,synaptek/TypeScript,weswigham/TypeScript,kpreisser/TypeScript,minestarks/TypeScript,alexeagle/TypeScript,nojvek/TypeScript,nojvek/TypeScript,minestarks/TypeScript,mihailik/TypeScript,mihailik/TypeScript,donaldpipowitch/TypeScript,kpreisser/TypeScript,microsoft/TypeScript,SaschaNaz/TypeScript,chuckjaz/TypeScript,Eyas/TypeScript,donaldpipowitch/TypeScript,SaschaNaz/TypeScript,chuckjaz/TypeScript,SaschaNaz/TypeScript,Microsoft/TypeScript,Eyas/TypeScript,basarat/TypeScript,chuckjaz/TypeScript,RyanCavanaugh/TypeScript,RyanCavanaugh/TypeScript,TukekeSoft/TypeScript,microsoft/TypeScript,Microsoft/TypeScript,kitsonk/TypeScript,alexeagle/TypeScript,kitsonk/TypeScript,basarat/TypeScript,mihailik/TypeScript,donaldpipowitch/TypeScript,kpreisser/TypeScript