Microsoft/TypeScript — pull request #1465 by CyrusNajmabadi (2014-12-12 19:39:36+00:00)
Title: Avoid lookahead when parsing a statement.

If a statement started with an identifier, then we'd normally lookahead to see if the next token
was a colon. Lookahead is expensive (as it has to rescan tokens). Instead, we do the same thing
we do for arrow-functions. We just parse out the identifier, and afterwards we check if there is
a colon as the current token. Now, no lookahead is required.