Microsoft/TypeScript — pull request #932 by DanielRosenwasser (2014-10-21 21:51:09+00:00)
Title: Removed Diagnostics from sys.ts in order to avoid cyclical build dependency

Specifically, processDiagnosticMessages.ts was dependent on sys.ts, which was dependent on the rest of the compiler, which meant that after merge, you could never compile processDiagnosticMessages.ts.