identifierCount may not be correct

TypeScript Version: 3.2.0-dev.20181114

In parser.ts, there is an identifierCount variable that is incremented every time createIdentifier is called.
Unfortunately, not all createIdentifier calls will result in an identifier in the AST, since some may have happened during speculative parsing. It may be necessary to reset identifierCount after speculative parsing fails.

[ahejlsberg]

Just for context, the identifierCount is computed solely for diagnostic reporting purposes. But, you're right, it ought to be saved and restored during speculative parsing.