Yesterday, there was news that Facebook was porting Yarn from Flow to TypeScript for ease of new contributors. That ease is a shared goal of one of my projects, and yesterday I tried porting it as well.

I discovered that in contrast to Flow, TypeScript has horrible errors. Often I ran into errors that would not give much more information than "error" -- no line information, no file information, nothing. One of the causes of such opaque errors was empty Flow-style typecasts, so they were pervasive throughout a large project.

In contrast, Flow has beautiful error messages.