Comment by andrewl-hn

> "a static type check is just a stand-in for a unit test."

This is not an original argument. Rich Hickey made a similar argument in his "Simple made easy" talk in 2011, though his focus was on a fact that every bug that easiest in a software system has passed unnoticed through both a type checker and a test suit. And even before that similar ideas of test suits being a suitable replacement for a type checker have percolated through Python and Ruby communities, too.

I distinctly remember that the "tests makes static type checks unnecessary" was in fact so prevalent in JavaScript community that TypeScript had really hard time getting adoption in its first 3-4 years, and only the introduction of VSCode in 2015 and subsequent growth of its marketshare over Atom and SublimeText got more people exposed to TypeScript and the benefits of a type checker. Overall it took almost 10 years for Typescript to become the "default" language for web projects.