Flow understands this code perfectly well too. https://tryflow.org/?code=Y2xhc3MgRm9vIHsKICBmb28gPSAoKSA9PiBjb25zb2xlLmxvZygnRm9vIScpCn0KCmxldCBmID0gbmV3IEZvby

Flow understands this code perfectly well too. https://tryflow.org/?code=Y2xhc3MgRm9vIHsKICBmb28gPSAoKSA9PiBjb25zb2xlLmxvZygnRm9vIScpCn0KCmxldCBmID0gbmV3IEZvbygpCgpmLmZvbygp https://tryflow.org/?code=Y2xhc3MgRm9vIHsKICBmb28gPSAoKSA9Pi... You get no errors. Additionally, TypeScript's stated design goal is to not deviate from current or future EcmaScript [1] You want more control over exactly what gets transpiled i.e. "I don't want to use ES.next, only ES6". Thats a valid point, but really far from your original assessment that there is a fundamental difference between the languages. [1]: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals https://github.com/Microsoft/TypeScript/wiki/TypeScript-Desi... - goal 6