Yeah but in Rust and Haskell it's isolated to clearly marked code (except for some minor bugs in Rust that will be fixed - see https://github.com/rust-lang/rust

Yeah but in Rust and Haskell it's isolated to clearly marked code (except for some minor bugs in Rust that will be fixed - see https://github.com/rust-lang/rust/issues?utf8=%E2%9C%93&q=is%3Aissue+label%3AI-unsound+is%3Aopen https://github.com/rust-lang/rust/issues?utf8=%E2%9C%93&q=is... ). Instead TypeScript has a bunch of serious unfixed design flaws that make the problem pervasive, plus they refuse to fix them (see https://github.com/Microsoft/TypeScript/issues/9825 https://github.com/Microsoft/TypeScript/issues/9825 ).