I started using Evan Wallace's TypeScript [0] implementation (and bundler) written in Go and it's pretty fast (there are benchmarks too). I'm surprised this kind of thing is not something Deno's pursuing. Having used esbuild I see the future of web tooling as not necessarily written in (or compiled to) JavaScript.
They are considering switching from tsc to a TypeScript compiler written in Rust[0][1], and `deno fmt` subcommand already uses it internally.
[0] https://github.com/denoland/deno/issues/5432 [1] https://github.com/swc-project/swc