Consider replacing rollup/plugin-sucrase with rollup-plugin-typescript2

One of the most impactful changes that we made in the Sapper codebase recently was replacing rollup/plugin-sucrase with rollup-plugin-typescript2. It uncovered lots of type checking errors and made the codebase far more robust because sucrase doesn’t do any type checking. There was some concern about speed but rollup-plugin-typescript2 allows you to pass a flag that disables type checking, so we did that by default, which was just as fast (or faster? I can’t remember), but then added a command in package.json that does type checking which we’re able to run on the GitHub Actions CI

[dummdidumm]

+1 on adding type checking early, or at least adding it soon, at some point it may become hard to sort out all the type errors that sneaked in.

[benmccann]

typescript-eslint is mainly around checking style rules. It has a bit different set of functionality than the TypeScript compiler. They’re both helpful, but check different things