Rename assertion functions to clarify that they're not "real" assertions which we can rely on for validating input, and are only for compile-time testing or debug assertions.
`typeAssertIs` is not a great name, but I couldn't come up with anything better. `debugAssertIs` would be not be accurate, as it'd imply that in debug builds in performs an actual assertion, which it doesn't.
In any case, we should replace `typeAssertIs` with specialized assertion functions which do actually perform runtime assertions in debug builds (e.g. `typeAssertIs<Fix>()` -> `debugAssertIsFix()`).
Pure refactor. Split up `plugins/utils.ts` into 3 files in `utils` directory.
Most importantly, assertion functions are by themselves in an `asserts.ts` file. This paves the way for the next PR (#15946).
Adapted from #15868. Enable `strictNullChecks` in TSConfig for `apps/oxlint`.
Rather than using `!` all over the place, I've added a function `assertIsNonNull`, which performs the same function. Idea is that we can later on produce a debug build where `assertIsNonNull` does an actual runtime assertion (rather than just a TS `asserts`) that the value is not `null` or `undefined`. We can use the debug build in tests, and catch any logic errors.
Unfortunately, TypeScript doesn't seem able to track side effects, so there seems to be no way to tell it "after calling `initAst()`, `ast` is always non-null". Don't want to switch to a having a `getAst` function which returns a non-null value, as that'd introduce unnecessary temp vars, and function calls, on hot paths. So this seems to be the best we can do without incurring runtime cost.
overlookmotel