things I've changed from the PR:
- dropped legacy (i.e. non-flake) compat stuff, which turns out to account for most of the diff
- dropped `packages.garnet` since it doesn't work with `nix build .#garnet`
- back to using Rust-extended packages everywhere, which _seems_ fine
the rest is just re-inlining things and other refactors
note that changes we keep are essentially:
- not using Crane's extended packages everywhere
- bumping `nix-haskell` to avoid shell hook workaround
- various changes in how we call `nix-haskell`
- using `libCgarnet_rs` name, which Cabal expects
- adding proper non-dev-shell targets, so that e.g. `nix run` works
stuff we should still take a look at:
- seems a bit weird that `garnet-rs` arg to `project.nix` was always same (and therefore now we always pass the ) - might be a mistake, and we're supposed to be using local for local build?
- similar `libCgarnet_rs.a` logic appears in three places - see if we can deduplicate to some extent somehow
- I haven't even checked all steps are necessary
This reverts commit 1f1c0d959da699ce04f7951ecbcdb7976c8c0750.
This doesn't work well with multi-component builds. For example, it requires `"haskell.sessionLoading": "singleComponent"` in VSCode, which makes HLS work less reliably.
The script addition is a bit hacky, but there's no obvious straightforward arch/version-independent way to get most of the build path. And eventually, once issues with HLS etc. are sorted out we will revert to using Cabal hooks anyway.
Even though `Int` and `isize` should be the same in practice, we can't cleanly convert, as the type information isn't quite there. And anyway, strictly speaking per the report, `Int` is only guaranteed to hold 30 bits.
Note that this is essentially unchanged even if we specify `usize_is_size_t = true` for `cbindgen`.
We drop the tools specifically designed for Haskell and Rust together, in favour of general tools for using each with C.
Namely, we use Mozilla's `cbindgen` for generating header files from the Rust source, and Well-Typed's new `hs-bindgen` tool for generating Haskell from those header files.
The Rust code here is essentially the result of expanding the old macro, then inlining and renaming internals.
The most important thing here is that we're now relying solely on robust well-maintained tools.
See https://sraka.xyz/posts/hs-bindgen-introduction.html.
For now, this is a shell-based workflow, rather than using Nix to build everything, i.e. `nix develop` works but `nix build` doesn't. And `cargo build` has to be called manually to create the C library, rather than `cabal` being clever enough to invoke it itself.
We ran `cargo cabal init` from the `rust` directory (`nix shell github:yvan-sraka/cargo-cabal`), which generated `hsbindgen.toml` (which we use), and `Setup.lhs` (which just added `extra-lib-dirs`, and with the wrong paths, so we dspecify those statically instead in `garnet.cabal`). We also follow its advice to use `staticlib`.
Also, after we ran the first `cargo build` (requiring a `mkdir rust/src` before it would run), we took the generated the Haskell file, and moved the main contents in to `Main.hs` manually.
