Make syntex optional with nightly rustc

[jdub]

The start of a change, suggested by @emilio, that will allow users of nightly rustc to drop syntex. It doesn't currently build -- probably requires aster and quasi updates. That might get hairy, so consider this a work in progress and a proposal that can be quickly refused if it's totally off base.

This depends on #269 so currently includes those commits.

[jdub]

Here's a compare and contrast, using cargo-tree…

libbindgen with syntex:

libbindgen v0.17.0 (file:///tmp/rust-bindgen/libbindgen)
├── aster v0.33.1
│   └── syntex_syntax v0.48.0
│       ├── bitflags v0.7.0
│       ├── libc v0.2.17
│       ├── log v0.3.6
│       ├── rustc-serialize v0.3.21
│       ├── syntex_errors v0.48.0
│       │   ├── libc v0.2.17 (*)
│       │   ├── log v0.3.6 (*)
│       │   ├── rustc-serialize v0.3.21 (*)
│       │   ├── syntex_pos v0.48.0
│       │   │   └── rustc-serialize v0.3.21 (*)
│       │   ├── term v0.4.4
│       │   │   ├── kernel32-sys v0.2.2
│       │   │   │   └── winapi v0.2.8
│       │   │   └── winapi v0.2.8 (*)
│       │   └── unicode-xid v0.0.3
│       ├── syntex_pos v0.48.0 (*)
│       ├── term v0.4.4 (*)
│       └── unicode-xid v0.0.3 (*)
├── cexpr v0.2.0
│   └── nom v1.2.4
├── cfg-if v0.1.0
├── clang-sys v0.8.1
│   ├── bitflags v0.7.0 (*)
│   ├── glob v0.2.11
│   └── libc v0.2.17 (*)
├── env_logger v0.3.5
│   ├── log v0.3.6 (*)
│   └── regex v0.1.80
│       ├── aho-corasick v0.5.3
│       │   └── memchr v0.1.11
│       │       └── libc v0.2.17 (*)
│       ├── memchr v0.1.11 (*)
│       ├── regex-syntax v0.3.9
│       ├── thread_local v0.2.7
│       │   └── thread-id v2.0.0
│       │       ├── kernel32-sys v0.2.2 (*)
│       │       └── libc v0.2.17 (*)
│       └── utf8-ranges v0.1.3
├── lazy_static v0.1.16
├── libc v0.2.17 (*)
├── log v0.3.6 (*)
├── quasi v0.25.1
│   ├── syntex_errors v0.48.0 (*)
│   └── syntex_syntax v0.48.0 (*)
├── regex v0.1.80 (*)
├── rustc-serialize v0.3.21 (*)
└── syntex_syntax v0.48.0 (*)

libbindgen without syntex:

libbindgen v0.17.0 (file:///tmp/rust-bindgen/libbindgen)
├── aster v0.33.1
├── cexpr v0.2.0
│   └── nom v1.2.4
├── cfg-if v0.1.0
├── clang-sys v0.8.1
│   ├── bitflags v0.7.0
│   ├── glob v0.2.11
│   └── libc v0.2.17
├── lazy_static v0.1.16
├── libc v0.2.17 (*)
├── quasi v0.25.1
├── regex v0.1.80
│   ├── aho-corasick v0.5.3
│   │   └── memchr v0.1.11
│   │       └── libc v0.2.17 (*)
│   ├── memchr v0.1.11 (*)
│   ├── regex-syntax v0.3.9
│   ├── thread_local v0.2.7
│   │   └── thread-id v2.0.0
│   │       ├── kernel32-sys v0.2.2
│   │       │   └── winapi v0.2.8
│   │       └── libc v0.2.17 (*)
│   └── utf8-ranges v0.1.3
└── rustc-serialize v0.3.21

(Oops, that's slightly overstated, because --no-default-features also drops the logging feature. But hey, here's what you get with both turned off.)

[emilio]

From the travis logs it seems after updating quasi_codegen the macros we define are broken? gah, that's a nasty bug... we can probably work around it, but I'd prefer not.

[jdub]

Yeah, from helpers.rs:

    pub fn float_kind_rust_type(ctx: &BindgenContext,
                                fk: FloatKind)
                                -> P<ast::Ty> {
        macro_rules! raw {
            ($ty: ident) => {
                raw_type(ctx, stringify!($ty))
            }
        }
...
        match (fk, ctx.options().convert_floats) {
...

And from the generated codegen.rs:

        pub fn float_kind_rust_type(ctx: &BindgenContext, fk: FloatKind)
         -> P<ast::Ty> {
            match (fk, ctx.options().convert_floats) {
...

I'll contact upstream.

[jdub]

It's a known issue upstream: serde-rs/serde#608

[bors-servo]

☔ The latest upstream changes (presumably #269) made this pull request unmergeable. Please resolve the merge conflicts.

[nox]

I'm -1 on this, libsyntax is one of the most unstable crates in Rust private parts. Could we just switch to quote and friends?

[jdub]

Hmm, I'm not sure I'm clever enough to help with that… but then, I've enjoyed my little adventure through bindgen thus far, so I'll take a look.

[jdub]

Oh, maybe this isn't so hard. (Probably saying that too soon.)

[bors-servo]

☔ The latest upstream changes (presumably #275) made this pull request unmergeable. Please resolve the merge conflicts.

[bors-servo]

☔ The latest upstream changes (presumably #329) made this pull request unmergeable. Please resolve the merge conflicts.

[emilio]

I believe this can be closed for now. Not sure if it's still needed, we're going to transition from syntext to syn soon-ish, I guess :)

[dtolnay]

There is another parser that might be a better fit - https://github.com/shepmaster/strata-rust. It is pretty young at this point but looks super promising.