commit	ff8e52f171ed65b04993829f1f6fb7be54079661	[log] [tgz]
author	David Tolnay <dtolnay@gmail.com>	Thu Aug 16 23:07:51 2018 -0700
committer	David Tolnay <dtolnay@gmail.com>	Thu Aug 16 23:07:51 2018 -0700
tree	f76d7b4db2429c8219d5853f731529d122f36ca1
parent	5463bb1a3a84339d2588a280c0d54577346e00b4 [diff]

tree: f76d7b4db2429c8219d5853f731529d122f36ca1

README.md

proc-macro2

A small shim over the proc_macro crate in the compiler intended to multiplex the current stable interface (as of 2017-07-05) and the upcoming richer interface.

The upcoming support has features like:

Span information on tokens
No need to go in/out through strings
Structured input/output

The hope is that libraries ported to proc_macro2 will be trivial to port to the real proc_macro crate once the support on nightly is stabilized.

Usage

This crate by default compiles on the stable version of the compiler. It only uses the stable surface area of the proc_macro crate upstream in the compiler itself. Usage is done via:

[dependencies]
proc-macro2 = "0.4"

followed by

extern crate proc_macro;
extern crate proc_macro2;

#[proc_macro_derive(MyDerive)]
pub fn my_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input: proc_macro2::TokenStream = input.into();

    let output: proc_macro2::TokenStream = {
        /* transform input */
    };

    output.into()
}

If you'd like you can enable the nightly feature in this crate. This will cause it to compile against the unstable and nightly-only features of the proc_macro crate. This in turn requires a nightly compiler. This should help preserve span information, however, coming in from the compiler itself.

You can enable this feature via:

[dependencies]
proc-macro2 = { version = "0.4", features = ["nightly"] }

Unstable Features

proc-macro2 supports exporting some methods from proc_macro which are currently highly unstable, and may not be stabilized in the first pass of proc_macro stabilizations. These features are not exported by default. Minor versions of proc-macro2 may make breaking changes to them at any time.

To enable these features, the procmacro2_semver_exempt config flag must be passed to rustc.

RUSTFLAGS='--cfg procmacro2_semver_exempt' cargo build

Note that this must not only be done for your crate, but for any crate that depends on your crate. This infectious nature is intentional, as it serves as a reminder that you are outside of the normal semver guarantees.

License

This project is licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Serde by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.