Macros 1.1

[dtolnay]

RFC: 1681-macros-1.1.md
Implementation: rust-lang/rust#35957

[dtolnay]

Some limitations:

• #[derive(Deserialize)] always panics. I have not debugged this yet.
• #[derive(Serialize)] for ordinary structs always panics. Newtype structs, unit structs, and enums not containing ordinary struct variants all seem to work.

Both panics are this:

thread 'rustc' panicked at 'fold_mac disabled by default', src/libsyntax/fold.rs:171

EDIT: it is a rustc bug.

[dtolnay]

Sorry for the confusing diff - this is just splitting expand into expand and expand_str with common code in syntex_registry.

[erickt]

Looks good to me!

[dtolnay]

I added a test suite but we need to fix rust-lang/rust#36211 before it will pass.

[tikue]

Trying to use this, I get

error: the `#[rustc_macro_derive]` attribute is only usable with crates of the `rustc-macro` crate type

[dtolnay]

@tikue you need a version of Cargo that supports rustc-macro crates. My Cargo PR merged a few hours ago so it will be in the next nightly. If you need it now you can build cargo yourself from the master branch. It should be as simple as cloning and running cargo install.

[tikue]

@dtolnay cool, thanks!