Type Definition syntax::ext::base::MacroExpanderFn

type MacroExpanderFn = fn<'cx>(_: &'cx mut ExtCtxt, _: Span, _: &[TokenTree]) -> Box<MacResult + 'cx>;

🔬 This is a nightly-only experimental API. (rustc_private)

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?