Constant syntax::feature_gate::EXPLAIN_PROC_MACROS_IN_EXTERN[][src]

pub const EXPLAIN_PROC_MACROS_IN_EXTERN: &'static str = "Macro and proc-macro invocations in `extern {}` blocks are experimental."
🔬 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?