Macro syntax::struct_span_warn

macro_rules! struct_span_warn {
    ($session:expr, $span:expr, $code:ident, $($message:tt)*) => { ... };
}

🔬 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?