Function syntax::feature_gate::check::feature_err

pub fn feature_err<'a>(
    sess: &'a ParseSess, 
    feature: Symbol, 
    span: impl Into<MultiSpan>, 
    explain: &str
) -> DiagnosticBuilder<'a>

⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.