Function syntax::feature_gate::feature_err

pub fn feature_err<'a>(
    sess: &'a ParseSess, 
    feature: &str, 
    span: Span, 
    issue: GateIssue, 
    explain: &str
) -> DiagnosticBuilder<'a>

🔬 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?