Function syntax::feature_gate::emit_feature_err

pub fn emit_feature_err(
    sess: &ParseSess, 
    feature: &str, 
    span: Span, 
    issue: GateIssue, 
    explain: &str
)

🔬 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?