pub fn feature_err_issue<'a>(
    sess: &'a ParseSess,
    feature: Symbol,
    span: impl Into<MultiSpan>,
    issue: GateIssue,
    explain: impl Into<DiagnosticMessage>
) -> DiagnosticBuilder<'a, ErrorGuaranteed>
Expand description

Construct a diagnostic for a feature gate error.

This variant allows you to control whether it is a library or language feature. Almost always, you want to use this for a language feature. If so, prefer feature_err.