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## warn_on_format_spec

# Function warn_on_format_spec

Source

    fn warn_on_format_spec(
        spec: &FormatSpec<'_>,
        warnings: &mut Vec<FormatWarning>,
        input_span: Span,
        is_source_literal: bool,
    )

Expand description

`#[rustc_on_unimplemented]` and `#[diagnostic::...]` don’t actually do anything with specifiers, so emit a warning if they are used.