Function rustc_builtin_macros::format::parse_args

fn parse_args<'a>(
    ecx: &mut ExtCtxt<'a>, 
    sp: Span, 
    tts: TokenStream
) -> Result<(P<Expr>, Vec<P<Expr>>, FxHashMap<Symbol, usize>), DiagnosticBuilder<'a>>

Parses the arguments from the given list of tokens, returning the diagnostic if there’s a parse error so we can continue parsing other format! expressions.

If parsing succeeds, the return value is:

Some((fmtstr, parsed arguments, index map for named arguments))