fn lex_decimal() {
            let source = r"0.0 -0.0e0 -.0 .0e0 0e-1";
            let data = [
                ((0.0, 0), (0..3), "0.0"),
                ((-0.0, 0), (4..10), "-0.0e0"),
                ((-0.0, 0), (11..14), "-.0"),
                ((0.0, 0), (15..19), ".0e0"),
                ((0.0, -1), (20..24), "0e-1"),
            ];
            let lexer = Token::lexer(source);
            for ((_, (tok, span)), (parsed, tspan, tslice)) in lexer
                .spanned()
                .enumerate()
                // Skip all odd-indexed tokens (it's whitespace)
                .filter(|(idx, _)| idx % 2 == 0)
                .zip(data.into_iter())
            {
                let slice = &source[span.clone()];
                assert!(tok == Ok(Token::Decimal(parsed)));
                assert!(span == tspan);
                assert!(slice == tslice);
            }
        }
        #[test]