format_args!("{a} {}", 1)

0-before.rs

// format_args!("{a} {}", 1);
::core::fmt::Arguments::new_v1_formatted(
        &["", " "],
        &[
            ::core::fmt::ArgumentV1::new_display(&1),
            ::core::fmt::ArgumentV1::new_display(&a),
        ],
        &[
            ::core::fmt::rt::v1::Argument {
                position: 1usize,
                format: ::core::fmt::rt::v1::FormatSpec {
                    fill: ' ',
                    align: ::core::fmt::rt::v1::Alignment::Unknown,
                    flags: 0u32,
                    precision: ::core::fmt::rt::v1::Count::Implied,
                    width: ::core::fmt::rt::v1::Count::Implied,
                },
            },
            ::core::fmt::rt::v1::Argument {
                position: 0usize,
                format: ::core::fmt::rt::v1::FormatSpec {
                    fill: ' ',
                    align: ::core::fmt::rt::v1::Alignment::Unknown,
                    flags: 0u32,
                    precision: ::core::fmt::rt::v1::Count::Implied,
                    width: ::core::fmt::rt::v1::Count::Implied,
                },
            },
        ],
        unsafe { ::core::fmt::UnsafeArg::new() },
    );

1-after.rs

// format_args!("{a} {}", 1);
::core::fmt::Arguments::new_v1(
        &["", " "],
        &match (&1, &a) {
            args => [
                ::core::fmt::ArgumentV1::new_display(args.1),
                ::core::fmt::ArgumentV1::new_display(args.0),
            ],
        },
    );