Macro write 

macro_rules! write {
    ($self:expr, $($arg:tt)*) => { ... };
}

Drop-in replacement for core::write! that block-wraps the call so the format_args! temporary is dropped before any .await, keeping the resulting future Send. Sync callers see no behavior difference.

Workaround for a recurring footgun: core::write!($self, "...", x).await holds a fmt::Arguments<'_> temporary (containing !Send vtable pointers) across the await point, poisoning the dispatcher’s Send bound. The block scope ends the temporary’s lifetime before the future is awaited.

Escape hatch: core_write! is the unmodified macro.