Design Notes#

Architecture decisions and rationale for future_form.

Topics#

Document	Summary
Send/!Send Fragmentation	The core problem and the design space of solutions
Boxing Costs	Performance implications of `BoxFuture` / `LocalBoxFuture`
Macro Architecture	How `#[future_form]` parses, rewrites, and generates code
Host-Driven FFI	Sans-IO polling pattern for foreign language consumers
Sans-IO Comparison	`PollOnce` vs pure sans-IO state machines: trade-offs and when to use each
Extensibility	Implementing custom `FutureForm` types
TAIT Migration	Future direction when `impl_trait_in_assoc_type` stabilizes