Why Pin is difficult to use

  • Pin<Ptr> is “just” a type defined in the standard library
  • This satisfied the needs of its original audience, the creators of async runtimes, without needing to extending the core language
  • That audience could accept some of its ergonomic downsides, as users of async would rarely interact with Pin directly

“You might wonder why Pin is so awkward to use. The answer is largely historical.”

“Pin<Ptr> offered a simpler implementation for the Rust project than alternatives”.

“Pin was designed primarily for the ~100 people in the world who write async runtimes. The Rust team chose a simpler (for the compiler) but less ergonomic design.”

“More user-friendly proposals existed but were rejected as too complex for the primary audience, who could handle the complexity.”