[native/gba] E0425: a boxed closure cannot WRITE an outer module 'export let' — the cell is not captured for assignments

[spacedevin]

Summary

A boxed closure that WRITES a module-level export let fails to compile on the GBA target: the generated closure body emits *name.borrow_mut() = ... without the cell in scope → E0425.

error[E0425]: cannot find value `deadCol` in this scope
  --> src/main.rs:13691:437
   | ...  *deadCol.borrow_mut() = _v.clone(); _v };

Repro (minimal shape)

export let deadCol: i32 = -1

function makeCast() {
  function noteDeath(c: i32) { deadCol = c }   // write to outer exported let
  return { noteDeath: noteDeath }
}
let mk = [makeCast]
const M = mk[0]()
export function noteDeath(c: i32) { return M.noteDeath(c) }

Reads of the outer exported let capture fine; the WRITE path doesn't capture the VmRef cell into the closure. This blocks the factory-wrapping pattern that is currently the only game-side mitigation for the run()-frame stack ceiling (see the companion frame-size issue) on any module whose functions mutate their exported state — which is most of them.

Ask

Capture the module cell (<name>_cell) into boxed closures for assignments the same way reads are captured.