Body-local interface types are dropped, so a user push() on such a variable lowers to ArrayPush #11138

An interface declared inside a block or function body is dropped without being recorded as an interface type. A variable typed with that interface is then treated as a possible array. So a push method (and other names that collide with Array methods) on such a variable is lowered to Expr::ArrayPush instead of calling the user's method.

Module-level interfaces are recorded correctly and do not show this.

Shape:

function f(make: any) {
  interface Stack { push(x: number): void; size(): number }
  const s: Stack = make();
  s.push(1);
  console.log(s.size()); // Node: 1
}

Found while fixing #11128 (PR #11137). That PR makes dynamic new C() and InstanceType<...> receivers dispatch normally, but it does not cover this route. The fix is probably to register body-local interfaces the same way module-level ones are, so that the array gate in local_array_methods.rs / array_only_methods.rs sees a known non-array type.

Not yet reduced against a real package; confirm the exact output before fixing.