Per CLAUDE.md IMPASSIBLE RULES. Attempted Phase 3.2 C4 migration of
the UIKit chrome cluster in `library/modules/platform/uikit.sx`
(UIScreen / UIWindow / UIViewController / UITextField / UIView)
surfaced a real compiler bug: when a function body contains
`recv.method(...)` calls against an `#objc_class` receiver AND that
body is reached via `lazyLowerFunction` invoked from another
`inline if OS == ...` branch, the method dispatch fails with
"unresolved 'methodName'".
Specifically: `uikit_scene_will_connect_ios` (the iOS-sim crashing
case) contains `UIWindow.alloc().initWithWindowScene(scene)` etc.
The same calls compile cleanly in isolated probes — only the lazy-
lower-via-inline-if entry chain reproduces the bug. macOS target
builds fine throughout; ios-sim trips it.
C1/C2/C3 (commits 1ea9cda / 17775b2 / 2a7c8e0) happen to land cleanly
because the methods they migrate are reached eagerly (or are niladic
so the dispatch path doesn't hit the failing branch). C4 + C5 stay
blocked pending issue-0043's fix in a separate session.
Issue filed at `issues/0043-lazy-lower-loses-foreign-class-method-dispatch.md`
with the reproduction, stack trace, and investigation prompt
pointing at `lower.zig:1057` (`lazyLowerFunction`) and
`lower.zig:5290` (the field-access foreign-class dispatch chain).
FFI checkpoint updated to mark C4+C5 as BLOCKED on 0043.
The in-progress C4 working-tree changes were reverted; tree is at
the C3 commit `2a7c8e0` and chess on macOS/iOS-sim/Android builds
cleanly.
15f10c5031