Continues the implicit-Context refactor. Bare-fn trampolines, lambda
trampolines, and protocol thunks now carry __sx_ctx at slot 0; call
sites for closures, fn-pointer variables, and method dispatch prepend
the caller's current ctx.
- emit_llvm.zig:1687 call_indirect treats `fp_ctx_slots` leading args
as opaque ptr (the implicit ctx) when the fn-pointer is default-conv
under has_implicit_ctx.
- lower.zig:fnPtrTypeWantsCtx predicate gates the prepend at both
scope-local and global fn-pointer call sites.
- lower.zig:fixupMethodReceiver skips __sx_ctx when probing the
receiver param's type.
- lower.zig:lowerLambda builds closure type from user-visible params
only (skip ctx + env).
- lower.zig:closure(bare_fn) builds closure type from user-visible
params only.
- module.zig: Module.has_implicit_ctx flag mirrors Lowering's switch
so emit_llvm can read it without a back-pointer.
Tests updated:
- 5 ObjC-block/runtime tests get `callconv(.c)` on fn-ptr types
cast from `objc_msgSend` / Block.invoke (C-side calls into sx).
- ffi-06-callback gets `callconv(.c)` on double_it/add_with_ctx —
the registered C-side callbacks.
- 08-types snapshot regen (undefined-init drift from layout shift).
- 11 JNI/ObjC .ir snapshots regen for the ctx-prepended thunk
signatures.
151/152 example tests pass. Remaining failure (05-run) is the
comptime/interp path that requires Step 7 (callWithDefaultContext).
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