Arrays the checker types with unknown elements are stored checked-dynamic,
and their methods dispatch on the runtime array. splice was missing from
that dispatch table, so unknown[] receivers refused it, including generic
bodies instantiated at unknown (pool.splice(i, 1) in a sample<T> helper
gets such an instantiation once a program has a dynamic tier). The
runtime's dynInvoke already implements splice; the table now names it,
and arrays of unknown elements take the dispatch from the array-method
lowering.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
