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Enable assigning a child interface variable to a parent interface variable (e.g. refIA := refIB where IB EXTENDS IA) by embedding flattened __upcast_<ancestor> pointer fields in each itable struct. Table generation (table/interface.rs): - Each itable struct now includes a POINTER TO __VOID field per proper ancestor interface, sorted alphabetically and placed before the function pointer fields - Each itable instance initializes these fields to point directly to the corresponding ancestor itable instance for the same POU, giving O(1) upcast resolution regardless of hierarchy depth Dispatch lowering (dispatch/interface.rs): - Interface-to-interface assignments copy .data directly and read the target itable pointer through the __upcast_* field on the RHS itable - Call arguments where a child interface is passed for a parent interface parameter allocate a temp fat pointer with the upcasted table - Same-interface assignments and arguments remain unchanged (memcpy)
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ghaith
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Mar 18, 2026
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Allow for upcasting between interfaces, e.g.