def def_reach(dct):
        """Find all variable definition reachable at the entry of a block
        """
        for offset in var_def_map:
            used_or_defined = var_def_map[offset] | var_use_map[offset]
            dct[offset] |= used_or_defined
            # Propagate to outgoing nodes
            for out_blk, _ in cfg.successors(offset):
                dct[out_blk] |= dct[offset]
Find all variable definition reachable at the entry of a block
        
numba/core/analysis.py