# Buggy code
def compute_use_defs(blocks):
    """
    Find variable use/def per block.
    """

    var_use_map = {}  # { block offset -> set of vars }
    var_def_map = {}  # { block offset -> set of vars }
    for offset, ir_block in blocks.items():
        var_use_map[offset] = use_set = set()
        var_def_map[offset] = def_set = set()
        for stmt in ir_block.body:
            for T, def_func in ir_extension_defs.items():
                if isinstance(stmt, T):
                    def_set.update(def_func(stmt))
            if isinstance(stmt, ir.Assign):
                if isinstance(stmt.value, ir.Inst):
                    rhs_set = set(var.name for var in stmt.value.list_vars())
                elif isinstance(stmt.value, ir.Var):
                    rhs_set = set([stmt.value.name])
                elif isinstance(stmt.value, (ir.Arg, ir.Const, ir.Global, ir.FreeVar)):
                    rhs_set = ()
                else:
                    raise AssertionError("unreachable", type(stmt.value))
                # If lhs not in rhs of the assignment
                if stmt.target.name not in rhs_set:
                    def_set.add(stmt.target.name)

            for var in stmt.list_vars():
                # do not include locally defined vars to use-map
                if var.name not in def_set:
                    use_set.add(var.name)

    return _use_defs_result(usemap=var_use_map, defmap=var_def_map)


# Traceback (TypeError)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-15-3b23f7331ceb> in <module>()
----> 1 @jit(arg_types=[numba.double], ret_type=numba.double)
2 def is_REALLY_five(some_value):
3     for i in range(5):
4         if some_value == 5.0:
5             return 1.0

/Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/numba/decorators.pyc in _jit(func)
77                   "garbage collected!" % (func,))
78         t = Translate(func, *args, **kws)
---> 79         t.translate()
80         __tr_map__[func] = t
81         return t.get_ctypes_func(llvm)

/Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/numba/translate.pyc in translate(self)
926                     # Ensure we are playing with locals that might
927                     # actually precede the next block.
--> 928                     self.check_locals(i)
929
930                 self.crnt_block = i

/Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/numba/translate.pyc in check_locals(self, i)
1135                 else:
1136                     assert next_locals is not None, "Internal compiler error!"
-> 1137             self._locals = next_locals[:]
1138
1139     def get_ctypes_func(self, llvm=True):

TypeError: 'NoneType' object has no attribute '__getitem__'

# Fixed code
def compute_use_defs(blocks):
    """
    Find variable use/def per block.
    """

    var_use_map = {}  # { block offset -> set of vars }
    var_def_map = {}  # { block offset -> set of vars }
    for offset, ir_block in blocks.items():
        var_use_map[offset] = use_set = set()
        var_def_map[offset] = def_set = set()
        for stmt in ir_block.body:
            if type(stmt) in ir_extension_usedefs:
                func = ir_extension_usedefs[type(stmt)]
                func(stmt, use_set, def_set)
                continue
            if isinstance(stmt, ir.Assign):
                if isinstance(stmt.value, ir.Inst):
                    rhs_set = set(var.name for var in stmt.value.list_vars())
                elif isinstance(stmt.value, ir.Var):
                    rhs_set = set([stmt.value.name])
                elif isinstance(stmt.value, (ir.Arg, ir.Const, ir.Global, ir.FreeVar)):
                    rhs_set = ()
                else:
                    raise AssertionError("unreachable", type(stmt.value))
                # If lhs not in rhs of the assignment
                if stmt.target.name not in rhs_set:
                    def_set.add(stmt.target.name)

            for var in stmt.list_vars():
                # do not include locally defined vars to use-map
                if var.name not in def_set:
                    use_set.add(var.name)

    return _use_defs_result(usemap=var_use_map, defmap=var_def_map)