# Buggy code
def _extract_loop_lifting_candidates(cfg, blocks):
    """
    Returns a list of loops that are candidate for loop lifting
    """

    # check well-formed-ness of the loop
    def same_exit_point(loop):
        "all exits must point to the same location"
        outedges = set()
        for k in loop.exits:
            succs = set(x for x, _ in cfg.successors(k))
            if not succs:
                # If the exit point has no successor, it contains an return
                # statement, which is not handled by the looplifting code.
                # Thus, this loop is not a candidate.
                _logger.debug("return-statement in loop.")
                return False
            outedges |= succs
        ok = len(outedges) == 1
        _logger.debug("same_exit_point=%s", ok)
        return ok

    def one_entry(loop):
        "there is one entry"
        ok = len(loop.entries) == 1
        _logger.debug("one_entry=%s", ok)
        return ok

    def cannot_yield(loop):
        "cannot have yield inside the loop"
        insiders = set(loop.body) | set(loop.entries) | set(loop.exits)
        for blk in map(blocks.__getitem__, insiders):
            for inst in blk.body:
                if isinstance(inst, ir.Assign):
                    if isinstance(inst.value, ir.Yield):
                        _logger.debug("has yield")
                        return False
        _logger.debug("no yield")
        return True

    _logger.info("finding looplift candidates")
    # the check for cfg.entry_point in the loop.entries is to prevent a bad
    # rewrite where a prelude for a lifted loop would get written into block -1
    # if a loop entry were in block 0
    candidates = []
    for loop in find_top_level_loops(cfg):
        _logger.debug("top-level loop: %s", loop)
        if (
            same_exit_point(loop)
            and one_entry(loop)
            and cannot_yield(loop)
            and cfg.entry_point() not in loop.entries
        ):
            candidates.append(loop)
            _logger.debug("add candidate: %s", loop)
    return candidates


# Traceback (IndexError)
Traceback (most recent call last):
File "/home/ibutygin/miniconda3/envs/NUMBA_CUSTOM/lib/python3.7/site-packages/llvmlite/ir/instructions.py", line 619, in __init__
typ = typ.elements[i]
IndexError: tuple index out of range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/ibutygin/src/numba/numba/numba/errors.py", line 717, in new_error_context
yield
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 260, in lower_block
self.lower_inst(inst)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 303, in lower_inst
val = self.lower_assign(ty, inst)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 467, in lower_assign
return self.lower_expr(ty, value)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 932, in lower_expr
res = self.lower_call(resty, expr)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 724, in lower_call
res = self._lower_call_normal(fnty, expr, signature)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 903, in _lower_call_normal
res = impl(self.builder, argvals, self.loc)
File "/home/ibutygin/src/numba/numba/numba/targets/base.py", line 1132, in __call__
res = self._imp(self._context, builder, self._sig, args, loc=loc)
File "/home/ibutygin/src/numba/numba/numba/targets/base.py", line 1157, in wrapper
return fn(*args, **kwargs)
File "/home/ibutygin/src/numba/numba/numba/typing/templates.py", line 778, in method_impl
return call(builder, args)
File "/home/ibutygin/src/numba/numba/numba/targets/base.py", line 1132, in __call__
res = self._imp(self._context, builder, self._sig, args, loc=loc)
File "/home/ibutygin/src/numba/numba/numba/targets/base.py", line 1157, in wrapper
return fn(*args, **kwargs)
File "/home/ibutygin/src/numba/numba/numba/targets/imputils.py", line 193, in imp
builder, func, fndesc.restype, fndesc.argtypes, args)
File "/home/ibutygin/src/numba/numba/numba/targets/callconv.py", line 477, in call_function
args = list(arginfo.as_arguments(builder, args))
File "/home/ibutygin/src/numba/numba/numba/datamodel/packer.py", line 100, in as_arguments
for dm, val in zip(self._dm_args, values)
File "/home/ibutygin/src/numba/numba/numba/datamodel/packer.py", line 100, in <listcomp>
for dm, val in zip(self._dm_args, values)
File "/home/ibutygin/src/numba/numba/numba/datamodel/models.py", line 447, in as_argument
v = builder.extract_value(value, [i])
File "/home/ibutygin/miniconda3/envs/NUMBA_CUSTOM/lib/python3.7/site-packages/llvmlite/ir/builder.py", line 927, in extract_value
instr = instructions.ExtractValue(self.block, agg, idx, name=name)
File "/home/ibutygin/miniconda3/envs/NUMBA_CUSTOM/lib/python3.7/site-packages/llvmlite/ir/instructions.py", line 622, in __init__
% (list(indices), agg.type))
TypeError: Can't index at [0] in {}

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "test.py", line 73, in <module>
print(bar(Dummy()))
File "/home/ibutygin/src/numba/numba/numba/dispatcher.py", line 420, in _compile_for_args
raise e
File "/home/ibutygin/src/numba/numba/numba/dispatcher.py", line 353, in _compile_for_args
return self.compile(tuple(argtypes))
File "/home/ibutygin/src/numba/numba/numba/compiler_lock.py", line 32, in _acquire_compile_lock
return func(*args, **kwargs)
File "/home/ibutygin/src/numba/numba/numba/dispatcher.py", line 768, in compile
cres = self._compiler.compile(args, return_type)
File "/home/ibutygin/src/numba/numba/numba/dispatcher.py", line 77, in compile
status, retval = self._compile_cached(args, return_type)
File "/home/ibutygin/src/numba/numba/numba/dispatcher.py", line 91, in _compile_cached
retval = self._compile_core(args, return_type)
File "/home/ibutygin/src/numba/numba/numba/dispatcher.py", line 109, in _compile_core
pipeline_class=self.pipeline_class)
File "/home/ibutygin/src/numba/numba/numba/compiler.py", line 543, in compile_extra
return pipeline.compile_extra(func)
File "/home/ibutygin/src/numba/numba/numba/compiler.py", line 328, in compile_extra
return self._compile_bytecode()
File "/home/ibutygin/src/numba/numba/numba/compiler.py", line 389, in _compile_bytecode
return self._compile_core()
File "/home/ibutygin/src/numba/numba/numba/compiler.py", line 368, in _compile_core
raise e
File "/home/ibutygin/src/numba/numba/numba/compiler.py", line 359, in _compile_core
pm.run(self.state)
File "/home/ibutygin/src/numba/numba/numba/compiler_machinery.py", line 331, in run
raise patched_exception
File "/home/ibutygin/src/numba/numba/numba/compiler_machinery.py", line 322, in run
self._runPass(idx, pass_inst, state)
File "/home/ibutygin/src/numba/numba/numba/compiler_lock.py", line 32, in _acquire_compile_lock
return func(*args, **kwargs)
File "/home/ibutygin/src/numba/numba/numba/compiler_machinery.py", line 281, in _runPass
mutated |= check(pss.run_pass, internal_state)
File "/home/ibutygin/src/numba/numba/numba/compiler_machinery.py", line 268, in check
mangled = func(compiler_state)
File "/home/ibutygin/src/numba/numba/numba/typed_passes.py", line 391, in run_pass
NativeLowering().run_pass(state)
File "/home/ibutygin/src/numba/numba/numba/typed_passes.py", line 333, in run_pass
lower.lower()
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 179, in lower
self.lower_normal_function(self.fndesc)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 220, in lower_normal_function
entry_block_tail = self.lower_function_body()
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 245, in lower_function_body
self.lower_block(block)
File "/home/ibutygin/src/numba/numba/numba/lowering.py", line 260, in lower_block
self.lower_inst(inst)
File "/home/ibutygin/miniconda3/envs/NUMBA_CUSTOM/lib/python3.7/contextlib.py", line 130, in __exit__
self.gen.throw(type, value, traceback)
File "/home/ibutygin/src/numba/numba/numba/errors.py", line 725, in new_error_context
six.reraise(type(newerr), newerr, tb)
File "/home/ibutygin/src/numba/numba/numba/six.py", line 669, in reraise
raise value
numba.errors.LoweringError: Failed in nopython mode pipeline (step: nopython mode backend)
Can't index at [0] in {}

File "test.py", line 71:
def bar(obj):
return obj.inline_method(123,456)
^

[1] During: lowering "$10call_method.4 = call $4load_method.1($const6.2, $const8.3, func=$4load_method.1, args=[Var($const6.2, test.py:71), Var($const8.3, test.py:71)], kws=(), vararg=None)" at test.py (71)

# Fixed code
def _extract_loop_lifting_candidates(cfg, blocks):
    """
    Returns a list of loops that are candidate for loop lifting
    """

    # check well-formed-ness of the loop
    def same_exit_point(loop):
        "all exits must point to the same location"
        outedges = set()
        for k in loop.exits:
            succs = set(x for x, _ in cfg.successors(k))
            if not succs:
                # If the exit point has no successor, it contains an return
                # statement, which is not handled by the looplifting code.
                # Thus, this loop is not a candidate.
                _logger.debug("return-statement in loop.")
                return False
            outedges |= succs
        ok = len(outedges) == 1
        _logger.debug("same_exit_point=%s (%s)", ok, outedges)
        return ok

    def one_entry(loop):
        "there is one entry"
        ok = len(loop.entries) == 1
        _logger.debug("one_entry=%s", ok)
        return ok

    def cannot_yield(loop):
        "cannot have yield inside the loop"
        insiders = set(loop.body) | set(loop.entries) | set(loop.exits)
        for blk in map(blocks.__getitem__, insiders):
            for inst in blk.body:
                if isinstance(inst, ir.Assign):
                    if isinstance(inst.value, ir.Yield):
                        _logger.debug("has yield")
                        return False
        _logger.debug("no yield")
        return True

    _logger.info("finding looplift candidates")
    # the check for cfg.entry_point in the loop.entries is to prevent a bad
    # rewrite where a prelude for a lifted loop would get written into block -1
    # if a loop entry were in block 0
    candidates = []
    for loop in find_top_level_loops(cfg):
        _logger.debug("top-level loop: %s", loop)
        if (
            same_exit_point(loop)
            and one_entry(loop)
            and cannot_yield(loop)
            and cfg.entry_point() not in loop.entries
        ):
            candidates.append(loop)
            _logger.debug("add candidate: %s", loop)
    return candidates