mainline @ 159510a is failing CI

[stuartarchibald]

Failing run: https://dev.azure.com/numba/numba/_build/results?buildId=6831&view=logs&j=a506c6d0-8428-5bb5-7d36-c242a5467a36&t=3b81a997-a0fe-5621-27e6-18b6744841b9&l=9361

Details: https://gist.github.com/stuartarchibald/ace0bea10f04abb44d65a0ed9f8ba2cb

[stuartarchibald]

Dumping out the error:

AssertionError: 'cannot index array' not found in 'Failed in nopython mode pipeline (step: nopython frontend)
No implementation of function Function(<function flipud at 0x7f64ef745b00>) found for signature:
 
 >>> flipud(int64)
 
There are 2 candidate implementations:
  - Of which 1 did not match due to:
  Overload in function \'np_flip_ud\': File: numba/np/arrayobj.py: Line 4917.
    With argument(s): \'(int64)\':
   Rejected as the implementation raised a specific error:
     TypingError: Failed in nopython mode pipeline (step: nopython frontend)
   Internal error at <numba.core.typeinfer.StaticGetItemConstraint object at 0x7f64cd53e4d0>.
   \'TestOverloadInlining\' object has no attribute \'DummyType\'
   During: typing of intrinsic-call at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
   During: typing of static-get-item at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
   Enable logging at debug level for details.
   
   File "numba/np/arrayobj.py", line 4930:
       def impl(a):
           <source elided>
               raise ValueError(\'Input must be >= 1-d.\')
           return A[::-1, ...]
           ^
   
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 677, in _get_impl
           impl, args = self._impl_cache[cache_key]
       KeyError: (<numba.core.typing.context.Context object at 0x7f64e14c37d0>, (int64,), ())
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 677, in _get_impl
           impl, args = self._impl_cache[cache_key]
       KeyError: (<numba.core.typing.context.Context object at 0x7f64e14c37d0>, (array(int64, 0d, C), Tuple(slice<a:b:c>, ...)), ())
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/errors.py", line 738, in new_error_context
           yield
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 689, in __call__
           self.resolve(typeinfer, typeinfer.typevars, fnty=fnty)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 586, in resolve
           sig = typeinfer.resolve_call(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 1535, in resolve_call
           return self.context.resolve_function_type(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 207, in resolve_function_type
           res = self._resolve_builtin_function_type(func, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 224, in _resolve_builtin_function_type
           res = defn.apply(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 345, in apply
           sig = generic(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 597, in generic
           disp, new_args = self._get_impl(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 679, in _get_impl
           impl, args = self._build_impl(cache_key, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 710, in _build_impl
           ovf_result = self._overload_func(*args, **kws)
         File "/home/vsts/work/1/s/numba/tests/test_ir_inlining.py", line 660, in overload_dummy_getitem
           if isinstance(obj, self.DummyType):
       AttributeError: \'TestOverloadInlining\' object has no attribute \'DummyType\'
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 154, in propagate
           constraint(typeinfer)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 469, in __call__
           self.fallback(typeinfer)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 689, in __call__
           self.resolve(typeinfer, typeinfer.typevars, fnty=fnty)
         File "/home/vsts/miniconda3/envs/travisci/lib/python3.7/contextlib.py", line 130, in __exit__
           self.gen.throw(type, value, traceback)
         File "/home/vsts/work/1/s/numba/core/errors.py", line 745, in new_error_context
           raise newerr.with_traceback(tb)
         File "/home/vsts/work/1/s/numba/core/errors.py", line 738, in new_error_context
           yield
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 689, in __call__
           self.resolve(typeinfer, typeinfer.typevars, fnty=fnty)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 586, in resolve
           sig = typeinfer.resolve_call(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 1535, in resolve_call
           return self.context.resolve_function_type(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 207, in resolve_function_type
           res = self._resolve_builtin_function_type(func, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 224, in _resolve_builtin_function_type
           res = defn.apply(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 345, in apply
           sig = generic(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 597, in generic
           disp, new_args = self._get_impl(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 679, in _get_impl
           impl, args = self._build_impl(cache_key, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 710, in _build_impl
           ovf_result = self._overload_func(*args, **kws)
         File "/home/vsts/work/1/s/numba/tests/test_ir_inlining.py", line 660, in overload_dummy_getitem
           if isinstance(obj, self.DummyType):
       numba.core.errors.InternalError: \'TestOverloadInlining\' object has no attribute \'DummyType\'
       During: typing of intrinsic-call at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       During: typing of static-get-item at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       The above exception was the direct cause of the following exception:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/types/functions.py", line 298, in get_call_type
           sig = temp.apply(nolitargs, nolitkws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 345, in apply
           sig = generic(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 597, in generic
           disp, new_args = self._get_impl(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 679, in _get_impl
           impl, args = self._build_impl(cache_key, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 740, in _build_impl
           disp_type.get_call_type(self.context, args, kws)
         File "/home/vsts/work/1/s/numba/core/types/functions.py", line 511, in get_call_type
           self.dispatcher.get_call_template(args, kws)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 311, in get_call_template
           self.compile(tuple(args))
         File "/home/vsts/work/1/s/numba/core/compiler_lock.py", line 32, in _acquire_compile_lock
           return func(*args, **kwargs)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 818, in compile
           cres = self._compiler.compile(args, return_type)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 81, in compile
           raise retval
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 91, in _compile_cached
           retval = self._compile_core(args, return_type)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 109, in _compile_core
           pipeline_class=self.pipeline_class)
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 602, in compile_extra
           return pipeline.compile_extra(func)
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 352, in compile_extra
           return self._compile_bytecode()
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 414, in _compile_bytecode
           return self._compile_core()
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 394, in _compile_core
           raise e
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 385, in _compile_core
           pm.run(self.state)
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 339, in run
           raise patched_exception
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 330, in run
           self._runPass(idx, pass_inst, state)
         File "/home/vsts/work/1/s/numba/core/compiler_lock.py", line 32, in _acquire_compile_lock
           return func(*args, **kwargs)
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 289, in _runPass
           mutated |= check(pss.run_pass, internal_state)
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 262, in check
           mangled = func(compiler_state)
         File "/home/vsts/work/1/s/numba/core/typed_passes.py", line 99, in run_pass
           raise_errors=self._raise_errors)
         File "/home/vsts/work/1/s/numba/core/typed_passes.py", line 71, in type_inference_stage
           infer.propagate(raise_errors=raise_errors)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 1071, in propagate
           raise errors[0]
       numba.core.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
       Internal error at <numba.core.typeinfer.StaticGetItemConstraint object at 0x7f64cd53e4d0>.
       \'TestOverloadInlining\' object has no attribute \'DummyType\'
       During: typing of intrinsic-call at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       During: typing of static-get-item at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       Enable logging at debug level for details.
       File "numba/np/arrayobj.py", line 4930:
           def impl(a):
               <source elided>
                   raise ValueError(\'Input must be >= 1-d.\')
               return A[::-1, ...]
               ^
  raised from /home/vsts/work/1/s/numba/core/typeinfer.py:1071
  - Of which 1 did not match due to:
  Overload in function \'np_flip_ud\': File: numba/np/arrayobj.py: Line 4917.
    With argument(s): \'(int64)\':
   Rejected as the implementation raised a specific error:
     TypingError: Failed in nopython mode pipeline (step: nopython frontend)
   Internal error at <numba.core.typeinfer.StaticGetItemConstraint object at 0x7f64ce4bfb50>.
   \'TestOverloadInlining\' object has no attribute \'DummyType\'
   During: typing of intrinsic-call at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
   During: typing of static-get-item at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
   Enable logging at debug level for details.
   
   File "numba/np/arrayobj.py", line 4930:
       def impl(a):
           <source elided>
               raise ValueError(\'Input must be >= 1-d.\')
           return A[::-1, ...]
           ^
   
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 677, in _get_impl
           impl, args = self._impl_cache[cache_key]
       KeyError: (<numba.core.typing.context.Context object at 0x7f64e14c37d0>, (int64,), ())
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 677, in _get_impl
           impl, args = self._impl_cache[cache_key]
       KeyError: (<numba.core.typing.context.Context object at 0x7f64e14c37d0>, (array(int64, 0d, C), Tuple(slice<a:b:c>, ...)), ())
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/errors.py", line 738, in new_error_context
           yield
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 689, in __call__
           self.resolve(typeinfer, typeinfer.typevars, fnty=fnty)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 586, in resolve
           sig = typeinfer.resolve_call(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 1535, in resolve_call
           return self.context.resolve_function_type(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 207, in resolve_function_type
           res = self._resolve_builtin_function_type(func, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 224, in _resolve_builtin_function_type
           res = defn.apply(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 345, in apply
           sig = generic(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 597, in generic
           disp, new_args = self._get_impl(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 679, in _get_impl
           impl, args = self._build_impl(cache_key, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 710, in _build_impl
           ovf_result = self._overload_func(*args, **kws)
         File "/home/vsts/work/1/s/numba/tests/test_ir_inlining.py", line 660, in overload_dummy_getitem
           if isinstance(obj, self.DummyType):
       AttributeError: \'TestOverloadInlining\' object has no attribute \'DummyType\'
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 154, in propagate
           constraint(typeinfer)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 469, in __call__
           self.fallback(typeinfer)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 689, in __call__
           self.resolve(typeinfer, typeinfer.typevars, fnty=fnty)
         File "/home/vsts/miniconda3/envs/travisci/lib/python3.7/contextlib.py", line 130, in __exit__
           self.gen.throw(type, value, traceback)
         File "/home/vsts/work/1/s/numba/core/errors.py", line 745, in new_error_context
           raise newerr.with_traceback(tb)
         File "/home/vsts/work/1/s/numba/core/errors.py", line 738, in new_error_context
           yield
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 689, in __call__
           self.resolve(typeinfer, typeinfer.typevars, fnty=fnty)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 586, in resolve
           sig = typeinfer.resolve_call(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 1535, in resolve_call
           return self.context.resolve_function_type(fnty, pos_args, kw_args)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 207, in resolve_function_type
           res = self._resolve_builtin_function_type(func, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/context.py", line 224, in _resolve_builtin_function_type
           res = defn.apply(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 345, in apply
           sig = generic(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 597, in generic
           disp, new_args = self._get_impl(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 679, in _get_impl
           impl, args = self._build_impl(cache_key, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 710, in _build_impl
           ovf_result = self._overload_func(*args, **kws)
         File "/home/vsts/work/1/s/numba/tests/test_ir_inlining.py", line 660, in overload_dummy_getitem
           if isinstance(obj, self.DummyType):
       numba.core.errors.InternalError: \'TestOverloadInlining\' object has no attribute \'DummyType\'
       During: typing of intrinsic-call at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       During: typing of static-get-item at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       The above exception was the direct cause of the following exception:
       Traceback (most recent call last):
         File "/home/vsts/work/1/s/numba/core/types/functions.py", line 293, in get_call_type
           sig = temp.apply(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 345, in apply
           sig = generic(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 597, in generic
           disp, new_args = self._get_impl(args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 679, in _get_impl
           impl, args = self._build_impl(cache_key, args, kws)
         File "/home/vsts/work/1/s/numba/core/typing/templates.py", line 740, in _build_impl
           disp_type.get_call_type(self.context, args, kws)
         File "/home/vsts/work/1/s/numba/core/types/functions.py", line 511, in get_call_type
           self.dispatcher.get_call_template(args, kws)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 311, in get_call_template
           self.compile(tuple(args))
         File "/home/vsts/work/1/s/numba/core/compiler_lock.py", line 32, in _acquire_compile_lock
           return func(*args, **kwargs)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 818, in compile
           cres = self._compiler.compile(args, return_type)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 81, in compile
           raise retval
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 91, in _compile_cached
           retval = self._compile_core(args, return_type)
         File "/home/vsts/work/1/s/numba/core/dispatcher.py", line 109, in _compile_core
           pipeline_class=self.pipeline_class)
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 602, in compile_extra
           return pipeline.compile_extra(func)
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 352, in compile_extra
           return self._compile_bytecode()
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 414, in _compile_bytecode
           return self._compile_core()
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 394, in _compile_core
           raise e
         File "/home/vsts/work/1/s/numba/core/compiler.py", line 385, in _compile_core
           pm.run(self.state)
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 339, in run
           raise patched_exception
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 330, in run
           self._runPass(idx, pass_inst, state)
         File "/home/vsts/work/1/s/numba/core/compiler_lock.py", line 32, in _acquire_compile_lock
           return func(*args, **kwargs)
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 289, in _runPass
           mutated |= check(pss.run_pass, internal_state)
         File "/home/vsts/work/1/s/numba/core/compiler_machinery.py", line 262, in check
           mangled = func(compiler_state)
         File "/home/vsts/work/1/s/numba/core/typed_passes.py", line 99, in run_pass
           raise_errors=self._raise_errors)
         File "/home/vsts/work/1/s/numba/core/typed_passes.py", line 71, in type_inference_stage
           infer.propagate(raise_errors=raise_errors)
         File "/home/vsts/work/1/s/numba/core/typeinfer.py", line 1071, in propagate
           raise errors[0]
       numba.core.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
       Internal error at <numba.core.typeinfer.StaticGetItemConstraint object at 0x7f64ce4bfb50>.
       \'TestOverloadInlining\' object has no attribute \'DummyType\'
       During: typing of intrinsic-call at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       During: typing of static-get-item at /home/vsts/work/1/s/numba/np/arrayobj.py (4930)
       Enable logging at debug level for details.
       File "numba/np/arrayobj.py", line 4930:
           def impl(a):
               <source elided>
                   raise ValueError(\'Input must be >= 1-d.\')
               return A[::-1, ...]
               ^
  raised from /home/vsts/work/1/s/numba/core/typeinfer.py:1071

During: resolving callee type: Function(<function flipud at 0x7f64ef745b00>)
During: typing of call at /home/vsts/work/1/s/numba/tests/test_np_functions.py (121)


File "numba/tests/test_np_functions.py", line 121:
def flipud(a):
    return np.flipud(a)
    ^

[stuartarchibald]

Suspect this is due to #6027.

[stuartarchibald]

Think the issue is as follows...

This:

numba/numba/tests/test_ir_inlining.py

Lines 511 to 513 in 159510a

	if 'operator' in self._testMethodName:
	self.make_dummy_type()
	super(TestOverloadInlining, self).setUp()

calls this:

numba/numba/tests/test_ir_inlining.py

Lines 135 to 155 in 159510a

	def make_dummy_type(self):
	# Use test_id to make sure no collision is possible.
	test_id = self.id()
	DummyType = type('DummyTypeFor{}'.format(test_id), (types.Opaque,), {})
	dummy_type = DummyType("my_dummy")
	register_model(DummyType)(OpaqueModel)
	class Dummy(object):
	pass
	@typeof_impl.register(Dummy)
	def typeof_dummy(val, c):
	return dummy_type
	@unbox(DummyType)
	def unbox_dummy(typ, obj, c):
	return NativeValue(c.context.get_dummy_value())
	self.Dummy = Dummy
	self.DummyType = DummyType

the problem being the mutation of self:

        self.Dummy = Dummy
        self.DummyType = DummyType

these two tests then register overloads for static getitem on these types:

numba/numba/tests/test_ir_inlining.py

Lines 647 to 691 in 159510a

	def test_inline_always_operators_getitem(self):
	def impl(x, idx):
	return x[idx]
	def impl_static_getitem(x):
	return x[1]
	dummy_getitem_impl = lambda obj, idx: None
	setattr(self.Dummy, '__getitem__', dummy_getitem_impl)
	@overload(operator.getitem, inline='always')
	def overload_dummy_getitem(obj, idx):
	if isinstance(obj, self.DummyType):
	return dummy_getitem_impl
	# note getitem and static_getitem Exprs refer to operator.getitem
	# hence they are checked using the same expected key
	self.check(impl, self.Dummy(), 1, inline_expect={'getitem': True})
	self.check(impl_static_getitem,
	self.Dummy(),
	inline_expect={'getitem': True})
	def test_inline_never_operators_getitem(self):
	def impl(x, idx):
	return x[idx]
	def impl_static_getitem(x):
	return x[1]
	dummy_getitem_impl = lambda obj, idx: None
	setattr(self.Dummy, '__getitem__', dummy_getitem_impl)
	@overload(operator.getitem, inline='never')
	def overload_dummy_getitem(obj, idx):
	if isinstance(obj, self.DummyType):
	return dummy_getitem_impl
	# noth getitem and static_getitem Exprs refer to opertor.getitem
	# hence they are checked using the same expect key
	self.check(impl, self.Dummy(), 1, inline_expect={'getitem': False})
	self.check(impl_static_getitem,
	self.Dummy(),
	inline_expect={'getitem': False})

the problem appears in typing when the StaticGetItemConstraint searches overloads and finds that TestOverloadInlining has no DummyType attr, question is why.

[stuartarchibald]

An intermittently successful method of reproducing is:

NUMBA_ENABLE_CUDASIM=1 python -m numba.runtests -f -b -j "2,None,18" --exclude-tags='long_running' -m 2 -v  -- numba.tests

[sklam]

the problem appears in typing when the StaticGetItemConstraint searches overloads and finds that TestOverloadInlining has no DummyType attr, question is why.

Did you figure out why? setUp is executed once per test method. I wonder if it's because self.Dummy and self.DummyType may sometimes leak into the next test because there were no tearDown.