Support for try-finally.

[jriehl]

Meta doesn't support try-finally.

Expected (please note I am using a personal version of the Numba dump() utility which has not been merged upstream at time of this report):

>>> from meta.decompiler import decompile_func
>>> from numba.utils import dump
>>> def testfn():
...     try:
...         init()
...     finally:
...         deinit()
... 
>>> dump(decompile_func(testfn), False)
('FunctionDef',
 {'args': ('arguments',
           {'args': [], 'defaults': [], 'kwarg': None, 'vararg': None}),
  'body': [('TryFinally',
            {'body': [('Expr',
                       {'value': ('Call',
                                  {'args': [],
                                   'func': ('Name',
                                            {'ctx': ('Load', {}),
                                             'id': 'init'}),
                                   'keywords': [],
                                   'kwargs': None,
                                   'starargs': None})})],
             'finalbody': [('Expr',
                            {'value': ('Call',
                                       {'args': [],
                                        'func': ('Name',
                                                 {'ctx': ('Load',
                                                          {}),
                                                  'id': 'deinit'}),
                                        'keywords': [],
                                        'kwargs': None,
                                        'starargs': None})})]})],
  'decorator_list': [],
  'name': 'testfn'})

Got:

>>> dump(decompile_func(testfn), False)
('FunctionDef',
 {'args': ('arguments',
           {'args': [], 'defaults': [], 'kwarg': None, 'vararg': None}),
  'body': [('Expr',
            {'value': ('Call',
                       {'args': [],
                        'func': ('Name',
                                 {'ctx': ('Load', {}), 'id': 'init'}),
                        'keywords': [],
                        'kwargs': None,
                        'starargs': None})}),
           ('Return',
            {'value': ('Name', {'ctx': ('Load', {}), 'id': 'None'})})],
  'decorator_list': [],
  'name': 'testfn'})

Worse still, having an except clause causes meta to blow up:

>>> def testfn2():
...     try:
...         init()
...         do_something()
...     except Exception as e:
...         handle(e)
...     finally:
...         deinit()
... 
>>> dump(decompile_func(testfn2), False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/__init__.py", line 37, in decompile_func
    ast_node = make_function(code, defaults=[], lineno=code.co_firstlineno)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/instructions.py", line 86, in make_function
    stmnts = instructions.stmnt()
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/instructions.py", line 310, in stmnt
    self.visit(instr)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/instructions.py", line 324, in visit
    method(instr)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/control_flow_instructions.py", line 305, in SETUP_FINALLY
    self.do_try_except_block(try_except_block)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/control_flow_instructions.py", line 262, in do_try_except_block
    try_except = self.decompile_block(block).stmnt()
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/instructions.py", line 310, in stmnt
    self.visit(instr)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/instructions.py", line 324, in visit
    method(instr)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/control_flow_instructions.py", line 346, in SETUP_EXCEPT
    end, handlers = self.split_handlers(handlers_blocks)
  File "/home/jriehl/.virtualenvs/numba/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/decompiler/control_flow_instructions.py", line 204, in split_handlers
    assert except_instrs[-2].opname == 'POP_TOP'
AssertionError

[srossross]

Thanks for writing this up John, I'll take a look early next week.