def visit_Name(self, node):
    self.generic_visit(node)
    if isinstance(node.ctx, gast.Load):
      assert anno.hasanno(node, NodeAnno.IS_LOCAL), node
      symbol_is_local = anno.getanno(node, NodeAnno.IS_LOCAL)
      assert anno.hasanno(node, NodeAnno.IS_MODIFIED_SINCE_ENTRY), node
      symbol_is_modified = anno.getanno(node, NodeAnno.IS_MODIFIED_SINCE_ENTRY)
      assert anno.hasanno(node, NodeAnno.IS_PARAM), node
      symbol_is_param = anno.getanno(node, NodeAnno.IS_PARAM)

      if not symbol_is_local and not symbol_is_param:
        if node.id in self.literals:
          anno.setanno(node, 'live_val', self.literals[node.id])
          # TODO(mdan): Could live values have FQNs? i.e. 'a'.join()
        elif node.id in self.context.namespace:
          obj = self.context.namespace[node.id]
          anno.setanno(node, 'live_val', obj)
          anno.setanno(node, 'fqn', (obj.__name__,))
        else:
          pass
          # TODO(mdan): Should we raise an error here?
          # Can encounter this when:
          #  * a symbol truly lacks reference
          #  * a symbol is new, like the new name of a function we just renamed.
      else:
        pass
        # TODO(mdan): Attempt to trace its value through the local chain.
        # TODO(mdan): Use type annotations as fallback.

      if not symbol_is_modified:
        if node.id in self.context.arg_values:
          obj = self.context.arg_values[node.id]
          anno.setanno(node, 'live_val', obj)
          anno.setanno(node, 'fqn', (obj.__class__.__name__,))
    return node

  def visit_Call(self, node):
    # If the function is wrapped by one of the marker decorators,
    # consider it graph ready.
    if anno.hasanno(node.func, 'live_val'):
      target_entity = anno.getanno(node.func, 'live_val')
      if target_entity in self.nocompile_decorators:
        if len(node.args) < 1:
          raise ValueError(
              'Found call to decorator function "%s", but it had no arguments. '
              'A decorator needs at least an argument.')
        anno.setanno(node.args[0], 'graph_ready', True)

    self.generic_visit(node)
    if anno.hasanno(node.func, 'live_val'):
      target_entity = anno.getanno(node.func, 'live_val')
      if anno.hasanno(node.func, 'fqn'):
        target_fqn = anno.getanno(node.func, 'fqn')
      if self._function_is_compilable(target_entity):
        node = self._rename_compilable_function(node)
      elif target_fqn in KNOWN_NUMPY_FUNCTIONS:
        # TODO(mdan): Should we replace these with equivalent TF ops instead?
        node = self._wrap_to_py_func_single_return(node, target_fqn)
      else:
        raise NotImplementedError(
            'py_func with return values (unknown function)')
    else:
      if self.context.recursive:
        node = self._insert_dynamic_conversion(node)
      else:
        # Unresolved functions are allowed in non-recursive mode.
        pass
    return node

  def _rename_compilable_function(self, node):
    assert anno.hasanno(node.func, 'live_val')
    assert anno.hasanno(node.func, 'fqn')
    target_entity = anno.getanno(node.func, 'live_val')
    target_fqn = anno.getanno(node.func, 'fqn')

    if not self._should_compile(node, target_fqn):
      return node

    if anno.hasanno(node, 'is_constructor'):
      new_name = self.context.namer.compiled_class_name(
          target_fqn, live_entity=target_entity)
      do_rename = True
    else:
      owner_type = self._determine_function_owner(target_entity)
      new_name, do_rename = self.context.namer.compiled_function_name(
          target_fqn, live_entity=target_entity, owner_type=owner_type)

    if do_rename:
      if target_entity is not None:
        if tf_inspect.ismethod(target_entity):
          # The renaming process will transform it into a regular function.
          # TODO(mdan): Is this complete? How does it work with nested members?
          node.args = [node.func.value] + node.args
      node.func = templates.replace('func_name', func_name=new_name)[0]
    return node

  def visit_Call(self, node):
    # If the function is wrapped by one of the marker decorators,
    # consider it graph ready.
    if anno.hasanno(node.func, 'live_val'):
      target_obj = anno.getanno(node.func, 'live_val')
      if target_obj in self.nocompile_decorators:
        if len(node.args) < 1:
          raise ValueError(
              'Found call to decorator function "%s", but it had no arguments. '
              'A decorator needs at least an argument.')
        anno.setanno(node.args[0], 'graph_ready', True)

    self.generic_visit(node)
    if anno.hasanno(node.func, 'live_val'):
      target_obj = anno.getanno(node.func, 'live_val')
      if self._function_is_compilable(target_obj):
        node = self._rename_compilable_function(node)
      else:
        raise NotImplementedError('py_func with return values')
    elif anno.hasanno(node.func, 'type_fqn'):
      node = self._rename_member_function_of_known_type(node)
    else:
      raise NotImplementedError(
          'Member function call (of unknown type): %s.' % node.func.id)
    return node

 def visit_Call(self, node):
   target = node.func
   if not anno.hasanno(target, 'live_val'):
     if not isinstance(target, gast.Attribute):
       # Suspecting this pattern would reach here:
       #   foo = bar
       #   foo()
       raise ValueError('Dont know how to handle dynamic functions.')
     if not isinstance(target.value, gast.Name):
       # Possible example of this kind:
       #   foo = module.Foo()
       #   foo.bar.baz()
       # TODO(mdan): This should be doable by using the FQN.
       raise ValueError('Dont know how to handle object properties yet.')
     # In the example below, object_source is 'tr.train.Optimizer()':
     #   opt = tf.train.Optimizer()
     #   opt.foo()
     if self.scope.hasval(target.value.id):
       object_source = self.scope.getval(target.value.id)
       if not anno.hasanno(object_source, 'type'):
         raise ValueError('Could not determine type of "%s". Is it dynamic?' %
                          (target.value.id))
       anno.setanno(target, 'type', anno.getanno(object_source, 'type'))
       anno.setanno(target, 'type_fqn', anno.getanno(object_source,
                                                     'type_fqn'))
     else:
       # TODO(mdan): Figure out what could the user do to get past this.
       raise ValueError('No info on "%s". Is it dynamically built?' %
                        (target.value.id))
   self.generic_visit(node)
   return node

 def visit_Call(self, node):
   if anno.hasanno(node.func, 'live_val'):
     # Symbols targeted by the "set_type" marker function are assigned the data
     # type that it specified.
     if (anno.getanno(node.func, 'live_val') is
         self.context.type_annotation_func):
       # Expecting the actual type to be the second argument.
       if len(node.args) != 2:
         raise ValueError('"%s" must have exactly two parameters'
                          % self.context.type_annotation_func)
       if not anno.hasanno(node.args[0], anno.Basic.QN):
         raise ValueError('the first argument of "%s" must by a symbol'
                          % self.context.type_annotation_func)
       if not anno.hasanno(node.args[1], 'live_val'):
         raise ValueError(
             'the second argument of "%s" must be statically resolvable' %
             self.context.type_annotation_func)
       target_symbol = anno.getanno(node.args[0], anno.Basic.QN)
       element_type = anno.getanno(node.args[1], 'live_val')
       # Find the definition of this symbol and annotate it with the given
       # data type. That in turn will cause future uses of the symbol
       # to receive the same type annotation.
       definition = self.scope.getval(target_symbol)
       anno.setanno(node, 'element_type', element_type)
       anno.setanno(definition, 'element_type', element_type)
       # TODO(mdan): Should we update references between definition and here?
   return self.generic_visit(node)

 def visit_Attribute(self, node):
   self.generic_visit(node)
   if anno.hasanno(node.value, 'live_val'):
     assert anno.hasanno(node.value, 'fqn')
     parent_object = anno.getanno(node.value, 'live_val')
     if not hasattr(parent_object, node.attr):
       raise AttributeError('%s has no attribute %s' % (parent_object,
                                                        node.attr))
     anno.setanno(node, 'parent_type', type(parent_object))
     anno.setanno(node, 'live_val', getattr(parent_object, node.attr))
     anno.setanno(node, 'fqn', anno.getanno(node.value, 'fqn') + (node.attr,))
   # TODO(mdan): Investigate the role built-in annotations can play here.
   elif anno.hasanno(node.value, 'type'):
     parent_type = anno.getanno(node.value, 'type')
     if hasattr(parent_type, node.attr):
       # This should hold for static members like methods.
       # This would not hold for dynamic members like function attributes.
       # For the dynamic case, we simply leave the node without an annotation,
       # and let downstream consumers figure out what to do.
       anno.setanno(node, 'parent_type', parent_type)
       anno.setanno(node, 'live_val', getattr(parent_type, node.attr))
       anno.setanno(node, 'fqn',
                    anno.getanno(node.value, 'type_fqn') + (node.attr,))
   elif isinstance(node.value, gast.Name):
     stem_name = node.value
     # All nonlocal symbols should be fully resolved.
     assert anno.hasanno(stem_name, NodeAnno.IS_LOCAL), stem_name
     # TODO(mdan): Figure out what to do when calling attribute on local object
     # Maybe just leave as-is?
   return node

  def visit_Name(self, node):
    self.generic_visit(node)
    if isinstance(node.ctx, gast.Load):
      assert anno.hasanno(node, 'is_local'), node
      symbol_is_local = anno.getanno(node, 'is_local')
      assert anno.hasanno(node, 'is_modified_since_entry'), node
      symbol_is_modified = anno.getanno(node, 'is_modified_since_entry')
      assert anno.hasanno(node, 'is_param'), node
      symbol_is_param = anno.getanno(node, 'is_param')

      if not symbol_is_local and not symbol_is_param:
        if node.id in self.literals:
          anno.setanno(node, 'live_val', self.literals[node.id])
          # TODO(mdan): Could live values have FQNs? i.e. 'a'.join()
        elif node.id in self.context.namespace:
          obj = self.context.namespace[node.id]
          anno.setanno(node, 'live_val', obj)
          anno.setanno(node, 'fqn', (obj.__name__,))
        else:
          raise ValueError('Could not resolve symbol "%s".' % node.id)
      else:
        pass
        # TODO(mdan): Attempt to trace its value through the local chain.
        # TODO(mdan): Use type annotations as fallback.

      if not symbol_is_modified:
        if node.id in self.context.arg_values:
          obj = self.context.arg_values[node.id]
          anno.setanno(node, 'live_val', obj)
          anno.setanno(node, 'fqn', (obj.__class__.__name__,))
    return node

  def visit_Call(self, node):
    # If the function is wrapped by one of the marker decorators,
    # consider it graph ready.
    if anno.hasanno(node.func, 'live_val'):
      target_entity = anno.getanno(node.func, 'live_val')
      if target_entity in self.nocompile_decorators:
        if len(node.args) < 1:
          raise ValueError(
              'Found call to decorator function "%s", but it had no arguments. '
              'A decorator needs at least an argument.')
        anno.setanno(node.args[0], 'graph_ready', True)

    self.generic_visit(node)
    if anno.hasanno(node.func, 'live_val'):
      target_entity = anno.getanno(node.func, 'live_val')
      if self._function_is_compilable(target_entity):
        node = self._rename_compilable_function(node)
      else:
        raise NotImplementedError('py_func with return values')
    else:
      if self.context.recursive:
        raise NotImplementedError('Could not resolve target function.')
      else:
        # TODO(mdan): Double check. Is this reachable code?
        pass
    return node

 def _try_resolve_target(self, node):
   """Works for methods of objects of known type."""
   if anno.hasanno(node, 'live_val'):
     return anno.getanno(node, 'live_val')
   if isinstance(node, gast.Attribute) and anno.hasanno(node, 'type'):
     member = getattr(anno.getanno(node, 'type'), node.attr)
     return member
   return None

  def test_copyanno(self):
    node_1 = ast.Name()
    anno.setanno(node_1, 'foo', 3)

    node_2 = ast.Name()
    anno.copyanno(node_1, node_2, 'foo')
    anno.copyanno(node_1, node_2, 'bar')

    self.assertTrue(anno.hasanno(node_2, 'foo'))
    self.assertFalse(anno.hasanno(node_2, 'bar'))

  def test_basic(self):
    node = ast.Name()

    self.assertFalse(anno.hasanno(node, 'foo'))
    with self.assertRaises(AttributeError):
      anno.getanno(node, 'foo')

    anno.setanno(node, 'foo', 3)
    self.assertTrue(anno.hasanno(node, 'foo'))
    self.assertEqual(3, anno.getanno(node, 'foo'))

 def _try_resolve_target(self, node):
   """Works for methods of objects of known type."""
   if anno.hasanno(node, 'live_val'):
     return anno.getanno(node, 'live_val')
   if isinstance(node, gast.Attribute) and anno.hasanno(node, 'type'):
     owner_type = anno.getanno(node, 'type')
     if hasattr(owner_type, node.attr):
       return getattr(owner_type, node.attr)
     else:
       raise ValueError('Type "%s" has not attribute "%s". Is it dynamic?' %
                        (owner_type, node.attr))
   return None

  def _rename_compilable_function(self, node):
    assert anno.hasanno(node.func, 'live_val')
    assert anno.hasanno(node.func, 'fqn')
    target_obj = anno.getanno(node.func, 'live_val')
    target_fqn = anno.getanno(node.func, 'fqn')

    if not self._should_compile(target_fqn):
      return node

    new_name = self.namer.compiled_function_name(
        '.'.join(target_fqn), live_object=target_obj)
    node.func = gast.Name(id=new_name, ctx=gast.Load(), annotation=None)
    return node

 def visit_Call(self, node):
   self.generic_visit(node)
   if anno.hasanno(node.func, 'live_val'):
     target_obj = anno.getanno(node.func, 'live_val')
     if self._function_is_compilable(target_obj):
       node = self._rename_compilable_function(node)
     else:
       raise NotImplementedError('py_func with return values')
   elif anno.hasanno(node.func, 'type_fqn'):
     node = self._rename_member_function_of_known_type(node)
   else:
     raise NotImplementedError(
         'Member function call (of unknown type): %s.' % node.func.id)
   return node

  def _track_symbol(self, node):
    # This can happen when we have an attribute (or subscript) on a function
    # call.  Example: a().b
    if not anno.hasanno(node, anno.Basic.QN):
      return
    qn = anno.getanno(node, anno.Basic.QN)

    if isinstance(node.ctx, gast.Store):
      self.scope.mark_write(qn)
    elif isinstance(node.ctx, gast.Load):
      self.scope.mark_read(qn)
    elif isinstance(node.ctx, gast.Param):
      # Param contexts appear in function defs, so they have the meaning of
      # defining a variable.
      # TODO(mdan): This bay be incorrect with nested functions.
      # For nested functions, we'll have to add the notion of hiding args from
      # the parent scope, not writing to them.
      self.scope.mark_creation(qn)
      self.scope.mark_param(qn)
    else:
      raise ValueError('Unknown context %s for node %s.' % (type(node.ctx), qn))

    anno.setanno(node, NodeAnno.IS_LOCAL, self.scope.has(qn))
    anno.setanno(node, NodeAnno.IS_MODIFIED_SINCE_ENTRY,
                 self.scope.is_modified_since_entry(qn))
    anno.setanno(node, NodeAnno.IS_PARAM, self.scope.is_param(qn))

    if self._in_return_statement:
      self.scope.mark_returned(qn)

  def _process_variable_assignment(self, source, targets):
    if isinstance(source, gast.Call):
      func = source.func
      if anno.hasanno(func, 'live_val'):
        func_obj = anno.getanno(func, 'live_val')
        if tf_inspect.isclass(func_obj):
          anno.setanno(source, 'is_constructor', True)
          anno.setanno(source, 'type', func_obj)
          anno.setanno(source, 'type_fqn', anno.getanno(func, 'fqn'))
          # TODO(mdan): Raise an error if constructor has side effects.
          # We can have a whitelist of no-side-effects constructors.
          # We can also step inside the constructor and further analyze.

    for t in targets:
      if isinstance(t, gast.Tuple):
        for i, e in enumerate(t.elts):
          self.scope.setval(e.id,
                            gast.Subscript(
                                source, gast.Index(i), ctx=gast.Store()))
      elif isinstance(t, gast.Name):
        self.scope.setval(t.id, source)
      elif isinstance(t, gast.Attribute):
        if not (isinstance(t.value, gast.Name) and t.value.id == 'self'):
          raise ValueError(
              'Dont know how to handle assignment to attributes of objects'
              ' other than "self": [%s].%s' % (t.value, t.attr))
      else:
        raise ValueError('Dont know how to handle assignment to %s' % t)

  def _wrap_to_py_func_no_return(self, node):
    func_qn = anno.getanno(node.func, anno.Basic.QN)
    args_scope = anno.getanno(node, NodeAnno.ARGS_SCOPE)
    wrapper_name = self.context.namer.new_symbol(func_qn.ssf(),
                                                 args_scope.referenced)
    wrapper_args = []
    for arg in node.args:
      if anno.hasanno(arg, anno.Basic.QN):
        arg_qn = anno.getanno(arg, anno.Basic.QN)
      else:
        arg_qn = qual_names.QN('arg')
      wrapper_args.append(
          self.context.namer.new_symbol(arg_qn.ssf(), args_scope.referenced))
    # TODO(mdan): Properly handle varargs, kwargs, etc.
    # TODO(mdan): This is best handled as a dynamic dispatch.
    # That way we can separate tensors from non-tensor args.
    template = """
      def wrapper(wrapper_args):
        call(wrapper_args)
        return 1
      tf.py_func(wrapper, original_args, [tf.int64])
    """
    wrapper_def, call_expr = templates.replace(
        template,
        call=node.func,
        wrapper=wrapper_name,
        original_args=gast.List(elts=node.args, ctx=None),
        wrapper_args=wrapper_args)
    anno.setanno(wrapper_def, anno.Basic.SKIP_PROCESSING, True)

    return (wrapper_def, call_expr)

  def test_nested_assignment(self):

    def test_fn(foo):
      a, (b, c) = foo
      return a, b, c

    node = self._parse_and_analyze(test_fn, {'foo': (1, 2, 3)})
    lhs = node.body[0].body[1].value.elts
    a = lhs[0]
    b = lhs[1]
    c = lhs[2]
    # TODO(mdan): change these once we have the live values propagating
    # correctly
    self.assertFalse(anno.hasanno(a, 'live_val'))
    self.assertFalse(anno.hasanno(b, 'live_val'))
    self.assertFalse(anno.hasanno(c, 'live_val'))

 def _visit_and_reindent(self, nodes):
   new_nodes = []
   current_dest = new_nodes
   alias_map = {}
   reindent_requested = False
   for n in nodes:
     n = self.visit(n)
     # NOTE: the order in which these statements execute is important; in
     # particular, watch out for ending up with cycles in the AST.
     if alias_map:
       n = ast_util.rename_symbols(n, alias_map)
     if isinstance(n, (list, tuple)):
       current_dest.extend(n)
     else:
       current_dest.append(n)
     if anno.hasanno(n, anno.Basic.INDENT_BLOCK_REMAINDER):
       reindent_requested = True
       new_dest, new_alias_map = anno.getanno(
           n, anno.Basic.INDENT_BLOCK_REMAINDER)
       anno.delanno(n, anno.Basic.INDENT_BLOCK_REMAINDER)
       new_alias_map.update(alias_map)
       alias_map = new_alias_map
       current_dest = new_dest
   if reindent_requested and not current_dest:
     # TODO(mdan): There may still be something that could be done.
     raise ValueError('Unable to insert statement into the computation flow: '
                      'it is not followed by any computation which '
                      'the statement could gate.')
   return new_nodes