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mojo/public/third_party/jinja2/nodes.py

Index: mojo/public/third_party/jinja2/nodes.py
diff --git a/mojo/public/third_party/jinja2/nodes.py b/mojo/public/third_party/jinja2/nodes.py
deleted file mode 100644
index c5697e6b5ec3737a0e43656c883340656c4544d3..0000000000000000000000000000000000000000
--- a/mojo/public/third_party/jinja2/nodes.py
+++ /dev/null
@@ -1,914 +0,0 @@
-# -*- coding: utf-8 -*-
-"""
-    jinja2.nodes
-    ~~~~~~~~~~~~
-
-    This module implements additional nodes derived from the ast base node.
-
-    It also provides some node tree helper functions like `in_lineno` and
-    `get_nodes` used by the parser and translator in order to normalize
-    python and jinja nodes.
-
-    :copyright: (c) 2010 by the Jinja Team.
-    :license: BSD, see LICENSE for more details.
-"""
-import operator
-
-from collections import deque
-from jinja2.utils import Markup
-from jinja2._compat import next, izip, with_metaclass, text_type, \
-     method_type, function_type
-
-
-#: the types we support for context functions
-_context_function_types = (function_type, method_type)
-
-
-_binop_to_func = {
-    '*':        operator.mul,
-    '/':        operator.truediv,
-    '//':       operator.floordiv,
-    '**':       operator.pow,
-    '%':        operator.mod,
-    '+':        operator.add,
-    '-':        operator.sub
-}
-
-_uaop_to_func = {
-    'not':      operator.not_,
-    '+':        operator.pos,
-    '-':        operator.neg
-}
-
-_cmpop_to_func = {
-    'eq':       operator.eq,
-    'ne':       operator.ne,
-    'gt':       operator.gt,
-    'gteq':     operator.ge,
-    'lt':       operator.lt,
-    'lteq':     operator.le,
-    'in':       lambda a, b: a in b,
-    'notin':    lambda a, b: a not in b
-}
-
-
-class Impossible(Exception):
-    """Raised if the node could not perform a requested action."""
-
-
-class NodeType(type):
-    """A metaclass for nodes that handles the field and attribute
-    inheritance.  fields and attributes from the parent class are
-    automatically forwarded to the child."""
-
-    def __new__(cls, name, bases, d):
-        for attr in 'fields', 'attributes':
-            storage = []
-            storage.extend(getattr(bases[0], attr, ()))
-            storage.extend(d.get(attr, ()))
-            assert len(bases) == 1, 'multiple inheritance not allowed'
-            assert len(storage) == len(set(storage)), 'layout conflict'
-            d[attr] = tuple(storage)
-        d.setdefault('abstract', False)
-        return type.__new__(cls, name, bases, d)
-
-
-class EvalContext(object):
-    """Holds evaluation time information.  Custom attributes can be attached
-    to it in extensions.
-    """
-
-    def __init__(self, environment, template_name=None):
-        self.environment = environment
-        if callable(environment.autoescape):
-            self.autoescape = environment.autoescape(template_name)
-        else:
-            self.autoescape = environment.autoescape
-        self.volatile = False
-
-    def save(self):
-        return self.__dict__.copy()
-
-    def revert(self, old):
-        self.__dict__.clear()
-        self.__dict__.update(old)
-
-
-def get_eval_context(node, ctx):
-    if ctx is None:
-        if node.environment is None:
-            raise RuntimeError('if no eval context is passed, the '
-                               'node must have an attached '
-                               'environment.')
-        return EvalContext(node.environment)
-    return ctx
-
-
-class Node(with_metaclass(NodeType, object)):
-    """Baseclass for all Jinja2 nodes.  There are a number of nodes available
-    of different types.  There are four major types:
-
-    -   :class:`Stmt`: statements
-    -   :class:`Expr`: expressions
-    -   :class:`Helper`: helper nodes
-    -   :class:`Template`: the outermost wrapper node
-
-    All nodes have fields and attributes.  Fields may be other nodes, lists,
-    or arbitrary values.  Fields are passed to the constructor as regular
-    positional arguments, attributes as keyword arguments.  Each node has
-    two attributes: `lineno` (the line number of the node) and `environment`.
-    The `environment` attribute is set at the end of the parsing process for
-    all nodes automatically.
-    """
-    fields = ()
-    attributes = ('lineno', 'environment')
-    abstract = True
-
-    def __init__(self, *fields, **attributes):
-        if self.abstract:
-            raise TypeError('abstract nodes are not instanciable')
-        if fields:
-            if len(fields) != len(self.fields):
-                if not self.fields:
-                    raise TypeError('%r takes 0 arguments' %
-                                    self.__class__.__name__)
-                raise TypeError('%r takes 0 or %d argument%s' % (
-                    self.__class__.__name__,
-                    len(self.fields),
-                    len(self.fields) != 1 and 's' or ''
-                ))
-            for name, arg in izip(self.fields, fields):
-                setattr(self, name, arg)
-        for attr in self.attributes:
-            setattr(self, attr, attributes.pop(attr, None))
-        if attributes:
-            raise TypeError('unknown attribute %r' %
-                            next(iter(attributes)))
-
-    def iter_fields(self, exclude=None, only=None):
-        """This method iterates over all fields that are defined and yields
-        ``(key, value)`` tuples.  Per default all fields are returned, but
-        it's possible to limit that to some fields by providing the `only`
-        parameter or to exclude some using the `exclude` parameter.  Both
-        should be sets or tuples of field names.
-        """
-        for name in self.fields:
-            if (exclude is only is None) or \
-               (exclude is not None and name not in exclude) or \
-               (only is not None and name in only):
-                try:
-                    yield name, getattr(self, name)
-                except AttributeError:
-                    pass
-
-    def iter_child_nodes(self, exclude=None, only=None):
-        """Iterates over all direct child nodes of the node.  This iterates
-        over all fields and yields the values of they are nodes.  If the value
-        of a field is a list all the nodes in that list are returned.
-        """
-        for field, item in self.iter_fields(exclude, only):
-            if isinstance(item, list):
-                for n in item:
-                    if isinstance(n, Node):
-                        yield n
-            elif isinstance(item, Node):
-                yield item
-
-    def find(self, node_type):
-        """Find the first node of a given type.  If no such node exists the
-        return value is `None`.
-        """
-        for result in self.find_all(node_type):
-            return result
-
-    def find_all(self, node_type):
-        """Find all the nodes of a given type.  If the type is a tuple,
-        the check is performed for any of the tuple items.
-        """
-        for child in self.iter_child_nodes():
-            if isinstance(child, node_type):
-                yield child
-            for result in child.find_all(node_type):
-                yield result
-
-    def set_ctx(self, ctx):
-        """Reset the context of a node and all child nodes.  Per default the
-        parser will all generate nodes that have a 'load' context as it's the
-        most common one.  This method is used in the parser to set assignment
-        targets and other nodes to a store context.
-        """
-        todo = deque([self])
-        while todo:
-            node = todo.popleft()
-            if 'ctx' in node.fields:
-                node.ctx = ctx
-            todo.extend(node.iter_child_nodes())
-        return self
-
-    def set_lineno(self, lineno, override=False):
-        """Set the line numbers of the node and children."""
-        todo = deque([self])
-        while todo:
-            node = todo.popleft()
-            if 'lineno' in node.attributes:
-                if node.lineno is None or override:
-                    node.lineno = lineno
-            todo.extend(node.iter_child_nodes())
-        return self
-
-    def set_environment(self, environment):
-        """Set the environment for all nodes."""
-        todo = deque([self])
-        while todo:
-            node = todo.popleft()
-            node.environment = environment
-            todo.extend(node.iter_child_nodes())
-        return self
-
-    def __eq__(self, other):
-        return type(self) is type(other) and \
-               tuple(self.iter_fields()) == tuple(other.iter_fields())
-
-    def __ne__(self, other):
-        return not self.__eq__(other)
-
-    # Restore Python 2 hashing behavior on Python 3
-    __hash__ = object.__hash__
-
-    def __repr__(self):
-        return '%s(%s)' % (
-            self.__class__.__name__,
-            ', '.join('%s=%r' % (arg, getattr(self, arg, None)) for
-                      arg in self.fields)
-        )
-
-
-class Stmt(Node):
-    """Base node for all statements."""
-    abstract = True
-
-
-class Helper(Node):
-    """Nodes that exist in a specific context only."""
-    abstract = True
-
-
-class Template(Node):
-    """Node that represents a template.  This must be the outermost node that
-    is passed to the compiler.
-    """
-    fields = ('body',)
-
-
-class Output(Stmt):
-    """A node that holds multiple expressions which are then printed out.
-    This is used both for the `print` statement and the regular template data.
-    """
-    fields = ('nodes',)
-
-
-class Extends(Stmt):
-    """Represents an extends statement."""
-    fields = ('template',)
-
-
-class For(Stmt):
-    """The for loop.  `target` is the target for the iteration (usually a
-    :class:`Name` or :class:`Tuple`), `iter` the iterable.  `body` is a list
-    of nodes that are used as loop-body, and `else_` a list of nodes for the
-    `else` block.  If no else node exists it has to be an empty list.
-
-    For filtered nodes an expression can be stored as `test`, otherwise `None`.
-    """
-    fields = ('target', 'iter', 'body', 'else_', 'test', 'recursive')
-
-
-class If(Stmt):
-    """If `test` is true, `body` is rendered, else `else_`."""
-    fields = ('test', 'body', 'else_')
-
-
-class Macro(Stmt):
-    """A macro definition.  `name` is the name of the macro, `args` a list of
-    arguments and `defaults` a list of defaults if there are any.  `body` is
-    a list of nodes for the macro body.
-    """
-    fields = ('name', 'args', 'defaults', 'body')
-
-
-class CallBlock(Stmt):
-    """Like a macro without a name but a call instead.  `call` is called with
-    the unnamed macro as `caller` argument this node holds.
-    """
-    fields = ('call', 'args', 'defaults', 'body')
-
-
-class FilterBlock(Stmt):
-    """Node for filter sections."""
-    fields = ('body', 'filter')
-
-
-class Block(Stmt):
-    """A node that represents a block."""
-    fields = ('name', 'body', 'scoped')
-
-
-class Include(Stmt):
-    """A node that represents the include tag."""
-    fields = ('template', 'with_context', 'ignore_missing')
-
-
-class Import(Stmt):
-    """A node that represents the import tag."""
-    fields = ('template', 'target', 'with_context')
-
-
-class FromImport(Stmt):
-    """A node that represents the from import tag.  It's important to not
-    pass unsafe names to the name attribute.  The compiler translates the
-    attribute lookups directly into getattr calls and does *not* use the
-    subscript callback of the interface.  As exported variables may not
-    start with double underscores (which the parser asserts) this is not a
-    problem for regular Jinja code, but if this node is used in an extension
-    extra care must be taken.
-
-    The list of names may contain tuples if aliases are wanted.
-    """
-    fields = ('template', 'names', 'with_context')
-
-
-class ExprStmt(Stmt):
-    """A statement that evaluates an expression and discards the result."""
-    fields = ('node',)
-
-
-class Assign(Stmt):
-    """Assigns an expression to a target."""
-    fields = ('target', 'node')
-
-
-class Expr(Node):
-    """Baseclass for all expressions."""
-    abstract = True
-
-    def as_const(self, eval_ctx=None):
-        """Return the value of the expression as constant or raise
-        :exc:`Impossible` if this was not possible.
-
-        An :class:`EvalContext` can be provided, if none is given
-        a default context is created which requires the nodes to have
-        an attached environment.
-
-        .. versionchanged:: 2.4
-           the `eval_ctx` parameter was added.
-        """
-        raise Impossible()
-
-    def can_assign(self):
-        """Check if it's possible to assign something to this node."""
-        return False
-
-
-class BinExpr(Expr):
-    """Baseclass for all binary expressions."""
-    fields = ('left', 'right')
-    operator = None
-    abstract = True
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        # intercepted operators cannot be folded at compile time
-        if self.environment.sandboxed and \
-           self.operator in self.environment.intercepted_binops:
-            raise Impossible()
-        f = _binop_to_func[self.operator]
-        try:
-            return f(self.left.as_const(eval_ctx), self.right.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
-
-
-class UnaryExpr(Expr):
-    """Baseclass for all unary expressions."""
-    fields = ('node',)
-    operator = None
-    abstract = True
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        # intercepted operators cannot be folded at compile time
-        if self.environment.sandboxed and \
-           self.operator in self.environment.intercepted_unops:
-            raise Impossible()
-        f = _uaop_to_func[self.operator]
-        try:
-            return f(self.node.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
-
-
-class Name(Expr):
-    """Looks up a name or stores a value in a name.
-    The `ctx` of the node can be one of the following values:
-
-    -   `store`: store a value in the name
-    -   `load`: load that name
-    -   `param`: like `store` but if the name was defined as function parameter.
-    """
-    fields = ('name', 'ctx')
-
-    def can_assign(self):
-        return self.name not in ('true', 'false', 'none',
-                                 'True', 'False', 'None')
-
-
-class Literal(Expr):
-    """Baseclass for literals."""
-    abstract = True
-
-
-class Const(Literal):
-    """All constant values.  The parser will return this node for simple
-    constants such as ``42`` or ``"foo"`` but it can be used to store more
-    complex values such as lists too.  Only constants with a safe
-    representation (objects where ``eval(repr(x)) == x`` is true).
-    """
-    fields = ('value',)
-
-    def as_const(self, eval_ctx=None):
-        return self.value
-
-    @classmethod
-    def from_untrusted(cls, value, lineno=None, environment=None):
-        """Return a const object if the value is representable as
-        constant value in the generated code, otherwise it will raise
-        an `Impossible` exception.
-        """
-        from .compiler import has_safe_repr
-        if not has_safe_repr(value):
-            raise Impossible()
-        return cls(value, lineno=lineno, environment=environment)
-
-
-class TemplateData(Literal):
-    """A constant template string."""
-    fields = ('data',)
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        if eval_ctx.volatile:
-            raise Impossible()
-        if eval_ctx.autoescape:
-            return Markup(self.data)
-        return self.data
-
-
-class Tuple(Literal):
-    """For loop unpacking and some other things like multiple arguments
-    for subscripts.  Like for :class:`Name` `ctx` specifies if the tuple
-    is used for loading the names or storing.
-    """
-    fields = ('items', 'ctx')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return tuple(x.as_const(eval_ctx) for x in self.items)
-
-    def can_assign(self):
-        for item in self.items:
-            if not item.can_assign():
-                return False
-        return True
-
-
-class List(Literal):
-    """Any list literal such as ``[1, 2, 3]``"""
-    fields = ('items',)
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return [x.as_const(eval_ctx) for x in self.items]
-
-
-class Dict(Literal):
-    """Any dict literal such as ``{1: 2, 3: 4}``.  The items must be a list of
-    :class:`Pair` nodes.
-    """
-    fields = ('items',)
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return dict(x.as_const(eval_ctx) for x in self.items)
-
-
-class Pair(Helper):
-    """A key, value pair for dicts."""
-    fields = ('key', 'value')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return self.key.as_const(eval_ctx), self.value.as_const(eval_ctx)
-
-
-class Keyword(Helper):
-    """A key, value pair for keyword arguments where key is a string."""
-    fields = ('key', 'value')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return self.key, self.value.as_const(eval_ctx)
-
-
-class CondExpr(Expr):
-    """A conditional expression (inline if expression).  (``{{
-    foo if bar else baz }}``)
-    """
-    fields = ('test', 'expr1', 'expr2')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        if self.test.as_const(eval_ctx):
-            return self.expr1.as_const(eval_ctx)
-
-        # if we evaluate to an undefined object, we better do that at runtime
-        if self.expr2 is None:
-            raise Impossible()
-
-        return self.expr2.as_const(eval_ctx)
-
-
-class Filter(Expr):
-    """This node applies a filter on an expression.  `name` is the name of
-    the filter, the rest of the fields are the same as for :class:`Call`.
-
-    If the `node` of a filter is `None` the contents of the last buffer are
-    filtered.  Buffers are created by macros and filter blocks.
-    """
-    fields = ('node', 'name', 'args', 'kwargs', 'dyn_args', 'dyn_kwargs')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        if eval_ctx.volatile or self.node is None:
-            raise Impossible()
-        # we have to be careful here because we call filter_ below.
-        # if this variable would be called filter, 2to3 would wrap the
-        # call in a list beause it is assuming we are talking about the
-        # builtin filter function here which no longer returns a list in
-        # python 3.  because of that, do not rename filter_ to filter!
-        filter_ = self.environment.filters.get(self.name)
-        if filter_ is None or getattr(filter_, 'contextfilter', False):
-            raise Impossible()
-        obj = self.node.as_const(eval_ctx)
-        args = [x.as_const(eval_ctx) for x in self.args]
-        if getattr(filter_, 'evalcontextfilter', False):
-            args.insert(0, eval_ctx)
-        elif getattr(filter_, 'environmentfilter', False):
-            args.insert(0, self.environment)
-        kwargs = dict(x.as_const(eval_ctx) for x in self.kwargs)
-        if self.dyn_args is not None:
-            try:
-                args.extend(self.dyn_args.as_const(eval_ctx))
-            except Exception:
-                raise Impossible()
-        if self.dyn_kwargs is not None:
-            try:
-                kwargs.update(self.dyn_kwargs.as_const(eval_ctx))
-            except Exception:
-                raise Impossible()
-        try:
-            return filter_(obj, *args, **kwargs)
-        except Exception:
-            raise Impossible()
-
-
-class Test(Expr):
-    """Applies a test on an expression.  `name` is the name of the test, the
-    rest of the fields are the same as for :class:`Call`.
-    """
-    fields = ('node', 'name', 'args', 'kwargs', 'dyn_args', 'dyn_kwargs')
-
-
-class Call(Expr):
-    """Calls an expression.  `args` is a list of arguments, `kwargs` a list
-    of keyword arguments (list of :class:`Keyword` nodes), and `dyn_args`
-    and `dyn_kwargs` has to be either `None` or a node that is used as
-    node for dynamic positional (``*args``) or keyword (``**kwargs``)
-    arguments.
-    """
-    fields = ('node', 'args', 'kwargs', 'dyn_args', 'dyn_kwargs')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        if eval_ctx.volatile:
-            raise Impossible()
-        obj = self.node.as_const(eval_ctx)
-
-        # don't evaluate context functions
-        args = [x.as_const(eval_ctx) for x in self.args]
-        if isinstance(obj, _context_function_types):
-            if getattr(obj, 'contextfunction', False):
-                raise Impossible()
-            elif getattr(obj, 'evalcontextfunction', False):
-                args.insert(0, eval_ctx)
-            elif getattr(obj, 'environmentfunction', False):
-                args.insert(0, self.environment)
-
-        kwargs = dict(x.as_const(eval_ctx) for x in self.kwargs)
-        if self.dyn_args is not None:
-            try:
-                args.extend(self.dyn_args.as_const(eval_ctx))
-            except Exception:
-                raise Impossible()
-        if self.dyn_kwargs is not None:
-            try:
-                kwargs.update(self.dyn_kwargs.as_const(eval_ctx))
-            except Exception:
-                raise Impossible()
-        try:
-            return obj(*args, **kwargs)
-        except Exception:
-            raise Impossible()
-
-
-class Getitem(Expr):
-    """Get an attribute or item from an expression and prefer the item."""
-    fields = ('node', 'arg', 'ctx')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        if self.ctx != 'load':
-            raise Impossible()
-        try:
-            return self.environment.getitem(self.node.as_const(eval_ctx),
-                                            self.arg.as_const(eval_ctx))
-        except Exception:
-            raise Impossible()
-
-    def can_assign(self):
-        return False
-
-
-class Getattr(Expr):
-    """Get an attribute or item from an expression that is a ascii-only
-    bytestring and prefer the attribute.
-    """
-    fields = ('node', 'attr', 'ctx')
-
-    def as_const(self, eval_ctx=None):
-        if self.ctx != 'load':
-            raise Impossible()
-        try:
-            eval_ctx = get_eval_context(self, eval_ctx)
-            return self.environment.getattr(self.node.as_const(eval_ctx),
-                                            self.attr)
-        except Exception:
-            raise Impossible()
-
-    def can_assign(self):
-        return False
-
-
-class Slice(Expr):
-    """Represents a slice object.  This must only be used as argument for
-    :class:`Subscript`.
-    """
-    fields = ('start', 'stop', 'step')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        def const(obj):
-            if obj is None:
-                return None
-            return obj.as_const(eval_ctx)
-        return slice(const(self.start), const(self.stop), const(self.step))
-
-
-class Concat(Expr):
-    """Concatenates the list of expressions provided after converting them to
-    unicode.
-    """
-    fields = ('nodes',)
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return ''.join(text_type(x.as_const(eval_ctx)) for x in self.nodes)
-
-
-class Compare(Expr):
-    """Compares an expression with some other expressions.  `ops` must be a
-    list of :class:`Operand`\s.
-    """
-    fields = ('expr', 'ops')
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        result = value = self.expr.as_const(eval_ctx)
-        try:
-            for op in self.ops:
-                new_value = op.expr.as_const(eval_ctx)
-                result = _cmpop_to_func[op.op](value, new_value)
-                value = new_value
-        except Exception:
-            raise Impossible()
-        return result
-
-
-class Operand(Helper):
-    """Holds an operator and an expression."""
-    fields = ('op', 'expr')
-
-if __debug__:
-    Operand.__doc__ += '\nThe following operators are available: ' + \
-        ', '.join(sorted('``%s``' % x for x in set(_binop_to_func) |
-                  set(_uaop_to_func) | set(_cmpop_to_func)))
-
-
-class Mul(BinExpr):
-    """Multiplies the left with the right node."""
-    operator = '*'
-
-
-class Div(BinExpr):
-    """Divides the left by the right node."""
-    operator = '/'
-
-
-class FloorDiv(BinExpr):
-    """Divides the left by the right node and truncates conver the
-    result into an integer by truncating.
-    """
-    operator = '//'
-
-
-class Add(BinExpr):
-    """Add the left to the right node."""
-    operator = '+'
-
-
-class Sub(BinExpr):
-    """Substract the right from the left node."""
-    operator = '-'
-
-
-class Mod(BinExpr):
-    """Left modulo right."""
-    operator = '%'
-
-
-class Pow(BinExpr):
-    """Left to the power of right."""
-    operator = '**'
-
-
-class And(BinExpr):
-    """Short circuited AND."""
-    operator = 'and'
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return self.left.as_const(eval_ctx) and self.right.as_const(eval_ctx)
-
-
-class Or(BinExpr):
-    """Short circuited OR."""
-    operator = 'or'
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return self.left.as_const(eval_ctx) or self.right.as_const(eval_ctx)
-
-
-class Not(UnaryExpr):
-    """Negate the expression."""
-    operator = 'not'
-
-
-class Neg(UnaryExpr):
-    """Make the expression negative."""
-    operator = '-'
-
-
-class Pos(UnaryExpr):
-    """Make the expression positive (noop for most expressions)"""
-    operator = '+'
-
-
-# Helpers for extensions
-
-
-class EnvironmentAttribute(Expr):
-    """Loads an attribute from the environment object.  This is useful for
-    extensions that want to call a callback stored on the environment.
-    """
-    fields = ('name',)
-
-
-class ExtensionAttribute(Expr):
-    """Returns the attribute of an extension bound to the environment.
-    The identifier is the identifier of the :class:`Extension`.
-
-    This node is usually constructed by calling the
-    :meth:`~jinja2.ext.Extension.attr` method on an extension.
-    """
-    fields = ('identifier', 'name')
-
-
-class ImportedName(Expr):
-    """If created with an import name the import name is returned on node
-    access.  For example ``ImportedName('cgi.escape')`` returns the `escape`
-    function from the cgi module on evaluation.  Imports are optimized by the
-    compiler so there is no need to assign them to local variables.
-    """
-    fields = ('importname',)
-
-
-class InternalName(Expr):
-    """An internal name in the compiler.  You cannot create these nodes
-    yourself but the parser provides a
-    :meth:`~jinja2.parser.Parser.free_identifier` method that creates
-    a new identifier for you.  This identifier is not available from the
-    template and is not threated specially by the compiler.
-    """
-    fields = ('name',)
-
-    def __init__(self):
-        raise TypeError('Can\'t create internal names.  Use the '
-                        '`free_identifier` method on a parser.')
-
-
-class MarkSafe(Expr):
-    """Mark the wrapped expression as safe (wrap it as `Markup`)."""
-    fields = ('expr',)
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        return Markup(self.expr.as_const(eval_ctx))
-
-
-class MarkSafeIfAutoescape(Expr):
-    """Mark the wrapped expression as safe (wrap it as `Markup`) but
-    only if autoescaping is active.
-
-    .. versionadded:: 2.5
-    """
-    fields = ('expr',)
-
-    def as_const(self, eval_ctx=None):
-        eval_ctx = get_eval_context(self, eval_ctx)
-        if eval_ctx.volatile:
-            raise Impossible()
-        expr = self.expr.as_const(eval_ctx)
-        if eval_ctx.autoescape:
-            return Markup(expr)
-        return expr
-
-
-class ContextReference(Expr):
-    """Returns the current template context.  It can be used like a
-    :class:`Name` node, with a ``'load'`` ctx and will return the
-    current :class:`~jinja2.runtime.Context` object.
-
-    Here an example that assigns the current template name to a
-    variable named `foo`::
-
-        Assign(Name('foo', ctx='store'),
-               Getattr(ContextReference(), 'name'))
-    """
-
-
-class Continue(Stmt):
-    """Continue a loop."""
-
-
-class Break(Stmt):
-    """Break a loop."""
-
-
-class Scope(Stmt):
-    """An artificial scope."""
-    fields = ('body',)
-
-
-class EvalContextModifier(Stmt):
-    """Modifies the eval context.  For each option that should be modified,
-    a :class:`Keyword` has to be added to the :attr:`options` list.
-
-    Example to change the `autoescape` setting::
-
-        EvalContextModifier(options=[Keyword('autoescape', Const(True))])
-    """
-    fields = ('options',)
-
-
-class ScopedEvalContextModifier(EvalContextModifier):
-    """Modifies the eval context and reverts it later.  Works exactly like
-    :class:`EvalContextModifier` but will only modify the
-    :class:`~jinja2.nodes.EvalContext` for nodes in the :attr:`body`.
-    """
-    fields = ('body',)
-
-
-# make sure nobody creates custom nodes
-def _failing_new(*args, **kwargs):
-    raise TypeError('can\'t create custom node types')
-NodeType.__new__ = staticmethod(_failing_new); del _failing_new