Python ast.Mod() Examples

def visit_BinOp(self, node):
    # Examples:
    #   BinOp(left=Bytes(s=b'%4x'), op=Mod(), right=Num(n=10))
    #   BinOp(left=Call(func=Name(id='bytearray', ctx=Load()), args=[Bytes(s=b'%x')], keywords=[]),
    #         op=Mod(), right=Num(n=10))
    if (hasattr(ast, "Bytes") and isinstance(node.left, ast.Bytes))\
       and isinstance(node.op, ast.Mod):
      self.__bytes_format = True
      self.__vvprint("bytes `%` formatting requires 3.5+ (or 2.6+ as `str` synonym)")

    if (isinstance(node.left, ast.Call) and isinstance(node.left.func, ast.Name) and
         node.left.func.id == "bytearray") and isinstance(node.op, ast.Mod):
      self.__bytearray_format = True
      self.__vvprint("bytearray `%` formatting requires 3.5+")

    self.generic_visit(node) 

def visit_AugAssign(self, node):
        # XXX apparently no signed context required for augmented assigns
        left, op, right = node.target, node.op, node.value
        isFunc = False
        pre, suf = "", ""
        if isinstance(op, (ast.Add, ast.Sub, ast.Mult, ast.Mod, ast.FloorDiv)):
            pre, suf = self.inferBinaryOpCast(node, left, right, op)
        elif isinstance(op, (ast.LShift, ast.RShift)):
            isFunc = True
            pre, suf = self.inferShiftOpCast(node, left, right, op)
        self.visit(left)
        self.write(" := ")
        self.write(pre)
        if isFunc:
            self.write("%s(" % opmap[type(op)])
        self.visit(left)
        if isFunc:
            self.write(", ")
        else:
            self.write(" %s " % opmap[type(op)])
        self.visit(right)
        if isFunc:
            self.write(")")
        self.write(suf)
        self.write(";") 

def __build_unconditional_arg_check(self, argname, argtype):

		presence_check = ast.Call(func = ast.Name(id='isinstance', ctx=ast.Load()),
				args         = [ast.Name(id=argname, ctx=ast.Load()), argtype],
				keywords     = [],
				lineno       = self.__get_line())

		types = [t.id for t in argtype.elts]
		check_message = ast.BinOp(
				left         = ast.Str(s='Argument \'{}\' must be of type \'{}\'. Received type: \'%s\''.format(argname, types)),
				op           = ast.Mod(),
				right        = ast.Call(func=ast.Name(id='type', ctx=ast.Load()), args=[ast.Name(id=argname, ctx=ast.Load())], keywords=[]),
				lineno       = self.__get_line())

		new_ret = ast.Assert(
			test         = presence_check,
			msg          = check_message,
			lineno       = self.__get_line())


		return new_ret 

def term_rewrite(head, tail):
    if tail:
        for op, each in tail:
            head = ast.BinOp(
                head,
                {
                    '*': ast.Mult,
                    '@': ast.MatMult,
                    '%': ast.Mod,
                    '//': ast.FloorDiv,
                    '/': ast.Div
                }[op.value](),
                each,
                **loc @ op,
            )
    return head 

def augassign_rewrite(it: Tokenizer):
    return {
        '+=': ast.Add,
        '-=': ast.Sub,
        '*=': ast.Mult,
        '/=': ast.Div,
        '//=': ast.FloorDiv,
        '@=': ast.MatMult,
        '%=': ast.Mod,
        '&=': ast.BitAnd,
        '|=': ast.BitOr,
        '^=': ast.BitXor,
        '<<=': ast.LShift,
        '>>=': ast.RShift,
        '**=': ast.Pow,
    }[it.value] 

def visit_BinOp(self, node):
        'If node is a constant expression, replace it with its evaluated value'
        if node in self.constexpr:
            # evaluation
            fake_node = ast.Expression(ast.BinOp(node, ast.Mod(),
                                                 ast.Num(self.mod)))
            ast.fix_missing_locations(fake_node)
            code = compile(fake_node, '<constant folding>', 'eval')
            obj_env = globals().copy()
            exec code in obj_env
            value = eval(code, obj_env)

            new_node = ast.Num(value)
            return new_node
        else:
            return self.generic_visit(node) 

def visit_UnaryOp(self, node):
        'Same idea as visit_BinOp'
        if node in self.constexpr:
            # evaluation
            fake_node = ast.Expression(ast.BinOp(node, ast.Mod(),
                                                 ast.Num(self.mod)))
            ast.fix_missing_locations(fake_node)
            code = compile(fake_node, '<constant folding>', 'eval')
            obj_env = globals().copy()
            exec code in obj_env

            value = eval(code, obj_env)
            new_node = ast.Num(value)
            return new_node
        else:
            return self.generic_visit(node) 

def pop_format_context(self, expl_expr):
        """Format the %-formatted string with current format context.

        The expl_expr should be an ast.Str instance constructed from
        the %-placeholders created by .explanation_param().  This will
        add the required code to format said string to .expl_stmts and
        return the ast.Name instance of the formatted string.

        """
        current = self.stack.pop()
        if self.stack:
            self.explanation_specifiers = self.stack[-1]
        keys = [ast.Str(key) for key in current.keys()]
        format_dict = ast.Dict(keys, list(current.values()))
        form = ast.BinOp(expl_expr, ast.Mod(), format_dict)
        name = "@py_format" + str(next(self.variable_counter))
        if self.enable_assertion_pass_hook:
            self.format_variables.append(name)
        self.expl_stmts.append(ast.Assign([ast.Name(name, ast.Store())], form))
        return ast.Name(name, ast.Load()) 

def pop_format_context(self, expl_expr):
        """Format the %-formatted string with current format context.

        The expl_expr should be an ast.Str instance constructed from
        the %-placeholders created by .explanation_param().  This will
        add the required code to format said string to .expl_stmts and
        return the ast.Name instance of the formatted string.

        """
        current = self.stack.pop()
        if self.stack:
            self.explanation_specifiers = self.stack[-1]
        keys = [ast.Str(key) for key in current.keys()]
        format_dict = ast.Dict(keys, list(current.values()))
        form = ast.BinOp(expl_expr, ast.Mod(), format_dict)
        name = "@py_format" + str(next(self.variable_counter))
        if self.enable_assertion_pass_hook:
            self.format_variables.append(name)
        self.expl_stmts.append(ast.Assign([ast.Name(name, ast.Store())], form))
        return ast.Name(name, ast.Load()) 

def visit_BinOp(self, node):
        if isinstance(node.op, ast.Mod) and self.context == _context.PRINT:
            self.visit(node.left)
            self.write(", ")
            self.visit(node.right)
        else:
            if isinstance(node.op, ast.RShift):
                # Additional cast to signed of the full expression
                # this is apparently required by cver - not sure if it
                # is actually required by standard Verilog.
                # It shouldn't hurt however.
                if node.signed:
                    self.write("$signed")
            self.context = None
            if node.signed:
                self.context = _context.SIGNED
            self.write("(")
            self.visit(node.left)
            self.write(" %s " % opmap[type(node.op)])
            self.visit(node.right)
            self.write(")")
            self.context = None 

def transform2call(var):
    if isinstance(var, ast.BinOp):
        is_mod = isinstance(var.op, ast.Mod)
        is_left_str = isinstance(var.left, ast.Str)
        if is_mod and is_left_str:
            new_call = ast.Call()
            new_call.args = []
            new_call.args = []
            if six.PY2:
                new_call.starargs = None
            new_call.keywords = None
            if six.PY2:
                new_call.kwargs = None
            new_call.lineno = var.lineno
            new_call.func = ast.Attribute()
            new_call.func.value = var.left
            new_call.func.attr = 'format'
            if isinstance(var.right, ast.Tuple):
                new_call.args = var.right.elts
            elif six.PY2 and isinstance(var.right, ast.Dict):
                new_call.kwargs = var.right
            else:
                new_call.args = [var.right]
            return new_call 

def pop_format_context(self, expl_expr: ast.expr) -> ast.Name:
        """Format the %-formatted string with current format context.

        The expl_expr should be an str ast.expr instance constructed from
        the %-placeholders created by .explanation_param().  This will
        add the required code to format said string to .expl_stmts and
        return the ast.Name instance of the formatted string.

        """
        current = self.stack.pop()
        if self.stack:
            self.explanation_specifiers = self.stack[-1]
        keys = [ast.Str(key) for key in current.keys()]
        format_dict = ast.Dict(keys, list(current.values()))
        form = ast.BinOp(expl_expr, ast.Mod(), format_dict)
        name = "@py_format" + str(next(self.variable_counter))
        if self.enable_assertion_pass_hook:
            self.format_variables.append(name)
        self.expl_stmts.append(ast.Assign([ast.Name(name, ast.Store())], form))
        return ast.Name(name, ast.Load()) 

def BINOP(self, node):
        if (
                isinstance(node.op, ast.Mod) and
                isinstance(node.left, ast.Str)
        ):
            self._handle_percent_format(node)
        self.handleChildren(node) 

def __build_conditional_arg_check(self, argname, argtype):

		target_value = ast.Subscript(
							value=ast.Name(id='kwargs', ctx=ast.Load()),
							slice=ast.Index(ast.Str(s=argname)),
							ctx=ast.Load()
							)

		presence_check = ast.Call(func = ast.Name(id='isinstance', ctx=ast.Load()),
				args         = [target_value, argtype],
				keywords     = [],
				lineno       = self.__get_line())

		# Assumes that argtype is a ast.Tuple of ast.Name items
		types = [t.id for t in argtype.elts]

		check_message = ast.BinOp(
				left         = ast.Str(s='Optional argument \'{}\' must be of type \'{}\'. Received type: \'%s\''.format(argname, types)),
				op           = ast.Mod(),
				right        = ast.Call(func=ast.Name(id='type', ctx=ast.Load()), args=[target_value], keywords=[]),
				lineno       = self.__get_line())

		assert_check = ast.Assert(
			test         = presence_check,
			msg          = check_message,
			lineno       = self.__get_line())

		check_body = [assert_check]

		check = ast.Compare(left=ast.Str(s=argname, ctx=ast.Load()), ops=[ast.In()], comparators=[ast.Name(id='kwargs', ctx=ast.Load())])

		new_ret = ast.If(
			test   = check,
			body   = check_body,
			orelse = [],
			lineno = self.__get_line())

		return new_ret 

def binop(self, block, node, var=None):
    if var is None:
      var = self.add_variable(None)
    left = self.expression(block, node.left)
    right = self.expression(block, node.right)
    if isinstance(node.op, ast.Add):
      op = Operator.add
    elif isinstance(node.op, ast.Sub):
      op = Operator.subtract
    elif isinstance(node.op, ast.Mult):
      op = Operator.multiply
    elif isinstance(node.op, ast.Div):
      op = Operator.divide
    elif isinstance(node.op, ast.FloorDiv):
      op = Operator.divide_int
    elif isinstance(node.op, ast.Mod):
      op = Operator.mod
    elif isinstance(node.op, ast.Pow):
      op = Operator.pow
    elif isinstance(node.op, ast.BitAnd):
      op = Operator.bit_and
    elif isinstance(node.op, ast.BitOr):
      op = Operator.bit_or
    elif isinstance(node.op, ast.BitXor):
      op = Operator.bit_xor
    elif isinstance(node.op, ast.LShift):
      op = Operator.shift_left
    elif isinstance(node.op, ast.RShift):
      op = Operator.shift_right
    else:
      raise Exception('Unexpected BinOp (%s)'%(node.op.__class__))
    operation = BinaryOperation(left, op, right)
    assignment = Assignment(var, operation)
    block.add(assignment)
    return var

  #Parses a unary uperation (AST UnaryOp) 

def p_augassign_5(p):
    '''augassign : PERCENTEQUAL'''
    #                         1
    p[0] = ast.Mod(rule=inspect.currentframe().f_code.co_name, **p[1][1]) 

def p_term_star_3(p):
    '''term_star : PERCENT factor'''
    #                    1      2
    p[0] = [ast.Mod(rule=inspect.currentframe().f_code.co_name, **p[1][1]), p[2]] 

def p_term_star_7(p):
    '''term_star : term_star PERCENT factor'''
    #                      1       2      3
    p[0] = p[1] + [ast.Mod(rule=inspect.currentframe().f_code.co_name, **p[2][1]), p[3]] 

def mod_operator(d: ast.Mod):
    return "%" 

def visit_BinOp(self, node: ast.BinOp) -> Any:
        """Recursively visit the left and right operand, respectively, and apply the operation on the results."""
        # pylint: disable=too-many-branches
        left = self.visit(node=node.left)
        right = self.visit(node=node.right)

        if isinstance(node.op, ast.Add):
            result = left + right
        elif isinstance(node.op, ast.Sub):
            result = left - right
        elif isinstance(node.op, ast.Mult):
            result = left * right
        elif isinstance(node.op, ast.Div):
            result = left / right
        elif isinstance(node.op, ast.FloorDiv):
            result = left // right
        elif isinstance(node.op, ast.Mod):
            result = left % right
        elif isinstance(node.op, ast.Pow):
            result = left**right
        elif isinstance(node.op, ast.LShift):
            result = left << right
        elif isinstance(node.op, ast.RShift):
            result = left >> right
        elif isinstance(node.op, ast.BitOr):
            result = left | right
        elif isinstance(node.op, ast.BitXor):
            result = left ^ right
        elif isinstance(node.op, ast.BitAnd):
            result = left & right
        elif isinstance(node.op, ast.MatMult):
            result = left @ right
        else:
            raise NotImplementedError("Unhandled op of {}: {}".format(node, node.op))

        self.recomputed_values[node] = result
        return result 

def _get_value(self, node):
        """Get mock.patch string argument regexp.

        It is either a string (if we are lucky), string-format of
        ("%s.something" % GVAL) or (GVAL + ".something")
        """
        val = None
        if isinstance(node, ast.Str):
            val = node.s
        elif isinstance(node, ast.BinOp):
            if pairwise_isinstance(
                    (node.op, ast.Mod), (node.left, ast.Str),
                    (node.right, ast.Name)):
                val = node.left.s % self.globals_[node.right.id]
            elif pairwise_isinstance(
                    (node.op, ast.Add), (node.left, ast.Name),
                    (node.right, ast.Str)):
                val = self.globals_[node.left.id] + node.right.s
        elif isinstance(node, ast.Name):
            val = self.globals_[node.id]

        if val is None:
            raise ValueError(
                "Unable to find value in %s, only the following are parsed: "
                "GLOBAL, 'pkg.foobar', '%%s.foobar' %% GLOBAL or 'GLOBAL + "
                "'.foobar'"
                % ast.dump(node))

        return val 

def visit_Call(self, node):
        """iX(Y) -> ExprIntX(Y),
        'X'(Y) -> ExprOp('X', Y), ('X' % Y)(Z) -> ExprOp('X' % Y, Z)"""

        # Recursive visit
        node = self.generic_visit(node)
        if isinstance(node.func, ast.Name):
            # iX(Y) -> ExprInt(Y, X)
            fc_name = node.func.id

            # Match the function name
            new_name = fc_name
            integer = self.parse_integer.search(fc_name)

            # Do replacement
            if integer is not None:
                size = int(integer.groups()[0])
                new_name = "ExprInt"
                # Replace in the node
                node.func.id = new_name
                node.args.append(ast.Num(n=size))

        elif (isinstance(node.func, ast.Str) or
              (isinstance(node.func, ast.BinOp) and
               isinstance(node.func.op, ast.Mod) and
               isinstance(node.func.left, ast.Str))):
            # 'op'(args...) -> ExprOp('op', args...)
            # ('op' % (fmt))(args...) -> ExprOp('op' % (fmt), args...)
            op_name = node.func

            # Do replacement
            node.func = ast.Name(id="ExprOp", ctx=ast.Load())
            node.args[0:0] = [op_name]

        return node 

def __init__( s, component ):
    super().__init__( component )
    s.loop_var_env = set()
    s.tmp_var_env = set()

    # opmap maps an ast operator to its RTLIR counterpart.
    s.opmap = {
      # Bool operators
      # Note: we do not support boolean operators because Python does
      # not allow overloading And and Or operators. Using them in
      # expressions might lead to inconsistent semantics.
      # ast.And    : bir.And(),       ast.Or     : bir.Or(),
      # Unary operators
      # Note: ast.Not is disallowed because it is a boolean operator
      # ast.Not    : bir.Not(),
      ast.Invert : bir.Invert(),
      ast.UAdd   : bir.UAdd(),      ast.USub   : bir.USub(),
      # Binary operators
      ast.Add    : bir.Add(),       ast.Sub    : bir.Sub(),
      ast.Mult   : bir.Mult(),      ast.Div    : bir.Div(),
      ast.Mod    : bir.Mod(),       ast.Pow    : bir.Pow(),
      ast.LShift : bir.ShiftLeft(), ast.RShift : bir.ShiftRightLogic(),
      ast.BitOr  : bir.BitOr(),     ast.BitAnd : bir.BitAnd(),
      ast.BitXor : bir.BitXor(),
      # Compare bir.bir.operators
      ast.Eq     : bir.Eq(),        ast.NotEq  : bir.NotEq(),
      ast.Lt     : bir.Lt(),        ast.LtE    : bir.LtE(),
      ast.Gt     : bir.Gt(),        ast.GtE    : bir.GtE()
    }

  # Override 

def visit_BinOp(self, node: ast.BinOp) -> None:
        if isinstance(node.op, ast.Mod) and isinstance(node.left, ast.Str):
            try:
                parsed = parse_percent_format(node.left.s)
            except ValueError:
                pass
            else:
                for _, fmt in parsed:
                    if not fmt:
                        continue
                    key, conversion_flag, width, precision, conversion = fmt
                    # timid: these require out-of-order parameter consumption
                    if width == '*' or precision == '.*':
                        break
                    # these conversions require modification of parameters
                    if conversion in {'d', 'i', 'u', 'c'}:
                        break
                    # timid: py2: %#o formats different from {:#o} (--py3?)
                    if '#' in (conversion_flag or '') and conversion == 'o':
                        break
                    # no equivalent in format
                    if key == '':
                        break
                    # timid: py2: conversion is subject to modifiers (--py3?)
                    nontrivial_fmt = any((conversion_flag, width, precision))
                    if conversion == '%' and nontrivial_fmt:
                        break
                    # no equivalent in format
                    if conversion in {'a', 'r'} and nontrivial_fmt:
                        break
                    # all dict substitutions must be named
                    if isinstance(node.right, ast.Dict) and not key:
                        break
                else:
                    self.found[_ast_to_offset(node)] = node
        self.generic_visit(node) 

def visit_BinOp(self, node):
        self.generic_visit(node)
        if isinstance(node.op, (ast.LShift, ast.RShift)):
            self.inferShiftType(node)
        elif isinstance(node.op, (ast.BitAnd, ast.BitOr, ast.BitXor)):
            self.inferBitOpType(node)
        elif isinstance(node.op, ast.Mod) and isinstance(node.left, ast.Str):  # format string
            pass
        else:
            self.inferBinOpType(node) 

def _expr(expr):
    node = type(expr)

    if node is ast.Name:
        return _build_atomic(expr.id)

    if node is ast.Call:
        args = _parse_args(expr.args)
        kwargs = _parse_kwargs(expr.keywords)
        return _build_predicate(expr.func.id, args, kwargs)

    if node is ast.Subscript:
        field_expr = expr.slice.value

        if type(field_expr) is ast.Tuple:
            field_expr = field_expr.elts
        else:
            field_expr = (field_expr,)

        base = _expr(expr.value)
        base['fields'] = [_expr(e) for e in field_expr]
        return base

    if node is ast.BinOp:
        op = type(expr.op)
        left = _expr(expr.left)
        right = _expr(expr.right)

        if op is ast.Mod:
            left['predicate'] = right
            return left
        if op is ast.BitOr:
            return _build_union(left, right)
        if op is ast.BitAnd:
            return _build_intersection(left, right)

    raise ValueError("Unknown expression: %r" % node) 

def visit_BinOp (self, node):
        if type (node.op) == ast.FloorDiv:
            if self.allowOperatorOverloading:
                self.emit ('__floordiv__ (')
                self.visitSubExpr (node, node.left)
                self.emit (', ')
                self.visitSubExpr (node, node.right)
                self.emit (')')
            else:
                self.emit ('Math.floor (')
                self.visitSubExpr (node, node.left)
                self.emit (' / ')
                self.visitSubExpr (node, node.right)
                self.emit (')')
        elif (
            type (node.op) in (ast.Pow, ast.MatMult) or
            (type (node.op) == ast.Mod and (self.allowOperatorOverloading or not self.allowJavaScriptMod)) or
            (type (node.op) in (
                ast.Mult, ast.Div, ast.Add, ast.Sub,
                ast.LShift, ast.RShift, ast.BitOr, ast.BitXor, ast.BitAnd
            ) and self.allowOperatorOverloading)
        ):
            self.emit ('{} ('.format (self.filterId (
                # Non-overloaded
                ('__floordiv__' if self.allowOperatorOverloading else 'Math.floor') if type (node.op) == ast.FloorDiv else
                ('__pow__' if self.allowOperatorOverloading else 'Math.pow') if type (node.op) == ast.Pow else
                '__matmul__' if type (node.op) == ast.MatMult else
                ('__jsmod__' if self.allowJavaScriptMod else '__mod__') if type (node.op) == ast.Mod else

                # Overloaded arithmetic
                '__mul__' if type (node.op) == ast.Mult else
                '__truediv__' if type (node.op) == ast.Div else
                '__add__' if type (node.op) == ast.Add else
                '__sub__' if type (node.op) == ast.Sub else

                # Overloaded bitwise
                '__lshift__' if type (node.op) == ast.LShift else
                '__rshift__' if type (node.op) == ast.RShift else
                '__or__' if type (node.op) == ast.BitOr else
                '__xor__' if type (node.op) == ast.BitXor else
                '__and__' if type (node.op) == ast.BitAnd else

                'Never here'
            )))
            self.visit (node.left)
            self.emit (', ')
            self.visit (node.right)
            self.emit (')')
        else:
            self.visitSubExpr (node, node.left)
            self.emit (' {} '.format (self.operators [type (node.op)][0]))
            self.visitSubExpr (node, node.right) 

def check_risk(node):
    description = "Potential XSS on mark_safe function."
    xss_var = node.args[0]

    secure = False

    if isinstance(xss_var, ast.Name):
        # Check if the var are secure
        parent = node._bandit_parent
        while not isinstance(parent, (ast.Module, ast.FunctionDef)):
            parent = parent._bandit_parent

        is_param = False
        if isinstance(parent, ast.FunctionDef):
            for name in parent.args.args:
                arg_name = name.id if six.PY2 else name.arg
                if arg_name == xss_var.id:
                    is_param = True
                    break

        if not is_param:
            secure = evaluate_var(xss_var, parent, node.lineno)
    elif isinstance(xss_var, ast.Call):
        parent = node._bandit_parent
        while not isinstance(parent, (ast.Module, ast.FunctionDef)):
            parent = parent._bandit_parent
        secure = evaluate_call(xss_var, parent)
    elif isinstance(xss_var, ast.BinOp):
        is_mod = isinstance(xss_var.op, ast.Mod)
        is_left_str = isinstance(xss_var.left, ast.Str)
        if is_mod and is_left_str:
            parent = node._bandit_parent
            while not isinstance(parent, (ast.Module, ast.FunctionDef)):
                parent = parent._bandit_parent
            new_call = transform2call(xss_var)
            secure = evaluate_call(new_call, parent)

    if not secure:
        return bandit.Issue(
            severity=bandit.MEDIUM,
            confidence=bandit.HIGH,
            text=description
        ) 

def visit_BinOp(self, node):
        """Convert `ast.BinOp` to `ast.JoinedStr` f-string

        Currently only if a string literal `ast.Str` is on the left side of the `%`
        and one of `ast.Tuple`, `ast.Name`, `ast.Dict` is on the right

        Args:
            node (ast.BinOp): The node to convert to a f-string

        Returns ast.JoinedStr (f-string)
        """

        percent_stringify = (
            isinstance(node.left, ast.Str)
            and isinstance(node.op, ast.Mod)
            and isinstance(
                node.right,
                tuple( [ast.Tuple, ast.Dict] + supported_operands),
            )
        )

        if percent_stringify:
            state.percent_candidates += 1

            # bail in these edge cases...
            no_good = ["}", "{"]
            for ng in no_good:
                if ng in node.left.s:
                    return node
            for ch in ast.walk(node.right):
                # f-string expression part cannot include a backslash
                if isinstance(ch, ast.Str) and (
                    any(
                        map(
                            lambda x: x in ch.s,
                            ("\n", "\t", "\r", "'", '"', "%s", "%%"),
                        )
                    )
                    or "\\" in ch.s
                ):
                    return node

            result_node, str_in_str = transform_binop(node)
            self.string_in_string = str_in_str
            self.counter += 1
            state.percent_transforms += 1
            return result_node

        return node 

def inferBinaryOpCast(self, node, left, right, op):
        ns, os = node.vhd.size, node.vhdOri.size
        ds = ns - os
        if ds > 0:
            if isinstance(left.vhd, vhd_vector) and isinstance(right.vhd, vhd_vector):
                if isinstance(op, (ast.Add, ast.Sub)):
                    left.vhd.size = ns
                    # in general, resize right also
                    # for a simple name, resizing is not necessary
                    if not isinstance(right, ast.Name):
                        right.vhd.size = ns
                    node.vhdOri.size = ns
                elif isinstance(op, ast.Mod):
                    right.vhd.size = ns
                    node.vhdOri.size = ns
                elif isinstance(op, ast.FloorDiv):
                    left.vhd.size = ns
                    node.vhdOri.size = ns
                elif isinstance(op, ast.Mult):
                    left.vhd.size += ds
                    node.vhdOri.size = ns
                else:
                    raise AssertionError("unexpected op %s" % op)
            elif isinstance(left.vhd, vhd_vector) and isinstance(right.vhd, vhd_int):
                if isinstance(op, (ast.Add, ast.Sub, ast.Mod, ast.FloorDiv)):
                    left.vhd.size = ns
                    node.vhdOri.size = ns
                elif isinstance(op, ast.Mult):
                    left.vhd.size += ds
                    node.vhdOri.size = 2 * left.vhd.size
                else:
                    raise AssertionError("unexpected op %s" % op)
            elif isinstance(left.vhd, vhd_int) and isinstance(right.vhd, vhd_vector):
                if isinstance(op, (ast.Add, ast.Sub, ast.Mod, ast.FloorDiv)):
                    right.vhd.size = ns
                    node.vhdOri.size = ns
                elif isinstance(op, ast.Mult):
                    node.vhdOri.size = 2 * right.vhd.size
                else:
                    raise AssertionError("unexpected op %s" % op)
        pre, suf = self.inferCast(node.vhd, node.vhdOri)
        if pre == "":
            pre, suf = "(", ")"
        return pre, suf