Slither crashes when parsing access to anonymous array

[Xenomega]

The following contract will crash slither:

contract C {
    function f(uint x) public returns (uint){
         return [0, 1][x];
    }
}

Stack trace:

ERROR:root:Traceback (most recent call last):
  File "c:\users\vyper\documents\github\slither\slither\__main__.py", line 250, in main_impl
    (results, number_contracts) = process(filename, args, detector_classes, printer_classes)
  File "c:\users\vyper\documents\github\slither\slither\__main__.py", line 35, in process
    slither = Slither(filename, args.solc, args.disable_solc_warnings, args.solc_args, ast)
  File "c:\users\vyper\documents\github\slither\slither\slither.py", line 41, in __init__
    self._analyze_contracts()
  File "c:\users\vyper\documents\github\slither\slither\solc_parsing\slitherSolc.py", line 214, in _analyze_contracts
    self._convert_to_slithir()
  File "c:\users\vyper\documents\github\slither\slither\solc_parsing\slitherSolc.py", line 341, in _convert_to_slithir
    contract.convert_expression_to_slithir()
  File "c:\users\vyper\documents\github\slither\slither\solc_parsing\declarations\contract.py", line 367, in convert_expression_to_slithir
    func.generate_slithir_and_analyze()
  File "c:\users\vyper\documents\github\slither\slither\solc_parsing\declarations\function.py", line 927, in generate_slithir_and_analyze
    node.slithir_generation()
  File "c:\users\vyper\documents\github\slither\slither\core\cfg\node.py", line 506, in slithir_generation
    self._irs = convert_expression(expression, self)
  File "c:\users\vyper\documents\github\slither\slither\slithir\convert.py", line 734, in convert_expression
    visitor = ExpressionToSlithIR(expression, node)
  File "c:\users\vyper\documents\github\slither\slither\visitors\slithir\expression_to_slithir.py", line 70, in __init__
    self._visit_expression(self.expression)
  File "c:\users\vyper\documents\github\slither\slither\visitors\expression\expression.py", line 92, in _visit_expression
    self._post_visit(expression)
  File "c:\users\vyper\documents\github\slither\slither\visitors\expression\expression.py", line 275, in _post_visit
    self._post_index_access(expression)
  File "c:\users\vyper\documents\github\slither\slither\visitors\slithir\expression_to_slithir.py", line 163, in _post_index_access
    operation = Index(val, left, right, expression.type)
  File "c:\users\vyper\documents\github\slither\slither\slithir\operations\index.py", line 13, in __init__
    assert is_valid_lvalue(left_variable) or left_variable == SolidityVariableComposed('msg.data')
AssertionError

[montyly]

Fixed in dev