[Bug-Candidate]: Fails to generate IR for solidity file that reads an Event Selector

[hamdiallam]

Describe the issue:

slither checks fails due to an error in this PR: ethereum-optimism/optimism#11592

With some debugging on when it fails, the faulty line is the SentMessage member here

if (selector != SentMessage.selector) revert EventPayloadNotSentMessage();

Looking at when the assertion fails, it seems like adding Event as a a valid instance of variable_left for Member fixes this bug

Code example to reproduce the issue:

if (selector != SentMessage.selector) revert EventPayloadNotSentMessage();

Version:

0.10.4

Relevant log output:

Failed to generate IR for L2ToL2CrossDomainMessenger.relayMessage. Please open an issue https://github.com/crytic/slither/issues.
L2ToL2CrossDomainMessenger.relayMessage (src/L2/L2ToL2CrossDomainMessenger.sol#132-182):
 	_id.origin != Predeploys.L2_TO_L2_CROSS_DOMAIN_MESSENGER
	revert IdentifierOriginNotL2ToL2CrossDomainMessenger()()
	CrossL2Inbox(Predeploys.CROSS_L2_INBOX).validateMessage(_id,keccak256(bytes)(_sentMessage))
	(selector,_destination,_target,_nonce) = abi.decode(_sentMessage,(bytes32,uint256,address,uint256))
	selector != SentMessage.selector
	revert EventPayloadNotSentMessage()()
	_destination != block.chainid
	revert MessageDestinationNotRelayChain()()
	_target == Predeploys.CROSS_L2_INBOX
	revert MessageTargetCrossL2Inbox()()
	_target == Predeploys.L2_TO_L2_CROSS_DOMAIN_MESSENGER
	revert MessageTargetL2ToL2CrossDomainMessenger()()
	(_sender,_message) = abi.decode(_sentMessage,(address,bytes))
	_source = _id.chainId
	messageHash = keccak256(bytes)(abi.encode(_destination,_source,_nonce,_sender,_target,_message))
	successfulMessages[messageHash]
	revert MessageAlreadyRelayed()()
	_storeMessageMetadata(_source,_sender)
	success = SafeCall.call(_target,msg.value,_message)
	success
	successfulMessages[messageHash] = true
	RelayedMessage(_source,_nonce,messageHash)
	FailedRelayedMessage(_source,_nonce,messageHash)
	_storeMessageMetadata(0,address(0))
	nonReentrant()
Traceback (most recent call last):
  File "/opt/slither/bin/slither", line 8, in <module>
    sys.exit(main())
  File "/opt/slither/lib/python3.9/site-packages/slither/__main__.py", line 776, in main
    main_impl(all_detector_classes=detectors, all_printer_classes=printers)
  File "/opt/slither/lib/python3.9/site-packages/slither/__main__.py", line 882, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/opt/slither/lib/python3.9/site-packages/slither/__main__.py", line 107, in process_all
    ) = process_single(compilation, args, detector_classes, printer_classes)
  File "/opt/slither/lib/python3.9/site-packages/slither/__main__.py", line 80, in process_single
    slither = Slither(target, ast_format=ast, **vars(args))
  File "/opt/slither/lib/python3.9/site-packages/slither/slither.py", line 202, in __init__
    self._init_parsing_and_analyses(kwargs.get("skip_analyze", False))
  File "/opt/slither/lib/python3.9/site-packages/slither/slither.py", line 221, in _init_parsing_and_analyses
    raise e
  File "/opt/slither/lib/python3.9/site-packages/slither/slither.py", line 217, in _init_parsing_and_analyses
    parser.analyze_contracts()
  File "/opt/slither/lib/python3.9/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 593, in analyze_contracts
    self._convert_to_slithir()
  File "/opt/slither/lib/python3.9/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 827, in _convert_to_slithir
    raise e
  File "/opt/slither/lib/python3.9/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 812, in _convert_to_slithir
    func.generate_slithir_and_analyze()
  File "/opt/slither/lib/python3.9/site-packages/slither/core/declarations/function.py", line 1827, in generate_slithir_and_analyze
    node.slithir_generation()
  File "/opt/slither/lib/python3.9/site-packages/slither/core/cfg/node.py", line 717, in slithir_generation
    self._irs = convert_expression(expression, self)  # type:ignore
  File "/opt/slither/lib/python3.9/site-packages/slither/slithir/convert.py", line 115, in convert_expression
    visitor = ExpressionToSlithIR(expression, node)
  File "/opt/slither/lib/python3.9/site-packages/slither/visitors/slithir/expression_to_slithir.py", line 174, in __init__
    self._visit_expression(self.expression)
  File "/opt/slither/lib/python3.9/site-packages/slither/visitors/expression/expression.py", line 76, in _visit_expression
    visitor(expression)
  File "/opt/slither/lib/python3.9/site-packages/slither/visitors/expression/expression.py", line 88, in _visit_binary_operation
    self._visit_expression(expression.expression_right)
  File "/opt/slither/lib/python3.9/site-packages/slither/visitors/expression/expression.py", line 78, in _visit_expression
    self._post_visit(expression)
  File "/opt/slither/lib/python3.9/site-packages/slither/visitors/expression/expression.py", line 276, in _post_visit
    self._post_member_access(expression)
  File "/opt/slither/lib/python3.9/site-packages/slither/visitors/slithir/expression_to_slithir.py", line 612, in _post_member_access
    member = Member(expr, Constant(expression.member_name), val_ref)
  File "/opt/slither/lib/python3.9/site-packages/slither/slithir/operations/member.py", line 34, in __init__
    assert is_valid_rvalue(variable_left) or isinstance(
AssertionError