[Bug]: Impossible to generate IR: 'NoneType' object has no attribute 'type'

[0xPhaze]

Describe the issue:

It seems that slither is unable to work with the import ... as ... syntax.

Code example to reproduce the issue:

Types.sol:

struct SimpleStruct {
    uint256 a;
}

Contract.sol:

import "./Types.sol" as Types;

contract Contract {
    Types.SimpleStruct simple;

    constructor() {
        simple = Types.SimpleStruct(0);
    }
}

Version:

0.9.1

Relevant log output:

Function not found SimpleStruct
Impossible to generate IR for Contract.constructor:
 'NoneType' object has no attribute 'type'

[0xPhaze]

Related:

Code example to reproduce the issue:

Types.sol:

type Fixed256x18 is int256;

Contract.sol:

import "./Types.sol" as Types;

contract Contract {
    Types.Fixed256x18 value = Types.Fixed256x18.wrap(0);
}

Relevant log output:

Error in .
Traceback (most recent call last):
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 826, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 97, in process_all
    ) = process_single(compilation, args, detector_classes, printer_classes)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 75, in process_single
    slither = Slither(target, ast_format=ast, **vars(args))
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slither.py", line 130, in __init__
    parser.analyze_contracts()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 500, in analyze_contracts
    self._convert_to_slithir()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 685, in _convert_to_slithir
    func.generate_slithir_and_analyze()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/core/declarations/function.py", line 1705, in generate_slithir_and_analyze
    node.slithir_generation()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/core/cfg/node.py", line 719, in slithir_generation
    self._irs = convert_expression(expression, self)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slithir/convert.py", line 119, in convert_expression
    result = apply_ir_heuristics(result, node)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slithir/convert.py", line 1792, in apply_ir_heuristics
    find_references_origin(irs)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slithir/convert.py", line 1594, in find_references_origin
    ir.lvalue.points_to = ir.variable_left
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slithir/variables/reference.py", line 52, in points_to
    assert is_valid_lvalue(points_to) or isinstance(
AssertionError

[0xalpharush]

Related to #1452

[0xalpharush]

Tracking in #1452