[Bug-Candidate]: source_mapping property failing on `assert self.compilation_unit is not None`

[plotchy]

Describe the issue:

Slither has tons of amazing properties on objects, and I recently found beeprint to conveniently dump out all property information recursively to aid in understanding the info available to functions/nodes/irs/etc.

Using this on a simple contract pointed out a bug with compilation_unit not always being initialized for some objects in the Slither objects list.

In this case, it failed when attempting to get information on a return_type list with object instance(ElementaryType)'s source_mapping with error assert self.compilation_unit is not None

I also have tests of it failing on instance(Literal) and instance(TemporaryVariable) source_mapping

Code example to reproduce the issue:

Contract:

pragma solidity ^0.8.13;
contract printOut {
    function a() pure public returns (uint) {
        return 1;
    }
}

Printer:

from slither.printers.abstract_printer import AbstractPrinter
from beeprint import pp

class Beeprint(AbstractPrinter):

    ARGUMENT = "beeprint"
    HELP = "Print out all of beeprint found props"

    WIKI = "not documented"

    def output(self, _filename):

        for contract in self.contracts:
            functions = [function for function in contract.functions_declared]
            for function in functions:
                for node in function.nodes:
                    pp(node) # Just printing out to stdout directly
        

        txt = ""
        self.info(txt)
        res = self.generate_output(txt)
        return res

Version:

0.8.3 on dev branch

Relevant log output:

instance(Node):
  ...
  _function: instance(FunctionContract):
    ...
    return_type: [
      instance(ElementaryType):
        _abc_impl: <_abc._abc_data object at 0x7fb28f0cdb80>,
        _context: {
          'MEMBERS': defaultdict(None, {}),
        },
        _type: 'uint256',
        context: {
          'MEMBERS': defaultdict(None, {}),
        },
        is_dynamic: False,
        max: 115792089237316195423570985008687907853269984665640564039457584007913129639935,
        min: 0,
        name: 'uint256',
        references: [],
        size: 256,
        source_mapping: Traceback (most recent call last):
...
assert self.compilation_unit is not None
AssertionError

Steps to Reproduce

• pip install beeprint
• save contract to file and add printer to slither
• slither <contract> --print beeprint &> out.md
  • Highly recommend piping output as it's very long

Non-Beeprint reproduction

pragma solidity ^0.8.13;
contract printOut {
    function a() pure public returns (uint) {
        return 1;
    }
}

from slither.printers.abstract_printer import AbstractPrinter

class Beeprint(AbstractPrinter):

    ARGUMENT = "beeprint"
    HELP = "Print out all of beeprint found props"

    WIKI = "not documented"

    def output(self, _filename):
        txt = ""
        for contract in self.contracts:
            functions = [function for function in contract.functions_declared]
            for function in functions:
                for node in function.nodes:
                    for r_type in node.function.return_type:
                        print(r_type.source_mapping)

        self.info(txt)
        res = self.generate_output(txt)
        return res

Output:

Traceback (most recent call last):
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 781, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 88, in process_all
    ) = process_single(compilation, args, detector_classes, printer_classes)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 73, in process_single
    return _process(slither, detector_classes, printer_classes)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 120, in _process
    printer_results = slither.run_printers()
  File "/home/plotchy/code/packages/slither-dev/slither/slither/slither.py", line 216, in run_printers
    return [p.output(self._crytic_compile.target).data for p in self._printers]
  File "/home/plotchy/code/packages/slither-dev/slither/slither/slither.py", line 216, in <listcomp>
    return [p.output(self._crytic_compile.target).data for p in self._printers]
  File "/home/plotchy/code/packages/slither-dev/slither/slither/printers/full/beeprint.py", line 27, in output
    print(r_type.source_mapping)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/core/source_mapping/source_mapping.py", line 77, in __str__
    lines = self._get_lines_str()
  File "/home/plotchy/code/packages/slither-dev/slither/slither/core/source_mapping/source_mapping.py", line 63, in _get_lines_str
    assert self.compilation_unit is not None
AssertionError
None
Error in h.sol
Traceback (most recent call last):
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 781, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 88, in process_all
    ) = process_single(compilation, args, detector_classes, printer_classes)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 73, in process_single
    return _process(slither, detector_classes, printer_classes)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/__main__.py", line 120, in _process
    printer_results = slither.run_printers()
  File "/home/plotchy/code/packages/slither-dev/slither/slither/slither.py", line 216, in run_printers
    return [p.output(self._crytic_compile.target).data for p in self._printers]
  File "/home/plotchy/code/packages/slither-dev/slither/slither/slither.py", line 216, in <listcomp>
    return [p.output(self._crytic_compile.target).data for p in self._printers]
  File "/home/plotchy/code/packages/slither-dev/slither/slither/printers/full/beeprint.py", line 27, in output
    print(r_type.source_mapping)
  File "/home/plotchy/code/packages/slither-dev/slither/slither/core/source_mapping/source_mapping.py", line 77, in __str__
    lines = self._get_lines_str()
  File "/home/plotchy/code/packages/slither-dev/slither/slither/core/source_mapping/source_mapping.py", line 63, in _get_lines_str
    assert self.compilation_unit is not None
AssertionError