[Bug-Candidate]: Fails to parse structs outside of library

[kevzettler]

Describe the issue:

I run slither . and get a python stack trace containing errors listed below.

Code example to reproduce the issue:

slither.config.json

{
  "hardhat_artifacts_directory": "build/contracts"
}

Version:

kevzettler@kevs-mbp-3 contracts % slither --version
0.8.3

Relevant log output:

kevzettler@kevs-mbp-3 contracts % slither .
'npx hardhat compile --force' running
Generating typings for: 50 artifacts in dir: ./build/typechain for target: ethers-v5
Successfully generated 150 typings!
Compiled 33 Solidity files successfully

(node:73260) ExperimentalWarning: stream/web is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)

Traceback (most recent call last):
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 744, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 87, in process_all
    ) = process_single(compilation, args, detector_classes, printer_classes)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 70, in process_single
    slither = Slither(target, ast_format=ast, **vars(args))
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slither.py", line 118, in __init__
    parser.parse_contracts()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 485, in parse_contracts
    self._analyze_second_part(contracts_to_be_analyzed, libraries)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 553, in _analyze_second_part
    self._analyze_top_level_structures()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 631, in _analyze_top_level_structures
    struct.analyze()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/declarations/structure_top_level.py", line 57, in analyze
    elem_parser.analyze(self)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/variables/variable_declaration.py", line 210, in analyze
    self._variable.type = parse_type(self._elem_to_parse, caller_context)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/solidity_types/type_parsing.py", line 414, in parse_type
    mappingTo = parse_type(t["valueType"], next_context)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/solidity_types/type_parsing.py", line 400, in parse_type
    length = parse_expression(t["length"], caller_context)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/expressions/expression_parsing.py", line 255, in parse_expression
    assert isinstance(caller_context, CallerContextExpression)
AssertionError
None
Error in .
Traceback (most recent call last):
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 744, in main_impl
    ) = process_all(filename, args, detector_classes, printer_classes)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 87, in process_all
    ) = process_single(compilation, args, detector_classes, printer_classes)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/__main__.py", line 70, in process_single
    slither = Slither(target, ast_format=ast, **vars(args))
  File "/opt/homebrew/lib/python3.10/site-packages/slither/slither.py", line 118, in __init__
    parser.parse_contracts()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 485, in parse_contracts
    self._analyze_second_part(contracts_to_be_analyzed, libraries)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 553, in _analyze_second_part
    self._analyze_top_level_structures()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/slither_compilation_unit_solc.py", line 631, in _analyze_top_level_structures
    struct.analyze()
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/declarations/structure_top_level.py", line 57, in analyze
    elem_parser.analyze(self)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/variables/variable_declaration.py", line 210, in analyze
    self._variable.type = parse_type(self._elem_to_parse, caller_context)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/solidity_types/type_parsing.py", line 414, in parse_type
    mappingTo = parse_type(t["valueType"], next_context)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/solidity_types/type_parsing.py", line 400, in parse_type
    length = parse_expression(t["length"], caller_context)
  File "/opt/homebrew/lib/python3.10/site-packages/slither/solc_parsing/expressions/expression_parsing.py", line 255, in parse_expression
    assert isinstance(caller_context, CallerContextExpression)
AssertionError

[0xalpharush]

Can you share your code or an example to reproduce this?

If you have similar code to this issue, you can try moving the struct into the contract.

[kevzettler]

Hi @0xalpharush you can reproduce with the following chain of shell commands. This assumes you have git, yarn and slither installed

git clone --single-branch --branch slither-v2.5.0 https://github.com/kevzettler/semaphore && \
cd semaphore && \ 
yarn && \ 
cd packages/contracts && \
slither .

[kevzettler]

I have confirmed that this parsing failure was due to a scenario where a shared library had a struct defined outside of it like:

struct SharedStruct{}
library SharedLibrary{}

contract Testcontract{
    using SharedLibrary for SharedStruct;
}

If I modify it to nest the struct within the library like:

library SharedLibrary{
    struct SharedStruct{}
}

contract Testcontract{
    using SharedLibrary for SharedLibrary.SharedStruct;
}

slither is able to parse.