”read_storage cannot determine the storage layout of custom type variables within a struct.

[Subway2023]

Describe the issue:

If a structure contains custom types, the read_storage tool cannot determine the storage layout of that struct variable.

Code example to reproduce the issue:

test.py

from slither.tools.read_storage import SlitherReadStorage
srs = SlitherReadStorage([c], 20)
srs.get_all_storage_variables()
srs.get_storage_layout()

error.sol

type MyUint64 is uint64;
contract C {
    struct S {
        MyUint64 y;
        MyUint64 z;
    }
    S s;
}

correct.sol

contract C {
    struct S {
        unit64 y;
        unit64 z;
    }
    S s;
}

Version:

0.10.3

Relevant log output:

When perform test.py for program of error.sol, there is an error

  File "/mnt/sdd1/sbw/slither/slither/tools/read_storage/read_storage.py", line 837, in _all_struct_slots
    info = self.get_storage_slot(
  File "/mnt/sdd1/sbw/slither/slither/tools/read_storage/read_storage.py", line 256, in get_storage_slot
    info, type_to, slot, size, offset = self._find_struct_var_slot(elems, slot, struct_var)
  File "/mnt/sdd1/sbw/slither/slither/tools/read_storage/read_storage.py", line 597, in _find_struct_var_slot
    return info, type_to, slot_as_bytes, size, offset
UnboundLocalError: local variable 'size' referenced before assignment

[0xalpharush]

Right now, only elementary types are being considered.

slither/slither/core/solidity_types/type_alias.py

Lines 13 to 17 in 9a5b4f5

	class TypeAlias(Type):
	def __init__(self, underlying_type: ElementaryType, name: str) -> None:
	super().__init__()
	self.name = name
	self.underlying_type = underlying_type

We'd need to add a way to get the user defined type's underlying type

slither/slither/tools/read_storage/read_storage.py

Lines 592 to 593 in 9a5b4f5

	else:
	logger.info(f"{type(var_type)} is current not implemented in _find_struct_var_slot")

Fwiw we also don't support nested structs yet
#2077