Cannot declare HashMap inside struct

[arjunaskykok]

Version Information

• vyper Version (output of vyper --version): 0.2.10+commit.418c85b
• OS: linux
• Python Version (output of python --version): Python 3.8.5
• Environment (output of pip freeze):

apipkg==1.5
asttokens==2.0.4
attrs==20.3.0
base58==2.0.1
bitarray==1.2.2
blake2b-py==0.1.3
cached-property==1.5.2
certifi==2020.12.5
chardet==4.0.0
coverage==5.3.1
cytoolz==0.11.0
eth-abi==2.1.1
eth-account==0.5.4
eth-bloom==1.0.3
eth-hash==0.2.0
eth-keyfile==0.5.1
eth-keys==0.3.3
eth-rlp==0.2.1
eth-tester==0.5.0b3
eth-typing==2.2.2
eth-utils==1.9.5
execnet==1.7.1
hexbytes==0.2.1
hypothesis==5.46.0
idna==2.10
iniconfig==1.1.1
ipfshttpclient==0.7.0a1
jsonschema==3.2.0
lark==0.11.1
lru-dict==1.1.6
multiaddr==0.0.9
mypy-extensions==0.4.3
netaddr==0.8.0
packaging==20.8
parsimonious==0.8.1
pluggy==0.13.1
protobuf==3.14.0
py==1.10.0
py-ecc==4.1.0
py-evm==0.3.0a20
pycryptodome==3.9.9
pyethash==0.1.27
pyparsing==2.4.7
pyrsistent==0.17.3
pytest==6.2.1
pytest-cov==2.10.1
pytest-forked==1.3.0
pytest-xdist==2.2.0
requests==2.25.1
rlp==2.0.1
semantic-version==2.8.5
six==1.15.0
sortedcontainers==2.3.0
toml==0.10.2
toolz==0.11.1
trie==2.0.0a5
typing-extensions==3.7.4.3
urllib3==1.26.2
varint==1.0.2
vyper==0.2.10
web3==5.13.1
websockets==8.1

What's your issue about?

$ cat /tmp/a.vy
struct a:
  map: HashMap[address, bool]
$ vyper /tmp/a.vy
Error compiling: /tmp/a.vy
vyper.exceptions.StructureException: HashMap can only be declared as a storage variable
  contract "/tmp/a.vy", line 2:7 
       1 struct a:
  ---> 2   map: HashMap[address, bool]
  --------------^
       3

I would like to have HashMap inside struct. Right now I am translating OpenZeppelin code to Vyper. For example I'm translating this code: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/AccessControl.sol

They got mapping inside struct.

    struct RoleData {
        mapping (address => bool) members;
        bytes32 adminRole;
    }

[iamdefinitelyahuman]

This is a documented behavior. Including a mapping within a struct means the struct cannot be used in calldata or memory, and so creates an inconsistent behavior dependent upon the shape of the struct.

[fubuloubu]

Seems like a better approach here would be a simple HashMap[address, bytes32] and use bitand-masking to compute inclusion/exclusion checks, with each bit serving as a role. and bitorA maximum of 256 roles would therefore be possible.

Better support for Enums would make this easier (similar to IntFlagEnum), you could then add an API for something like this:

enum Roles:
    admin  # bit 0
    ...  # bits 1 - N-1

user_role: HashMap[address, Roles]

def only_admin():
    # NOTE: The following performs `self.roles[msg.sender] & Roles.admin == Roles.admin`
    assert self.roles[msg.sender] is Roles.admin  # weird semantics...
    # OR
    assert Roles.admin in self.roles[msg.sender]  # weird to read, but makes sense if you think about it

---

Enums would make a good candidate for a VIP!

[arjunaskykok]

So we are not going to support this? Feel free to close this issue.

Right now I compensate the lacking of HashMap inside struct with two arrays:

_roles: HashMap[bytes32, HashMap[address, bool]]
_admin_roles: HashMap[bytes32, bytes32]

[fubuloubu]

So we are not going to support this? Feel free to close this issue.

IMO it's a bad idea to support that behavior, without letting them be used in similar contexts between storage and memory.

[charles-cooper]

won't fix, it's a feature not a bug!