Ivy

• an AST interpreter for Vyper with a custom EVM backend

How it works

• uses the Vyper compiler as a library

• calls the compiler to get the annotated AST

• an Account in the EVM doesn't contain the code, but the contract's annotated AST

• when a tx/call is made to the contract, the AST (instead of bytecode) is interpreted

• as in boa contracts can be deployed using load function

  • it returns a user-facing contract representation for user interaction

• the interpreter maintains a global state (storage, balances, etc.)

Run & Test

• run: uv run python -m ivy tests/example_contracts/example.vy
• test: uv run pytest tests

from ivy.frontend.loader import loads


def test_deploy_and_call():
    src = """
@external
def foo(a: uint256=42) -> uint256:
    return a
    """

    c = loads(src)
    assert c.foo() == 42

Implementation notes

• the concept of gas is not supported (can't map gas costs to AST interpretation)
• delegatecall support is basic - it's true semantics are tied to the storage layout, however, in Ivy we used a simplified adressing model.It is thus impossible to properly map variables from the caller to the callee. Therefore, delegatecall works as expected only if the contracts satisfy specific layout requirements.
• frontend of the interpreter is heavily inspired by boa, and it's code is often reused in the frontend parts (user-facing contracts, environment, etc.)