Testing: Set-Storage Determine Storage Slot from contract type VYPER-ONLY

[NotPeopling2day]

Overview

See the output format for storage slots from vyperlang/vyper#2572

Specification

The deliverable may just be a method (or helper method) on the vyper compiler
for getting the storage slot.

Dependencies

#360

This ticket can probably be moved to ape-vyper at some point.

[fubuloubu]

see output format for storage slots from vyperlang/vyper#2572

[fubuloubu]

Further sketch here:

assert token.balanceOf(a) == 0
# NOTE: `balanceOf` and `totalSupply` are storage slots, as well as public view methods
# NOTE: `balanceOf` is a `HashMap`, which can be used like a Python `dict`
token.storage.balanceOf[a] += 1000
token.storage.totalSupply += 1000  # To keep invariant in sync

assert token.balanceOf(a) == 1000