VIP: Remove required keyword arguments from builtin functions

[iamdefinitelyahuman]

Simple Summary

Vyper should not use required keyword arguments in built-in functions.

1. raw_call requires outsize and gas as keyword args.
2. slice requires start and len as keyword args.

Motivation

Given the similarity to between Vyper syntax and Python syntax, the current style is unintuitive to write and misleading to read. I believe keyword arguments should only be used for optional fields. All required arguments should always be positional.

Specification

1. For raw_call, convert outsize and gas to positional arguments.
   a. Alternatively, gas could become an optional argument that defaults to gasLeft.
2. For slice, convert start and len to positional arguments.

# current
raw_call(_addr, b"moose", outsize=7, gas=50000)
slice(inp1, start=3, len=3)


# proposed
raw_call(_addr, b"moose", 7, 50000)
slice(inp1, 3, 3)

Backwards Compatibility

This is a breaking change, but it will only require slight modifications to existing contracts.

Copyright

Copyright and related rights waived via CC0

[iamdefinitelyahuman]

I might have missed some builtins, will update this VIP if I encounter any others.

[fubuloubu]

Alternatively, gas could become an optional argument that defaults to gasLeft

This would be what I prefer

[charles-cooper]

Alternatively, gas could become an optional argument that defaults to gasLeft

I like this but it should be a different VIP

[charles-cooper]

slice requires start and len as keyword args.

nice to have: just use python slice syntax (but should also be new VIP)

[fubuloubu]

Update this VIP to talk just about slice. All conversation from meeting about raw_call is moved to #1890