VIP: Allow environment variables and constants as "default value" in public functions

[haydenadams]

There are a number of Uniswap functions that have a recipient field. It would be great to default this field to msg.sender like so:

@public
@payable
def ethToTokenSwap(minTokens: uint256, recipient: address = msg.sender):

Currently I have to do something along these lines:

@public
@payable
def ethToTokenSwap(minTokens: uint256, recipient: address = 0x000...000):
   if(recipient == ZERO_ADDRESS):
      recipient = msg.sender

which isn't the worst but it would be great to have msg.sender, msg.value, and constants available here.

[jakerockland]

I'm a fan of this idea 👍

[fubuloubu]

So, allow constants and environment variables? I'm on board with that too