Add ERC-20 compatibility check when creating a new exchange

[gundas]

Hello,
I have a small suggestion - currently Uniswap has about 2400 exchanges deployed. A few of the tokens (still) do no fully support ERC-20. The worst was BNB, but there are others - PKG, XYO etc.

Maybe it would be a good idea to a do a simple token compatibility test when creating a new exchange:

assert(token.transferFrom(msg.sender, address(this),1))
assert(token.transfer(msg.sender,1))

This small check would prevent people from loosing money.

What do you think? Maybe it is not too late to implement it in V2?

[gundas]

Alternatively, the Exchange contract could require that addLiquidity/removeLiquidity operations should be tested before allowing to add liquidity to the exchange (this could be done by having a method which adds and removes liquidity as well as sets a flag one the two operations are successful).

There are many ways to implement this safeguard.