Preconditions for Zero Slot

[DavePearce]

The slot at address 0x60 is reserved as the zero slot. We could include this by default. Noting, however, that I don't think the WETH contract actually does this. So, I suppose earlier versions of Solidity didn't use it?

[DavePearce]

Looks like it changed from 0.4.19 => 0.5.0. Looking at this versus this and searching for 0x60 is revealing.

[DavePearce]

Looks like 0.4.22 was the first version where the zero slot exists.