Support a signer object where address is expected

[frangio]

Having to add signer.address when calling a contract function with an address argument makes the code more verbose. I'm particularly interested in the effect of this verbosity on tests, which become harder to read.

As far as I can tell, it would be possible for Ethers.js to accept signers where addresses are expected. If this is not feasible for all kinds of signers, it is probably feasible for some, and I think it should be considered for that subset at least.

[ricmoo]

This is already in v6, which will be available as a beta soon. :)

It isn’t a change that will be made in v5 though, as it required substantial code changes, updates to method signatures and new types, which aren’t backwards compatible.

Also, quick note: Signer doesn’t have an address property (some Signer sub-classes do though, like Wallet), so you need to use signer.getAddress(). ;)