No support for decoding Yul immutables

[haltman-at]

Issue

As of Solidity 0.8.12, it's finally possible for us to get information about Yul immutables. So, it would be nice to support decoding these in at least some contexts. I'm thinking primarily here of supporting them when decoding bytecode (in decoder or at the end of a deployment in the debugger); I don't know that I want to support them as proper variables in the debugger, that seems like it might be problematic, but we could consider that too.

Note that just doing this in decoder probably shouldn't be too bad; however, it would mean allowing the decoder to see Yul ASTs, which we would have to make sure to avoid any unintended consequences of. Doing it in the debugger unfortunately would first require fixing #3831 (or at least fixing it for Yul; we could continue to leave Vyper alone, which I think we probably should).

(Note of course that since we're talking about Yul here, "decoding" really mostly means "extracting"; they'd all just be treated as type bytes32, same as how we handle other Yul variables.)

Environment

• Truffle version (truffle version): 5.4.33

[kevinbluer]

Fixed in https://github.com/trufflesuite/truffle/releases/tag/v5.5.0

[haltman-at]

Reopening, there was nothing in 5.5.0 to fix this. #4746 did other things with Yul Immutables, not fix this. That's why this was filed later than it, and it made no claim to fix this.