Notes: ErrorDefinition will need to extend SourceUnit too, need to check parts of code that rely on instance checks.
Possibility to use bytes.concat with variable number of bytes and bytesNN arguments which behaves as a restricted version of abi.encodePacked with a more descriptive name.
https://blog.soliditylang.org/2021/04/21/solidity-0.8.4-release-announcement/
Add support to parser, AST1 and AST2.
https://blog.soliditylang.org/2021/04/21/custom-errors/
Notes: ErrorDefinition will need to extend SourceUnit too, need to check parts of code that rely on instance checks.
Notes: add builtin call