Feature: Versioning

[Sdoba16]

Project

compiler

Describe the feature

Current version of Simplicity is

1. Not backward compatible
2. Each user could produce different hex-string depending on the crate versions, hardware or etc.
   Since that we need to add versioning to simplicity, which will help to keep determinism and keep ability not to rewrite each smart-contract whether the compiler changes.

The proposed versioning solution is to keep Solidity's pragma version usage. So we would write pragma version X.Y.Z; at the top of the file, and it will lock the compilation to those rules.

Implementation plan:

1. Update the lexer and parser to read the pragma at the start of the file.
2. Read the compiler's actual version from Cargo.toml at build time.
3. Show version errors if there is a mismatch (for example, if a user tries to use new functions in an old version, or old functions in a new one).
4. Create a tool that reads the pragma and automatically downloads and executes the correct compiler binary for the requested version.
5. To handle cases where a user tries to use a newer feature on an older compiler, update error messages to include a helpful hint to check their pragma and compiler version. (Reads an error message after compiler work, so that each binary is deterministic)

[stringhandler]

This is actually possible already with asdf-vm. You just need to create .tool-versions file with

simc 0.4.0

[stringhandler]

asdf is not supported on windows though. I was looking at mise as an alternative.

[stringhandler]

Do you have an example of a contract that is not backwards compatible?

[Sdoba16]

Do you have an example of a contract that is not backwards compatible?

I don't have an exact contract example, but I mean "Not backward compatible" in the context of future updates. If we find out some vulnerabilities in special version(e.g. jets vulnerability), in this case we will need to forbid usage of vulnerable versions and show warning to user. Old contracts relying on those removed jets would no longer be backwards compatible with the new compiler.

This is actually possible already with asdf-vm. You just need to create .tool-versions file with

simc 0.4.0

This is good tool for developers managing environments natively, but for external users it is not the best option. We do not want to force user to interact with compiler. The user could just write pragma version X.Y.Z in source code and the tooling will automatically manage it(or show version incompatibility error).

[apoelstra]

We should also confirm that we're at a state now where we want to commit to maintaining the language in that state forever. (Sounds like we've deployed some stuff so "yes" but we should be explicit about it.)