Lower IfLet expressions

[antego]

This PR addresses #1177. This change implements the "hir-lowering" part of the plan outlined here #1177 (comment).

[philberty]

Would you like a review @antego or would you still like to do more here?

[antego]

Ideally I'd like to make the compilation work. But now I'm not sure since there are possibly too many changes for one PR judging by this #1177 (comment)

[CohenArthur]

@antego all the steps mentioned in the issue should be done in multiple PRs imo. It's a good idea to have a PR dedicated to lowering, one to name resolution, one to type checking, one to backend compilation etc.

[antego]

It's a good idea to have a PR dedicated to lowering, one to name resolution, one to type checking, one to backend compilation etc.

Thanks! I'll create separate PRs.

[CohenArthur]

I think that overall this looks good :)

[CohenArthur]

Any reason why you chose to add a new visitor class instead of simply implementing the function in ASTLoweringIfBlock? It seems you're not using new class members or anything, so it might be simpler to reuse this existing class.

[antego]

The only reason is because the translated field in the ASTLoweringIfBlock is of type HIR::IfExpr and can't accomodate the HIR::IfLetExpr.

[CohenArthur]

Then I think it would make more sense to turn that into an HIR::ExprWithBlock * but @philberty might think your approach is better. I'm honestly fine with both, I just think it's easier for you to not have to reimplement an entire class/visitor :)

[philberty]

Refactoring to use ExprWithBlock might be a really good idea to cleanup the code a bit here but lets do that as a separate piece since it will affect other code we can raise this as a good-first-pr refactor.

[philberty]

LGTM we can do the refactor down the line.

[CohenArthur]

bors r+

[bors]

Build succeeded:

• build-and-check