feat: Lower collections extension

[mark-koch]

Closes #1701 and fixes #1645.

Note that destructors and ref-counting hooks are still missing. These will follow in a future PR once they are available in hugr-llvm.

[codecov]

Codecov Report

Attention: Patch coverage is 82.88591% with 51 lines in your changes missing coverage. Please review.

Project coverage is 86.35%. Comparing base (fc609a2) to head (31b06a7).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
hugr-llvm/src/extension/collections.rs	83.65%	4 Missing and 39 partials ⚠️
hugr-llvm/src/emit/func.rs	71.42%	0 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1720      +/-   ##
==========================================
- Coverage   86.38%   86.35%   -0.03%     
==========================================
  Files         166      167       +1     
  Lines       30063    30361     +298     
  Branches    26975    27273     +298     
==========================================
+ Hits        25969    26219     +250     
- Misses       2558     2559       +1     
- Partials     1536     1583      +47     

Flag	Coverage Δ
python	92.42% <ø> (ø)
rust	85.67% <82.88%> (-0.02%)	⬇️

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[doug-q]

Looks great! Some nits, see what you think. I understand execution tests would be hard, could you add an issue for those?

[doug-q]

I think this is more idomatic returning &[Value]. Not too bothered.

[doug-q]

Suggested change

	fn list_type<'c>(&self, session: &TypingSession<'c, '_>) -> BasicTypeEnum<'c> {
	fn list_type<'c>(&self, session: TypingSession<'c, '_>) -> BasicTypeEnum<'c> {

[doug-q]

I don't like these bools, I would prefer something like pub enum CollectionRuntimeFunc { ... }. If you do keep the bools please elaborate in the comment what they mean.

[doug-q]

I understand that this is not the worst. Users with a different function name could reimplement this. I would much prefer self.runtime_func_name(CollectionsRuntimeFunc::new) though.

[doug-q]

This would be better as a free function in crate::emit::func, there are many other places that would like it.

[doug-q]

as for build_option

[doug-q]

My current thinking is that the free add_collections_extension is unnecessary, we should just put it's implementation here. What do you think?

[doug-q]

Suggested change

	_ => {
	return Err(anyhow!("Collections: invalid type args for list op"));
	args => bail!("Collections: invalid type args for list op: {args:?}"));

[mark-koch]

I added the runtime function enum and removed most of the functions in CollectionsCodegen. Agreed that this is a lot nicer 👍

Also created issue #1722 for execution tests

[doug-q]

Awesome, thank you Mark.

[doug-q]

Suggested change

	#[derive(Clone, Copy, Debug, PartialEq, Hash)]
	#[derive(Clone, Copy, Debug, PartialEq, Hash)]
	#[non_exhaustive]

would mean adding enums isn't a breaking change