Rework Collections for `Expect` and `Name`

[JSAbrahams]

Relevant issues

• Do not merge before #440
• Resolves #437
• Might resolve #432

Summary

As has been a running theme for the past few days, this PR changes quite a lot more than originally intended. However, we had some sloppy code which I figured would be best to clean up now instead of laborously splitting it over many PR's. For now I see this a one in a set of major refactors, which for now is fine since I'm the only active developer. Best to just improve the quality of the codebase now and get rid of as many bugs as possible by generalizing the type system as much as possible. This includes getting rid of as much superfluous logic as possible.

Main change: Except::Collection to Expect::Call { ... }

Remove the collection Expect construct. Instead, we use generics now and substitution of generics to deal with unification of collections.

• Trim Collection type in annotated AST since that is not a valid type annotation in Python.
• Add recursive substitution of names. Useful if we want to substitute temporary names.
• Add unification and substitution of generics within names. Useful if we want to substitute generics which are temporary names.

This greatly simplifies a lot of exceptions we had to make for collections. We also get to make use of type annotation logic now.

Secondary: Remove NameVariant

Instead, we just make use of Tuple[...] and Callable[Tuple[...],[...] by making helper methods which create these for us on the fly. Under the hood, it's always StringName. For now, I leave optionality untouched, so we don't make use of Optional[...], but instead have a boolean in TrueName.

This makes it much easier to match names directly and simplifies a lot of substitution logic within Name. The changes here don't affect the codebase outside of name too much, because most of it was abstracted away. But it does greatly reduce the chances of introducing a bug. And it also simplifies the unification stage even further.

To accomodate these changes, we also revamp the generic system:

• The context now also substitutes the generics within parents when performing a class lookup.
• We perform matching when checking if a class if a class of another class. Specifically, if the literal of the names are equal (checking the lits in StringName { lit1, generics: [Name] }), we check proceed to check for each generic whether self is name of other as long as the generic count is the same.

Added Tests

TODO: list tests

[JSAbrahams]

Add issue that we should only override identifiers with Python type in:

• types
• constructor calls

[codecov[bot]]

Codecov Report

Merging #439 (cb8fb18) into develop (7d06ae2) will decrease coverage by 0.13%. The diff coverage is 85.27%.

@@             Coverage Diff             @@
##           develop     #439      +/-   ##
===========================================
- Coverage    88.59%   88.46%   -0.14%     
===========================================
  Files          110      107       -3     
  Lines        11956    11729     -227     
===========================================
- Hits         10593    10376     -217     
+ Misses        1363     1353      -10     

Impacted Files	Coverage Δ
src/check/constrain/constraint/iterator.rs	84.61% <0.00%> (ø)
src/check/constrain/unify/mod.rs	75.00% <ø> (ø)
src/check/context/field/mod.rs	54.28% <ø> (ø)
src/generate/convert/control_flow.rs	90.25% <ø> (ø)
src/parse/lex/result.rs	14.28% <0.00%> (ø)
src/parse/result.rs	43.07% <0.00%> (ø)
src/check/result.rs	76.92% <33.33%> (+1.36%)	:arrow_up:
src/generate/convert/ty.rs	57.14% <33.33%> (-12.25%)	:arrow_down:
src/check/context/parent/mod.rs	42.85% <42.85%> (ø)
src/check/context/arg/generic.rs	76.54% <50.00%> (ø)
... and 71 more