Add `usize` and `isize` as a primitive type about fe

[Y-Nak]

Yes, of course!

[Y-Nak]

So this task includes mentoring from you?

yep!

if you have any guidance on how to start with the parser

Sorry, I made the wrong description for the issue; you don't need to modify the parser. So, the first step for this issue would be to make the name resolution handle the two types properly.

The concrete steps would be

1. Add usize and isize tohir::hir_def::ident::kw.
2. Modify hir::hir_def::prim_ty to accommodate those two types(IntTy and UintTy are the places where you would need to modify).
3. Modify hir::hir_def::PrimTy::all_types so that it includes the newly added usize and isize in step 2.

[Y-Nak]

Oh, currently, the head of v2 is #1007, which will be merged soon.
Please use that branch as a base.

[lana-shanghai]

Hey, could I work on this? @Y-Nak

[lana-shanghai]

Yes, of course!

Sweet! So this task includes mentoring from you? :) if you have any guidance on how to start with the parser, please share, otherwise I am diving into the codebase for now!

[Y-Nak]

For the type checker module, the steps would be

1. Modify hir_analysis::ty::ty_def::PrimTy.
2. Modify impl From<HirPrimty> for TyBase in ty_def module.

In addition to that, you probably need to modify some auxiliary methods like ty_def::PrimTy::is_integral.

Basically, that'd be all necessary things(I might miss something, though).
Please feel free to ask any questions.

[Y-Nak]

resolved in #1012