Factor out several utils, add path_def_id

[camsteffen]

changelog: none

This is generally an effort to reduce the total number of utils. path_def_id is added which I believe is more "cross-cutting" and also complements path_to_local. Best reviewed one commit at a time.

Added:

• path_def_id
• path_res

Removed:

• is_qpath_def_path
• match_any_diagnostic_items
• expr_path_res
• single_segment_path
• differing_macro_contexts
• is_ty_param_lang_item
• is_ty_param_diagnostic_item
• get_qpath_generics

Renamed:

• path_to_res to def_path_res
• get_qpath_generic_tys to qpath_generic_tys

CC @Jarcho since this relates to some of your work and you may have input.

[rust-highfive]

r? @giraffate

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[Jarcho]

The only thing I would question here is how much utility path_def_id really gives over just having path_res. It's only slightly shorter and does the obvious thing (it's 10 characters shorter).

Other than that I think this is good. It's an improvement over what currently exists and no matter what changes happen afterwards related to identifying items, paths will need to be resolved. Having all path resolution go through the same place will probably make future changes easier.

[camsteffen]

Yeah path_res(expr).opt_def_id() isn't bad. I was thinking that path_def_id is so widely applicable that it's worth it but now I'm not so sure.

Also is the distinction between def_path_res and path_res good enough? path_res should be much more widely used so the short name is nice. But it could be path_node_res...liking that as I type it.

[Jarcho]

def_path_res should be rare enough that it isn't that big of a deal. Could name it resolve_def_path as it's actually resolving the path and not just looking up what the given path resolves to.

path_node_res sounds fine.

[bors]

☔ The latest upstream changes (presumably #8271) made this pull request unmergeable. Please resolve the merge conflicts.

[camsteffen]

Rebased. I searched the code for opt_def_id() and we really do that a lot so I think path_def_id is worth it (again). I also figured adding _node doesn't ultimately add much clarity. 🤷

[flip1995]

This looks like a great simplification of our utils!

Regarding the naming, I'm fine with how it is now. But I'll leave that decision up to you @Jarcho & @camsteffen.

r=me if you settled on the naming of the functions.

[Jarcho]

I think the name is fine as is. One small quip here is it doesn't actually take a Path or QPath despite what the name might lead one to believe. Not really an issue though.

[camsteffen]

@bors r=flip1995

[bors]

📌 Commit bd583d9 has been approved by flip1995

[bors]

⌛ Testing commit bd583d9 with merge 3d43826...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 3d43826 to master...