Clean up clean/types.rs file by making the implementations follow the type declaration

[GuillaumeGomez]

This PR doesn't change anything, it simply moves things around: when reading the code, I realized a few times that a type declaration and implementations on it might be separated by some other type declarations, which makes the reading much more complicated. I put back impl and declaration together.

r? @camelid

[camelid]

There's a cost-benefit ratio to moving code: the cost of the Git churn (primarily merge conflicts, but also making Git blame more annoying to use), and the benefit of the new version of the code.

Some of the changes here feel to me like the benefit outweighs the cost (e.g., for small sections of code, like Attributes, that also aren't changed that often), while others feel like the cost outweighs the benefit (e.g., moving Type and its impls, which are large amounts of code that change somewhat frequently, and which I'm currently in the process of refactoring).

I left comments on the main parts where I feel the cost outweighs the benefit and asked to revert them.

[camelid]

Can you leave this part as it was before? Both Argument and SelfTy are logically connected to the following impl, so this feels like unnecessary churn. I'm likely going to be removing SelfTy soon anyway.

[GuillaumeGomez]

Oh nice!

[camelid]

Moving Type and its impls will cause a lot of conflicts with my "Cleanup clean" PR and probably other PRs as well. Can you please revert this part of the change? I'm okay with keeping the merging of the two inherent impls on Type (the general one and the inner_def_id one), and maybe also moving trait GetDefId { ... } so it's not in the middle of the Type code, but most of the other changes feel like unnecessary churn to me.

[GuillaumeGomez]

Ok!

[GuillaumeGomez]

Done!

[GuillaumeGomez]

Done as well.

[camelid]

Thanks!

@bors r+ rollup=iffy

(iffy because it has some potential for merge conflicts)

[bors]

📌 Commit 1c23349 has been approved by camelid

[jyn514]

@camelid bors will automatically keep the PR out of the rollup if it conflicts with other PRs, so there's no need to mark it as iffy.

@bors rollup=maybe

[bors]

⌛ Testing commit 1c23349 with merge 583437a...

[bors]

☀️ Test successful - checks-actions
Approved by: camelid
Pushing 583437a to master...

[rust-timer]

Finished benchmarking commit (583437a): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression