compiler: Document and reduce fn provides in hir crates

[workingjubilee]

I found it hard to follow all these tiny micro-indirections. Much like you shouldn't pass around &u32 if you can help it, you probably shouldn't use an indirection if the indirection overhead itself is literally bigger than the amount of data you are organizing. Generally a new fn provide amounts to around 3 LOC:

• the signature with opening brace
• the rustc_middle::query::Providers import
• an end brace

I am not even counting the cost in time and thought to go find the other provide, read it, understand, "Ah, yes, these functions", and then go to those. Thus I say we should collapse indirections of provide for modules that only export 1~2 queries. For higher-count indirections, I left them as-is, as I don't understand the crate well enough to judge their worth.

Then I dropped a pointer to the actual module of interest for all these instances of the same function. I think documenting them is important because the comment that it relates to the query system makes it obvious that they have nothing to do with the rest of the module's logic and I can carry on ignoring them. Actively doing so is another cognitive cost, but much more minimal.

There is also a small correctness issue in that all of these functions are technically mutating state. It's not a huge deal, but it's still easier to check all these mutations do not overlap if we have less instances of fn provide to check.

[rustbot]

r? @spastorino

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[workingjubilee]

It might also be the case that the inlining should be reversed until there are no more individual queries being assigned in the root fn provide of this crate. Either direction seems like one to head in.

[workingjubilee]

There was one other one in hir_typeck that I simplified also.

[compiler-errors]

should probably pluralize the direct object in "Adds query fn to the [...]", since rn is a bit awkward, but I prefer "query implementations" bc that's more descriptive.

[compiler-errors]

Update the comments, then r=me

[compiler-errors]

Also please squash all the inlining commits, since they kinda all do the same thing

[workingjubilee]

Done~

[compiler-errors]

thanks

@bors r+ rollup

[bors]

📌 Commit 3b7f9f9 has been approved by compiler-errors

It is now in the queue for this repository.