Cleanup query macros

[nnethercote]

Some readability improvements.

r? @Zalathar

[rustbot]

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  • b83aff6

[Zalathar]

I find that the query_impl module serves two useful purposes:

• It groups the per-query submodules so that they aren’t expanded directly into the crate root.
• It provides a named “anchor” that indicates when code in one part of the macro is using definitions from another part of the macro; seeing query_impl::$name in a path is much more helpful than just seeing $name.

In #151893 it’s less necessary because $crate::queries ends up serving roughly those same roles.

[Zalathar]

I agree with giving $( … )* its own indentation level in the general case; it’s nicer than having them squished away and invisible.

The exception I sometimes make is for relatively simple struct field declarations and struct/slice initialisation. If the whole thing can clearly and comfortably fit on one line, then I tend to prefer this more compact style:

Struct {
    $( $name: FieldType<$name::Thing>, )*
}

(Take this as a suggestion rather than a request for changes; use it if you agree it’s an improvement in particular places, but otherwise the fully-indented style is fine.)

[Zalathar]

Remark: I intend to dismantle and remove QueryDispatcherUnerased (and therefore QueryType) at some point, but no harm in simplifying this now.

[rust-bors]

☔ The latest upstream changes (presumably #152437) made this pull request unmergeable. Please resolve the merge conflicts.

[nnethercote]

I have filed #152459 as an alternative to the first commit in this PR. It aims to make rustc_query_impl::define_queries much more similar to rustc_middle::define_callbacks, which I think is a useful aim. See what you think.