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Reduce generics use in the query system. #151777

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Reduce generics use in the query system. #151777

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@nnethercote nnethercote commented Jan 28, 2026 •
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In #151203 I tried and failed to simplify QueryStackFrame. This is an alternative approach. There is no functional change, just tweaking of some names and types to make things clearer. Best reviewed one commit at a time.

r? @oli-obk

@nnethercote
Simplify QueryStackFrame::new.
c8237b1 
Instead of passing a closure that computes a hash and immediately
calling it, just compute the hash and pass the value.
@nnethercote
Rename create_query_frame_extra.
60f61d3 
It produces a `QueryStackFrameExtra`, so `stack_` should be in the name.
@nnethercote
Reduce generics use in the query system.
2afcbf6 
`QueryStackFrame<I>` is a generic type, and the `I` parameter leaks out
to many other related types. However, it only has two instantiations in
practice:
- `QueryStackFrame<QueryStackFrameExtra>`
- `QueryStackFrame<QueryStackDeferred<'tcx>>`

And most of the places that currently use `QueryStackFrame<I>` are
actually specific to one of the instantiations. This commit removes the
unneeded genericity.

The following types are only ever used with `QueryStackDeferred<'tcx>`:
- QueryMap
- QueryJobInfo
- QueryJob
- QueryWaiter
- QueryLatchInfo
- QueryLatch
- QueryState
- QueryResult
and their `<I>` parameter is changed to `<'tcx>`.

Also, the `QueryContext::QueryInfo` associated type is removed.

`CycleError<I>` and `QueryInfo<I>` are still generic over type, because
they are used with both instantiations.

This required also adding a `<'tcx>` parameter to the traits
`QueryConfig` and `QueryContext`, which is annoying but I can't see how
to avoid it.
@rustbot rustbot added A-query-system Area: The rustc query system (https://rustc-dev-guide.rust-lang.org/query.html) S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jan 28, 2026
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rustbot commented Jan 28, 2026

oli-obk is not on the review rotation at the moment.
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oli-obk commented Jan 28, 2026

Yea this makes sense. Not much of an improvement, but lifetime generics are better than type generics for readability
@bors r+ rollup

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rust-bors bot commented Jan 28, 2026

📌 Commit 2afcbf6 has been approved by oli-obk

It is now in the queue for this repository.

@rust-bors rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 28, 2026
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Zalathar commented Jan 28, 2026 •
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Be aware that this will textually conflict with some of the renames in #151666, though the changes should be compatible.

Also, after that PR I intend to change the generic type of QueryConfig (renamed to QueryDispatcher) to an associated type, so having the 'tcx will be a bit less annoying after that.

@rust-bors rust-bors bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jan 28, 2026
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rust-bors bot commented Jan 28, 2026

☔ The latest upstream changes (presumably #151778) made this pull request unmergeable. Please resolve the merge conflicts.

This pull request was unapproved.

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petrochenkov commented Jan 28, 2026 •
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The original implementation tried to avoid adding the 'tcx parameter everywhere, as I understand - #138672 (comment).
If it's added anyway, then perhaps my suggestion about using an enum or dyn trait from that comment can be implemented too.

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A-query-system Area: The rustc query system (https://rustc-dev-guide.rust-lang.org/query.html) S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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