[rustdoc] Fix how `Deref` items is handled. - #160915

GuillaumeGomez · 2026-08-11T14:37:27Z

This PR fixes a few things around how we handle Deref:

Since nothing except for methods is callable through a Deref, only methods should be kept
If the Deref::Target is a type implementing Copy, then methods taking self work and should be displayed.

During the clean pass, I store the item DefId on which Deref is implemented in a DefIdSet if the Deref::Target implements Copy. Then during rendering, we check if the "parent item" is in in the DefIdSet, and if so, we keep methods with self.

Now you might wonder why the item and not the derefed item. It's because the DefId we get from the computed type doesn't match the DefId of the actual type (that's where I spent most of my time, finding an ID (DefId/ItemId) I can use as key T_T).

It computes in html/render if the Deref::Target item is copy before rendering it.

So to resume:

&self is always kept.
&mut self is kept if DerefMut is implemented (nothing changed there).
self is kept only if Deref::Target is Copy.
Everything else disappears as they're not callable through Deref.

r? @camelid

rustbot · 2026-08-11T14:37:34Z

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GuillaumeGomez · 2026-08-11T14:38:24Z

Oof, that's a big diff. It's mostly because of reindent, not much that we can do about. ^^'

GuillaumeGomez · 2026-08-11T16:00:25Z

Fixed fmt. ^^'

camelid

Btw there's some missing wording in this sentence of the PR description, so I'm not quite sure what it says:

Since since except for methods is callable through a Deref, only methods should be kept

View changes since this review

GuillaumeGomez · 2026-08-11T19:16:27Z

Btw there's some missing wording in this sentence of the PR description, so I'm not quite sure what it says:

Since since except for methods is callable through a Deref, only methods should be kept

Fixed the typo. Correct sentence is:

Since nothing except for methods is callable through a Deref, only methods should be kept

GuillaumeGomez · 2026-08-11T23:15:04Z

Thanks to @camelid's suggestion, code is now much simpler. Thanks!

@rustbot ready

camelid · 2026-08-12T15:32:07Z

+    let for_ = clean_ty(impl_.self_ty, cx);
+


nit: Moving this let is now unnecessary. Better to move it back to where it's used.

View changes since the review

camelid · 2026-08-12T15:32:41Z

@@ -295,6 +295,8 @@ pub(crate) fn build_deref_target_impls(
                    inline::build_impls(cx, did, None, ret);
                });
            }
+        } else {
+            break;


Why was this break added?

View changes since the review

Because it's actually looking for the Deref::Target item and doesn't do anything. So at that point, we can break as soon as we found it. Can remove it though, considering there are only 2 items, doesn't matter much.

Also just realized that it shouldn't be in a else condition. Anyway, removing it.

camelid · 2026-08-12T15:34:26Z

@@ -3150,3 +3174,30 @@ fn repr_attribute<'tcx>(

    (!result.is_empty()).then(|| format!("#[repr({})]", result.join(", ")).into())
 }
+
+pub(crate) fn compute_if_deref_target_implements_copy(
+    cx: &Context<'_>,


Let's have this take TyCtxt instead of Context and change the callers as well. It's better to take as little input as possible.

View changes since the review

camelid · 2026-08-12T15:35:00Z

    AlsoCollectAssocFns { assoc_fns: &'r mut Vec<Link<'l>> },
 }

 fn get_methods<'a>(
    i: &'a clean::Impl,
    mut mode: GetMethodsMode<'_, 'a>,
    used_links: &mut FxHashSet<String>,
-    tcx: TyCtxt<'_>,
+    cx: &Context<'_>,


Ditto here.

View changes since the review

…opy`

…t in `Cache`

rustbot · 2026-08-12T20:43:23Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

GuillaumeGomez · 2026-08-12T20:44:39Z

Applied suggestions.

@rustbot ready

rustbot assigned camelid Aug 11, 2026

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GuillaumeGomez force-pushed the deref-items branch from 32c5654 to e3fb18c Compare August 11, 2026 14:58

camelid requested changes Aug 11, 2026

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Comment thread src/librustdoc/clean/inline.rs Outdated

Comment thread src/librustdoc/clean/utils.rs Outdated

Comment thread tests/rustdoc-html/deref/deref-to-primitive.rs

rustbot 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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 11, 2026

GuillaumeGomez removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 11, 2026

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 11, 2026

camelid reviewed Aug 12, 2026

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camelid 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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 12, 2026

GuillaumeGomez added 3 commits August 12, 2026 22:05

rustdoc: Only show useable impl items through Deref

9d8966a

Correctly show methods taking self if the target type implements `C…

240a859

…opy`

Compute "is copy" information directly in render instead of storing i…

7a71fdf

…t in `Cache`

GuillaumeGomez force-pushed the deref-items branch from ca399ba to 7a71fdf Compare August 12, 2026 20:43

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 12, 2026

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