smart pointer (try_)map #144420

Qelxiros · 2025-07-24T21:13:53Z

Tracking issue: #144419

rustbot · 2025-07-25T00:12:56Z

rustbot has assigned @thomcc.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Qelxiros · 2025-07-25T00:12:59Z

As far as I can tell, the ICE here is because of the function signature of Box::try_map. The return type is equivalent to ChangeOutputType<...> from the ACP, but that definition is in core, so I implemented it manually here. However, when I add the same type alias to alloc, the ICE persists. Is there a workaround here that remains in the spirit of the ACP? Is this a known compiler bug?

joboet

I have no clue about the ICE – perhaps try filing an issue?

View changes since this review

library/alloc/src/boxed.rs

Qelxiros · 2025-09-04T13:55:27Z

I'm not sure how to move forward given the ICE (issue #146174).

@rustbot label +S-blocked

…iler-errors fix ICE when suggesting `::new` fixes rust-lang#146174 This code suggests to write `Foo::new(...)` when the user writes `Foo(...)` or `Foo { ... }` and the constructor is private, where `new` is some associated function that returns `Self`. When checking that the return type of `new` is `Self`, we need to instantiate the parameters of `new` with infer vars, so we don't end up with a type like `Box<$param(0)>` in a context that doesn't have any parameters. But then we can't use `normalize_erasing_late_bound_regions` anymore because that goes though a query that can't deal with infer vars. Since this is diagnostic-only code that is supposed to check for exactly `-> Self`, I think it's fine to just skip normalizing here, especially since The Correct WayTM would involve a probe and make this code even more complicated. Also, the code here does almost the same thing, and these suggestions can probably be unified in the future: https://github.com/rust-lang/rust/blob/4ca8078d37c53ee4ff8fb32b4453b915116f25b8/compiler/rustc_hir_typeck/src/method/suggest.rs#L2123-L2129 r? `@compiler-errors` cc `@Qelxiros` -- this should unblock rust-lang#144420

…iler-errors fix ICE when suggesting `::new` fixes rust-lang#146174 This code suggests to write `Foo::new(...)` when the user writes `Foo(...)` or `Foo { ... }` and the constructor is private, where `new` is some associated function that returns `Self`. When checking that the return type of `new` is `Self`, we need to instantiate the parameters of `new` with infer vars, so we don't end up with a type like `Box<$param(0)>` in a context that doesn't have any parameters. But then we can't use `normalize_erasing_late_bound_regions` anymore because that goes though a query that can't deal with infer vars. Since this is diagnostic-only code that is supposed to check for exactly `-> Self`, I think it's fine to just skip normalizing here, especially since The Correct WayTM would involve a probe and make this code even more complicated. Also, the code here does almost the same thing, and these suggestions can probably be unified in the future: https://github.com/rust-lang/rust/blob/4ca8078d37c53ee4ff8fb32b4453b915116f25b8/compiler/rustc_hir_typeck/src/method/suggest.rs#L2123-L2129 r? ```@compiler-errors``` cc ```@Qelxiros``` -- this should unblock rust-lang#144420

…iler-errors fix ICE when suggesting `::new` fixes rust-lang#146174 This code suggests to write `Foo::new(...)` when the user writes `Foo(...)` or `Foo { ... }` and the constructor is private, where `new` is some associated function that returns `Self`. When checking that the return type of `new` is `Self`, we need to instantiate the parameters of `new` with infer vars, so we don't end up with a type like `Box<$param(0)>` in a context that doesn't have any parameters. But then we can't use `normalize_erasing_late_bound_regions` anymore because that goes though a query that can't deal with infer vars. Since this is diagnostic-only code that is supposed to check for exactly `-> Self`, I think it's fine to just skip normalizing here, especially since The Correct WayTM would involve a probe and make this code even more complicated. Also, the code here does almost the same thing, and these suggestions can probably be unified in the future: https://github.com/rust-lang/rust/blob/4ca8078d37c53ee4ff8fb32b4453b915116f25b8/compiler/rustc_hir_typeck/src/method/suggest.rs#L2123-L2129 r? ````@compiler-errors```` cc ````@Qelxiros```` -- this should unblock rust-lang#144420

Rollup merge of #146217 - lukas-code:suggest-new-ice, r=compiler-errors fix ICE when suggesting `::new` fixes #146174 This code suggests to write `Foo::new(...)` when the user writes `Foo(...)` or `Foo { ... }` and the constructor is private, where `new` is some associated function that returns `Self`. When checking that the return type of `new` is `Self`, we need to instantiate the parameters of `new` with infer vars, so we don't end up with a type like `Box<$param(0)>` in a context that doesn't have any parameters. But then we can't use `normalize_erasing_late_bound_regions` anymore because that goes though a query that can't deal with infer vars. Since this is diagnostic-only code that is supposed to check for exactly `-> Self`, I think it's fine to just skip normalizing here, especially since The Correct WayTM would involve a probe and make this code even more complicated. Also, the code here does almost the same thing, and these suggestions can probably be unified in the future: https://github.com/rust-lang/rust/blob/4ca8078d37c53ee4ff8fb32b4453b915116f25b8/compiler/rustc_hir_typeck/src/method/suggest.rs#L2123-L2129 r? ````@compiler-errors```` cc ````@Qelxiros```` -- this should unblock #144420

rustbot · 2025-09-07T20:04:28Z

This PR was rebased onto a different master 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.

Qelxiros · 2025-09-18T16:41:38Z

@rustbot label -S-blocked

joboet

This looks great! Is it actually still a WIP? Otherwise, maybe change the PR title 😉.

One suggestion, and then I think this is ready to merge.

View changes since this review

library/alloc/src/boxed.rs

joboet · 2025-09-19T09:43:54Z

r? joboet

Qelxiros · 2025-09-19T15:23:07Z

The ACP also specifies by-value implementations for UniqueRc and UniqueArc. I can add those to this PR, or I can open a separate one if you think this one is scope creeping too much.

joboet · 2025-09-19T15:34:51Z

I don't mind either way.

joboet · 2025-09-25T14:57:39Z

library/alloc/src/rc.rs

+    /// an `Rc`.
+    ///
+    /// Note: this is an associated function, which means that you have
+    /// to call it as `Rc::map(&r, f)` instead of `r.map(f)`. This


Suggested change

/// to call it as `Rc::map(&r, f)` instead of `r.map(f)`. This

/// to call it as `Rc::map(r, f)` instead of `r.map(f)`. This

joboet · 2025-09-25T14:59:59Z

library/alloc/src/rc.rs

+    /// result is returned, also in an `Rc`.
+    ///
+    /// Note: this is an associated function, which means that you have
+    /// to call it as `Rc::try_map(&r, f)` instead of `r.try_map(f)`. This


Suggested change

/// to call it as `Rc::try_map(&r, f)` instead of `r.try_map(f)`. This

/// to call it as `Rc::try_map(r, f)` instead of `r.try_map(f)`. This

joboet · 2025-09-25T15:00:52Z

library/alloc/src/rc.rs

+    /// also in a `UniqueRc`.
+    ///
+    /// Note: this is an associated function, which means that you have
+    /// to call it as `UniqueRc::map(&u, f)` instead of `u.map(f)`. This


Suggested change

/// to call it as `UniqueRc::map(&u, f)` instead of `u.map(f)`. This

/// to call it as `UniqueRc::map(u, f)` instead of `u.map(f)`. This

joboet · 2025-09-25T15:10:15Z

library/alloc/src/rc.rs

+        let this = ManuallyDrop::new(this);
+        let val: T = unsafe { ptr::read(&**this) };
+
+        this.inner().dec_strong();


The strong count of a UniqueRc is already zero.

joboet · 2025-09-25T15:13:51Z

library/alloc/src/sync.rs

+        // We know there's only one strong reference, so the ordering doesn't matter.
+        this.inner().strong.fetch_sub(1, Relaxed);


Same here: there is no strong reference.

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 24, 2025

Qelxiros mentioned this pull request Jul 24, 2025

Tracking Issue for smart pointer (try_)map #144419

Open

3 tasks

This comment has been minimized.

Sign in to view

Qelxiros marked this pull request as ready for review July 25, 2025 00:12

rustbot assigned thomcc Jul 25, 2025

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 Jul 25, 2025

joboet reviewed Aug 30, 2025

View reviewed changes

library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

Qelxiros force-pushed the smart_pointer_try_map branch from d5d5fea to 929d326 Compare September 2, 2025 20:53

This comment has been minimized.

Sign in to view

Qelxiros force-pushed the smart_pointer_try_map branch from 929d326 to 6a69f39 Compare September 2, 2025 20:57

This comment has been minimized.

Sign in to view

joboet reviewed Sep 2, 2025

View reviewed changes

library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

Qelxiros force-pushed the smart_pointer_try_map branch from 6a69f39 to 64b65c1 Compare September 3, 2025 19:47

Qelxiros mentioned this pull request Sep 3, 2025

Complex function signature in Box method causes ICE #146174

Closed

This comment has been minimized.

Sign in to view

joboet reviewed Sep 3, 2025

View reviewed changes

library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

Qelxiros force-pushed the smart_pointer_try_map branch from 64b65c1 to bfc61d6 Compare September 4, 2025 00:21

This comment has been minimized.

Sign in to view

rustbot added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Sep 4, 2025

lukas-code mentioned this pull request Sep 4, 2025

fix ICE when suggesting ::new #146217

Merged

This comment has been minimized.

Sign in to view

Qelxiros force-pushed the smart_pointer_try_map branch from 0c65df4 to 59acdbc Compare September 8, 2025 12:44

This comment has been minimized.

Sign in to view

Qelxiros force-pushed the smart_pointer_try_map branch from 59acdbc to 2ee0f1d Compare September 8, 2025 14:54

add Box::(try_)map

dd0846e

Qelxiros force-pushed the smart_pointer_try_map branch from 2ee0f1d to dd0846e Compare September 8, 2025 15:01

This comment has been minimized.

Sign in to view

Qelxiros force-pushed the smart_pointer_try_map branch from 3c27222 to 375c036 Compare September 18, 2025 12:14

This comment has been minimized.

Sign in to view

Qelxiros force-pushed the smart_pointer_try_map branch from 375c036 to 0ee6d47 Compare September 18, 2025 13:23

This comment has been minimized.

Sign in to view

Qelxiros force-pushed the smart_pointer_try_map branch from 0ee6d47 to 41ce8ad Compare September 18, 2025 14:28

rustbot removed the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Sep 18, 2025

joboet approved these changes Sep 19, 2025

View reviewed changes

library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

rustbot assigned joboet and unassigned thomcc Sep 19, 2025

add by-reference implementations for Rc and Arc

cdb8d49

Qelxiros force-pushed the smart_pointer_try_map branch from 41ce8ad to cdb8d49 Compare September 19, 2025 15:22

Qelxiros changed the title ~~WIP: smart pointer (try_)map~~ smart pointer (try_)map Sep 22, 2025

This comment has been minimized.

Sign in to view

add Unique{Rc,Arc}::(try_)map

88ac38e

Qelxiros force-pushed the smart_pointer_try_map branch from 91cc3b0 to 88ac38e Compare September 22, 2025 14:56

joboet requested changes Sep 25, 2025

View reviewed changes

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 Sep 25, 2025

	/// to call it as `Rc::map(&r, f)` instead of `r.map(f)`. This
	/// to call it as `Rc::map(r, f)` instead of `r.map(f)`. This

	/// to call it as `Rc::try_map(&r, f)` instead of `r.try_map(f)`. This
	/// to call it as `Rc::try_map(r, f)` instead of `r.try_map(f)`. This

	/// to call it as `UniqueRc::map(&u, f)` instead of `u.map(f)`. This
	/// to call it as `UniqueRc::map(u, f)` instead of `u.map(f)`. This

		// We know there's only one strong reference, so the ordering doesn't matter.
		this.inner().strong.fetch_sub(1, Relaxed);

smart pointer (try_)map #144420

Are you sure you want to change the base?

smart pointer (try_)map #144420

Uh oh!

Conversation

Qelxiros commented Jul 24, 2025 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

This comment has been minimized.

rustbot commented Jul 25, 2025

Uh oh!

Qelxiros commented Jul 25, 2025

Uh oh!

joboet left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

Uh oh!

This comment has been minimized.

Uh oh!

Uh oh!

This comment has been minimized.

Qelxiros commented Sep 4, 2025

Uh oh!

rustbot commented Sep 7, 2025

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

Qelxiros commented Sep 18, 2025

Uh oh!

joboet left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

joboet commented Sep 19, 2025

Uh oh!

Qelxiros commented Sep 19, 2025

Uh oh!

joboet commented Sep 19, 2025

Uh oh!

This comment has been minimized.

joboet Sep 25, 2025

Choose a reason for hiding this comment

Uh oh!

joboet Sep 25, 2025

Choose a reason for hiding this comment

Uh oh!

joboet Sep 25, 2025

Choose a reason for hiding this comment

Uh oh!

joboet Sep 25, 2025

Choose a reason for hiding this comment

Uh oh!

joboet Sep 25, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Qelxiros commented Jul 24, 2025 •

edited by rustbot

Loading

joboet left a comment •

edited by rustbot

Loading

joboet left a comment •

edited by rustbot

Loading