WIP: smart pointer (try_)map #144420

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

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Aug 30, 2025

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edited by rustbot

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

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library/alloc/src/boxed.rs Outdated Show resolved Hide resolved

@Qelxiros Qelxiros force-pushed the smart_pointer_try_map branch from d5d5fea to 929d326 Compare

September 2, 2025 20:53

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@Qelxiros Qelxiros force-pushed the smart_pointer_try_map branch from 929d326 to 6a69f39 Compare

September 2, 2025 20:57

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rustbot commented Sep 2, 2025

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.

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joboet

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Sep 2, 2025

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library/alloc/src/boxed.rs Outdated

if size_of::<T>() == size_of::() && align_of::<T>() == align_of::() {

let ptr = &raw const *this;

unsafe {

let new = f(ptr.read());

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If f panics, this will lead to a double-free.

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Ok, I think this iteration works. I'm still wrapping my head around working with closures that can panic, so thanks for bearing with me.

@Qelxiros Qelxiros force-pushed the smart_pointer_try_map branch from 6a69f39 to 64b65c1 Compare

September 3, 2025 19:47

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Sep 3, 2025

Complex function signature in Box method causes ICE #146174

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joboet

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Sep 3, 2025

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library/alloc/src/boxed.rs Outdated

impl<T> Drop for Guard<T> {

fn drop(&mut self) {

let _box = unsafe { Box::from_raw(self.0) };

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This will still drop the Box's contents and hence result in a double-free.

library/alloc/src/boxed.rs Outdated

Comment on lines 421 to 428

let guard = Guard(Box::into_raw(this));

unsafe {

let new = f(guard.0.read());

let ptr = guard.0;

mem::forget(guard);

ptr.cast::().write(new);

Box::from_raw(ptr.cast::())

}

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I'd recommend converting the Box<T> to a Box<MaybeUninit> before calling f. This ensures that the allocation is freed, but won't drop the old value on panic. After reading from that, you can use Box::write to write the final value back.

Suggested change

let guard = Guard(Box::into_raw(this));

unsafe{

let new = f(guard.0.read());

let ptr = guard.0;

mem::forget(guard);

ptr.cast::().write(new);

Box::from_raw(ptr.cast::())

}

let (allocation, value) = unsafe{

let ptr = Box::into_raw(this);

let value = ptr.read();

let allocation = Box::from_raw(ptr.cast::<MaybeUninit());

(allocation, value)

};

Box::write(allocation,f(value))

@Qelxiros


 add Box::(try_)map

bfc61d6

@Qelxiros Qelxiros force-pushed the smart_pointer_try_map branch from 64b65c1 to bfc61d6 Compare

September 4, 2025 00:21

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The job aarch64-gnu-llvm-19-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

To only update this specific test, also pass `--test-args parallel-rustc/ty-variance-issue-124423.rs`
error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/parallel-rustc/ty-variance-issue-124423" "-A" "unused" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-Z" "threads=16"
stdout: none
--- stderr -------------------------------
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:8:15
 |
LL | fn elided(_: &impl Copy + 'a) -> _ { x }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn elided(_: &(impl Copy + 'a)) -> _ { x }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:13:24
 |
LL | fn explicit<'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn explicit<'b>(_: &'a (impl Copy + 'a)) -> impl 'a { x }
 | + +
error: expected identifier, found keyword `impl`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:20:13
 |
LL | fn elided2( impl 'b) -> impl 'a + 'a { x }
 | ^^^^ expected identifier, found keyword
error: expected one of `:` or `|`, found `'b`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:20:18
 |
LL | fn elided2( impl 'b) -> impl 'a + 'a { x }
 | ^^ expected one of `:` or `|`
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:27:25
 |
LL | fn explicit2<'a>(_: &'a impl Copy + 'a) -> impl Copy + 'a { x }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn explicit2<'a>(_: &'a (impl Copy + 'a)) -> impl Copy + 'a { x }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:30:16
 |
LL | fn foo<'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn foo<'a>(_: &(impl Copy + 'a)) -> impl 'b + 'a { x }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:35:16
 |
LL | fn elided3(_: &impl Copy + 'a) -> Box<dyn 'a> { Box::new(x) }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn elided3(_: &(impl Copy + 'a)) -> Box<dyn 'a> { Box::new(x) }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:41:17
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn x<'b>(_: &'a (impl Copy + 'a)) -> Box<dyn 'b> { Box::u32(x) }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:48:16
 |
LL | fn elided4(_: &impl Copy + 'a) -> new { x(x) }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn elided4(_: &(impl Copy + 'a)) -> new { x(x) }
 | + +
error: at least one trait must be specified
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:13:43
 |
LL | fn explicit<'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | ^^^^^^^
error: at least one trait must be specified
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:20:25
 |
LL | fn elided2( impl 'b) -> impl 'a + 'a { x }
 | ^^^^^^^^^^^^
error: at least one trait must be specified
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:30:35
 |
LL | fn foo<'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | ^^^^^^^^^^^^
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:8:27
 |
LL | fn elided(_: &impl Copy + 'a) -> _ { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided<'a>(_: &impl Copy + 'a) -> _ { x }
 | ++++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:13:21
 |
LL | fn explicit<'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn explicit<'a, 'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:13:36
 |
LL | fn explicit<'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn explicit<'a, 'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:13:48
 |
LL | fn explicit<'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn explicit<'a, 'b>(_: &'a impl Copy + 'a) -> impl 'a { x }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:20:30
 |
LL | fn elided2( impl 'b) -> impl 'a + 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided2<'a>( impl 'b) -> impl 'a + 'a { x }
 | ++++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:20:35
 |
LL | fn elided2( impl 'b) -> impl 'a + 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided2<'a>( impl 'b) -> impl 'a + 'a { x }
 | ++++
error[E0261]: use of undeclared lifetime name `'b`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:30:40
 |
LL | fn foo<'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'b` here
 |
LL | fn foo<'b, 'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:35:28
 |
LL | fn elided3(_: &impl Copy + 'a) -> Box<dyn 'a> { Box::new(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided3<'a>(_: &impl Copy + 'a) -> Box<dyn 'a> { Box::new(x) }
 | ++++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:35:43
 |
LL | fn elided3(_: &impl Copy + 'a) -> Box<dyn 'a> { Box::new(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided3<'a>(_: &impl Copy + 'a) -> Box<dyn 'a> { Box::new(x) }
 | ++++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:41:14
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn x<'a, 'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:41:29
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn x<'a, 'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:48:28
 |
LL | fn elided4(_: &impl Copy + 'a) -> new { x(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided4<'a>(_: &impl Copy + 'a) -> new { x(x) }
 | ++++
error[E0412]: cannot find type `new` in this scope
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:48:36
 |
LL | fn elided4(_: &impl Copy + 'a) -> new { x(x) }
 | ^^^ not found in this scope
error[E0224]: at least one trait is required for an object type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:55:40
 |
LL | impl<'a> LifetimeTrait<'a> for &'a Box<dyn 'a> {}
 | ^^^^^^
error[E0224]: at least one trait is required for an object type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:35:39
 |
LL | fn elided3(_: &impl Copy + 'a) -> Box<dyn 'a> { Box::new(x) }
 | ^^^^^^
error[E0224]: at least one trait is required for an object type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:41:40
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^^^^^
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:8:34
 |
LL | fn elided(_: &impl Copy + 'a) -> _ { x }
 | ^ not allowed in type signatures
error[E0599]: no function or associated item named `u32` found for struct `Box<_, _>` in the current scope
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-124423.rs:41:55
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^^ function or associated item not found in `Box<_, _>`
 |
note: if you're trying to build a new `Box<_, _>` consider using one of the following associated functions:
 Box::<T>::new
 Box::<T>::new_uninit
 Box::<T>::new_zeroed
 Box::<T>::try_new
 and 23 others
---
To only update this specific test, also pass `--test-args parallel-rustc/ty-variance-issue-127971.rs`
error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/parallel-rustc/ty-variance-issue-127971" "-A" "unused" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-Z" "threads=16"
stdout: none
--- stderr -------------------------------
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:8:15
 |
LL | fn elided(_: &impl Copy + 'a) -> _ { x }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn elided(_: &(impl Copy + 'a)) -> _ { x }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:13:16
 |
LL | fn foo<'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn foo<'a>(_: &(impl Copy + 'a)) -> impl 'b + 'a { x }
 | + +
error: ambiguous `+` in a type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:18:17
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^^^^^^^^^^^^^
 |
help: try adding parentheses
 |
LL | fn x<'b>(_: &'a (impl Copy + 'a)) -> Box<dyn 'b> { Box::u32(x) }
 | + +
error: at least one trait must be specified
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:13:35
 |
LL | fn foo<'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | ^^^^^^^^^^^^
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:8:27
 |
LL | fn elided(_: &impl Copy + 'a) -> _ { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn elided<'a>(_: &impl Copy + 'a) -> _ { x }
 | ++++
error[E0261]: use of undeclared lifetime name `'b`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:13:40
 |
LL | fn foo<'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'b` here
 |
LL | fn foo<'b, 'a>(_: &impl Copy + 'a) -> impl 'b + 'a { x }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:18:14
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn x<'a, 'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | +++
error[E0261]: use of undeclared lifetime name `'a`
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:18:29
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^ undeclared lifetime
 |
help: consider introducing lifetime `'a` here
 |
LL | fn x<'a, 'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | +++
error[E0224]: at least one trait is required for an object type
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:18:40
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^^^^^
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:8:34
 |
LL | fn elided(_: &impl Copy + 'a) -> _ { x }
 | ^ not allowed in type signatures
error[E0599]: no function or associated item named `u32` found for struct `Box<_, _>` in the current scope
##[error] --> /checkout/tests/ui/parallel-rustc/ty-variance-issue-127971.rs:18:55
 |
LL | fn x<'b>(_: &'a impl Copy + 'a) -> Box<dyn 'b> { Box::u32(x) }
 | ^^^ function or associated item not found in `Box<_, _>`
 |
note: if you're trying to build a new `Box<_, _>` consider using one of the following associated functions:
 Box::<T>::new
 Box::<T>::new_uninit
 Box::<T>::new_zeroed
 Box::<T>::try_new
 and 23 others
---
---- [ui] tests/ui/privacy/suggest-box-new.rs stdout ----
error: Error: expected failure status (Some(1)) but received status Some(101).
status: exit status: 101
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/privacy/suggest-box-new.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/privacy/suggest-box-new" "-A" "unused" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error[E0423]: expected function, tuple struct or tuple variant, found struct `std::collections::HashMap`
##[error] --> /checkout/tests/ui/privacy/suggest-box-new.rs:14:13
 |
---
 |
LL - let _ = std::collections::HashMap();
LL + let _ = std::collections::HashMap::with_hasher(_);
 |
LL - let _ = std::collections::HashMap();
LL + let _ = std::collections::HashMap::with_capacity_and_hasher(_, _);
 |
help: consider using the `Default` trait
 |
LL | let _ = <std::collections::HashMap as std::default::Default>::default();
 | + ++++++++++++++++++++++++++++++++++
error[E0423]: cannot initialize a tuple struct which contains private fields
##[error] --> /checkout/tests/ui/privacy/suggest-box-new.rs:8:19
 |
LL | wtf: Some(Box(U { //~ ERROR cannot initialize a tuple struct which contains private fields
 | ^^^
 |
note: constructor is not visible here due to private fields
 --> /rustc/FAKE_PREFIX/library/alloc/src/boxed.rs:234:14
 |
 = note: private field
 |
 = note: private field
help: you might have meant to use an associated function to build this type
 |
LL - wtf: Some(Box(U { //~ ERROR cannot initialize a tuple struct which contains private fields
LL - wtf: None,
LL - x: (),
LL - })),
LL + wtf: Some(Box::new(_)),
 |
LL - wtf: Some(Box(U { //~ ERROR cannot initialize a tuple struct which contains private fields
LL - wtf: None,
LL - x: (),
LL - })),
LL + wtf: Some(Box::new_uninit()),
 |
LL - wtf: Some(Box(U { //~ ERROR cannot initialize a tuple struct which contains private fields
LL - wtf: None,
LL - x: (),
LL - })),
LL + wtf: Some(Box::new_zeroed()),
 |
LL - wtf: Some(Box(U { //~ ERROR cannot initialize a tuple struct which contains private fields
LL - wtf: None,
LL - x: (),
LL - })),
LL + wtf: Some(Box::new_in(_, _)),
 |
 = and 13 other candidates
help: consider using the `Default` trait
 |
LL - wtf: Some(Box(U { //~ ERROR cannot initialize a tuple struct which contains private fields
LL + wtf: Some(<Box as std::default::Default>::default()),
 |
error: cannot construct `HashMap<_, _, _>` with struct literal syntax due to private fields
##[error] --> /checkout/tests/ui/privacy/suggest-box-new.rs:16:13
 |
---
 |
LL - let _ = std::collections::HashMap {};
LL + let _ = std::collections::HashMap::with_hasher(_);
 |
LL - let _ = std::collections::HashMap {};
LL + let _ = std::collections::HashMap::with_capacity_and_hasher(_, _);
 |
help: consider using the `Default` trait
 |
LL - let _ = std::collections::HashMap {};
LL + let _ = <std::collections::HashMap as std::default::Default>::default();

@Qelxiros

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Qelxiros commented Sep 4, 2025

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

@rustbot label +S-blocked

@rustbot rustbot added the S-blocked label

Sep 4, 2025

@lukas-code lukas-code mentioned this pull request

Sep 4, 2025

fix ICE when suggesting ::new #146217

Open

tgross35 added a commit to tgross35/rust that referenced this pull request

Sep 5, 2025

@tgross35


 Rollup merge of rust-lang#146217 - lukas-code:suggest-new-ice, r=comp...

d879821

...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 Way<sup>TM</sup> 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

tgross35 added a commit to tgross35/rust that referenced this pull request

Sep 5, 2025

@tgross35


 Rollup merge of rust-lang#146217 - lukas-code:suggest-new-ice, r=comp...

3baf985

...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 Way<sup>TM</sup> 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

Labels

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WIP: smart pointer (try_)map #144420

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WIP: smart pointer (try_)map #144420

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rust-log-analyzer commented Sep 4, 2025

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@Qelxiros Qelxiros commented Jul 24, 2025 •

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