# Rust 1.92.0 pre-release testing

**URL:** <https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805>\
**Category:** announcements\
**Created:** [December 8, 2025, 9:33pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805 "2025-12-08T21:33:17Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![system](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/system/32/14092_2.png) [@system](https://internals.rust-lang.org/u/system)\
**Post date:** [December 8, 2025, 9:33pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/1 "2025-12-08T21:33:17Z")

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The 1.92.0 pre-release is ready for testing. The release is scheduled for December 11. [Release notes can be found here.](https://dev-doc.rust-lang.org/1.92.0/releases.html)

You can try it out locally by running:

```plaintext
RUSTUP_DIST_SERVER=https://dev-static.rust-lang.org rustup update stable

```

The index is [https://dev-static.rust-lang.org/dist/2025-12-08/index.html](https://dev-static.rust-lang.org/dist/2025-12-08/index.html).

The release team is also thinking about changes to our pre-release process: we'd love your feedback [on this GitHub issue](https://github.com/rust-lang/release-team/issues/16).

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**Author:** ![josh](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/josh/32/5934_2.png) [@josh](https://internals.rust-lang.org/u/josh)\
**Post date:** [December 8, 2025, 11:24pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/2 "2025-12-08T23:24:38Z")

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Tried this with two large projects (one of which builds ~1000 crates across a multitarget build); no issues at all.

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**Author:** ![pacak](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/pacak/32/11934_2.png) [@pacak](https://internals.rust-lang.org/u/pacak)\
**Post date:** [December 9, 2025, 7:51pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/3 "2025-12-09T19:51:21Z")

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Now it complains if you have a function that produces error with `Infallible` value in `Result` (think `exec` or similar call that won't return if succeeds, but will return error if fails. I'm trying to use `unwrap()` to cause panic

```rust
use std::convert::Infallible;

pub fn dummy() -> Result<Infallible, &'static str> {
    Err("nope")
}

pub fn complains() {
    // note: this expression has type `Infallible`, which is uninhabited
    dummy().unwrap();
}

pub fn also_complains() {
    // = note: this `Result` may be an `Err` variant, which should be handled
    dummy();
}

```

This works, but ugly.

```rust
panic!("{:?}", dummy().unwrap_err());

```

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**Author:** ![Vorpal](https://avatars.discourse-cdn.com/v4/letter/v/aca169/32.png) [@Vorpal](https://internals.rust-lang.org/u/Vorpal)\
**Post date:** [December 9, 2025, 8:11pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/4 "2025-12-09T20:11:55Z")

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You should probably report a bug on github / check if one was already reported.

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**Author:** ![dtolnay](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/dtolnay/32/1447_2.png) [@dtolnay](https://internals.rust-lang.org/u/dtolnay)\
**Post date:** [December 9, 2025, 8:19pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/5 "2025-12-09T20:19:25Z")

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That is from:

> <https://github.com/rust-lang/rust/pull/142390>
>
> Rebase of https://github.com/rust-lang/rust/pull/101500
> 
> Fixes https://github.…com/rust-lang/rust/issues/51003.
> 
> The first commit moves detection of uninhabited types from the current liveness pass to MIR building.
> 
> In order to keep the same level of diagnostics, I had to instrument MIR a little more:
> \- keep for which original local a guard local is created;
> \- store in the \`VarBindingForm\` the list of introducer places and whether this was a shorthand pattern.
> 
> I am not very proud of the handling of self-assignments. The proposed scheme is in two parts: first detect probable self-assignments, by pattern matching on MIR, and second treat them specially during dataflow analysis. I welcome ideas.
> 
> Please review carefully the changes in tests. There are many small changes to behaviour, and I'm not sure all of them are desirable.

and fixed in:

> <https://github.com/rust-lang/rust/pull/149044>
>
> Closes rust-lang/rust#149042
> 
> Attempts to be smarter about identifying 'real'/…user-written unreachable code to raise the lint

but not backported into 1.92.0.

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<div class="post-metadata">

**Author:** ![tdelmas](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/tdelmas/32/10601_2.png) [@tdelmas](https://internals.rust-lang.org/u/tdelmas)\
**Post date:** [December 10, 2025, 12:35pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/6 "2025-12-10T12:35:36Z")

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[Rust Release Notes](https://dev-doc.rust-lang.org/1.92.0/releases.html) :

> - [`iter::Repeat::last`](https://github.com/rust-lang/rust/pull/147258) and [`count`](https://github.com/rust-lang/rust/pull/146410) will now panic, rather than looping infinitely.

It seems they added a `panic!` for `last` without documenting it, or am I missing it? (`count` does document the `panic!` in `Iterator`: [Iterator in std::iter - Rust](https://doc.rust-lang.org/beta/std/iter/trait.Iterator.html#method.count))

- `last` in [Iterator in std::iter - Rust](https://doc.rust-lang.org/beta/std/iter/trait.Iterator.html#method.last)
- `last` in [Repeat in std::iter - Rust](https://doc.rust-lang.org/beta/std/iter/struct.Repeat.html#method.last)

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<div class="post-metadata">

**Author:** ![josh](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/josh/32/5934_2.png) [@josh](https://internals.rust-lang.org/u/josh)\
**Post date:** [December 10, 2025, 1:04pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/7 "2025-12-10T13:04:46Z")

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May warrant a quick backport so we don't innundate folks with new warnings.

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<div class="post-metadata">

**Author:** ![dlight](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/dlight/32/8462_2.png) [@dlight](https://internals.rust-lang.org/u/dlight)\
**Post date:** [December 10, 2025, 1:31pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/8 "2025-12-10T13:31:42Z")

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Is the dec 11 release date a hard deadline? It could be delayed for a day or two to make time for this fix to be backported

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**Author:** ![jhpratt](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/jhpratt/32/11640_2.png) [@jhpratt](https://internals.rust-lang.org/u/jhpratt)\
**Post date:** [December 10, 2025, 1:59pm UTC](https://internals.rust-lang.org/t/rust-1-92-0-pre-release-testing/23805/9 "2025-12-10T13:59:42Z")

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1.0 and 1.2 were released on Fridays; every other release has been on the Thursday fixed by the six week cadence. It's certainly possible, but more likely that we'd get a quick point release imo