Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound by Muhtasim-Rasheed · Pull Request #157966 · rust-lang/rust

Muhtasim-Rasheed · 2026-06-16T13:09:25Z

rustbot · 2026-06-16T13:09:30Z

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qaijuang

Took a quick glance 👀

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qaijuang · 2026-06-16T14:28:45Z

+                    let snippet = tcx.sess.source_map().span_to_snippet(span).unwrap();
+                    if span != expr.span {
+                        err.help(format!(
+                            "`!` can be coerced to any type; consider casting to a concrete type that implements the trait, e.g. \
+                            `{} as SomeType`", snippet
+                        ));
+                    }


Suggested change

let snippet = tcx.sess.source_map().span_to_snippet(span).unwrap();

if span != expr.span {

err.help(format!(

"`!` can be coerced to any type; consider casting to a concrete type that implements the trait, e.g. \

`{} as SomeType`", snippet

));

}

if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(span)

&& span != expr.span

{

err.help(format!(

"`!` can be coerced to any type; consider casting to a concrete type that implements the trait, e.g. \

`{snippet} as SomeType`"

));

}

mati865 · 2026-06-17T12:42:52Z

@rustbot reroll

davidtwco

This seems reasonable to me, one comment

View changes since this review

rustbot · 2026-07-02T15:00:21Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

… fails to satisfy an `impl Trait` bound

rustbot · 2026-07-05T13:56:58Z

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.

Muhtasim-Rasheed · 2026-07-05T14:00:19Z

@rustbot ready

davidtwco · 2026-07-06T11:11:37Z

@bors r+ rollup

rust-bors · 2026-07-06T11:11:41Z

📌 Commit c9ad0e5 has been approved by davidtwco

It is now in the queue for this repository.

…estion-cast-never-type, r=davidtwco Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound Fixes rust-lang#157923

…uwer Rollup of 12 pull requests Successful merges: - #156976 (enable eager `param_env` norm in new solver) - #158537 (Add `std::io::cursor::WriteThroughCursor`) - #158540 (Move `std::io::Seek` to `core::io`) - #157820 (consider subtyping when checking if an infer var is sized) - #158505 (Update POSIX edition links) - #158853 (Fix typo for link on nto-qnx.md) - #157466 (Better error message when bare type in impl parameter list) - #157966 (Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound) - #158381 (Expose debug scope of statement and terminator in rustc_public) - #158405 (rustc_target: Add ARMv8-M related target features) - #158770 (Weaken guarantee for `From<legacy::RangeInclusive> for RangeInclusive`) - #158820 (Fix rustdoc ICE on deprecated note in inlined re-export chain)

Rollup merge of #157966 - Muhtasim-Rasheed:issue-157923-suggestion-cast-never-type, r=davidtwco Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound Fixes #157923

…nathanBrouwer Rollup of 12 pull requests Successful merges: - rust-lang#156976 (enable eager `param_env` norm in new solver) - rust-lang#158537 (Add `std::io::cursor::WriteThroughCursor`) - rust-lang#158540 (Move `std::io::Seek` to `core::io`) - rust-lang#157820 (consider subtyping when checking if an infer var is sized) - rust-lang#158505 (Update POSIX edition links) - rust-lang#158853 (Fix typo for link on nto-qnx.md) - rust-lang#157466 (Better error message when bare type in impl parameter list) - rust-lang#157966 (Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound) - rust-lang#158381 (Expose debug scope of statement and terminator in rustc_public) - rust-lang#158405 (rustc_target: Add ARMv8-M related target features) - rust-lang#158770 (Weaken guarantee for `From<legacy::RangeInclusive> for RangeInclusive`) - rust-lang#158820 (Fix rustdoc ICE on deprecated note in inlined re-export chain)

…uwer Rollup of 12 pull requests Successful merges: - rust-lang/rust#156976 (enable eager `param_env` norm in new solver) - rust-lang/rust#158537 (Add `std::io::cursor::WriteThroughCursor`) - rust-lang/rust#158540 (Move `std::io::Seek` to `core::io`) - rust-lang/rust#157820 (consider subtyping when checking if an infer var is sized) - rust-lang/rust#158505 (Update POSIX edition links) - rust-lang/rust#158853 (Fix typo for link on nto-qnx.md) - rust-lang/rust#157466 (Better error message when bare type in impl parameter list) - rust-lang/rust#157966 (Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound) - rust-lang/rust#158381 (Expose debug scope of statement and terminator in rustc_public) - rust-lang/rust#158405 (rustc_target: Add ARMv8-M related target features) - rust-lang/rust#158770 (Weaken guarantee for `From<legacy::RangeInclusive> for RangeInclusive`) - rust-lang/rust#158820 (Fix rustdoc ICE on deprecated note in inlined re-export chain)

rustbot assigned mati865 Jun 16, 2026

rustbot added 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 Jun 16, 2026

qaijuang reviewed Jun 16, 2026

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rustbot assigned davidtwco and unassigned mati865 Jun 17, 2026

davidtwco requested changes Jul 2, 2026

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Comment thread compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs Resolved

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 Jul 2, 2026

Emit a suggestion to cast the never type into a concrete type when it…

c9ad0e5

… fails to satisfy an `impl Trait` bound

Muhtasim-Rasheed force-pushed the issue-157923-suggestion-cast-never-type branch from e0182f3 to c9ad0e5 Compare July 5, 2026 13:56

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 5, 2026

davidtwco approved these changes Jul 6, 2026

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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 Jul 6, 2026

This was referenced Jul 6, 2026

Rollup of 12 pull requests #158858

Closed

Rollup of 12 pull requests #158864

Merged

rust-bors Bot merged commit 1c30ae0 into rust-lang:main Jul 6, 2026
13 checks passed

rustbot added this to the 1.99.0 milestone Jul 6, 2026

Muhtasim-Rasheed deleted the issue-157923-suggestion-cast-never-type branch October 25, 2026 11:57

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Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound - #157966

Emit a suggestion to cast the never type into a concrete type when it fails to satisfy an `impl Trait` bound#157966
rust-bors[bot] merged 1 commit into
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Muhtasim-Rasheed:issue-157923-suggestion-cast-never-type

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