Add a regression test for an unconstrained TransmuteFrom ICE by johnproblems · Pull Request #157366 · rust-lang/rust

johnproblems · 2026-06-03T08:01:33Z

#151314: calling a function with an unconstrained TransmuteFrom obligation used to ICE with layout_of: unexpected type under the next-gen trait solver. It now reports type annotations needed (E0283) as expected. Fixed in #154991, but the issue was labelled E-needs-test and lacked a regression test, so this adds the original reproducer so it can't silently regress.

Closes #151314

rustbot · 2026-06-03T08:01:40Z

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An unconstrained `TransmuteFrom` obligation used to ICE with `layout_of: unexpected type` under the next-gen trait solver; it now reports `type annotations needed` (E0283). Add a regression test for that case, which the fix's own test suite did not cover.

johnproblems · 2026-06-03T09:08:55Z

Thanks for catching that — you're right. I'd only checked that the original const repro now errors cleanly; I hadn't tried the type const form the diagnostic suggests, which still ICEs, so the issue isn't actually resolved. I've removed that test and kept just the next-solver TransmuteFrom one. Appreciate the review!

reddevilmidzy · 2026-06-04T01:52:12Z

Good, and please also change the PR title and description.

nikomatsakis · 2026-06-10T19:59:17Z

bors r+

johnproblems · 2026-06-11T12:58:22Z

Thanks for the review @nikomatsakis! Just flagging that the PR still seems to be showing S-waiting-on-review with no confirmation from bors — wasn't sure if it queued okay. Thanks again!

nikomatsakis · 2026-06-11T16:57:38Z

@bors r+

I forgot we need the @...

rust-bors · 2026-06-11T16:57:41Z

📌 Commit 8e7be34 has been approved by nikomatsakis

It is now in the queue for this repository.

nikomatsakis · 2026-06-11T16:57:48Z

@bors rollup

…sts, r=nikomatsakis Add a regression test for an unconstrained TransmuteFrom ICE rust-lang#151314: calling a function with an unconstrained `TransmuteFrom` obligation used to ICE with `layout_of: unexpected type` under the next-gen trait solver. It now reports `type annotations needed` (E0283) as expected. Fixed in rust-lang#154991, but the issue was labelled `E-needs-test` and lacked a regression test, so this adds the original reproducer so it can't silently regress. Closes rust-lang#151314

…uwer Rollup of 23 pull requests Successful merges: - #157716 (update Enzyme, June'26) - #149793 (Add inline asm support for amdgpu) - #152852 (Remove driver_lint_caps) - #155299 (make repr_transparent_non_zst_fields a hard error) - #155439 (Enable Cargo's new build-dir layout) - #157612 (Add a test where subtyping inhibits coercion.) - #157626 (Autogenerate unstable compiler flag stubs for unstable-book) - #157667 (Rename typing modes to better describe real usage) - #156212 (Additionally gate negative bounds behind new `-Zinternal-testing-features`) - #157342 (Reduce verbosity of cycle errors when possible) - #157366 (Add a regression test for an unconstrained TransmuteFrom ICE) - #157459 (rustc_target: callconv: powerpc64: Remove unreachable fallback code path) - #157658 (UnsafeCell: mention shared-ref-to-interior case, fix aliasing model inaccuracy) - #157698 (Remove an unnecessary cloning) - #157699 (Arg splat experiment - hir FnDecl impl) - #157713 (resolve: Remove exported imports from `maybe_unused_trait_imports`) - #157722 (Move create_scope_map to rustc_codegen_ssa.) - #157725 (Keep generic suggestion for macro-expanded missing-type items) - #157733 (Remove old FIXMEs about nocapture attribute) - #157737 (Reorganize `tests/ui/issues` [7/N]) - #157746 (supports_c_variadic_definitions: extend checklist for new targets) - #157763 (Move unused target expression error to appropriate place and rename it) - #157768 (codegen_ssa: peel trans. wrappers on scalable vecs)

…sts, r=nikomatsakis Add a regression test for an unconstrained TransmuteFrom ICE rust-lang#151314: calling a function with an unconstrained `TransmuteFrom` obligation used to ICE with `layout_of: unexpected type` under the next-gen trait solver. It now reports `type annotations needed` (E0283) as expected. Fixed in rust-lang#154991, but the issue was labelled `E-needs-test` and lacked a regression test, so this adds the original reproducer so it can't silently regress. Closes rust-lang#151314

…uwer Rollup of 23 pull requests Successful merges: - #157716 (update Enzyme, June'26) - #149793 (Add inline asm support for amdgpu) - #155299 (make repr_transparent_non_zst_fields a hard error) - #155439 (Enable Cargo's new build-dir layout) - #157612 (Add a test where subtyping inhibits coercion.) - #157626 (Autogenerate unstable compiler flag stubs for unstable-book) - #157667 (Rename typing modes to better describe real usage) - #149749 (Make `BorrowedBuf` and `BorrowedCursor` generic over the data) - #156212 (Additionally gate negative bounds behind new `-Zinternal-testing-features`) - #157342 (Reduce verbosity of cycle errors when possible) - #157366 (Add a regression test for an unconstrained TransmuteFrom ICE) - #157459 (rustc_target: callconv: powerpc64: Remove unreachable fallback code path) - #157658 (UnsafeCell: mention shared-ref-to-interior case, fix aliasing model inaccuracy) - #157698 (Remove an unnecessary cloning) - #157699 (Arg splat experiment - hir FnDecl impl) - #157713 (resolve: Remove exported imports from `maybe_unused_trait_imports`) - #157722 (Move create_scope_map to rustc_codegen_ssa.) - #157725 (Keep generic suggestion for macro-expanded missing-type items) - #157733 (Remove old FIXMEs about nocapture attribute) - #157737 (Reorganize `tests/ui/issues` [7/N]) - #157746 (supports_c_variadic_definitions: extend checklist for new targets) - #157763 (Move unused target expression error to appropriate place and rename it) - #157768 (codegen_ssa: peel trans. wrappers on scalable vecs)

Rollup of 24 pull requests Successful merges: - #157716 (update Enzyme, June'26) - #149793 (Add inline asm support for amdgpu) - #155299 (make repr_transparent_non_zst_fields a hard error) - #157612 (Add a test where subtyping inhibits coercion.) - #157626 (Autogenerate unstable compiler flag stubs for unstable-book) - #157667 (Rename typing modes to better describe real usage) - #149749 (Make `BorrowedBuf` and `BorrowedCursor` generic over the data) - #155113 (Ensure Send/Sync impl for std::process::CommandArgs) - #156212 (Additionally gate negative bounds behind new `-Zinternal-testing-features`) - #157342 (Reduce verbosity of cycle errors when possible) - #157366 (Add a regression test for an unconstrained TransmuteFrom ICE) - #157459 (rustc_target: callconv: powerpc64: Remove unreachable fallback code path) - #157658 (UnsafeCell: mention shared-ref-to-interior case, fix aliasing model inaccuracy) - #157698 (Remove an unnecessary cloning) - #157699 (Arg splat experiment - hir FnDecl impl) - #157713 (resolve: Remove exported imports from `maybe_unused_trait_imports`) - #157722 (Move create_scope_map to rustc_codegen_ssa.) - #157723 (Move uninhabited unreachable code lint to rustc_mir_transform) - #157725 (Keep generic suggestion for macro-expanded missing-type items) - #157733 (Remove old FIXMEs about nocapture attribute) - #157737 (Reorganize `tests/ui/issues` [7/N]) - #157746 (supports_c_variadic_definitions: extend checklist for new targets) - #157763 (Move unused target expression error to appropriate place and rename it) - #157768 (codegen_ssa: peel trans. wrappers on scalable vecs)

Rollup merge of #157366 - johnproblems:add-ice-regression-tests, r=nikomatsakis Add a regression test for an unconstrained TransmuteFrom ICE #151314: calling a function with an unconstrained `TransmuteFrom` obligation used to ICE with `layout_of: unexpected type` under the next-gen trait solver. It now reports `type annotations needed` (E0283) as expected. Fixed in #154991, but the issue was labelled `E-needs-test` and lacked a regression test, so this adds the original reproducer so it can't silently regress. Closes #151314

rustbot assigned nikomatsakis Jun 3, 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. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jun 3, 2026

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johnproblems force-pushed the add-ice-regression-tests branch from f72a5de to 9eba2a4 Compare June 3, 2026 08:06

reddevilmidzy reviewed Jun 3, 2026

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Comment thread tests/ui/const-generics/mgca/inherent-assoc-const-array-length.rs Outdated

johnproblems force-pushed the add-ice-regression-tests branch from 9eba2a4 to 8e7be34 Compare June 3, 2026 09:08

johnproblems changed the title ~~Add regression tests for #151314 and #142773~~ Add a regression test for an unconstrained TransmuteFrom ICE Jun 4, 2026

nikomatsakis approved these changes Jun 10, 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 Jun 11, 2026

JonathanBrouwer mentioned this pull request Jun 11, 2026

Rollup of 23 pull requests #157784

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JonathanBrouwer mentioned this pull request Jun 11, 2026

Rollup of 23 pull requests #157790

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jhpratt mentioned this pull request Jun 12, 2026

Rollup of 24 pull requests #157794

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rust-bors Bot merged commit b63b2d9 into rust-lang:main Jun 12, 2026
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rustbot added this to the 1.98.0 milestone Jun 12, 2026

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Add a regression test for an unconstrained TransmuteFrom ICE#157366

Add a regression test for an unconstrained TransmuteFrom ICE#157366
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