Improve `-Zls` diagnostic message on `.rs` files by blyxyas · Pull Request #158859 · rust-lang/rust

blyxyas · 2026-07-06T13:59:01Z

Refer the user to use rustc -Zls on .rmeta files instead of .rs files. And if they're using cargo, warn them to use rustc directly.

Important

First few comments in this pull request refer to changing the flag itself to work on source files. This was instead overruled to warn the user about executing on .rmeta files instead of .rs files.

Old description

This unstable option has been broken since forever (more than 2.5 years, at least), but it's exactly what I need for debugging the new incremental system, so rather than removing it I opted for fixing it.

The issue was that we were feeding the source file like, src/lib.rs instead of the .rmeta file. So literally every use of -Zls=.. was returning invalid metadata version found: ..

This PR also includes some testing.

Relevant for rust-lang/rust-project-goals#641.

rustbot · 2026-07-06T13:59:08Z

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lqd · 2026-07-06T15:06:15Z

cc @bjorn3 for -Zls expertise

bjorn3 · 2026-07-06T15:32:27Z

rustc +nightly -Zls=all $(rustc +nightly --print target-libdir)/libcore-*.rmeta works just fine for me, while rustc +nightly -Zls=all $(rustc +nightly --print target-libdir)/libcore-*.rlib doesn't. Looks like the issue is that -Zls doesn't support the metadata stub in rlibs that -Zsplit-metadata produces. It should probably just show the CrateHeader and nothing else as that is the only thing the metadata stub contains.

blyxyas · 2026-07-06T17:05:25Z

Seems that I've misinterpreted how to use the -Zls option. I'll rework the PR to instead output a more meaningful error message.

…iles instead of .rs files

lqd · 2026-07-06T17:40:49Z

It'd be great to also expand the unstable book documentation for -Zls, so other people in the future are not also confused by this option.

blyxyas · 2026-07-06T20:43:04Z

Done!

Update unstable book with ls valid values

error if file ends in .rs

extension. Fix tests and update docs.

bjorn3 · 2026-07-09T13:47:03Z

@bors r+

rust-bors · 2026-07-09T13:47:06Z

📌 Commit ab8da78 has been approved by bjorn3

It is now in the queue for this repository.

Improve `-Zls` diagnostic message on `.rs` files Refer the user to use `rustc -Zls` on `.rmeta` files instead of `.rs` files. And if they're using cargo, warn them to use rustc directly. > [!IMPORTANT] > First few comments in this pull request refer to changing the flag itself to work on source files. This was instead overruled to warn the user about executing on `.rmeta` files instead of `.rs` files. <details><summary>Old description</summary> This unstable option has been broken since forever (more than 2.5 years, at least), but it's exactly what I need for debugging the new incremental system, so rather than removing it I opted for fixing it. The issue was that we were feeding the source file like, `src/lib.rs` instead of the `.rmeta` file. So literally every use of `-Zls=..` was returning `invalid metadata version found: ..` This PR also includes some testing. Relevant for rust-lang/rust-project-goals#641. </details>

…uwer Rollup of 21 pull requests Successful merges: - #150946 (intrinsics: Add a fallback for non-const libm float functions) - #158510 (Enable `static_position_independent_executables` on all gnu and musl targets) - #158541 (Move `std::io::Write` to `core::io`) - #158899 (Fix `unaligned_volatile_store` by removing `MemFlags::UNALIGNED`) - #155429 (Support `u128`/`i128` c-variadic arguments) - #156370 (Reject linked dylib EII default overrides) - #156508 (Infer all anonymous lifetimes in assoc consts as `'static`) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158859 (Improve `-Zls` diagnostic message on `.rs` files) - #158988 (Redo `TokenStreamIter`) - #158347 (Improve generic parameters handling for #[diagnostic::on_const]) - #158722 (delegation: do not always inherit `ConstArgHasType` predicates) - #158739 (view-types: HIR lowering) - #158883 (tests: fix enum-match.rs to handle LLVM 23) - #158886 (Add documentation for the `no_std` attribute) - #158940 (Implement feature `char_to_u32`) - #158951 (Merge three `MaxUniverse`s into one) - #158961 (Reapply "LLVM 23: Run AssignGUIDPass in some places") - #158996 ([compiler] Implement `PartialOrd` via `Ord` for `Span` and newtype_indexes) - #159005 (Use `as_lang_item` instead of repeatedly matching)

Improve `-Zls` diagnostic message on `.rs` files Refer the user to use `rustc -Zls` on `.rmeta` files instead of `.rs` files. And if they're using cargo, warn them to use rustc directly. > [!IMPORTANT] > First few comments in this pull request refer to changing the flag itself to work on source files. This was instead overruled to warn the user about executing on `.rmeta` files instead of `.rs` files. <details><summary>Old description</summary> This unstable option has been broken since forever (more than 2.5 years, at least), but it's exactly what I need for debugging the new incremental system, so rather than removing it I opted for fixing it. The issue was that we were feeding the source file like, `src/lib.rs` instead of the `.rmeta` file. So literally every use of `-Zls=..` was returning `invalid metadata version found: ..` This PR also includes some testing. Relevant for rust-lang/rust-project-goals#641. </details>

…uwer Rollup of 24 pull requests Successful merges: - #150946 (intrinsics: Add a fallback for non-const libm float functions) - #158510 (Enable `static_position_independent_executables` on all gnu and musl targets) - #158541 (Move `std::io::Write` to `core::io`) - #158899 (Fix `unaligned_volatile_store` by removing `MemFlags::UNALIGNED`) - #156027 (Consider captured regions for opaque type region liveness.) - #156370 (Reject linked dylib EII default overrides) - #156508 (Infer all anonymous lifetimes in assoc consts as `'static`) - #157561 (rustdoc: do not include extra stuff in span) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158859 (Improve `-Zls` diagnostic message on `.rs` files) - #158988 (Redo `TokenStreamIter`) - #158347 (Improve generic parameters handling for #[diagnostic::on_const]) - #158384 (Allow BackwardIncompatibleDropHint in polonius legacy) - #158722 (delegation: do not always inherit `ConstArgHasType` predicates) - #158739 (view-types: HIR lowering) - #158877 (borrowck: Keep returned `path` from `best_blame_constraint()` consistent) - #158883 (tests: fix enum-match.rs to handle LLVM 23) - #158886 (Add documentation for the `no_std` attribute) - #158940 (Implement feature `char_to_u32`) - #158951 (Merge three `MaxUniverse`s into one) - #158961 (Reapply "LLVM 23: Run AssignGUIDPass in some places") - #158995 (Use REST API in linkchecker script) - #158996 ([compiler] Implement `PartialOrd` via `Ord` for `Span` and newtype_indexes)

Improve `-Zls` diagnostic message on `.rs` files Refer the user to use `rustc -Zls` on `.rmeta` files instead of `.rs` files. And if they're using cargo, warn them to use rustc directly. > [!IMPORTANT] > First few comments in this pull request refer to changing the flag itself to work on source files. This was instead overruled to warn the user about executing on `.rmeta` files instead of `.rs` files. <details><summary>Old description</summary> This unstable option has been broken since forever (more than 2.5 years, at least), but it's exactly what I need for debugging the new incremental system, so rather than removing it I opted for fixing it. The issue was that we were feeding the source file like, `src/lib.rs` instead of the `.rmeta` file. So literally every use of `-Zls=..` was returning `invalid metadata version found: ..` This PR also includes some testing. Relevant for rust-lang/rust-project-goals#641. </details>

Rollup of 24 pull requests Successful merges: - #150946 (intrinsics: Add a fallback for non-const libm float functions) - #158541 (Move `std::io::Write` to `core::io`) - #156027 (Consider captured regions for opaque type region liveness.) - #156370 (Reject linked dylib EII default overrides) - #156508 (Infer all anonymous lifetimes in assoc consts as `'static`) - #157561 (rustdoc: do not include extra stuff in span) - #158617 (allow mGCA const arguments to fall back to anon consts) - #158645 (Fix splat ICEs and ban it in closures) - #158859 (Improve `-Zls` diagnostic message on `.rs` files) - #158988 (Redo `TokenStreamIter`) - #158347 (Improve generic parameters handling for #[diagnostic::on_const]) - #158384 (Allow BackwardIncompatibleDropHint in polonius legacy) - #158722 (delegation: do not always inherit `ConstArgHasType` predicates) - #158739 (view-types: HIR lowering) - #158877 (borrowck: Keep returned `path` from `best_blame_constraint()` consistent) - #158883 (tests: fix enum-match.rs to handle LLVM 23) - #158886 (Add documentation for the `no_std` attribute) - #158940 (Implement feature `char_to_u32`) - #158951 (Merge three `MaxUniverse`s into one) - #158960 (Fix bootstrap submodule path prefix matching) - #158961 (Reapply "LLVM 23: Run AssignGUIDPass in some places") - #158995 (Use REST API in linkchecker script) - #158996 ([compiler] Implement `PartialOrd` via `Ord` for `Span` and newtype_indexes) - #159036 (bootstrap: expand '@argfile' arguments to rustc shim)

Rollup merge of #158859 - blyxyas:fix-ls-unstable-opt, r=bjorn3 Improve `-Zls` diagnostic message on `.rs` files Refer the user to use `rustc -Zls` on `.rmeta` files instead of `.rs` files. And if they're using cargo, warn them to use rustc directly. > [!IMPORTANT] > First few comments in this pull request refer to changing the flag itself to work on source files. This was instead overruled to warn the user about executing on `.rmeta` files instead of `.rs` files. <details><summary>Old description</summary> This unstable option has been broken since forever (more than 2.5 years, at least), but it's exactly what I need for debugging the new incremental system, so rather than removing it I opted for fixing it. The issue was that we were feeding the source file like, `src/lib.rs` instead of the `.rmeta` file. So literally every use of `-Zls=..` was returning `invalid metadata version found: ..` This PR also includes some testing. Relevant for rust-lang/rust-project-goals#641. </details>

rustbot assigned fee1-dead Jul 6, 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 Jul 6, 2026

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blyxyas force-pushed the fix-ls-unstable-opt branch from f6dbcdc to dada58c Compare July 6, 2026 14:08

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blyxyas force-pushed the fix-ls-unstable-opt branch from dada58c to 5af51d2 Compare July 6, 2026 17:27

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Improve error message on -Zls, to direct the user to input .rmeta f…

ae82b10

…iles instead of .rs files

blyxyas force-pushed the fix-ls-unstable-opt branch from 5af51d2 to ae82b10 Compare July 6, 2026 17:34

blyxyas changed the title ~~Fix -Zls unstable opt~~ Improve -Zls diagnostic message on .rs files Jul 6, 2026

Update Unstable Book with some information about -Zls

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Comment thread src/doc/unstable-book/src/compiler-flags/ls.md

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Propagate errors from list_file_metadata into list_metadata

bbba496

Update unstable book with ls valid values

rust-cloud-vms Bot force-pushed the fix-ls-unstable-opt branch from 6d521fe to bbba496 Compare July 7, 2026 12:30

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blyxyas mentioned this pull request Jul 8, 2026

Incremental Systems Rethought rust-lang/rust-project-goals#641

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fix: Actually take error and panic by default, only emitting a custom

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error if file ends in .rs

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Propagate error downwards and emit it, even if not related to file

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extension. Fix tests and update docs.

rustbot added the A-run-make Area: port run-make Makefiles to rmake.rs label Jul 9, 2026

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Comment thread compiler/rustc_metadata/src/locator.rs Outdated

Do not write errors to out, return Err(..) directly

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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 9, 2026

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Rollup of 21 pull requests #159020

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Rollup of 21 pull requests #159024

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Rollup of 24 pull requests #159037

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This was referenced Jul 9, 2026

Rollup of 25 pull requests #159045

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Rollup of 24 pull requests #159046

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rust-bors Bot merged commit 1ae52bc into rust-lang:main Jul 10, 2026
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