rustc_public: Make Id types !Send / !Sync

[aDotInTheVoid]

These types are Id's to a table stored in TLS, so using them from another tread will either panic, or give wrong results.

Therefor, I've added a ReferencesTlsThreadLocalIndex marker type, which ensures types arn't Send/Sync.

This is a breaking change for users of the rustc_public crate.

It also changes how DefId and similar are Serialized. It would be possible to preserve the old behavior if that's needed, but I couldn't see any tests for these. EDIT: Not anymore: #148261 (comment)

Zulip Discussion: https://rust-lang.zulipchat.com/#narrow/channel/320896-project-stable-mir/topic/WDYM.20.22should.20not.20.20be.20shared.20across.20threads.22/with/547374171

[rustbot]

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a

[rustbot]

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[celinval]

It's too bad we cannot use negative trait here. KMIR actually uses the serialization. See: https://github.com/runtimeverification/stable-mir-json. They use IDs to map components and correlate then AFAIK.

So can you please make sure you skip the serialization of the new field in the structs you added them?

View changes since this review

[celinval]

I agree... Please don't.

[aDotInTheVoid]

Done in 97e6df4. It's sadly not as simple as using #[serde(skip)], as that still moves serde from serializing just the single field, to a list containing the single field: https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=b4aafe4ff5312c4ddedd5e17ee361d5a

Is there somewhere that tests for this could go?

[celinval]

why not include in this PR?

[aDotInTheVoid]

I wanted to keep this PR not doing too much at once. But I've added it in 8b3ee9f

[aDotInTheVoid]

I'd like to squash this after approval but before merging.

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 Checking rustc_lint v0.0.0 (/checkout/compiler/rustc_lint) error: unresolved link to `TLV` --> compiler/rustc_public/src/lib.rs:301:36 | 301 | /// Marker type for indexes into [`TLV`]. | ^^^ no item named `TLV` in scope | = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]` = note: `-D rustdoc::broken-intra-doc-links` implied by `-D warnings` = help: to override `-D warnings` add `#[allow(rustdoc::broken_intra_doc_links)]` error: could not document `rustc_public` warning: build failed, waiting for other jobs to finish... [RUSTC-TIMING] rustc_lint test:false 3.644 [RUSTC-TIMING] rustc_query_impl test:false 8.850 Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo doc --target x86_64-unknown-linux-gnu -Zbinary-dep-depinfo -j 4 -Zroot-dir=/checkout --locked --color always --release --features llvm --manifest-path /checkout/compiler/rustc/Cargo.toml -Zskip-rustdoc-fingerprint --no-deps -Zrustdoc-map -p rustc-main -p rustc_abi -p rustc_arena -p rustc_ast -p rustc_ast_ir -p rustc_ast_lowering -p rustc_ast_passes -p rustc_ast_pretty -p rustc_attr_parsing -p rustc_baked_icu_data -p rustc_borrowck -p rustc_builtin_macros -p rustc_codegen_llvm -p rustc_codegen_ssa -p rustc_const_eval -p rustc_data_structures -p rustc_driver -p rustc_driver_impl -p rustc_error_codes -p rustc_error_messages -p rustc_errors -p rustc_expand -p rustc_feature -p rustc_fluent_macro -p rustc_fs_util -p rustc_graphviz -p rustc_hashes -p rustc_hir -p rustc_hir_analysis -p rustc_hir_id -p rustc_hir_pretty -p rustc_hir_typeck -p rustc_incremental -p rustc_index -p rustc_index_macros -p rustc_infer -p rustc_interface -p rustc_lexer -p rustc_lint -p rustc_lint_defs -p rustc_llvm -p rustc_log -p rustc_macros -p rustc_metadata -p rustc_middle -p rustc_mir_build -p rustc_mir_dataflow -p rustc_mir_transform -p rustc_monomorphize -p rustc_next_trait_solver -p rustc_parse -p rustc_parse_format -p rustc_passes -p rustc_pattern_analysis -p rustc_privacy -p rustc_proc_macro -p rustc_public -p rustc_public_bridge -p rustc_query_impl -p rustc_query_system -p rustc_resolve -p rustc_sanitizers -p rustc_serialize -p rustc_session -p rustc_span -p rustc_symbol_mangling -p rustc_target -p rustc_thread_pool -p rustc_trait_selection -p rustc_traits -p rustc_transmute -p rustc_ty_utils -p rustc_type_ir -p rustc_type_ir_macros -p rustc_windows_rc [workdir=/checkout]` failed with exit code 101 Created at: src/bootstrap/src/core/build_steps/doc.rs:902:25 Executed at: src/bootstrap/src/core/build_steps/doc.rs:962:26 Command has failed. Rerun with -v to see more details. Bootstrap failed while executing `doc compiler --stage 1` Build completed unsuccessfully in 0:00:51 local time: Thu Oct 30 02:14:26 UTC 2025 network time: Thu, 30 Oct 2025 02:14:26 GMT ##[error]Process completed with exit code 1.