Refactor attribute parsing to improve ergonomics and some diagnostics

[jdonszelmann]

No description provided.

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r? @davidtwco

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[rustbot]

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
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[rust-log-analyzer]

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87 | / /// All the individual attribute parsers for each of rustc's built-in attributes.
   |
   = note: the link appears in this line:
           
           - [`SingleAttributeParser`]: makes it easy to implement an attribute which should error if it
              ^^^^^^^^^^^^^^^^^^^^^^^
   = note: no item named `SingleAttributeParser` 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)]`
---
87 | / /// All the individual attribute parsers for each of rustc's built-in attributes.
   |
   = note: the link appears in this line:
           
           - [`CombineAttributeParser`]: makes it easy to implement an attribute which should combine the
              ^^^^^^^^^^^^^^^^^^^^^^^^
   = note: no item named `CombineAttributeParser` in scope
   = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`

error: could not document `rustc_attr_parsing`
warning: build failed, waiting for other jobs to finish...
[RUSTC-TIMING] rustc_middle test:false 15.136
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_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 [workdir=/checkout]` failed with exit code 101
Created at: src/bootstrap/src/core/builder/cargo.rs:423:33
Executed at: src/bootstrap/src/core/build_steps/doc.rs:933:26

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  local time: Sat Aug 16 18:18:51 UTC 2025
  network time: Sat, 16 Aug 2025 18:18:51 GMT
##[error]Process completed with exit code 1.
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