# Data flow — rust-lang/rust

> Canonical page: https://codevetter.com/unpack/rust/data-flow

# Data flow — rust-lang/rust

Scanned commit c64de18c55c70d62aa88a5722dea8f8e263bacf3 (2026-09-22). Generated by codevetter codevetter 1.12.0 on 2026-09-22.

Data enters as a source file (or string) plus CLI options, is lexed/parsed into an AST, expanded and lowered to HIR, then nearly everything else is demand-driven through the TyCtxt query system: type checking, trait solving, borrow checking, MIR construction/transforms, monomorphization, and finally codegen through a CodegenBackend trait to object files and a linked binary. Cross-crate state travels via rustc_metadata .rmeta blobs in rlibs/dylibs; incremental state is a serialized dep-graph+query cache; diagnostics flow out through rustc_errors' DiagCtxt. Bootstrap's data flow is stage0 binaries -> stage1 artifacts -> stage2 artifacts under build/.
- Input boundary: run_compiler builds an interface::Config from CLI matches — Input::File/Str, output dir/file, crate_cfg/crate_check_cfg, and an optional FileLoader; the default RealFileLoader reads from disk but the hook exists for e.g. rust-analyzer VFS. — [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs) [compiler/rustc_interface/src/interface.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/interface.rs)
- Text -> tokens -> AST: rustc_lexer produces tokens, rustc_parse (new_parser_from_source_str / passes::parse) produces ast::Crate; only the crate root is parsed initially, submodules are parsed during macro expansion. — [compiler/rustc_parse/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_parse/src/lib.rs) [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs) [src/doc/rustc-dev-guide/src/overview.md](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/src/doc/rustc-dev-guide/src/overview.md)
- AST -> HIR: create_and_enter_global_ctxt forces tcx.resolver_for_lowering() which runs rustc_resolve + rustc_ast_lowering to produce resolutions and lowered HIR inside the GlobalCtxt; the 'tcx lifetime originates in this function's gcx_cell/arena setup. — [compiler/rustc_interface/src/passes.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/passes.rs) [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs)
- All mid/late compilation state is owned by the query system: queries.rs declares each query's key/value types and modifiers (caching, arena allocation, incremental), rustc_macros::rustc_queries generates TyCtxt accessors, and tcx.ensure_ok().analysis(()) drives typeck/borrowck/MIR construction. — [compiler/rustc_middle/src/queries.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_middle/src/queries.rs) [compiler/rustc_interface/src/passes.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/passes.rs) [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs)
- Provider wiring: each rustc_* crate exposes a provide() that fills fields of the generated Providers table; DEFAULT_QUERY_PROVIDERS chains ~25 such provide() calls, then codegen_backend.provide() and the Config::override_queries hook can overwrite individual providers before the GlobalCtxt is created. — [compiler/rustc_interface/src/passes.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/passes.rs)
- Codegen boundary: Linker::codegen_and_build_linker runs the backend's codegen queries producing object files/modules, then linker.link(sess, incr_comp_session, codegen_backend) runs outside the GlobalCtxt so the 'tcx arena can be freed earlier. — [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs)
- Backend abstraction: rustc_codegen_ssa::traits::CodegenBackend defines the contract (name, init, target_config, provide, codegen methods); rustc_codegen_llvm::LlvmCodegenBackend is the default implementation bridging to LLVM via compiler/rustc_llvm FFI. — [compiler/rustc_codegen_ssa/src/traits/backend.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_codegen_ssa/src/traits/backend.rs) [compiler/rustc_codegen_llvm/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_codegen_llvm/src/lib.rs)
- Cross-crate metadata: rustc_metadata encodes crate metadata (EncodedMetadata) into .rmeta sections inside rlibs/dylibs and reads dependencies back through creader.rs/locator.rs/native_libs.rs, including the MetadataLoaderDyn interface the backend supplies. — [compiler/rustc_metadata/src/creader.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_metadata/src/creader.rs) [compiler/rustc_codegen_ssa/src/traits/backend.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_codegen_ssa/src/traits/backend.rs)
- Incremental persistence: rustc_incremental::persist::{load,save,file_format,work_product,fs} manage an on-disk dep graph and query-result cache; create_and_enter_global_ctxt calls setup_dep_graph and rustc_incremental::load_query_result_cache before queries run. — [compiler/rustc_incremental/src/persist/save.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_incremental/src/persist/save.rs) [compiler/rustc_interface/src/passes.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/passes.rs)
- Dependency info output: passes::write_dep_info and passes::write_interface run inside the global-ctxt closure; Session exposes env_depinfo/file_depinfo that a driver's Config::track_state callback can populate for dep tracking. — [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs) [compiler/rustc_interface/src/passes.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/passes.rs) [compiler/rustc_interface/src/interface.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/interface.rs)
- Diagnostics flow: everything reports through rustc_errors Diag/DiagCtxt built on DiagMessage (Str or inline Fluent); early errors before a Session exists go through EarlyDiagCtxt, and ICEs are captured by install_ice_hook writing a report to config.ice_file. — [compiler/rustc_error_messages/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_error_messages/src/lib.rs) [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs) [compiler/rustc_interface/src/interface.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_interface/src/interface.rs)
- Bootstrap data flow: bootstrap.py reads src/stage0 for pinned toolchain hashes and downloads from static.rust-lang.org/ci-artifacts; the Rust bootstrap reads bootstrap.toml (defaults in src/bootstrap/defaults, schema in bootstrap.example.toml) and produces staged artifacts under build/. — [src/bootstrap/bootstrap.py](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/src/bootstrap/bootstrap.py) [src/stage0](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/src/stage0) [bootstrap.example.toml](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/bootstrap.example.toml) [src/bootstrap/README.md](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/src/bootstrap/README.md)
- Feature-gate state flows from rustc_feature's unstable.rs/accepted.rs/removed.rs tables into the session; tcx.report_unused_features() runs after codegen setup and -Zmetrics-dir dumps feature-usage metrics via dump_feature_usage_metrics. — [compiler/rustc_feature/src/unstable.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_feature/src/unstable.rs) [compiler/rustc_driver_impl/src/lib.rs](https://github.com/rust-lang/rust/blob/c64de18c55c70d62aa88a5722dea8f8e263bacf3/compiler/rustc_driver_impl/src/lib.rs)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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