Use -Wunused_crate_dependencies for compiler crates.

nnethercote · nnethercote · commit 3160090c23e4 · 2025-03-10T08:43:15.000+11:00
It's very useful. There are some false positives involving integration
tests in `rustc_pattern_analysis` and `rustc_serialize`; subsequent
commits will fix these. There is also a false positive involving
`rustc_driver_impl`'s `rustc_randomized_layouts` feature. And I removed
a `rustc_span` mention in a doc comment in `rustc_log` because it wasn't
integral to the comment but caused a dev-dependency.
diff --git a/Cargo.lock b/Cargo.lock
@@ -3227,7 +3227,6 @@ dependencies = [
  "rustc_index",
  "rustc_macros",
  "rustc_middle",
- "rustc_parse",
  "rustc_session",
  "rustc_span",
  "rustc_target",
@@ -3262,7 +3261,6 @@ version = "0.0.0"
 dependencies = [
  "itertools",
  "rustc_ast",
- "rustc_data_structures",
  "rustc_lexer",
  "rustc_span",
  "thin-vec",
@@ -3290,15 +3288,12 @@ dependencies = [
  "rustc_ast",
  "rustc_ast_pretty",
  "rustc_attr_data_structures",
- "rustc_data_structures",
  "rustc_errors",
  "rustc_feature",
  "rustc_fluent_macro",
  "rustc_hir",
  "rustc_lexer",
  "rustc_macros",
- "rustc_middle",
- "rustc_serialize",
  "rustc_session",
  "rustc_span",
  "thin-vec",
@@ -3425,15 +3420,13 @@ dependencies = [
  "rustc_abi",
  "rustc_arena",
  "rustc_ast",
- "rustc_ast_pretty",
  "rustc_attr_parsing",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_fluent_macro",
  "rustc_fs_util",
  "rustc_hashes",
  "rustc_hir",
- "rustc_hir_pretty",
  "rustc_incremental",
  "rustc_index",
  "rustc_macros",
@@ -3884,7 +3877,6 @@ dependencies = [
  "rustc_query_impl",
  "rustc_query_system",
  "rustc_resolve",
- "rustc_serialize",
  "rustc_session",
  "rustc_span",
  "rustc_symbol_mangling",
@@ -3960,7 +3952,6 @@ dependencies = [
 name = "rustc_log"
 version = "0.0.0"
 dependencies = [
- "rustc_span",
  "tracing",
  "tracing-core",
  "tracing-subscriber",
@@ -4050,13 +4041,11 @@ dependencies = [
 name = "rustc_mir_build"
 version = "0.0.0"
 dependencies = [
- "either",
  "itertools",
  "rustc_abi",
  "rustc_apfloat",
  "rustc_arena",
  "rustc_ast",
- "rustc_attr_parsing",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_fluent_macro",
@@ -4263,7 +4252,6 @@ name = "rustc_query_impl"
 version = "0.0.0"
 dependencies = [
  "measureme",
- "rustc_attr_data_structures",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_hashes",
@@ -4337,7 +4325,6 @@ version = "0.0.0"
 dependencies = [
  "bitflags",
  "rustc_abi",
- "rustc_ast",
  "rustc_data_structures",
  "rustc_hir",
  "rustc_middle",
@@ -4392,7 +4379,6 @@ name = "rustc_smir"
 version = "0.0.0"
 dependencies = [
  "rustc_abi",
- "rustc_ast",
  "rustc_data_structures",
  "rustc_hir",
  "rustc_hir_pretty",
@@ -4434,7 +4420,6 @@ dependencies = [
  "punycode",
  "rustc-demangle",
  "rustc_abi",
- "rustc_ast",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_hashes",
diff --git a/Cargo.toml b/Cargo.toml
@@ -76,6 +76,7 @@ exclude = [
 keyword_idents_2024 = "warn"
 unreachable_pub = "warn"
 unsafe_op_in_unsafe_fn = "warn"
+unused_crate_dependencies = "warn"
 
 [profile.release.package.rustc-rayon-core]
 # The rustc fork of Rayon has deadlock detection code which intermittently
diff --git a/compiler/rustc_ast_lowering/Cargo.toml b/compiler/rustc_ast_lowering/Cargo.toml
@@ -20,7 +20,6 @@ rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
-rustc_parse = { path = "../rustc_parse" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
diff --git a/compiler/rustc_ast_pretty/Cargo.toml b/compiler/rustc_ast_pretty/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2024"
 # tidy-alphabetical-start
 itertools = "0.12"
 rustc_ast = { path = "../rustc_ast" }
-rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_span = { path = "../rustc_span" }
 thin-vec = "0.2.12"
diff --git a/compiler/rustc_attr_parsing/Cargo.toml b/compiler/rustc_attr_parsing/Cargo.toml
@@ -9,15 +9,12 @@ rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
-rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_macros = { path = "../rustc_macros" }
-rustc_middle = { path = "../rustc_middle" }
-rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 thin-vec = "0.2.12"
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -19,15 +19,13 @@ regex = "1.4"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_fs_util = { path = "../rustc_fs_util" }
 rustc_hashes = { path = "../rustc_hashes" }
 rustc_hir = { path = "../rustc_hir" }
-rustc_hir_pretty = { path = "../rustc_hir_pretty" }
 rustc_incremental = { path = "../rustc_incremental" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
@@ -43,6 +43,10 @@ use rustc_errors::emitter::stderr_destination;
 use rustc_errors::registry::Registry;
 use rustc_errors::{ColorConfig, DiagCtxt, ErrCode, FatalError, PResult, markdown};
 use rustc_feature::find_gated_cfg;
+// This avoids a false positive with `unused_crate_dependencies`. `rust_index`
+// isn't used in this crate's code, but it must be named in the `Cargo.toml`
+// for the `rustc_randomized_layouts` feature.
+use rustc_index as _;
 use rustc_interface::util::{self, get_codegen_backend};
 use rustc_interface::{Linker, create_and_enter_global_ctxt, interface, passes};
 use rustc_lint::unerased_lint_store;
diff --git a/compiler/rustc_interface/Cargo.toml b/compiler/rustc_interface/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2024"
 # tidy-alphabetical-start
 rustc-rayon = { version = "0.5.0" }
 rustc-rayon-core = { version = "0.5.0" }
-rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
@@ -41,7 +40,6 @@ rustc_privacy = { path = "../rustc_privacy" }
 rustc_query_impl = { path = "../rustc_query_impl" }
 rustc_query_system = { path = "../rustc_query_system" }
 rustc_resolve = { path = "../rustc_resolve" }
-rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
@@ -52,6 +50,11 @@ rustc_ty_utils = { path = "../rustc_ty_utils" }
 tracing = "0.1"
 # tidy-alphabetical-end
 
+[dev-dependencies]
+# tidy-alphabetical-start
+rustc_abi = { path = "../rustc_abi" }
+# tidy-alphabetical-end
+
 [features]
 # tidy-alphabetical-start
 llvm = ['dep:rustc_codegen_llvm']
diff --git a/compiler/rustc_log/Cargo.toml b/compiler/rustc_log/Cargo.toml
@@ -11,11 +11,6 @@ tracing-subscriber = { version = "0.3.3", default-features = false, features = [
 tracing-tree = "0.3.1"
 # tidy-alphabetical-end
 
-[dev-dependencies]
-# tidy-alphabetical-start
-rustc_span = { path = "../rustc_span" }
-# tidy-alphabetical-end
-
 [features]
 # tidy-alphabetical-start
 max_level_info = ['tracing/max_level_info']
diff --git a/compiler/rustc_log/src/lib.rs b/compiler/rustc_log/src/lib.rs
@@ -9,17 +9,12 @@
 //! [dependencies]
 //! rustc_ast = { path = "../rust/compiler/rustc_ast" }
 //! rustc_log = { path = "../rust/compiler/rustc_log" }
-//! rustc_span = { path = "../rust/compiler/rustc_span" }
 //! ```
 //!
 //! ```
 //! fn main() {
 //!     rustc_log::init_logger(rustc_log::LoggerConfig::from_env("LOG")).unwrap();
-//!
-//!     let edition = rustc_span::edition::Edition::Edition2021;
-//!     rustc_span::create_session_globals_then(edition, None, || {
-//!         /* ... */
-//!     });
+//!     /* ... */
 //! }
 //! ```
 //!
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 bitflags = "2.4.1"
-libc = "0.2"
 libloading = "0.8.0"
 odht = { version = "0.3.1", features = ["nightly"] }
 rustc_abi = { path = "../rustc_abi" }
@@ -32,5 +31,10 @@ tempfile = "3.2"
 tracing = "0.1"
 # tidy-alphabetical-end
 
+[target.'cfg(target_os = "aix")'.dependencies]
+# tidy-alphabetical-start
+libc = "0.2"
+# tidy-alphabetical-end
+
 [lints]
 workspace = true
diff --git a/compiler/rustc_mir_build/Cargo.toml b/compiler/rustc_mir_build/Cargo.toml
@@ -5,14 +5,12 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-either = "1.5.0"
 itertools = "0.12"
 
 rustc_abi = { path = "../rustc_abi" }
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_parse_format/Cargo.toml b/compiler/rustc_parse_format/Cargo.toml
@@ -5,9 +5,11 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc_index = { path = "../rustc_index", default-features = false }
 rustc_lexer = { path = "../rustc_lexer" }
 # tidy-alphabetical-end
 
+[target.'cfg(target_pointer_width = "64")'.dependencies]
+rustc_index = { path = "../rustc_index", default-features = false }
+
 [lints]
 workspace = true
diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -5,6 +5,8 @@
 // tidy-alphabetical-start
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
+// FIXME
+#![allow(unused_crate_dependencies)]
 #![cfg_attr(feature = "rustc", feature(let_chains))]
 // tidy-alphabetical-end
 
diff --git a/compiler/rustc_pattern_analysis/tests/complexity.rs b/compiler/rustc_pattern_analysis/tests/complexity.rs
@@ -1,5 +1,8 @@
 //! Test the pattern complexity limit.
 
+// FIXME
+#![allow(unused_crate_dependencies)]
+
 use common::*;
 use rustc_pattern_analysis::MatchArm;
 use rustc_pattern_analysis::pat::DeconstructedPat;
diff --git a/compiler/rustc_pattern_analysis/tests/exhaustiveness.rs b/compiler/rustc_pattern_analysis/tests/exhaustiveness.rs
@@ -1,5 +1,8 @@
 //! Test exhaustiveness checking.
 
+// FIXME
+#![allow(unused_crate_dependencies)]
+
 use common::*;
 use rustc_pattern_analysis::MatchArm;
 use rustc_pattern_analysis::pat::{DeconstructedPat, WitnessPat};
diff --git a/compiler/rustc_pattern_analysis/tests/intersection.rs b/compiler/rustc_pattern_analysis/tests/intersection.rs
@@ -1,5 +1,8 @@
 //! Test the computation of arm intersections.
 
+// FIXME
+#![allow(unused_crate_dependencies)]
+
 use common::*;
 use rustc_pattern_analysis::MatchArm;
 use rustc_pattern_analysis::pat::DeconstructedPat;
diff --git a/compiler/rustc_query_impl/Cargo.toml b/compiler/rustc_query_impl/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 measureme = "11"
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_hashes = { path = "../rustc_hashes" }
diff --git a/compiler/rustc_sanitizers/Cargo.toml b/compiler/rustc_sanitizers/Cargo.toml
@@ -8,7 +8,6 @@ bitflags = "2.5.0"
 tracing = "0.1"
 twox-hash = "1.6.3"
 rustc_abi = { path = "../rustc_abi" }
-rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs
@@ -3,6 +3,8 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![allow(rustc::internal)]
+// FIXME
+#![allow(unused_crate_dependencies)]
 #![cfg_attr(test, feature(test))]
 #![doc(
     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
diff --git a/compiler/rustc_serialize/tests/leb128.rs b/compiler/rustc_serialize/tests/leb128.rs
@@ -1,3 +1,6 @@
+// FIXME
+#![allow(unused_crate_dependencies)]
+
 use rustc_serialize::Decoder;
 use rustc_serialize::leb128::*;
 use rustc_serialize::opaque::{MAGIC_END_BYTES, MemDecoder};
diff --git a/compiler/rustc_serialize/tests/opaque.rs b/compiler/rustc_serialize/tests/opaque.rs
@@ -1,4 +1,6 @@
 #![allow(rustc::internal)]
+// FIXME
+#![allow(unused_crate_dependencies)]
 
 use std::fmt::Debug;
 use std::fs;
diff --git a/compiler/rustc_smir/Cargo.toml b/compiler/rustc_smir/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
-rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_hir_pretty = { path = "../rustc_hir_pretty" }
diff --git a/compiler/rustc_symbol_mangling/Cargo.toml b/compiler/rustc_symbol_mangling/Cargo.toml
@@ -9,7 +9,6 @@ punycode = "0.4.0"
 rustc-demangle = "0.1.21"
 
 rustc_abi = { path = "../rustc_abi" }
-rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_hashes = { path = "../rustc_hashes" }
