Try removing UI test dependencies from clippy itself and see what breaks

Author: jyn514

Diff for: Cargo.lock

@@ -659,24 +659,14 @@ dependencies = [
  "clippy_lints",
  "clippy_utils",
  "compiletest_rs",
- "derive-new",
  "filetime",
- "futures 0.3.19",
- "if_chain",
- "itertools",
- "parking_lot 0.12.1",
- "quote",
  "regex",
- "rustc-semver",
  "rustc-workspace-hack",
  "rustc_tools_util 0.2.0",
  "semver",
- "serde",
- "syn",
  "tempfile",
  "termize",
  "tester",
- "tokio",
  "ui-test-dependencies",
 ]
 
@@ -5533,7 +5523,7 @@ dependencies = [
  "futures 0.3.19",
  "if_chain",
  "itertools",
- "parking_lot 0.11.2",
+ "parking_lot 0.12.1",
  "quote",
  "regex",
  "rustc-semver",

Diff for: src/tools/clippy/Cargo.toml

@@ -42,16 +42,6 @@ rustc-workspace-hack = "1.0"
 # UI test dependencies
 ui-test-dependencies = { path = "ui-test-dependencies" }
 clippy_utils = { path = "clippy_utils" }
-derive-new = "0.5"
-if_chain = "1.0"
-itertools = "0.10.1"
-quote = "1.0"
-serde = { version = "1.0.125", features = ["derive"] }
-syn = { version = "1.0", features = ["full"] }
-futures = "0.3"
-parking_lot = "0.12"
-tokio = { version = "1", features = ["io-util"] }
-rustc-semver = "1.1"
 
 [build-dependencies]
 rustc_tools_util = { version = "0.2", path = "rustc_tools_util" }

Diff for: src/tools/clippy/tests/compile-test.rs

@@ -39,29 +39,6 @@ static TEST_DEPENDENCIES: &[&str] = &[
     "rustc_semver",
 ];
 
-// Test dependencies may need an `extern crate` here to ensure that they show up
-// in the depinfo file (otherwise cargo thinks they are unused)
-#[allow(unused_extern_crates)]
-extern crate clippy_utils;
-#[allow(unused_extern_crates)]
-extern crate derive_new;
-#[allow(unused_extern_crates)]
-extern crate futures;
-#[allow(unused_extern_crates)]
-extern crate if_chain;
-#[allow(unused_extern_crates)]
-extern crate itertools;
-#[allow(unused_extern_crates)]
-extern crate parking_lot;
-#[allow(unused_extern_crates)]
-extern crate quote;
-#[allow(unused_extern_crates)]
-extern crate rustc_semver;
-#[allow(unused_extern_crates)]
-extern crate syn;
-#[allow(unused_extern_crates)]
-extern crate tokio;
-
 /// Produces a string with an `--extern` flag for all UI test crate
 /// dependencies.
 ///
@@ -124,7 +101,7 @@ static EXTERN_FLAGS: SyncLazy<String> = SyncLazy::new(|| {
         .filter(|n| !crates.contains_key(n))
         .collect();
     if option_env!("RUSTC_TEST_SUITE").is_some() {
-        // Bootstrap doesn't build clippy_utils, but that's ok since clippy only uses it for dogfood tests.
+        // Bootstrap doesn't build clippy_utils, but that's ok since clippy only uses it for internal UI tests.
         not_found.drain_filter(|x| *x == "clippy_utils");
     }
     assert!(

Diff for: src/tools/clippy/ui-test-dependencies/Cargo.toml

@@ -15,6 +15,6 @@ quote = "1.0"
 serde = { version = "1.0.125", features = ["derive"] }
 syn = { version = "1.0", features = ["full"] }
 futures = "0.3"
-parking_lot = "0.11.2"
+parking_lot = "0.12"
 tokio = { version = "1", features = ["io-util"] }
 rustc-semver = "1.1"