[DO NOT MERGE] rust-analyzer: hacks to get the main tests to build

I needed to:

- Consistently use `feature(rustc_private)` on all participating r-a
  crates under `test` scenario.
- Force an `extern crate rustc_driver;` on all the r-a crates for
  reasons I don't yet understand.

At least this builds, *at all*.

Author: jieyouxu

src/tools/rust-analyzer/crates/base-db/Cargo.toml

@@ -30,5 +30,8 @@ vfs.workspace = true
 span.workspace = true
 intern.workspace = true
 
+[features]
+in-rust-tree = []
+
 [lints]
 workspace = true

src/tools/rust-analyzer/crates/base-db/src/lib.rs

@@ -1,4 +1,9 @@
 //! base_db defines basic database traits. The concrete DB is defined by ide.
+
+#![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver as _;
+
 // FIXME: Rename this crate, base db is non descriptive
 mod change;
 mod input;

src/tools/rust-analyzer/crates/cfg/Cargo.toml

@@ -33,5 +33,9 @@ derive_arbitrary = "1.3.2"
 syntax-bridge.workspace = true
 syntax.workspace = true
 
+[features]
+default = []
+in-rust-tree = []
+
 [lints]
 workspace = true

src/tools/rust-analyzer/crates/cfg/src/lib.rs

@@ -1,5 +1,9 @@
 //! cfg defines conditional compiling options, `cfg` attribute parser and evaluator
 
+#![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver as _;
+
 mod cfg_expr;
 mod dnf;
 #[cfg(test)]

src/tools/rust-analyzer/crates/hir-def/Cargo.toml

@@ -54,6 +54,7 @@ expect-test.workspace = true
 test-utils.workspace = true
 test-fixture.workspace = true
 syntax-bridge.workspace = true
+
 [features]
 in-rust-tree = ["hir-expand/in-rust-tree"]
 

src/tools/rust-analyzer/crates/hir-def/src/lib.rs

@@ -8,6 +8,8 @@
 //! actually true.
 
 #![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver as _;
 
 #[cfg(feature = "in-rust-tree")]
 extern crate rustc_parse_format;

src/tools/rust-analyzer/crates/hir-expand/src/lib.rs

@@ -3,8 +3,13 @@
 //! Specifically, it implements a concept of `MacroFile` -- a file whose syntax
 //! tree originates not from the text of some `FileId`, but from some macro
 //! expansion.
+
 #![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
 
+#[cfg_attr(all(feature = "in-rust-tree", test), allow(unused_extern_crates))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver;
+
 pub mod attrs;
 pub mod builtin;
 pub mod change;

src/tools/rust-analyzer/crates/hir-ty/src/lib.rs

@@ -2,6 +2,8 @@
 //! information and various assists.
 
 #![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver as _;
 
 #[cfg(feature = "in-rust-tree")]
 extern crate rustc_index;

src/tools/rust-analyzer/crates/hir/src/lib.rs

@@ -17,9 +17,12 @@
 //! from the ide with completions, hovers, etc. It is a (soft, internal) boundary:
 //! <https://www.tedinski.com/2018/02/06/system-boundaries.html>.
 
-#![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
 #![recursion_limit = "512"]
 
+#![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver as _;
+
 mod attrs;
 mod from_id;
 mod has_source;

src/tools/rust-analyzer/crates/ide-assists/src/lib.rs

@@ -59,6 +59,8 @@
 //! <https://rust-analyzer.github.io/blog/2020/09/28/how-to-make-a-light-bulb.html>
 
 #![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+#[cfg(all(feature = "in-rust-tree", test))]
+extern crate rustc_driver as _;
 
 mod assist_config;
 mod assist_context;