Add missing rustc_private

Author: lnicola

src/tools/rust-analyzer/crates/ide-assists/Cargo.toml

@@ -34,5 +34,8 @@ expect-test = "1.4.0"
 test-utils.workspace = true
 test-fixture.workspace = true
 
+[features]
+in-rust-tree = []
+
 [lints]
 workspace = true

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

@@ -58,6 +58,8 @@
 //! See also this post:
 //! <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))]
+
 mod assist_config;
 mod assist_context;
 #[cfg(test)]

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

@@ -6,6 +6,8 @@
 //! The tests for this functionality live in another crate:
 //! `hir_def::macro_expansion_tests::mbe`.
 
+#![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
+
 #[cfg(not(feature = "in-rust-tree"))]
 extern crate ra_ap_rustc_lexer as rustc_lexer;
 #[cfg(feature = "in-rust-tree")]