Re-enable "jump to def" feature on rustc docs

compiler/rustc_interface/src/passes.rs

@@ -827,7 +827,9 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
     if tcx.sess.opts.unstable_opts.input_stats {
         rustc_passes::input_stats::print_hir_stats(tcx);
     }
-    #[cfg(debug_assertions)]
+    // When using rustdoc's "jump to def" feature, it enters this code and `check_crate`
+    // is not defined. So we need to cfg it out.
+    #[cfg(all(not(doc), debug_assertions))]
     rustc_passes::hir_id_validator::check_crate(tcx);
     let sess = tcx.sess;
     sess.time("misc_checking_1", || {

src/bootstrap/src/core/build_steps/doc.rs

@@ -830,7 +830,8 @@ impl Step for Rustc {
         cargo.rustdocflag("--show-type-layout");
         // FIXME: `--generate-link-to-definition` tries to resolve cfged out code
         // see https://github.com/rust-lang/rust/pull/122066#issuecomment-1983049222
-        // cargo.rustdocflag("--generate-link-to-definition");
+        // If there is any bug, please comment out the next line.
+        cargo.rustdocflag("--generate-link-to-definition");
 
         compile::rustc_cargo(builder, &mut cargo, target, &compiler, &self.crates);
         cargo.arg("-Zskip-rustdoc-fingerprint");