Avoid rustdoc ICE when an unstable feature is used

Author: sanxiyn

src/librustdoc/core.rs

@@ -156,9 +156,15 @@ pub fn run_core(search_paths: SearchPaths,
     let name = link::find_crate_name(Some(&sess), &krate.attrs, &input);
 
     let driver::ExpansionResult { defs, analysis, resolutions, mut hir_forest, .. } = {
-        driver::phase_2_configure_and_expand(
-            &sess, &cstore, krate, None, &name, None, resolve::MakeGlobMap::No, |_| Ok(()),
-        ).expect("phase_2_configure_and_expand aborted in rustdoc!")
+        let result = driver::phase_2_configure_and_expand(&sess,
+                                                          &cstore,
+                                                          krate,
+                                                          None,
+                                                          &name,
+                                                          None,
+                                                          resolve::MakeGlobMap::No,
+                                                          |_| Ok(()));
+        abort_on_err(result, &sess)
     };
 
     let arena = DroplessArena::new();