Auto merge of #23676 - servo:check, r=Manishearth

Share more `./mach build` logic with mach check, doc, test-unit

Fixes #23659

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23676)
<!-- Reviewable:end -->

2 files changed, 8 insertions, 11 deletions

diff --git a/components/script/dom/bindings/conversions.rs b/components/script/dom/bindings/conversions.rs
index 161354479b6..442648fb9c8 100644
--- a/components/script/dom/bindings/conversions.rs
+++ b/components/script/dom/bindings/conversions.rs
@@ -69,10 +69,7 @@ pub trait IDLInterface {
 }
 
 /// A trait to mark an IDL interface as deriving from another one.
-#[cfg_attr(
-    feature = "unstable",
-    rustc_on_unimplemented(message = "The IDL interface `{Self}` is not derived from `{T}`.")
-)]
+#[rustc_on_unimplemented(message = "The IDL interface `{Self}` is not derived from `{T}`.")]
 pub trait DerivedFrom<T: Castable>: Castable {}
 
 impl<T: Float + ToJSValConvertible> ToJSValConvertible for Finite<T> {
diff --git a/components/script/dom/bindings/root.rs b/components/script/dom/bindings/root.rs
index 228015b1275..c87c83a2469 100644
--- a/components/script/dom/bindings/root.rs
+++ b/components/script/dom/bindings/root.rs
@@ -330,13 +330,13 @@ impl<T: DomObject> Deref for Dom<T> {
 
 unsafe impl<T: DomObject> JSTraceable for Dom<T> {
     unsafe fn trace(&self, trc: *mut JSTracer) {
-        #[cfg(all(feature = "unstable", debug_assertions))]
-        let trace_str = format!("for {} on heap", ::std::intrinsics::type_name::<T>());
-        #[cfg(all(feature = "unstable", debug_assertions))]
-        let trace_info = &trace_str[..];
-        #[cfg(not(all(feature = "unstable", debug_assertions)))]
-        let trace_info = "for DOM object on heap";
-
+        let trace_string;
+        let trace_info = if cfg!(debug_assertions) {
+            trace_string = format!("for {} on heap", ::std::intrinsics::type_name::<T>());
+            &trace_string[..]
+        } else {
+            "for DOM object on heap"
+        };
         trace_reflector(trc, trace_info, (*self.ptr.as_ptr()).reflector());
     }
 }