Fix auto traits in rustdoc

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1270,7 +1270,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // the master cache. Since coherence executes pretty quickly,
         // it's not worth going to more trouble to increase the
         // hit-rate, I don't think.
-        if self.intercrate {
+        if self.intercrate || self.allow_negative_impls {
             return false;
         }
 
@@ -1287,7 +1287,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // mode, so don't do any caching. In particular, we might
         // re-use the same `InferCtxt` with both an intercrate
         // and non-intercrate `SelectionContext`
-        if self.intercrate {
+        if self.intercrate || self.allow_negative_impls {
             return None;
         }
         let tcx = self.tcx();

src/test/rustdoc/auto-trait-not-send.rs

@@ -0,0 +1,8 @@
+#![crate_name = "foo"]
+
+// @has 'foo/struct.Foo.html'
+// @has - '//*[@id="impl-Send"]' 'impl !Send for Foo'
+// @has - '//*[@id="impl-Sync"]' 'impl !Sync for Foo'
+pub struct Foo(*const i8);
+pub trait Whatever: Send {}
+impl<T: Send + ?Sized> Whatever for T {}