Implement implied_bounds functionality for generic type parameters.

Author: obi1kenobi

src/librustdoc/clean/auto_trait.rs

@@ -103,6 +103,7 @@ fn synthesize_auto_trait_impl<'tcx>(
             // regardless of the choice of `T`.
             let mut generics = clean_ty_generics_inner(
                 cx,
+                item_def_id,
                 tcx.generics_of(item_def_id),
                 ty::GenericPredicates::default(),
             );

src/librustdoc/clean/inline.rs

@@ -545,7 +545,7 @@ pub(crate) fn build_impl(
                 })
                 .map(|item| clean_impl_item(item, cx))
                 .collect::<Vec<_>>(),
-            clean_generics(impl_.generics, cx),
+            clean_generics(impl_.generics, did, cx),
         ),
         None => (
             tcx.associated_items(did)