rustdoc: properly elide cross-crate host effect args

Author: fmease

src/librustdoc/clean/mod.rs

@@ -2534,7 +2534,6 @@ fn clean_generic_args<'tcx>(
                     }
                     hir::GenericArg::Lifetime(_) => GenericArg::Lifetime(Lifetime::elided()),
                     hir::GenericArg::Type(ty) => GenericArg::Type(clean_ty(ty, cx)),
-                    // FIXME(effects): This will still emit `<true>` for non-const impls of const traits
                     hir::GenericArg::Const(ct)
                         if cx.tcx.has_attr(ct.value.def_id, sym::rustc_host) =>
                     {

src/librustdoc/clean/utils.rs

@@ -124,11 +124,7 @@ pub(crate) fn ty_args_to_args<'tcx>(
             )))
         }
         GenericArgKind::Const(ct) => {
-            // FIXME(effects): this relies on the host effect being called `host`, which users could also name
-            // their const generics.
-            // FIXME(effects): this causes `host = true` and `host = false` generics to also be emitted.
-            if let ty::ConstKind::Param(p) = ct.kind()
-                && p.name == sym::host
+            if let ty::GenericParamDefKind::Const { is_host_effect: true, .. } = params[index].kind
             {
                 return None;
             }