lower impl const to bind to host effect param

2 files changed, 7 insertions, 2 deletions

diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 5eef3e45f32..30f60abe31c 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1963,9 +1963,9 @@ impl<'tcx> TyCtxt<'tcx> {
         matches!(
             node,
             hir::Node::Item(hir::Item {
-                kind: hir::ItemKind::Impl(hir::Impl { constness: hir::Constness::Const, .. }),
+                kind: hir::ItemKind::Impl(hir::Impl { generics, .. }),
                 ..
-            })
+            }) if generics.params.iter().any(|p| self.has_attr(p.def_id, sym::rustc_host))
         )
     }
 
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index d3fd49150ba..ed0af6f5eb1 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -2841,6 +2841,11 @@ define_print_and_forward_display! {
 
     ty::TraitPredicate<'tcx> {
         p!(print(self.trait_ref.self_ty()), ": ");
+        if let Some(idx) = cx.tcx().generics_of(self.trait_ref.def_id).host_effect_index {
+            if self.trait_ref.args.const_at(idx) != cx.tcx().consts.true_ {
+                p!("~const ");
+            }
+        }
         // FIXME(effects) print `~const` here
         if let ty::ImplPolarity::Negative = self.polarity {
             p!("!");