hir_analysis: skip self type of host effect preds in variances_of

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -198,6 +198,10 @@ fn variance_of_opaque(
             ty::ClauseKind::Trait(ty::TraitPredicate {
                 trait_ref: ty::TraitRef { def_id: _, args, .. },
                 polarity: _,
+            })
+            | ty::ClauseKind::HostEffect(ty::HostEffectPredicate {
+                trait_ref: ty::TraitRef { def_id: _, args, .. },
+                constness: _,
             }) => {
                 for arg in &args[1..] {
                     arg.visit_with(&mut collector);

tests/ui/traits/const-traits/variance.rs

@@ -0,0 +1,13 @@
+#![feature(rustc_attrs, const_trait_impl)]
+#![allow(internal_features)]
+#![rustc_variance_of_opaques]
+
+#[const_trait]
+trait Foo {}
+
+impl const Foo for () {}
+
+fn foo<'a: 'a>() -> impl const Foo {}
+//~^ ERROR ['a: *]
+
+fn main() {}

tests/ui/traits/const-traits/variance.stderr

@@ -0,0 +1,8 @@
+error: ['a: *]
+  --> $DIR/variance.rs:10:21
+   |
+LL | fn foo<'a: 'a>() -> impl const Foo {}
+   |                     ^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+