hir_analysis: skip self type of host effect preds

Like trait predicates, the self type ought to be skipped here.

Author: davidtwco

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

@@ -8,7 +8,6 @@ trait Foo {}
 impl const Foo for () {}
 
 fn foo<'a: 'a>() -> impl const Foo {}
-//~^ ERROR ['a: o]
+//~^ ERROR ['a: *]
 
 fn main() {}
-

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

@@ -1,4 +1,4 @@
-error: ['a: o]
+error: ['a: *]
   --> $DIR/variance.rs:10:21
    |
 LL | fn foo<'a: 'a>() -> impl const Foo {}