Printing alias-relate goals correctly

compiler/rustc_middle/src/ty/mod.rs

@@ -661,6 +661,16 @@ impl AliasRelationDirection {
     }
 }
 
+impl std::fmt::Display for AliasRelationDirection {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            AliasRelationDirection::Equate => write!(f, " == "),
+            AliasRelationDirection::Subtype => write!(f, " <: "),
+            AliasRelationDirection::Supertype => write!(f, " :> "),
+        }
+    }
+}
+
 /// The crate outlives map is computed during typeck and contains the
 /// outlives of every item in the local crate. You should not use it
 /// directly, because to do so will make your pass dependent on the

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2847,8 +2847,7 @@ define_print_and_forward_display! {
                 p!("the type `", print(ty), "` is found in the environment")
             }
             ty::PredicateKind::Ambiguous => p!("ambiguous"),
-            // TODO
-            ty::PredicateKind::AliasRelate(t1, t2, _) => p!(print(t1), " == ", print(t2)),
+            ty::PredicateKind::AliasRelate(t1, t2, dir) => p!(print(t1), write(" {} ", dir), print(t2)),
         }
     }
 

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -177,8 +177,9 @@ impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
                 write!(f, "TypeWellFormedFromEnv({:?})", ty)
             }
             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
-            // TODO
-            ty::PredicateKind::AliasRelate(t1, t2, _) => write!(f, "AliasRelate({t1:?}, {t2:?})"),
+            ty::PredicateKind::AliasRelate(t1, t2, dir) => {
+                write!(f, "AliasRelate({t1:?}, {dir:?}, {t2:?})")
+            }
         }
     }
 }