When a or b is an error, relate ok

Author: jackh726

chalk-solve/src/infer/unify.rs

@@ -111,6 +111,7 @@ impl<'t, I: Interner> Unifier<'t, I> {
         }
 
         match (a.kind(interner), b.kind(interner)) {
+            (TyKind::Error, _) | (_, TyKind::Error) => Ok(()),
             // Relating two inference variables:
             // First, if either variable is a float or int kind, then we always
             // unify if they match. This is because float and ints don't have
@@ -349,7 +350,6 @@ impl<'t, I: Interner> Unifier<'t, I> {
             (TyKind::Foreign(id_a), TyKind::Foreign(id_b)) => {
                 Zip::zip_with(self, variance, id_a, id_b)
             }
-            (TyKind::Error, TyKind::Error) => Ok(()),
 
             (_, _) => Err(NoSolution),
         }