Re-land "fix #30462, update function_type tests to understand covariant generics"

tests/language_2/function_type/function_type18_test.dart

Index: tests/language_2/function_type/function_type18_test.dart
diff --git a/tests/language_2/function_type/function_type18_test.dart b/tests/language_2/function_type/function_type18_test.dart
index c5cd25bbee9d85026506be1135d177b0f5753edb..235f27ae8fad785809ab82343adf209788f91200 100644
--- a/tests/language_2/function_type/function_type18_test.dart
+++ b/tests/language_2/function_type/function_type18_test.dart
@@ -265,10 +265,10 @@ class U18<T> {
       });
     }
     if (tIsInt || tIsBool) {
-      Expect.equals(tIsInt, m2 is F2<int>);
-      Expect.equals(tIsBool, m2 is F2<bool>);
-      Expect.equals(tIsInt, confuse(m2) is F2<int>);
-      Expect.equals(tIsBool, confuse(m2) is F2<bool>);
+      Expect.equals(true, m2 is F2<int>);
+      Expect.equals(true, m2 is F2<bool>);
+      Expect.equals(true, confuse(m2) is F2<int>);
+      Expect.equals(true, confuse(m2) is F2<bool>);
     }
   }