Make sure callbacks are initialized

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Ordering.enso

@@ -130,20 +130,6 @@ type Comparable
 
     hash self -> Integer = self.comparator.hash self.value
 
-    ## PRIVATE
-       Called as a callback from internal engine code for an atom with a custom
-       comparator. It is assumed that the given atom has a custom comparator, that is
-       a comparator different than `Default_Comparator`.
-    hash_callback : Atom -> Integer
-    hash_callback atom = (Comparable.from atom).hash atom
-
-    ## PRIVATE
-       A callback allowing to compare two atoms with a custom comparator.
-    compare_callback : Atom -> Atom -> Integer | Nothing
-    compare_callback atom that =
-        ordering = Ordering.compare atom that
-        if ordering.is_error then Nothing else ordering.to_sign
-
 ## PRIVATE
    Default implementation of a _comparator_.
 @Builtin_Type
@@ -167,6 +153,20 @@ type Default_Comparator
     hash : Number -> Integer
     hash x = Comparable.hash_builtin x
 
+    ## PRIVATE
+       Called as a callback from internal engine code for an atom with a custom
+       comparator. It is assumed that the given atom has a custom comparator, that is
+       a comparator different than `Default_Comparator`.
+    hash_callback : Atom -> Integer
+    hash_callback atom = (Comparable.from atom).hash atom
+
+    ## PRIVATE
+       A callback allowing to compare two atoms with a custom comparator.
+    compare_callback : Atom -> Atom -> Integer | Nothing
+    compare_callback atom that =
+        ordering = Ordering.compare atom that
+        if ordering.is_error then Nothing else ordering.to_sign
+
 ## PRIVATE
 Comparable.from (that:Any) = Comparable.new that Default_Comparator
 

std-bits/base/src/main/java/org/enso/base/ObjectComparator.java

@@ -5,6 +5,7 @@
 import java.time.ZonedDateTime;
 import java.util.Comparator;
 import java.util.Locale;
+import java.util.Objects;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import org.graalvm.polyglot.Context;
@@ -22,9 +23,10 @@ private static void initCallbacks() {
           Context.getCurrent()
               .getBindings("enso")
               .invokeMember("get_module", "Standard.Base.Data.Ordering");
-      var type = module.invokeMember("get_type", "Comparable");
+      var type = module.invokeMember("get_type", "Default_Comparator");
 
       var hash_callback = module.invokeMember("get_method", type, "hash_callback");
+      Objects.requireNonNull(hash_callback, "hash_callback");
       ensoHashCodeCallback =
           v -> {
             var result = hash_callback.execute(null, v);
@@ -37,6 +39,7 @@ private static void initCallbacks() {
           };
 
       var compare_callback = module.invokeMember("get_method", type, "compare_callback");
+      Objects.requireNonNull(compare_callback, "compare_callback");
       ensoCompareCallback =
           (v, u) -> {
             var result = compare_callback.execute(null, v, u);