Fix convertion generator for manually written ones

pkg/runtime/conversion_generator.go

@@ -81,6 +81,9 @@ func (g *generator) generateConversionsBetween(inType, outType reflect.Type) err
 	}
 
 	if inType.Kind() != outType.Kind() {
+		if existingConversion {
+			return nil
+		}
 		return fmt.Errorf("cannot convert types of different kinds: %v %v", inType, outType)
 	}
 	// We should be able to generate conversions both sides.
@@ -173,9 +176,6 @@ func (g *generator) generateConversionsForStruct(inType, outType reflect.Type) e
 		if !found {
 			return fmt.Errorf("couldn't find a corresponding field %v in %v", inField.Name, outType)
 		}
-		if inField.Type.Kind() != outField.Type.Kind() {
-			return fmt.Errorf("cannot convert types of different kinds: %v %v", inField, outField)
-		}
 		if isComplexType(inField.Type) {
 			if err := g.generateConversionsBetween(inField.Type, outField.Type); err != nil {
 				return err
@@ -733,6 +733,11 @@ func (g *generator) existsDedicatedConversionFunction(inType, outType reflect.Ty
 			return false
 		}
 	}
+	if inType.Kind() != outType.Kind() {
+		// TODO(wojtek-t): Currently all conversions between types of different kinds are
+		// unnamed. Thus we return false here.
+		return false
+	}
 	return g.scheme.Converter().HasConversionFunc(inType, outType)
 }