Make locations map immutable

src/mdo/model.vm

@@ -136,9 +136,9 @@ public class ${class.name}
     final ${type} $field.name;
     #end
     #if ( $locationTracking )
-      #if ( ! $class.superClass )
     /** Locations */
     final Map<Object, InputLocation> locations;
+      #if ( ! $class.superClass )
     /** Location tracking */
     final InputLocation importedFrom;
       #end
@@ -170,14 +170,16 @@ public class ${class.name}
     #if ( $locationTracking )
         Map<Object, InputLocation> newlocs = builder.locations != null ? builder.locations : Collections.emptyMap();
         Map<Object, InputLocation> oldlocs = builder.base != null && builder.base.locations != null ? builder.base.locations : Collections.emptyMap();
+        this.locations = Map.ofEntries(
+            Map.entry("", newlocs.containsKey("") ? newlocs.get("") : oldlocs.get("")),
+        #foreach ( $field in $allFields )
+            #set ( $sep = "#if($field!=${allFields[${allFields.size()} - 1]}),#end" )
+            Map.entry("${field.name}", newlocs.containsKey("${field.name}") ? newlocs.get("${field.name}") : oldlocs.get("${field.name}"))${sep}
+        #end
+        );
       #if ( ! $class.superClass )
-        this.locations = new HashMap<>();
         this.importedFrom = builder.importedFrom;
-        this.locations.put("", newlocs.containsKey("") ? newlocs.get("") : oldlocs.get(""));
       #end
-        #foreach ( $field in $class.getFields($version) )
-        this.locations.put("${field.name}", newlocs.containsKey("${field.name}") ? newlocs.get("${field.name}") : oldlocs.get("${field.name}"));
-        #end
     #end
     }