Codegen: Fix return type of getResolveStep and resolve

misc/codegen/templates/ql_class.mustache

@@ -9,7 +9,9 @@ private import {{import_prefix}}.Raw
 {{#imports}}
 import {{.}}
 {{/imports}}
-
+{{#root}}
+private class {{name}}Alias = {{name}};
+{{/root}}
 /**
  * INTERNAL: This module contains the fully generated definition of `{{name}}` and should not
  * be referenced directly.
@@ -49,13 +51,13 @@ module Generated {
      * Classes can override this to indicate this node should be in the "hidden" AST, mostly reserved
      * for conversions and syntactic sugar nodes like parentheses.
      */
-    {{name}} getResolveStep() { none() } // overridden by subclasses
+    {{name}}Alias getResolveStep() { none() } // overridden by subclasses
 
     /**
      * Gets the element that should substitute this element in the explicit AST, applying `getResolveStep`
      * transitively.
      */
-    final {{name}} resolve() {
+    final {{name}}Alias resolve() {
       not exists(this.getResolveStep()) and result = this
       or
       result = this.getResolveStep().resolve()