@Nullable("null if ref is not actually 'this' reference")
  public static Collection<GroovyResolveResult> resolveThisExpression(@NotNull GrReferenceExpression ref) {
    GrExpression qualifier = ref.getQualifier();

    if (qualifier == null) {
      PsiClass aClass = PsiUtil.getContextClass(ref);
      if (aClass != null) {
        return Collections.singletonList(new ElementResolveResult<>(aClass));
      }
    }
    else if (qualifier instanceof GrReferenceExpression) {
      GroovyResolveResult result = ((GrReferenceExpression)qualifier).advancedResolve();
      PsiElement resolved = result.getElement();
      if (resolved instanceof PsiClass && PsiUtil.hasEnclosingInstanceInScope((PsiClass)resolved, ref, false)) {
        return Collections.singletonList(result);
      }
    }

    return null;
  }
@Nullable("null if ref is not actually 'this' reference")
  public static Collection<GroovyResolveResult> resolveThisExpression(@NotNull GrReferenceExpression ref)