@Nullable
    public PsiType fun(GrReferenceExpressionImpl refExpr) {
      PsiType result = GrReassignedLocalVarsChecker.checkReassignedVar(refExpr, true);
      if (result != null) return result;

      if (GrUnresolvedAccessInspection.isClassReference(refExpr)) {
        GrExpression qualifier = refExpr.getQualifier();
        LOG.assertTrue(qualifier != null);
        return TypesUtil.createJavaLangClassType(
            qualifier.getType(), refExpr.getProject(), refExpr.getResolveScope());
      }

      final PsiElement resolved = refExpr.resolve();
      final PsiType inferred = getInferredTypes(refExpr, resolved);
      final PsiType nominal = refExpr.getNominalType();
      if (inferred == null || PsiType.NULL.equals(inferred)) {
        if (nominal == null) {
          // inside nested closure we could still try to infer from variable initializer. Not sound,
          // but makes sense
          if (resolved instanceof GrVariable) {
            LOG.assertTrue(resolved.isValid());
            return ((GrVariable) resolved).getTypeGroovy();
          }
        }

        return nominal;
      }

      if (nominal == null) return inferred;
      if (!TypeConversionUtil.isAssignable(TypeConversionUtil.erasure(nominal), inferred, false)) {
        if (resolved instanceof GrVariable
            && ((GrVariable) resolved).getTypeElementGroovy() != null) {
          return nominal;
        }
      }
      return inferred;
    }
 private static void assertAllAreValid(GroovyResolveResult[] candidates) {
   for (GroovyResolveResult candidate : candidates) {
     final PsiElement element = candidate.getElement();
     LOG.assertTrue(element == null || element.isValid());
   }
 }