@Nullable
  public static GrVariable findVariableToUse(@NotNull GrParameterListOwner owner) {
    final PsiElement parent = owner.getParent();
    if (parent instanceof GrVariable) return (GrVariable)parent;
    if (parent instanceof GrAssignmentExpression &&
        ((GrAssignmentExpression)parent).getRValue() == owner &&
        !((GrAssignmentExpression)parent).isOperatorAssignment()) {
      final GrExpression lValue = ((GrAssignmentExpression)parent).getLValue();
      if (lValue instanceof GrReferenceExpression) {
        final PsiElement resolved = ((GrReferenceExpression)lValue).resolve();
        if (resolved instanceof GrVariable) {
          return (GrVariable)resolved;
        }
      }
    }
    return null;
  }
@Nullable
  public static GrVariable findVariableToUse(@NotNull GrParameterListOwner owner)