+++
title = "`static bool _has_error(Impl &&) noexcept`"
description = "Returns true if an error is present in the implementation passed in. Constexpr, never throws."
categories = ["observers"]
weight = 210
+++

Returns true if an error is present in the implementation passed in. Constexpr where possible.

*Requires*: Always available.

*Complexity*: Constant time.

*Guarantees*: Never throws an exception.
