std::expected<T,E>::error - cppreference.com

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constexpr const E& error() const& noexcept;

(1) (since C++23)

constexpr E& error() & noexcept;

(2) (since C++23)

constexpr const E&& error() const&& noexcept;

(3) (since C++23)

constexpr E&& error() && noexcept;

(4) (since C++23)

Accesses the unexpected value contained in *this.

If has_value() is true, the behavior is undefined.

(until C++26)

If has_value() is true:

  • If the implementation is hardened, a contract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined.
  • If the implementation is not hardened, the behavior is undefined.
(since C++26)

Return value

3,4) std::move(unex )

Example

See also