Aleph::unexpected< E > Class Template Reference

Wrapper for the error value used to initialize an expected. More...

#include <ah-cpp-compat.H>

Public Member Functions
template<class Err = E> requires (not std::is_same_v<std::remove_cvref_t<Err>, unexpected> and std::is_constructible_v<E, Err>)
constexpr	unexpected (Err &&e) noexcept(std::is_nothrow_constructible_v< E, Err >)
	Construct the stored error from any value convertible to E.
constexpr const E &	error () const &noexcept
	Access the error (const lvalue).
constexpr E &	error () &noexcept
	Access the error (lvalue).
constexpr E &&	error () &&noexcept
	Access the error (rvalue).

Private Attributes
E	err_

Detailed Description

template<class E>
class Aleph::unexpected< E >

Wrapper for the error value used to initialize an expected.

Represents an error in contexts where expected is used. Construct an unexpected to return an error from a function returning expected<T,E>:

expected<int, std::string> parse(const std::string &s) {
  if (bad) return unexpected<std::string>("parse error");
  return value;
}

Template Parameters

E	Error type (must be movable).

Exception Safety

Basic guarantee: if E construction throws, the object is not constructed.

Thread Safety

Value type with no shared state. Operations on distinct objects are safe.

Definition at line 182 of file ah-cpp-compat.H.

Constructor & Destructor Documentation

unexpected()

template<class E >

template<class Err = E>
requires (not std::is_same_v<std::remove_cvref_t<Err>, unexpected> and std::is_constructible_v<E, Err>)

constexpr Aleph::unexpected< E >::unexpected ( Err &&  e )

inlineexplicitconstexprnoexcept

Construct the stored error from any value convertible to E.

Mirrors std::unexpected's actual converting constructor: a single constrained, perfectly-forwarding constructor instead of separate const E& / E&& overloads. Two fixed overloads force the compiler to pick between them when the argument needs a user-defined conversion (e.g. building unexpected<std::string> from a string literal), which some MSVC versions fail to resolve (error C2672); a single template leaves exactly one candidate.

Template Parameters

Err	Deduced argument type.

Parameters

e	Value used to construct the stored error.

Exceptions

Any	exception thrown by constructing E from e.

Definition at line 204 of file ah-cpp-compat.H.

Member Function Documentation

error() [1/3]

template<class E >

constexpr E && Aleph::unexpected< E >::error ( ) &&

inlineconstexprnoexcept

Access the error (rvalue).

Returns

Rvalue reference to the stored error.

Complexity O(1).

Definition at line 224 of file ah-cpp-compat.H.

References Aleph::unexpected< E >::err_.

error() [2/3]

template<class E >

constexpr E & Aleph::unexpected< E >::error ( ) &

inlineconstexprnoexcept

Access the error (lvalue).

Returns

Mutable reference to the stored error.

Complexity O(1).

Definition at line 218 of file ah-cpp-compat.H.

References Aleph::unexpected< E >::err_.

error() [3/3]

template<class E >

constexpr const E & Aleph::unexpected< E >::error ( ) const &

inlineconstexprnoexcept

Access the error (const lvalue).

Returns

Const reference to the stored error.

Complexity O(1).

Definition at line 212 of file ah-cpp-compat.H.

References Aleph::unexpected< E >::err_.

Member Data Documentation

err_

template<class E >

E Aleph::unexpected< E >::err_

private

Definition at line 184 of file ah-cpp-compat.H.

Referenced by Aleph::unexpected< E >::error(), Aleph::unexpected< E >::error(), and Aleph::unexpected< E >::error().

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The documentation for this class was generated from the following file:

• ah-cpp-compat.H