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More restrictive assignment from optional<U>

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Andrzej Krzemienski
2015-03-06 19:20:45 +01:00
parent 16023fe934
commit 59266a2630
8 changed files with 444 additions and 175 deletions
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doc/20_reference.qbk
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@ -602,10 +602,11 @@ __SPACE__
* [*Requires:] `T` is __COPY_CONSTRUCTIBLE__ and `CopyAssignable`.
* [*Effects:]
* If `!*this && !rhs` no effect, otherwise
* if `bool(*this) && !rhs`, destroys the contained value by calling `val->T::~T()`, otherwise
* if `!*this && bool(rhs)`, initializes the contained value as if direct-initializing an object of type `T` with `*rhs`, otherwise
* (if `bool(*this) && bool(rhs)`) assigns `*rhs` to the contained value.
[table
[[][`*this` contains a value][`*this` does not contain a value]]
[[`rhs` contains a value][assigns `*rhs` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `*rhs`]]
[[`rhs` does not contain a value][destroys the contained value by calling `val->T::~T()`][no effect]]
]
* [*Returns:] `*this`;
* [*Postconditions:] `bool(rhs) == bool(*this)`.
* [*Exception Safety:] If any exception is thrown, the initialization state of `*this` and `rhs` remains unchanged.
@ -662,10 +663,11 @@ __SPACE__
* [*Requires:] `T` is __MOVE_CONSTRUCTIBLE__ and `MoveAssignable`.
* [*Effects:]
* If `!*this && !rhs` no effect, otherwise
* if `bool(*this) && !rhs`, destroys the contained value by calling `val->T::~T()`, otherwise
* if `!*this && bool(rhs)`, initializes the contained value as if direct-initializing an object of type `T` with `std::move(*rhs)`, otherwise
* (if `bool(*this) && bool(rhs)`) assigns `std::move(*rhs)` to the contained value.
[table
[[][`*this` contains a value][`*this` does not contain a value]]
[[`rhs` contains a value][assigns `std::move(*rhs)` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `std::move(*rhs)`]]
[[`rhs` does not contain a value][destroys the contained value by calling `val->T::~T()`][no effect]]
]
* [*Returns:] `*this`;
* [*Postconditions:] `bool(rhs) == bool(*this)`.
* [*Remarks:] The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value && is_nothrow_move_assignable<T>::value`.
@ -696,21 +698,17 @@ __SPACE__
[: `template<U> optional& optional<T` ['(not a ref)]`>::operator= ( optional<U> const& rhs ) ;`]
* [*Effect:] Assigns another convertible optional to an optional.
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
its value is a ['copy] of the value of `rhs` ['converted] to type `T`; else
`*this` is uninitialized.
* [*Throws:] Whatever `T::operator=( U const& )` or `T::T( U const& )` throws.
* [*Notes:] If both `*this` and rhs are initially initialized, `T`'s
['assignment operator] (from `U`) is used. If `*this` is initially initialized
but `rhs` is uninitialized, `T`'s ['destructor] is called. If `*this` is
initially uninitialized but rhs is initialized, `T`'s ['converting constructor]
(from `U`) is called.
* [*Exception Safety:] In the event of an exception, the initialization state
of `*this` is unchanged and its value unspecified as far as optional is
concerned (it is up to `T`'s `operator=()`). If `*this` is initially
uninitialized and `T`'s converting constructor fails, `*this` is left properly
uninitialized.
* [*Effect:]
[table
[[][`*this` contains a value][`*this` does not contain a value]]
[[`rhs` contains a value][assigns `*rhs` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `*rhs`]]
[[`rhs` does not contain a value][destroys the contained value by calling `val->T::~T()`][no effect]]
]
* [*Returns:] `*this`.
* [*Postconditions:] `bool(rhs) == bool(*this)`.
* [*Exception Safety:] If any exception is thrown, the result of the expression `bool(*this)` remains unchanged.
If an exception is thrown during the call to `T`'s constructor, no effect.
If an exception is thrown during the call to `T`'s assignment, the state of its contained value is as defined by the exception safety guarantee of `T`'s copy assignment.
* [*Example:]
``
T v;
@ -727,21 +725,17 @@ __SPACE__
[: `template<U> optional& optional<T` ['(not a ref)]`>::operator= ( optional<U>&& rhs ) ;`]
* [*Effect:] Move-assigns another convertible optional to an optional.
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
its value is moved from the value of `rhs`; else
`*this` is uninitialized.
* [*Throws:] Whatever `T::operator=( U&& )` or `T::T( U&& )` throws.
* [*Notes:] If both `*this` and `rhs` are initially initialized, `T`'s
[' assignment operator] (from `U&&`) is used. If `*this` is initially initialized
but `rhs` is uninitialized, `T`'s ['destructor] is called. If `*this` is
initially uninitialized but `rhs` is initialized, `T`'s ['converting constructor]
(from `U&&`) is called.
* [*Exception Safety:] In the event of an exception, the initialization state
of `*this` is unchanged and its value unspecified as far as optional is
concerned (it is up to `T`'s `operator=()`). If `*this` is initially
uninitialized and `T`'s converting constructor fails, `*this` is left properly
uninitialized.
* [*Effect:]
[table
[[][`*this` contains a value][`*this` does not contain a value]]
[[`rhs` contains a value][assigns `std::move(*rhs)` to the contained value][initializes the contained value as if direct-initializing an object of type `T` with `std::move(*rhs)`]]
[[`rhs` does not contain a value][destroys the contained value by calling `val->T::~T()`][no effect]]
]
* [*Returns:] `*this`.
* [*Postconditions:] `bool(rhs) == bool(*this)`.
* [*Exception Safety:] If any exception is thrown, the result of the expression `bool(*this)` remains unchanged.
If an exception is thrown during the call to `T`'s constructor, no effect.
If an exception is thrown during the call to `T`'s assignment, the state of its contained value is as defined by the exception safety guarantee of `T`'s copy assignment.
* [*Example:]
``
T v;
@ -1256,10 +1250,11 @@ __SPACE__
* [*Requires:] Lvalues of type `T` shall be swappable and `T` shall be __MOVE_CONSTRUCTIBLE__.
* [*Effects:]
* If `!*this && !rhs`, no effect, otherwise
* if `bool(*this) && !rhs`, initializes the contained value of `rhs` as if direct-initializing an object of type `T` with the expression `std::move(*(*this))`, followed by `val->T::~T()`, `*this` does not contain a value and `rhs` contains a value, otherwise
* if `!*this && bool(rhs)`, initializes the contained value of `*this` as if direct-initializing an object of type `T` with the expression `std::move(*rhs)`, followed by `rhs.val->T::~T()`, `*this` contains a value and `rhs` does not contain a value, otherwise
* (if `bool(*this) && bool(rhs)`) calls `swap(*(*this), *rhs)`.
[table
[[][`*this` contains a value][`*this` does not contain a value]]
[[`rhs` contains a value][calls `swap(*(*this), *rhs)`][initializes the contained value of `*this` as if direct-initializing an object of type `T` with the expression `std::move(*rhs)`, followed by `rhs.val->T::~T()`, `*this` contains a value and `rhs` does not contain a value]]
[[`rhs` does not contain a value][initializes the contained value of `rhs` as if direct-initializing an object of type `T` with the expression `std::move(*(*this))`, followed by `val->T::~T()`, `*this` does not contain a value and `rhs` contains a value][no effect]]
]
* [*Postconditions:] The states of `x` and `y` interchanged.
* [*Throws:] If both are initialized, whatever `swap(T&,T&)` throws. If only
one is initialized, whatever `T::T ( T&& )` throws.