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More restrictive assignment from optional<U>

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This commit is contained in:
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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79
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.

1
doc/91_relnotes.qbk
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@ -17,6 +17,7 @@
* Improved the trick that prevents streaming out `optional` without header `optional_io.hpp` by using safe-bool idiom. This addresses [@https://svn.boost.org/trac/boost/ticket/10825 Trac #10825]
* IOStream operators are now mentioned in documentation.
* Added a way to manually disable move semantics: just define macro `BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES`. This can be used to work around [@https://svn.boost.org/trac/boost/ticket/10399 Trac #10399]
* It is no longer possible to assign `optional<U>` to `optional<T>` when `U` is not assignable or convertible to `T`.
[heading Boost Release 1.57]

492
doc/html/boost_optional/reference/detailed_semantics.html
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@ -808,30 +808,74 @@
is <a href="../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">CopyAssignable</span></code>.
</li>
<li class="listitem">
<p class="simpara">
<span class="bold"><strong>Effects:</strong></span>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
If <code class="computeroutput"><span class="special">!*</span><span class="keyword">this</span>
<span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">rhs</span></code> no effect, otherwise
</li>
<li class="listitem">
if <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span>
<span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">rhs</span></code>, destroys the contained value
by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, otherwise
</li>
<li class="listitem">
if <code class="computeroutput"><span class="special">!*</span><span class="keyword">this</span>
<span class="special">&amp;&amp;</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>, initializes the contained value
as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code>
with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>,
otherwise
</li>
<li class="listitem">
(if <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span>
<span class="special">&amp;&amp;</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>) assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> to the contained value.
</li>
</ul></div>
</li>
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
contains a value
</p>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
does not contain a value
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> contains
a value
</p>
</td>
<td>
<p>
assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
to the contained value
</p>
</td>
<td>
<p>
initializes the contained value as if direct-initializing an
object of type <code class="computeroutput"><span class="identifier">T</span></code>
with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> does not
contain a value
</p>
</td>
<td>
<p>
destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
</p>
</td>
<td>
<p>
no effect
</p>
</td>
</tr>
</tbody>
</table></div>
</li>
<li class="listitem">
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
</li>
@ -919,30 +963,73 @@
and <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
</li>
<li class="listitem">
<p class="simpara">
<span class="bold"><strong>Effects:</strong></span>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
If <code class="computeroutput"><span class="special">!*</span><span class="keyword">this</span>
<span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">rhs</span></code> no effect, otherwise
</li>
<li class="listitem">
if <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span>
<span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">rhs</span></code>, destroys the contained value
by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, otherwise
</li>
<li class="listitem">
if <code class="computeroutput"><span class="special">!*</span><span class="keyword">this</span>
<span class="special">&amp;&amp;</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>, initializes the contained value
as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code>
with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>,
otherwise
</li>
<li class="listitem">
(if <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span>
<span class="special">&amp;&amp;</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>) assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value.
</li>
</ul></div>
</li>
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
contains a value
</p>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
does not contain a value
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> contains
a value
</p>
</td>
<td>
<p>
assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
</p>
</td>
<td>
<p>
initializes the contained value as if direct-initializing an
object of type <code class="computeroutput"><span class="identifier">T</span></code>
with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> does not
contain a value
</p>
</td>
<td>
<p>
destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
</p>
</td>
<td>
<p>
no effect
</p>
</td>
</tr>
</tbody>
</table></div>
</li>
<li class="listitem">
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
</li>
@ -997,40 +1084,88 @@
</p></blockquote></div>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<span class="bold"><strong>Effect:</strong></span> Assigns another convertible
optional to an optional.
<p class="simpara">
<span class="bold"><strong>Effect:</strong></span>
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
contains a value
</p>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
does not contain a value
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> contains
a value
</p>
</td>
<td>
<p>
assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
to the contained value
</p>
</td>
<td>
<p>
initializes the contained value as if direct-initializing an
object of type <code class="computeroutput"><span class="identifier">T</span></code>
with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> does not
contain a value
</p>
</td>
<td>
<p>
destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
</p>
</td>
<td>
<p>
no effect
</p>
</td>
</tr>
</tbody>
</table></div>
</li>
<li class="listitem">
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
</li>
<li class="listitem">
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the value
of <code class="computeroutput"><span class="identifier">rhs</span></code> <span class="emphasis"><em>converted</em></span>
to type <code class="computeroutput"><span class="identifier">T</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is uninitialized.
<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
</li>
<li class="listitem">
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">)</span></code> throws.
</li>
<li class="listitem">
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and rhs are initially initialized,
<code class="computeroutput"><span class="identifier">T</span></code>'s <span class="emphasis"><em>assignment
operator</em></span> (from <code class="computeroutput"><span class="identifier">U</span></code>)
is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
<span class="emphasis"><em>destructor</em></span> is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but rhs
is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
<span class="emphasis"><em>converting constructor</em></span> (from <code class="computeroutput"><span class="identifier">U</span></code>)
is called.
</li>
<li class="listitem">
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an
exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
converting constructor fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
<span class="bold"><strong>Exception Safety:</strong></span> If any exception is
thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception is
thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
constructor, no effect. If an exception is thrown during the call to
<code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the state
of its contained value is as defined by the exception safety guarantee
of <code class="computeroutput"><span class="identifier">T</span></code>'s copy assignment.
</li>
<li class="listitem">
<span class="bold"><strong>Example:</strong></span>
@ -1053,36 +1188,87 @@
</p></blockquote></div>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<span class="bold"><strong>Effect:</strong></span> Move-assigns another convertible
optional to an optional.
<p class="simpara">
<span class="bold"><strong>Effect:</strong></span>
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
contains a value
</p>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
does not contain a value
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> contains
a value
</p>
</td>
<td>
<p>
assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
</p>
</td>
<td>
<p>
initializes the contained value as if direct-initializing an
object of type <code class="computeroutput"><span class="identifier">T</span></code>
with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> does not
contain a value
</p>
</td>
<td>
<p>
destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
</p>
</td>
<td>
<p>
no effect
</p>
</td>
</tr>
</tbody>
</table></div>
</li>
<li class="listitem">
<span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
</li>
<li class="listitem">
<span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is initialized and its value is moved from the value of <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
<span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
</li>
<li class="listitem">
<span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">U</span><span class="special">&amp;&amp;</span> <span class="special">)</span></code>
or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&amp;&amp;</span>
<span class="special">)</span></code> throws.
</li>
<li class="listitem">
<span class="bold"><strong>Notes:</strong></span> If both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
are initially initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
<span class="emphasis"><em>assignment operator</em></span> (from <code class="computeroutput"><span class="identifier">U</span><span class="special">&amp;&amp;</span></code>) is used. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is initially initialized but <code class="computeroutput"><span class="identifier">rhs</span></code>
is uninitialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
<span class="emphasis"><em>destructor</em></span> is called. If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initially uninitialized but <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s
<span class="emphasis"><em>converting constructor</em></span> (from <code class="computeroutput"><span class="identifier">U</span><span class="special">&amp;&amp;</span></code>) is called.
</li>
<li class="listitem">
<span class="bold"><strong>Exception Safety:</strong></span> In the event of an
exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
as far as optional is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
<code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
converting constructor fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
<span class="bold"><strong>Exception Safety:</strong></span> If any exception is
thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception is
thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
constructor, no effect. If an exception is thrown during the call to
<code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the state
of its contained value is as defined by the exception safety guarantee
of <code class="computeroutput"><span class="identifier">T</span></code>'s copy assignment.
</li>
<li class="listitem">
<span class="bold"><strong>Example:</strong></span>
@ -2019,35 +2205,81 @@
<span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
</li>
<li class="listitem">
<p class="simpara">
<span class="bold"><strong>Effects:</strong></span>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
If <code class="computeroutput"><span class="special">!*</span><span class="keyword">this</span>
<span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">rhs</span></code>, no effect, otherwise
</li>
<li class="listitem">
if <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span>
<span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">rhs</span></code>, initializes the contained
value of <code class="computeroutput"><span class="identifier">rhs</span></code> as
if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code>
with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>, followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value and
<code class="computeroutput"><span class="identifier">rhs</span></code> contains a
value, otherwise
</li>
<li class="listitem">
if <code class="computeroutput"><span class="special">!*</span><span class="keyword">this</span>
<span class="special">&amp;&amp;</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>, initializes the contained value
of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code>
with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code> does not contain a value,
otherwise
</li>
<li class="listitem">
(if <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span>
<span class="special">&amp;&amp;</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>) calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>.
</li>
</ul></div>
</li>
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
contains a value
</p>
</th>
<th>
<p>
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
does not contain a value
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> contains
a value
</p>
</td>
<td>
<p>
calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing
an object of type <code class="computeroutput"><span class="identifier">T</span></code>
with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
does not contain a value
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">rhs</span></code> does not
contain a value
</p>
</td>
<td>
<p>
initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code>
as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code>
with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>, followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-&gt;</span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
<code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
does not contain a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
contains a value
</p>
</td>
<td>
<p>
no effect
</p>
</td>
</tr>
</tbody>
</table></div>
</li>
<li class="listitem">
<span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
interchanged.

4
doc/html/boost_optional/relnotes.html
View File

@ -52,6 +52,10 @@
This can be used to work around <a href="https://svn.boost.org/trac/boost/ticket/10399" target="_top">Trac
#10399</a>
</li>
<li class="listitem">
It is no longer possible to assign <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span></code> to <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> when <code class="computeroutput"><span class="identifier">U</span></code>
is not assignable or convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
</li>
</ul></div>
<h4>
<a name="boost_optional.relnotes.h1"></a>

2
doc/html/index.html
View File

@ -138,7 +138,7 @@
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"><p><small>Last revised: January 21, 2015 at 13:59:23 GMT</small></p></td>
<td align="left"><p><small>Last revised: March 06, 2015 at 18:13:34 GMT</small></p></td>
<td align="right"><div class="copyright-footer"></div></td>
</tr></table>
<hr>

13
include/boost/optional/optional.hpp
View File

@ -188,7 +188,7 @@ struct types_when_is_ref
template <class To, class From>
void prevent_binding_rvalue_ref_to_optional_lvalue_ref()
{
#ifndef BOOST_OPTIONAL_ALLOW_BINDING_TO_RVALUES
#ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
BOOST_STATIC_ASSERT_MSG(
!boost::is_lvalue_reference<To>::value || !boost::is_rvalue_reference<From>::value,
"binding rvalue references to optional lvalue references is disallowed");
@ -371,13 +371,22 @@ class optional_base : public optional_tag
if (is_initialized())
{
if ( rhs.is_initialized() )
assign_value(static_cast<value_type>(rhs.get()), is_reference_predicate() );
#ifndef BOOST_OPTIONAL_CONFIG_RESTORE_ASSIGNMENT_OF_NONCONVERTIBLE_TYPES
assign_value(rhs.get(), is_reference_predicate() );
#else
assign_value(static_cast<value_type>(rhs.get()), is_reference_predicate() );
#endif
else destroy();
}
else
{
if ( rhs.is_initialized() )
#ifndef BOOST_OPTIONAL_CONFIG_RESTORE_ASSIGNMENT_OF_NONCONVERTIBLE_TYPES
construct(rhs.get());
#else
construct(static_cast<value_type>(rhs.get()));
#endif
}
}

1
test/Jamfile.v2
View File

@ -56,5 +56,6 @@ import testing ;
[ compile-fail optional_test_fail_explicit_convert_in_value_or.cpp ]
[ compile-fail optional_test_fail_explicit_convert_in_value_or_call.cpp ]
[ compile-fail optional_test_fail_io_without_io.cpp ]
[ compile-fail optional_test_fail_convert_assign_of_enums.cpp ]
;
}

27
test/optional_test_fail_convert_assign_of_enums.cpp Normal file
View File

@ -0,0 +1,27 @@
// Copyright (C) 2015, Andrzej Krzemienski.
//
// Use, modification, and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/lib/optional for documentation.
//
// You are welcome to contact the author at:
// akrzemi1@gmail.com
#include <iostream>
#include "boost/optional.hpp"
// THIS TEST SHOULD FAIL TO COMPILE
enum E1 {e1};
enum E2 {e2};
void test_converitng_assignment_of_different_enums()
{
boost::optional<E2> o2(e2);
boost::optional<E1> o1;
o1 = o2;
}
int main() {}