qualify some assignment operators to disallow assignment to temporaries

bindings/python/src/bytes.hpp

@@ -14,7 +14,7 @@ struct bytes
 	bytes(std::string&& s): arr(std::move(s)) {}
 	bytes(bytes const&) = default;
 	bytes(bytes&&) noexcept = default;
-	bytes& operator=(bytes&&) noexcept = default;
+	bytes& operator=(bytes&&) & noexcept = default;
 	bytes() {}
 	std::string arr;
 };

include/libtorrent/aux_/win_crypto_provider.hpp

@@ -72,7 +72,7 @@ namespace libtorrent { namespace aux {
 		crypt_hash(crypt_hash const& h) { m_hash = duplicate(h); }
 		~crypt_hash() { CryptDestroyHash(m_hash); }
 
-		crypt_hash& crypt_hash::operator=(crypt_hash const& h)
+		crypt_hash& crypt_hash::operator=(crypt_hash const& h) &
 		{
 			if (this == &h) return *this;
 			HCRYPTHASH temp = duplicate(h);

include/libtorrent/chained_buffer.hpp

@@ -86,7 +86,7 @@ namespace libtorrent {
 				used_size = rhs.used_size;
 				move_holder(&holder, &rhs.holder);
 			}
-			buffer_t& operator=(buffer_t&& rhs) noexcept
+			buffer_t& operator=(buffer_t&& rhs) & noexcept
 			{
 				destruct_holder(&holder);
 				destruct_holder = rhs.destruct_holder;
@@ -99,7 +99,7 @@ namespace libtorrent {
 			}
 			buffer_t(buffer_t const& rhs) noexcept
 				: buffer_t(std::move(const_cast<buffer_t&>(rhs))) {}
-			buffer_t& operator=(buffer_t const& rhs) noexcept
+			buffer_t& operator=(buffer_t const& rhs) & noexcept
 			{ return this->operator=(std::move(const_cast<buffer_t&>(rhs))); }
 #else
 			buffer_t(buffer_t&&) = delete;

include/libtorrent/copy_ptr.hpp

@@ -46,13 +46,13 @@ namespace libtorrent {
 		copy_ptr(copy_ptr&& p) noexcept = default;
 
 		void reset(T* t = nullptr) { m_ptr.reset(t); }
-		copy_ptr& operator=(copy_ptr const& p)
+		copy_ptr& operator=(copy_ptr const& p) &
 		{
 			if (m_ptr == p.m_ptr) return *this;
 			m_ptr.reset(p.m_ptr ? new T(*p.m_ptr) : nullptr);
 			return *this;
 		}
-		copy_ptr& operator=(copy_ptr&& p) noexcept = default;
+		copy_ptr& operator=(copy_ptr&& p) & noexcept = default;
 		T* operator->() { return m_ptr.get(); }
 		T const* operator->() const { return m_ptr.get(); }
 		T& operator*() { return *m_ptr; }

include/libtorrent/disk_buffer_holder.hpp

@@ -60,7 +60,7 @@ namespace libtorrent {
 		disk_buffer_holder(buffer_allocator_interface& alloc
 			, char* buf, std::size_t sz) noexcept;
 
-		disk_buffer_holder& operator=(disk_buffer_holder&&) noexcept;
+		disk_buffer_holder& operator=(disk_buffer_holder&&) & noexcept;
 		disk_buffer_holder(disk_buffer_holder&&) noexcept;
 
 		disk_buffer_holder& operator=(disk_buffer_holder const&) = delete;

include/libtorrent/entry.hpp

@@ -191,17 +191,17 @@ namespace aux {
 		// copies the structure of the right hand side into this
 		// entry.
 #if TORRENT_ABI_VERSION == 1
-		entry& operator=(lazy_entry const&);
+		entry& operator=(lazy_entry const&) &;
 #endif
-		entry& operator=(bdecode_node const&);
-		entry& operator=(entry const&);
-		entry& operator=(entry&&) noexcept;
-		entry& operator=(dictionary_type);
-		entry& operator=(span<char const>);
+		entry& operator=(bdecode_node const&) &;
+		entry& operator=(entry const&) &;
+		entry& operator=(entry&&) & noexcept;
+		entry& operator=(dictionary_type) &;
+		entry& operator=(span<char const>) &;
 		template <typename U, typename Cond = typename std::enable_if<
 			std::is_same<U, entry::string_type>::value
 			|| std::is_same<U, char const*>::value>::type>
-		entry& operator=(U v)
+		entry& operator=(U v) &
 		{
 			destruct();
 			new(&data) string_type(std::move(v));
@@ -211,9 +211,9 @@ namespace aux {
 #endif
 			return *this;
 		}
-		entry& operator=(list_type);
-		entry& operator=(integer_type);
-		entry& operator=(preformatted_type);
+		entry& operator=(list_type) &;
+		entry& operator=(integer_type) &;
+		entry& operator=(preformatted_type) &;
 
 		// The ``integer()``, ``string()``, ``list()`` and ``dict()`` functions
 		// are accessors that return the respective type. If the ``entry`` object

include/libtorrent/file_storage.hpp

@@ -59,9 +59,9 @@ namespace libtorrent {
 		// hidden
 		~file_entry();
 		file_entry(file_entry const&) = default;
-		file_entry& operator=(file_entry const&) = default;
+		file_entry& operator=(file_entry const&) & = default;
 		file_entry(file_entry&&) noexcept = default;
-		file_entry& operator=(file_entry&&) noexcept = default;
+		file_entry& operator=(file_entry&&) & noexcept = default;
 
 		// the full path of this file. The paths are unicode strings
 		// encoded in UTF-8.
@@ -117,9 +117,9 @@ namespace libtorrent {
 
 		internal_file_entry();
 		internal_file_entry(internal_file_entry const& fe);
-		internal_file_entry& operator=(internal_file_entry const& fe);
+		internal_file_entry& operator=(internal_file_entry const& fe) &;
 		internal_file_entry(internal_file_entry&& fe) noexcept;
-		internal_file_entry& operator=(internal_file_entry&& fe) noexcept;
+		internal_file_entry& operator=(internal_file_entry&& fe) & noexcept;
 		~internal_file_entry();
 
 		void set_name(char const* n, bool borrow_string = false, int string_len = 0);

include/libtorrent/hasher.hpp

@@ -90,7 +90,7 @@ namespace libtorrent {
 		hasher(char const* data, int len);
 		explicit hasher(span<char const> data);
 		hasher(hasher const&);
-		hasher& operator=(hasher const&);
+		hasher& operator=(hasher const&) &;
 
 		// append the following bytes to what is being hashed
 		hasher& update(span<char const> data);

include/libtorrent/hasher512.hpp

@@ -91,7 +91,7 @@ namespace libtorrent {
 		// ``update(data)``.
 		explicit hasher512(span<char const> data);
 		hasher512(hasher512 const&);
-		hasher512& operator=(hasher512 const&);
+		hasher512& operator=(hasher512 const&) &;
 
 		// append the following bytes to what is being hashed
 		hasher512& update(span<char const> data);

include/libtorrent/union_endpoint.hpp

@@ -44,7 +44,7 @@ TORRENT_IPV6_NAMESPACE
 	{
 		union_address() { *this = address(); }
 		explicit union_address(address const& a) { *this = a; }
-		union_address& operator=(address const& a)
+		union_address& operator=(address const& a) &
 		{
 #if TORRENT_USE_IPV6
 			v4 = a.is_v4();
@@ -104,7 +104,7 @@ TORRENT_IPV6_NAMESPACE
 		explicit union_endpoint(udp::endpoint const& ep) { *this = ep; }
 		union_endpoint() { *this = tcp::endpoint(); }
 
-		union_endpoint& operator=(udp::endpoint const& ep)
+		union_endpoint& operator=(udp::endpoint const& ep) &
 		{
 			addr = ep.address();
 			port = ep.port();
@@ -113,7 +113,7 @@ TORRENT_IPV6_NAMESPACE
 
 		operator udp::endpoint() const { return udp::endpoint(addr, port); }
 
-		union_endpoint& operator=(tcp::endpoint const& ep)
+		union_endpoint& operator=(tcp::endpoint const& ep) &
 		{
 			addr = ep.address();
 			port = ep.port();

include/libtorrent/units.hpp

@@ -88,8 +88,8 @@ namespace libtorrent { namespace aux {
 		strong_typedef& operator-=(diff_type rhs)
 		{ m_val -= static_cast<UnderlyingType>(rhs); return *this; }
 
-		strong_typedef& operator=(strong_typedef const& rhs) noexcept = default;
-		strong_typedef& operator=(strong_typedef&& rhs) noexcept = default;
+		strong_typedef& operator=(strong_typedef const& rhs) & noexcept = default;
+		strong_typedef& operator=(strong_typedef&& rhs) & noexcept = default;
 	private:
 		UnderlyingType m_val;
 	};

src/disk_buffer_holder.cpp

@@ -39,7 +39,7 @@ namespace libtorrent {
 		: m_allocator(&alloc), m_buf(buf), m_size(sz), m_ref()
 	{}
 
-	disk_buffer_holder& disk_buffer_holder::operator=(disk_buffer_holder&& h) noexcept
+	disk_buffer_holder& disk_buffer_holder::operator=(disk_buffer_holder&& h) & noexcept
 	{
 		if (&h == this) return *this;
 		disk_buffer_holder(std::move(h)).swap(*this);

src/entry.cpp

@@ -132,7 +132,7 @@ namespace {
 
 	entry::~entry() { destruct(); }
 
-	entry& entry::operator=(const entry& e)
+	entry& entry::operator=(const entry& e) &
 	{
 		if (&e == this) return *this;
 		destruct();
@@ -140,7 +140,7 @@ namespace {
 		return *this;
 	}
 
-	entry& entry::operator=(entry&& e) noexcept
+	entry& entry::operator=(entry&& e) & noexcept
 	{
 		if (&e == this) return *this;
 		destruct();
@@ -360,7 +360,7 @@ namespace {
 	}
 
 	// convert a bdecode_node into an old skool entry
-	entry& entry::operator=(bdecode_node const& e)
+	entry& entry::operator=(bdecode_node const& e) &
 	{
 		switch (e.type())
 		{
@@ -399,7 +399,7 @@ namespace {
 
 #if TORRENT_ABI_VERSION == 1
 	// convert a lazy_entry into an old skool entry
-	entry& entry::operator=(lazy_entry const& e)
+	entry& entry::operator=(lazy_entry const& e) &
 	{
 		switch (e.type())
 		{
@@ -437,7 +437,7 @@ namespace {
 	}
 #endif
 
-	entry& entry::operator=(preformatted_type v)
+	entry& entry::operator=(preformatted_type v) &
 	{
 		destruct();
 		new(&data) preformatted_type(std::move(v));
@@ -448,7 +448,7 @@ namespace {
 		return *this;
 	}
 
-	entry& entry::operator=(dictionary_type v)
+	entry& entry::operator=(dictionary_type v) &
 	{
 		destruct();
 		new(&data) dictionary_type(std::move(v));
@@ -459,7 +459,7 @@ namespace {
 		return *this;
 	}
 
-	entry& entry::operator=(span<char const> v)
+	entry& entry::operator=(span<char const> v) &
 	{
 		destruct();
 		new(&data) string_type(v.data(), v.size());
@@ -470,7 +470,7 @@ namespace {
 		return *this;
 	}
 
-	entry& entry::operator=(list_type v)
+	entry& entry::operator=(list_type v) &
 	{
 		destruct();
 		new(&data) list_type(std::move(v));
@@ -481,7 +481,7 @@ namespace {
 		return *this;
 	}
 
-	entry& entry::operator=(integer_type v)
+	entry& entry::operator=(integer_type v) &
 	{
 		destruct();
 		new(&data) integer_type(std::move(v));

src/file_storage.cpp

@@ -241,7 +241,7 @@ namespace {
 			name = fe.name;
 	}
 
-	internal_file_entry& internal_file_entry::operator=(internal_file_entry const& fe)
+	internal_file_entry& internal_file_entry::operator=(internal_file_entry const& fe) &
 	{
 		if (&fe == this) return *this;
 		offset = fe.offset;
@@ -274,7 +274,7 @@ namespace {
 		fe.name = nullptr;
 	}
 
-	internal_file_entry& internal_file_entry::operator=(internal_file_entry&& fe) noexcept
+	internal_file_entry& internal_file_entry::operator=(internal_file_entry&& fe) & noexcept
 	{
 		if (&fe == this) return *this;
 		offset = fe.offset;

src/hasher.cpp

@@ -75,7 +75,7 @@ namespace libtorrent {
 		gcry_md_copy(&m_context, h.m_context);
 	}
 
-	hasher& hasher::operator=(hasher const& h)
+	hasher& hasher::operator=(hasher const& h) &
 	{
 		if (this == &h) return;
 		gcry_md_close(m_context);
@@ -84,7 +84,7 @@ namespace libtorrent {
 	}
 #else
 	hasher::hasher(hasher const&) = default;
-	hasher& hasher::operator=(hasher const&) = default;
+	hasher& hasher::operator=(hasher const&) & = default;
 #endif
 
 	hasher& hasher::update(char const* data, int len)

src/hasher512.cpp

@@ -68,7 +68,7 @@ namespace libtorrent {
 		gcry_md_copy(&m_context, h.m_context);
 	}
 
-	hasher512& hasher512::operator=(hasher512 const& h)
+	hasher512& hasher512::operator=(hasher512 const& h) &
 	{
 		if (this == &h) return;
 		gcry_md_close(m_context);
@@ -77,7 +77,7 @@ namespace libtorrent {
 	}
 #else
 	hasher512::hasher512(hasher512 const&) = default;
-	hasher512& hasher512::operator=(hasher512 const&) = default;
+	hasher512& hasher512::operator=(hasher512 const&) & = default;
 #endif
 
 	hasher512& hasher512::update(span<char const> data)