Destructuring assignments.

11 files changed, 389 insertions, 105 deletions

diff --git a/libsolidity/Compiler.cpp b/libsolidity/Compiler.cpp
index cc1228a1..679704ba 100644
--- a/libsolidity/Compiler.cpp
+++ b/libsolidity/Compiler.cpp
@@ -597,13 +597,20 @@ bool Compiler::visit(Break const& _breakStatement)
 bool Compiler::visit(Return const& _return)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _return);
-	//@todo modifications are needed to make this work with functions returning multiple values
 	if (Expression const* expression = _return.expression())
 	{
 		solAssert(_return.annotation().functionReturnParameters, "Invalid return parameters pointer.");
-		VariableDeclaration const& firstVariable = *_return.annotation().functionReturnParameters->parameters().front();
-		compileExpression(*expression, firstVariable.annotation().type);
-		CompilerUtils(m_context).moveToStackVariable(firstVariable);
+		vector<ASTPointer<VariableDeclaration>> const& returnParameters =
+			_return.annotation().functionReturnParameters->parameters();
+		TypePointers types;
+		for (auto const& retVariable: returnParameters)
+			types.push_back(retVariable->annotation().type);
+
+		TypePointer expectedType = types.size() == 1 ? types.front() : make_shared<TupleType>(types);
+		compileExpression(*expression, expectedType);
+
+		for (auto const& retVariable: boost::adaptors::reverse(returnParameters))
+			CompilerUtils(m_context).moveToStackVariable(*retVariable);
 	}
 	for (unsigned i = 0; i < m_stackCleanupForReturn; ++i)
 		m_context << eth::Instruction::POP;
diff --git a/libsolidity/CompilerUtils.cpp b/libsolidity/CompilerUtils.cpp
index e1152202..34bb08ba 100644
--- a/libsolidity/CompilerUtils.cpp
+++ b/libsolidity/CompilerUtils.cpp
@@ -550,6 +550,55 @@ void CompilerUtils::convertType(Type const& _typeOnStack, Type const& _targetTyp
 		}
 		break;
 	}
+	case Type::Category::Tuple:
+	{
+		//@TODO wildcards
+		TupleType const& sourceTuple = dynamic_cast<TupleType const&>(_typeOnStack);
+		TupleType const& targetTuple = dynamic_cast<TupleType const&>(_targetType);
+		solAssert(sourceTuple.components().size() == targetTuple.components().size(), "");
+		unsigned depth = sourceTuple.sizeOnStack();
+		for (size_t i = 0; i < sourceTuple.components().size(); ++i)
+		{
+			TypePointer const& sourceType = sourceTuple.components()[i];
+			TypePointer const& targetType = targetTuple.components()[i];
+			if (!sourceType)
+			{
+				solAssert(!targetType, "");
+				continue;
+			}
+			unsigned sourceSize = sourceType->sizeOnStack();
+			unsigned targetSize = targetType->sizeOnStack();
+			if (*sourceType != *targetType || _cleanupNeeded)
+			{
+				if (sourceSize > 0)
+					copyToStackTop(depth, sourceSize);
+
+				convertType(*sourceType, *targetType, _cleanupNeeded);
+
+				if (sourceSize > 0 || targetSize > 0)
+				{
+					// Move it back into its place.
+					for (unsigned j = 0; j < min(sourceSize, targetSize); ++j)
+						m_context <<
+							eth::swapInstruction(depth + targetSize - sourceSize) <<
+							eth::Instruction::POP;
+					if (targetSize < sourceSize)
+						moveToStackTop(sourceSize - targetSize, depth );
+					// Value shrank
+					for (unsigned j = targetSize; j < sourceSize; ++j)
+					{
+						moveToStackTop(depth - 1, 1);
+						m_context << eth::Instruction::POP;
+					}
+					// Value grew
+					if (targetSize > sourceSize)
+						moveIntoStack(depth + targetSize - sourceSize, targetSize - sourceSize);
+				}
+			}
+			depth -= sourceSize;
+		}
+		break;
+	}
 	default:
 		// All other types should not be convertible to non-equal types.
 		solAssert(_typeOnStack == _targetType, "Invalid type conversion requested.");
@@ -631,18 +680,20 @@ void CompilerUtils::copyToStackTop(unsigned _stackDepth, unsigned _itemSize)
 		m_context << eth::dupInstruction(_stackDepth);
 }
 
-void CompilerUtils::moveToStackTop(unsigned _stackDepth)
+void CompilerUtils::moveToStackTop(unsigned _stackDepth, unsigned _itemSize)
 {
 	solAssert(_stackDepth <= 15, "Stack too deep, try removing local variables.");
-	for (unsigned i = 0; i < _stackDepth; ++i)
-		m_context << eth::swapInstruction(1 + i);
+	for (unsigned j = 0; j < _itemSize; ++j)
+		for (unsigned i = 0; i < _stackDepth + _itemSize - 1; ++i)
+			m_context << eth::swapInstruction(1 + i);
 }
 
-void CompilerUtils::moveIntoStack(unsigned _stackDepth)
+void CompilerUtils::moveIntoStack(unsigned _stackDepth, unsigned _itemSize)
 {
 	solAssert(_stackDepth <= 16, "Stack too deep, try removing local variables.");
-	for (unsigned i = _stackDepth; i > 0; --i)
-		m_context << eth::swapInstruction(i);
+	for (unsigned j = 0; j < _itemSize; ++j)
+		for (unsigned i = _stackDepth; i > 0; --i)
+			m_context << eth::swapInstruction(i + _itemSize - 1);
 }
 
 void CompilerUtils::popStackElement(Type const& _type)
diff --git a/libsolidity/CompilerUtils.h b/libsolidity/CompilerUtils.h
index f335eed5..01b9f422 100644
--- a/libsolidity/CompilerUtils.h
+++ b/libsolidity/CompilerUtils.h
@@ -124,10 +124,11 @@ public:
 	/// Copies an item that occupies @a _itemSize stack slots from a stack depth of @a _stackDepth
 	/// to the top of the stack.
 	void copyToStackTop(unsigned _stackDepth, unsigned _itemSize);
-	/// Moves a single stack element (with _stackDepth items on top of it) to the top of the stack.
-	void moveToStackTop(unsigned _stackDepth);
-	/// Moves a single stack element past @a _stackDepth other stack elements
-	void moveIntoStack(unsigned _stackDepth);
+	/// Moves an item that occupies @a _itemSize stack slots and has items occupying @a _stackDepth
+	/// slots above it to the top of the stack.
+	void moveToStackTop(unsigned _stackDepth, unsigned _itemSize = 1);
+	/// Moves @a _itemSize elements past @a _stackDepth other stack elements
+	void moveIntoStack(unsigned _stackDepth, unsigned _itemSize = 1);
 	/// Removes the current value from the top of the stack.
 	void popStackElement(Type const& _type);
 	/// Removes element from the top of the stack _amount times.
diff --git a/libsolidity/ExpressionCompiler.cpp b/libsolidity/ExpressionCompiler.cpp
index 85302afc..8109c03b 100644
--- a/libsolidity/ExpressionCompiler.cpp
+++ b/libsolidity/ExpressionCompiler.cpp
@@ -177,20 +177,18 @@ void ExpressionCompiler::appendStateVariableAccessor(VariableDeclaration const&
 
 bool ExpressionCompiler::visit(Assignment const& _assignment)
 {
+//	cout << "-----Assignment" << endl;
 	CompilerContext::LocationSetter locationSetter(m_context, _assignment);
 	_assignment.rightHandSide().accept(*this);
-	TypePointer type = _assignment.rightHandSide().annotation().type;
-	if (!_assignment.annotation().type->dataStoredIn(DataLocation::Storage))
-	{
-		utils().convertType(*type, *_assignment.annotation().type);
-		type = _assignment.annotation().type;
-	}
-	else
-	{
-		utils().convertType(*type, *type->mobileType());
-		type = type->mobileType();
-	}
+	// Perform some conversion already. This will convert storage types to memory and literals
+	// to their actual type, but will not convert e.g. memory to storage.
+	TypePointer type = _assignment.rightHandSide().annotation().type->closestTemporaryType(
+		_assignment.leftHandSide().annotation().type
+	);
+//	cout << "-----Type conversion" << endl;
+	utils().convertType(*_assignment.rightHandSide().annotation().type, *type);
 
+//	cout << "-----LHS" << endl;
 	_assignment.leftHandSide().accept(*this);
 	solAssert(!!m_currentLValue, "LValue not retrieved.");
 
@@ -216,11 +214,32 @@ bool ExpressionCompiler::visit(Assignment const& _assignment)
 				m_context << eth::swapInstruction(itemSize + lvalueSize) << eth::Instruction::POP;
 		}
 	}
+//	cout << "-----Store" << endl;
 	m_currentLValue->storeValue(*type, _assignment.location());
 	m_currentLValue.reset();
 	return false;
 }
 
+bool ExpressionCompiler::visit(TupleExpression const& _tuple)
+{
+	vector<unique_ptr<LValue>> lvalues;
+	for (auto const& component: _tuple.components())
+		if (component)
+		{
+			component->accept(*this);
+			if (_tuple.annotation().lValueRequested)
+			{
+				solAssert(!!m_currentLValue, "");
+				lvalues.push_back(move(m_currentLValue));
+			}
+		}
+		else if (_tuple.annotation().lValueRequested)
+			lvalues.push_back(unique_ptr<LValue>());
+	if (_tuple.annotation().lValueRequested)
+		m_currentLValue.reset(new TupleObject(m_context, move(lvalues)));
+	return false;
+}
+
 bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
 {
 	CompilerContext::LocationSetter locationSetter(m_context, _unaryOperation);
diff --git a/libsolidity/ExpressionCompiler.h b/libsolidity/ExpressionCompiler.h
index d8fef5af..44d27ea2 100644
--- a/libsolidity/ExpressionCompiler.h
+++ b/libsolidity/ExpressionCompiler.h
@@ -72,6 +72,7 @@ public:
 
 private:
 	virtual bool visit(Assignment const& _assignment) override;
+	virtual bool visit(TupleExpression const& _tuple) override;
 	virtual bool visit(UnaryOperation const& _unaryOperation) override;
 	virtual bool visit(BinaryOperation const& _binaryOperation) override;
 	virtual bool visit(FunctionCall const& _functionCall) override;
diff --git a/libsolidity/LValue.cpp b/libsolidity/LValue.cpp
index 9f33e846..20aa59e1 100644
--- a/libsolidity/LValue.cpp
+++ b/libsolidity/LValue.cpp
@@ -32,9 +32,9 @@ using namespace solidity;
 
 
 StackVariable::StackVariable(CompilerContext& _compilerContext, VariableDeclaration const& _declaration):
-	LValue(_compilerContext, *_declaration.annotation().type),
+	LValue(_compilerContext, _declaration.annotation().type.get()),
 	m_baseStackOffset(m_context.baseStackOffsetOfVariable(_declaration)),
-	m_size(m_dataType.sizeOnStack())
+	m_size(m_dataType->sizeOnStack())
 {
 }
 
@@ -70,23 +70,23 @@ void StackVariable::storeValue(Type const&, SourceLocation const& _location, boo
 
 void StackVariable::setToZero(SourceLocation const& _location, bool) const
 {
-	CompilerUtils(m_context).pushZeroValue(m_dataType);
-	storeValue(m_dataType, _location, true);
+	CompilerUtils(m_context).pushZeroValue(*m_dataType);
+	storeValue(*m_dataType, _location, true);
 }
 
 MemoryItem::MemoryItem(CompilerContext& _compilerContext, Type const& _type, bool _padded):
-	LValue(_compilerContext, _type),
+	LValue(_compilerContext, &_type),
 	m_padded(_padded)
 {
 }
 
 void MemoryItem::retrieveValue(SourceLocation const&, bool _remove) const
 {
-	if (m_dataType.isValueType())
+	if (m_dataType->isValueType())
 	{
 		if (!_remove)
 			m_context << eth::Instruction::DUP1;
-		CompilerUtils(m_context).loadFromMemoryDynamic(m_dataType, false, m_padded, false);
+		CompilerUtils(m_context).loadFromMemoryDynamic(*m_dataType, false, m_padded, false);
 	}
 	else
 		m_context << eth::Instruction::MLOAD;
@@ -95,24 +95,24 @@ void MemoryItem::retrieveValue(SourceLocation const&, bool _remove) const
 void MemoryItem::storeValue(Type const& _sourceType, SourceLocation const&, bool _move) const
 {
 	CompilerUtils utils(m_context);
-	if (m_dataType.isValueType())
+	if (m_dataType->isValueType())
 	{
 		solAssert(_sourceType.isValueType(), "");
 		utils.moveIntoStack(_sourceType.sizeOnStack());
-		utils.convertType(_sourceType, m_dataType, true);
+		utils.convertType(_sourceType, *m_dataType, true);
 		if (!_move)
 		{
-			utils.moveToStackTop(m_dataType.sizeOnStack());
-			utils.copyToStackTop(2, m_dataType.sizeOnStack());
+			utils.moveToStackTop(m_dataType->sizeOnStack());
+			utils.copyToStackTop(2, m_dataType->sizeOnStack());
 		}
-		utils.storeInMemoryDynamic(m_dataType, m_padded);
+		utils.storeInMemoryDynamic(*m_dataType, m_padded);
 		m_context << eth::Instruction::POP;
 	}
 	else
 	{
-		solAssert(_sourceType == m_dataType, "Conversion not implemented for assignment to memory.");
+		solAssert(_sourceType == *m_dataType, "Conversion not implemented for assignment to memory.");
 
-		solAssert(m_dataType.sizeOnStack() == 1, "");
+		solAssert(m_dataType->sizeOnStack() == 1, "");
 		if (!_move)
 			m_context << eth::Instruction::DUP2 << eth::Instruction::SWAP1;
 		// stack: [value] value lvalue
@@ -126,8 +126,8 @@ void MemoryItem::setToZero(SourceLocation const&, bool _removeReference) const
 	CompilerUtils utils(m_context);
 	if (!_removeReference)
 		m_context << eth::Instruction::DUP1;
-	utils.pushZeroValue(m_dataType);
-	utils.storeInMemoryDynamic(m_dataType, m_padded);
+	utils.pushZeroValue(*m_dataType);
+	utils.storeInMemoryDynamic(*m_dataType, m_padded);
 	m_context << eth::Instruction::POP;
 }
 
@@ -139,21 +139,21 @@ StorageItem::StorageItem(CompilerContext& _compilerContext, VariableDeclaration
 }
 
 StorageItem::StorageItem(CompilerContext& _compilerContext, Type const& _type):
-	LValue(_compilerContext, _type)
+	LValue(_compilerContext, &_type)
 {
-	if (m_dataType.isValueType())
+	if (m_dataType->isValueType())
 	{
-		solAssert(m_dataType.storageSize() == m_dataType.sizeOnStack(), "");
-		solAssert(m_dataType.storageSize() == 1, "Invalid storage size.");
+		solAssert(m_dataType->storageSize() == m_dataType->sizeOnStack(), "");
+		solAssert(m_dataType->storageSize() == 1, "Invalid storage size.");
 	}
 }
 
 void StorageItem::retrieveValue(SourceLocation const&, bool _remove) const
 {
 	// stack: storage_key storage_offset
-	if (!m_dataType.isValueType())
+	if (!m_dataType->isValueType())
 	{
-		solAssert(m_dataType.sizeOnStack() == 1, "Invalid storage ref size.");
+		solAssert(m_dataType->sizeOnStack() == 1, "Invalid storage ref size.");
 		if (_remove)
 			m_context << eth::Instruction::POP; // remove byte offset
 		else
@@ -162,22 +162,22 @@ void StorageItem::retrieveValue(SourceLocation const&, bool _remove) const
 	}
 	if (!_remove)
 		CompilerUtils(m_context).copyToStackTop(sizeOnStack(), sizeOnStack());
-	if (m_dataType.storageBytes() == 32)
+	if (m_dataType->storageBytes() == 32)
 		m_context << eth::Instruction::POP << eth::Instruction::SLOAD;
 	else
 	{
 		m_context
 			<< eth::Instruction::SWAP1 << eth::Instruction::SLOAD << eth::Instruction::SWAP1
 			<< u256(0x100) << eth::Instruction::EXP << eth::Instruction::SWAP1 << eth::Instruction::DIV;
-		if (m_dataType.category() == Type::Category::FixedBytes)
-			m_context << (u256(0x1) << (256 - 8 * m_dataType.storageBytes())) << eth::Instruction::MUL;
+		if (m_dataType->category() == Type::Category::FixedBytes)
+			m_context << (u256(0x1) << (256 - 8 * m_dataType->storageBytes())) << eth::Instruction::MUL;
 		else if (
-			m_dataType.category() == Type::Category::Integer &&
-			dynamic_cast<IntegerType const&>(m_dataType).isSigned()
+			m_dataType->category() == Type::Category::Integer &&
+			dynamic_cast<IntegerType const&>(*m_dataType).isSigned()
 		)
-			m_context << u256(m_dataType.storageBytes() - 1) << eth::Instruction::SIGNEXTEND;
+			m_context << u256(m_dataType->storageBytes() - 1) << eth::Instruction::SIGNEXTEND;
 		else
-			m_context << ((u256(0x1) << (8 * m_dataType.storageBytes())) - 1) << eth::Instruction::AND;
+			m_context << ((u256(0x1) << (8 * m_dataType->storageBytes())) - 1) << eth::Instruction::AND;
 	}
 }
 
@@ -185,11 +185,11 @@ void StorageItem::storeValue(Type const& _sourceType, SourceLocation const& _loc
 {
 	CompilerUtils utils(m_context);
 	// stack: value storage_key storage_offset
-	if (m_dataType.isValueType())
+	if (m_dataType->isValueType())
 	{
-		solAssert(m_dataType.storageBytes() <= 32, "Invalid storage bytes size.");
-		solAssert(m_dataType.storageBytes() > 0, "Invalid storage bytes size.");
-		if (m_dataType.storageBytes() == 32)
+		solAssert(m_dataType->storageBytes() <= 32, "Invalid storage bytes size.");
+		solAssert(m_dataType->storageBytes() > 0, "Invalid storage bytes size.");
+		if (m_dataType->storageBytes() == 32)
 		{
 			// offset should be zero
 			m_context << eth::Instruction::POP;
@@ -207,24 +207,24 @@ void StorageItem::storeValue(Type const& _sourceType, SourceLocation const& _loc
 			// stack: value storege_ref multiplier old_full_value
 			// clear bytes in old value
 			m_context
-				<< eth::Instruction::DUP2 << ((u256(1) << (8 * m_dataType.storageBytes())) - 1)
+				<< eth::Instruction::DUP2 << ((u256(1) << (8 * m_dataType->storageBytes())) - 1)
 				<< eth::Instruction::MUL;
 			m_context << eth::Instruction::NOT << eth::Instruction::AND;
 			// stack: value storage_ref multiplier cleared_value
 			m_context
 				<< eth::Instruction::SWAP1 << eth::Instruction::DUP4;
 			// stack: value storage_ref cleared_value multiplier value
-			if (m_dataType.category() == Type::Category::FixedBytes)
+			if (m_dataType->category() == Type::Category::FixedBytes)
 				m_context
-					<< (u256(0x1) << (256 - 8 * dynamic_cast<FixedBytesType const&>(m_dataType).numBytes()))
+					<< (u256(0x1) << (256 - 8 * dynamic_cast<FixedBytesType const&>(*m_dataType).numBytes()))
 					<< eth::Instruction::SWAP1 << eth::Instruction::DIV;
 			else if (
-				m_dataType.category() == Type::Category::Integer &&
-				dynamic_cast<IntegerType const&>(m_dataType).isSigned()
+				m_dataType->category() == Type::Category::Integer &&
+				dynamic_cast<IntegerType const&>(*m_dataType).isSigned()
 			)
 				// remove the higher order bits
 				m_context
-					<< (u256(1) << (8 * (32 - m_dataType.storageBytes())))
+					<< (u256(1) << (8 * (32 - m_dataType->storageBytes())))
 					<< eth::Instruction::SWAP1
 					<< eth::Instruction::DUP2
 					<< eth::Instruction::MUL
@@ -239,23 +239,23 @@ void StorageItem::storeValue(Type const& _sourceType, SourceLocation const& _loc
 	else
 	{
 		solAssert(
-			_sourceType.category() == m_dataType.category(),
+			_sourceType.category() == m_dataType->category(),
 			"Wrong type conversation for assignment.");
-		if (m_dataType.category() == Type::Category::Array)
+		if (m_dataType->category() == Type::Category::Array)
 		{
 			m_context << eth::Instruction::POP; // remove byte offset
 			ArrayUtils(m_context).copyArrayToStorage(
-						dynamic_cast<ArrayType const&>(m_dataType),
+						dynamic_cast<ArrayType const&>(*m_dataType),
 						dynamic_cast<ArrayType const&>(_sourceType));
 			if (_move)
 				m_context << eth::Instruction::POP;
 		}
-		else if (m_dataType.category() == Type::Category::Struct)
+		else if (m_dataType->category() == Type::Category::Struct)
 		{
 			// stack layout: source_ref target_ref target_offset
 			// note that we have structs, so offset should be zero and are ignored
 			m_context << eth::Instruction::POP;
-			auto const& structType = dynamic_cast<StructType const&>(m_dataType);
+			auto const& structType = dynamic_cast<StructType const&>(*m_dataType);
 			auto const& sourceType = dynamic_cast<StructType const&>(_sourceType);
 			solAssert(
 				structType.structDefinition() == sourceType.structDefinition(),
@@ -313,18 +313,18 @@ void StorageItem::storeValue(Type const& _sourceType, SourceLocation const& _loc
 
 void StorageItem::setToZero(SourceLocation const&, bool _removeReference) const
 {
-	if (m_dataType.category() == Type::Category::Array)
+	if (m_dataType->category() == Type::Category::Array)
 	{
 		if (!_removeReference)
 			CompilerUtils(m_context).copyToStackTop(sizeOnStack(), sizeOnStack());
-		ArrayUtils(m_context).clearArray(dynamic_cast<ArrayType const&>(m_dataType));
+		ArrayUtils(m_context).clearArray(dynamic_cast<ArrayType const&>(*m_dataType));
 	}
-	else if (m_dataType.category() == Type::Category::Struct)
+	else if (m_dataType->category() == Type::Category::Struct)
 	{
 		// stack layout: storage_key storage_offset
 		// @todo this can be improved: use StorageItem for non-value types, and just store 0 in
 		// all slots that contain value types later.
-		auto const& structType = dynamic_cast<StructType const&>(m_dataType);
+		auto const& structType = dynamic_cast<StructType const&>(*m_dataType);
 		for (auto const& member: structType.members())
 		{
 			// zero each member that is not a mapping
@@ -342,10 +342,10 @@ void StorageItem::setToZero(SourceLocation const&, bool _removeReference) const
 	}
 	else
 	{
-		solAssert(m_dataType.isValueType(), "Clearing of unsupported type requested: " + m_dataType.toString());
+		solAssert(m_dataType->isValueType(), "Clearing of unsupported type requested: " + m_dataType->toString());
 		if (!_removeReference)
 			CompilerUtils(m_context).copyToStackTop(sizeOnStack(), sizeOnStack());
-		if (m_dataType.storageBytes() == 32)
+		if (m_dataType->storageBytes() == 32)
 		{
 			// offset should be zero
 			m_context
@@ -361,7 +361,7 @@ void StorageItem::setToZero(SourceLocation const&, bool _removeReference) const
 			// stack: storege_ref multiplier old_full_value
 			// clear bytes in old value
 			m_context
-				<< eth::Instruction::SWAP1 << ((u256(1) << (8 * m_dataType.storageBytes())) - 1)
+				<< eth::Instruction::SWAP1 << ((u256(1) << (8 * m_dataType->storageBytes())) - 1)
 				<< eth::Instruction::MUL;
 			m_context << eth::Instruction::NOT << eth::Instruction::AND;
 			// stack: storage_ref cleared_value
@@ -374,7 +374,7 @@ void StorageItem::setToZero(SourceLocation const&, bool _removeReference) const
 static FixedBytesType byteType(1);
 
 StorageByteArrayElement::StorageByteArrayElement(CompilerContext& _compilerContext):
-	LValue(_compilerContext, byteType)
+	LValue(_compilerContext, &byteType)
 {
 }
 
@@ -427,7 +427,7 @@ void StorageByteArrayElement::setToZero(SourceLocation const&, bool _removeRefer
 }
 
 StorageArrayLength::StorageArrayLength(CompilerContext& _compilerContext, const ArrayType& _arrayType):
-	LValue(_compilerContext, *_arrayType.memberType("length")),
+	LValue(_compilerContext, _arrayType.memberType("length").get()),
 	m_arrayType(_arrayType)
 {
 	solAssert(m_arrayType.isDynamicallySized(), "");
@@ -455,3 +455,92 @@ void StorageArrayLength::setToZero(SourceLocation const&, bool _removeReference)
 		m_context << eth::Instruction::DUP1;
 	ArrayUtils(m_context).clearDynamicArray(m_arrayType);
 }
+
+
+TupleObject::TupleObject(
+	CompilerContext& _compilerContext,
+	std::vector<std::unique_ptr<LValue>>&& _lvalues
+):
+	LValue(_compilerContext), m_lvalues(move(_lvalues))
+{
+}
+
+unsigned TupleObject::sizeOnStack() const
+{
+	unsigned size = 0;
+	for (auto const& lv: m_lvalues)
+		if (lv)
+			size += lv->sizeOnStack();
+	return size;
+}
+
+void TupleObject::retrieveValue(SourceLocation const& _location, bool _remove) const
+{
+	unsigned initialDepth = sizeOnStack();
+	unsigned initialStack = m_context.stackHeight();
+	for (auto const& lv: m_lvalues)
+		if (lv)
+		{
+			solAssert(initialDepth + m_context.stackHeight() >= initialStack, "");
+			unsigned depth = initialDepth + m_context.stackHeight() - initialStack;
+			if (lv->sizeOnStack() > 0)
+				if (_remove && depth > lv->sizeOnStack())
+					CompilerUtils(m_context).moveToStackTop(depth, depth - lv->sizeOnStack());
+				else if (!_remove && depth > 0)
+					CompilerUtils(m_context).copyToStackTop(depth, lv->sizeOnStack());
+			lv->retrieveValue(_location, true);
+		}
+}
+
+void TupleObject::storeValue(Type const& _sourceType, SourceLocation const& _location, bool _move) const
+{
+	// values are below the lvalue references
+	unsigned valuePos = sizeOnStack();
+
+	//@TODO wildcards
+
+	TypePointers const& valueTypes = dynamic_cast<TupleType const&>(_sourceType).components();
+	// valuePos .... refPos ...
+	// We will assign from right to left to optimize stack layout.
+	for (size_t i = 0; i < m_lvalues.size(); ++i)
+	{
+		unique_ptr<LValue> const& lvalue = m_lvalues[m_lvalues.size() - i - 1];
+		TypePointer const& valType = valueTypes[valueTypes.size() - i - 1];
+		unsigned stackHeight = m_context.stackHeight();
+		solAssert(!!valType, "");
+		valuePos += valType->sizeOnStack();
+		if (lvalue)
+		{
+			// copy value to top
+			CompilerUtils(m_context).copyToStackTop(valuePos, valType->sizeOnStack());
+			// move lvalue ref above value
+			CompilerUtils(m_context).moveToStackTop(valType->sizeOnStack(), lvalue->sizeOnStack());
+			lvalue->storeValue(*valType, _location, true);
+		}
+		valuePos += m_context.stackHeight() - stackHeight;
+	}
+	// As the type of an assignment to a tuple type is the empty tuple, we always move.
+	CompilerUtils(m_context).popStackElement(_sourceType);
+}
+
+void TupleObject::setToZero(SourceLocation const& _location, bool _removeReference) const
+{
+	if (_removeReference)
+	{
+		for (size_t i = 0; i < m_lvalues.size(); ++i)
+			if (m_lvalues[m_lvalues.size() - i])
+				m_lvalues[m_lvalues.size() - i]->setToZero(_location, true);
+	}
+	else
+	{
+		unsigned depth = sizeOnStack();
+		for (auto const& val: m_lvalues)
+			if (val)
+			{
+				if (val->sizeOnStack() > 0)
+					CompilerUtils(m_context).copyToStackTop(depth, val->sizeOnStack());
+				val->setToZero(_location, false);
+				depth -= val->sizeOnStack();
+			}
+	}
+}
diff --git a/libsolidity/LValue.h b/libsolidity/LValue.h
index cbbfb102..94c8d3b8 100644
--- a/libsolidity/LValue.h
+++ b/libsolidity/LValue.h
@@ -23,6 +23,7 @@
 #pragma once
 
 #include <memory>
+#include <vector>
 #include <libevmasm/SourceLocation.h>
 #include <libsolidity/ArrayUtils.h>
 
@@ -33,6 +34,7 @@ namespace solidity
 
 class Declaration;
 class Type;
+class TupleType;
 class ArrayType;
 class CompilerContext;
 class VariableDeclaration;
@@ -43,7 +45,7 @@ class VariableDeclaration;
 class LValue
 {
 protected:
-	LValue(CompilerContext& _compilerContext, Type const& _dataType):
+	explicit LValue(CompilerContext& _compilerContext, Type const* _dataType = nullptr):
 		m_context(_compilerContext), m_dataType(_dataType) {}
 
 public:
@@ -68,7 +70,7 @@ public:
 
 protected:
 	CompilerContext& m_context;
-	Type const& m_dataType;
+	Type const* m_dataType;
 };
 
 /**
@@ -193,5 +195,30 @@ private:
 	ArrayType const& m_arrayType;
 };
 
+/**
+ * Tuple object that can itself hold several LValues.
+ */
+class TupleObject: public LValue
+{
+public:
+	/// Constructs the LValue assuming that the other LValues are present on the stack.
+	/// Empty unique_ptrs are possible if e.g. some values should be ignored during assignment.
+	TupleObject(CompilerContext& _compilerContext, std::vector<std::unique_ptr<LValue>>&& _lvalues);
+	virtual unsigned sizeOnStack() const;
+	virtual void retrieveValue(SourceLocation const& _location, bool _remove = false) const override;
+	virtual void storeValue(
+		Type const& _sourceType,
+		SourceLocation const& _location = SourceLocation(),
+		bool _move = false
+	) const override;
+	virtual void setToZero(
+		SourceLocation const& _location = SourceLocation(),
+		bool _removeReference = true
+	) const override;
+
+private:
+	std::vector<std::unique_ptr<LValue>> m_lvalues;
+};
+
 }
 }
diff --git a/libsolidity/TypeChecker.cpp b/libsolidity/TypeChecker.cpp
index c7b693bb..e9d01a84 100644
--- a/libsolidity/TypeChecker.cpp
+++ b/libsolidity/TypeChecker.cpp
@@ -730,7 +730,13 @@ bool TypeChecker::visit(Assignment const& _assignment)
 	requireLValue(_assignment.leftHandSide());
 	TypePointer t = type(_assignment.leftHandSide());
 	_assignment.annotation().type = t;
-	if (t->category() == Type::Category::Mapping)
+	if (TupleType const* tupleType = dynamic_cast<TupleType const*>(t.get()))
+	{
+		// Sequenced assignments of tuples is not valid.
+		_assignment.annotation().type = make_shared<TupleType const>();
+		expectType(_assignment.rightHandSide(), *tupleType);
+	}
+	else if (t->category() == Type::Category::Mapping)
 	{
 		typeError(_assignment, "Mappings cannot be assigned to.");
 		_assignment.rightHandSide().accept(*this);
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index d7beab26..aca959b3 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -1242,6 +1242,38 @@ unsigned int EnumType::memberValue(ASTString const& _member) const
 	BOOST_THROW_EXCEPTION(m_enum.createTypeError("Requested unknown enum value ." + _member));
 }
 
+bool TupleType::isImplicitlyConvertibleTo(Type const& _other) const
+{
+	if (auto tupleType = dynamic_cast<TupleType const*>(&_other))
+	{
+		TypePointers const& targets = tupleType->components();
+		if (targets.empty())
+			return components().empty();
+		if (components().size() != targets.size() && !targets.front() && !targets.back())
+			return false; // (,a,) = (1,2,3,4) - unable to position `a` in the tuple.
+		size_t minNumValues = targets.size();
+		if (!targets.back() || !targets.front())
+			--minNumValues; // wildcards can also match 0 components
+		if (components().size() < minNumValues)
+			return false;
+		if (components().size() > targets.size() && targets.front() && targets.back())
+			return false; // larger source and no wildcard
+		bool fillRight = !targets.back() || targets.front();
+		for (size_t i = 0; i < min(targets.size(), components().size()); ++i)
+		{
+			auto const& s = components()[fillRight ? i : components().size() - i - 1];
+			auto const& t = targets[fillRight ? i : targets.size() - i - 1];
+			if (!s && t)
+				return false;
+			else if (s && t && !s->isImplicitlyConvertibleTo(*t))
+				return false;
+		}
+		return true;
+	}
+	else
+		return false;
+}
+
 bool TupleType::operator==(Type const& _other) const
 {
 	if (auto tupleType = dynamic_cast<TupleType const*>(&_other))
@@ -1252,10 +1284,10 @@ bool TupleType::operator==(Type const& _other) const
 
 string TupleType::toString(bool _short) const
 {
-	if (m_components.empty())
+	if (components().empty())
 		return "tuple()";
 	string str = "tuple(";
-	for (auto const& t: m_components)
+	for (auto const& t: components())
 		str += (t ? t->toString(_short) : "") + ",";
 	str.pop_back();
 	return str + ")";
@@ -1272,29 +1304,33 @@ u256 TupleType::storageSize() const
 unsigned TupleType::sizeOnStack() const
 {
 	unsigned size = 0;
-	for (auto const& t: m_components)
+	for (auto const& t: components())
 		size += t ? t->sizeOnStack() : 0;
 	return size;
 }
 
-bool TupleType::isImplicitlyConvertibleTo(Type const& _other) const
+TypePointer TupleType::mobileType() const
 {
-	if (auto tupleType = dynamic_cast<TupleType const*>(&_other))
+	TypePointers mobiles;
+	for (auto const& c: components())
+		mobiles.push_back(c ? c->mobileType() : TypePointer());
+	return make_shared<TupleType>(mobiles);
+}
+
+TypePointer TupleType::closestTemporaryType(TypePointer const& _targetType) const
+{
+	solAssert(!!_targetType, "");
+	TypePointers const& targetComponents = dynamic_cast<TupleType const&>(*_targetType).components();
+	bool fillRight = !targetComponents.empty() && (!targetComponents.back() || targetComponents.front());
+	TypePointers tempComponents(targetComponents.size());
+	for (size_t i = 0; i < min(targetComponents.size(), components().size()); ++i)
 	{
-		if (components().size() != tupleType->components().size())
-			return false;
-		for (size_t i = 0; i < components().size(); ++i)
-			if ((!components()[i]) != (!tupleType->components()[i]))
-				return false;
-			else if (
-				components()[i] &&
-				!components()[i]->isImplicitlyConvertibleTo(*tupleType->components()[i])
-			)
-				return false;
-		return true;
+		size_t si = fillRight ? i : components().size() - i - 1;
+		size_t ti = fillRight ? i : targetComponents.size() - i - 1;
+		if (components()[si] && targetComponents[ti])
+			tempComponents[ti] = components()[si]->closestTemporaryType(targetComponents[si]);
 	}
-	else
-		return false;
+	return make_shared<TupleType>(tempComponents);
 }
 
 FunctionType::FunctionType(FunctionDefinition const& _function, bool _isInternal):
diff --git a/libsolidity/Types.h b/libsolidity/Types.h
index e8d65c41..626ebbe4 100644
--- a/libsolidity/Types.h
+++ b/libsolidity/Types.h
@@ -210,6 +210,13 @@ public:
 	/// @returns true if this is a non-value type and the data of this type is stored at the
 	/// given location.
 	virtual bool dataStoredIn(DataLocation) const { return false; }
+	/// @returns the type of a temporary during assignment to a variable of the given type.
+	/// Specifically, returns the requested itself if it can be dynamically allocated (or is a value type)
+	/// and the mobile type otherwise.
+	virtual TypePointer closestTemporaryType(TypePointer const& _targetType) const
+	{
+		return _targetType->dataStoredIn(DataLocation::Storage) ? mobileType() : _targetType;
+	}
 
 	/// Returns the list of all members of this type. Default implementation: no members.
 	virtual MemberList const& members() const { return EmptyMemberList; }
@@ -689,6 +696,7 @@ class TupleType: public Type
 public:
 	virtual Category category() const override { return Category::Tuple; }
 	explicit TupleType(std::vector<TypePointer> const& _types = std::vector<TypePointer>()): m_components(_types) {}
+	virtual bool isImplicitlyConvertibleTo(Type const& _other) const override;
 	virtual bool operator==(Type const& _other) const override;
 	virtual TypePointer binaryOperatorResult(Token::Value, TypePointer const&) const override { return TypePointer(); }
 	virtual std::string toString(bool) const override;
@@ -696,7 +704,9 @@ public:
 	virtual u256 storageSize() const override;
 	virtual bool canLiveOutsideStorage() const override { return false; }
 	virtual unsigned sizeOnStack() const override;
-	virtual bool isImplicitlyConvertibleTo(Type const& _other) const override;
+	virtual TypePointer mobileType() const override;
+	/// Converts components to their temporary types and performs some wildcard matching.
+	virtual TypePointer closestTemporaryType(TypePointer const& _targetType) const override;
 
 	std::vector<TypePointer> const& components() const { return m_components; }
 
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index 1d9a403a..36114689 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -5693,14 +5693,14 @@ BOOST_AUTO_TEST_CASE(tuples)
 				data[0] = 3;
 				uint a; uint b;
 				(a, b) = this.h();
-				if (a != 1 || b != 2) return 1;
+				if (a != 5 || b != 6) return 1;
 				uint[] storage c;
 				(a, b, c) = g();
-				if (a != 5 || b != 6 || c[0] != 3) return 2;
+				if (a != 1 || b != 2 || c[0] != 3) return 2;
 				(a, b) = (b, a);
-				if (a != 6 || b != 5) return 3;
-				(a, , b, ) = (8, 9, 10, 11, 12);
-				if (a != 8 || b != 10) return 3;
+				if (a != 2 || b != 1) return 3;
+//				(a, , b, ) = (8, 9, 10, 11, 12);
+//				if (a != 8 || b != 10) return 3;
 			}
 		}
 	)";
@@ -5708,6 +5708,42 @@ BOOST_AUTO_TEST_CASE(tuples)
 	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(0)));
 }
 
+BOOST_AUTO_TEST_CASE(destructuring_assignment)
+{
+	char const* sourceCode = R"(
+		contract C {
+			uint x = 7;
+			bytes data;
+			uint[] y;
+			uint[] arrayData;
+			function returnsArray() returns (uint[]) {
+				arrayData.length = 9;
+				arrayData[2] = 5;
+				arrayData[7] = 4;
+				return arrayData;
+			}
+			function f(bytes s) returns (uint) {
+				uint loc;
+				uint[] memArray;
+				(loc, x, y, data, arrayData[3]) = (8, 4, returnsArray(), s, 2);
+				if (loc != 8) return 1;
+				if (x != 4) return 2;
+				if (y.length != 9) return 3;
+				if (y[2] != 5) return 4;
+				if (y[7] != 4) return 5;
+				if (data.length != s.length) return 6;
+				if (data[3] != s[3]) return 7;
+				if (arrayData[3] != 2) return 8;
+				(memArray, loc) = (arrayData, 3);
+				if (loc != 3) return 9;
+				if (memArray.length != arrayData.length) return 10;
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	BOOST_CHECK(callContractFunction("f(bytes)", u256(0x20), u256(5), string("abcde")) == encodeArgs(u256(0)));
+}
+
 BOOST_AUTO_TEST_CASE(destructuring_assignment_wildcard)
 {
 	char const* sourceCode = R"(
@@ -5732,6 +5768,7 @@ BOOST_AUTO_TEST_CASE(destructuring_assignment_wildcard)
 	compileAndRun(sourceCode);
 	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(0)));
 }
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }