Merge pull request #825 from chriseth/sol_contractInheritance

Contract inheritance

libsolidity/AST.cpp

@@ -43,6 +43,11 @@ TypeError ASTNode::createTypeError(string const& _description) const
 
 void ContractDefinition::checkTypeRequirements()
 {
+	for (ASTPointer<InheritanceSpecifier> const& base: getBaseContracts())
+		base->checkTypeRequirements();
+
+	checkIllegalOverrides();
+
 	FunctionDefinition const* constructor = getConstructor();
 	if (constructor && !constructor->getReturnParameters().empty())
 		BOOST_THROW_EXCEPTION(constructor->getReturnParameterList()->createTypeError(
@@ -52,7 +57,6 @@ void ContractDefinition::checkTypeRequirements()
 		function->checkTypeRequirements();
 
 	// check for hash collisions in function signatures
-	vector<pair<FixedHash<4>, FunctionDefinition const*>> exportedFunctionList = getInterfaceFunctionList();
 	set<FixedHash<4>> hashes;
 	for (auto const& hashAndFunction: getInterfaceFunctionList())
 	{
@@ -83,17 +87,59 @@ FunctionDefinition const* ContractDefinition::getConstructor() const
 	return nullptr;
 }
 
-vector<pair<FixedHash<4>, FunctionDefinition const*>> ContractDefinition::getInterfaceFunctionList() const
+void ContractDefinition::checkIllegalOverrides() const
 {
-	vector<pair<FixedHash<4>, FunctionDefinition const*>> exportedFunctions;
+	map<string, FunctionDefinition const*> functions;
-	for (ASTPointer<FunctionDefinition> const& f: m_definedFunctions)
+
-		if (f->isPublic() && f->getName() != getName())
+	// We search from derived to base, so the stored item causes the error.
+	for (ContractDefinition const* contract: getLinearizedBaseContracts())
+		for (ASTPointer<FunctionDefinition> const& function: contract->getDefinedFunctions())
+		{
+			if (function->getName() == contract->getName())
+				continue; // constructors can neither be overriden nor override anything
+			FunctionDefinition const*& override = functions[function->getName()];
+			if (!override)
+				override = function.get();
+			else if (override->isPublic() != function->isPublic() ||
+					 override->isDeclaredConst() != function->isDeclaredConst() ||
+					 FunctionType(*override) != FunctionType(*function))
+				BOOST_THROW_EXCEPTION(override->createTypeError("Override changes extended function signature."));
+		}
+}
+
+vector<pair<FixedHash<4>, FunctionDefinition const*>> const& ContractDefinition::getInterfaceFunctionList() const
+{
+	if (!m_interfaceFunctionList)
+	{
+		set<string> functionsSeen;
+		m_interfaceFunctionList.reset(new vector<pair<FixedHash<4>, FunctionDefinition const*>>());
+		for (ContractDefinition const* contract: getLinearizedBaseContracts())
+			for (ASTPointer<FunctionDefinition> const& f: contract->getDefinedFunctions())
+				if (f->isPublic() && f->getName() != contract->getName() &&
+						functionsSeen.count(f->getName()) == 0)
 				{
+					functionsSeen.insert(f->getName());
 					FixedHash<4> hash(dev::sha3(f->getCanonicalSignature()));
-			exportedFunctions.push_back(make_pair(hash, f.get()));
+					m_interfaceFunctionList->push_back(make_pair(hash, f.get()));
 				}
+	}
+	return *m_interfaceFunctionList;
+}
 
-	return exportedFunctions;
+void InheritanceSpecifier::checkTypeRequirements()
+{
+	m_baseName->checkTypeRequirements();
+	for (ASTPointer<Expression> const& argument: m_arguments)
+		argument->checkTypeRequirements();
+
+	ContractDefinition const* base = dynamic_cast<ContractDefinition const*>(m_baseName->getReferencedDeclaration());
+	solAssert(base, "Base contract not available.");
+	TypePointers parameterTypes = ContractType(*base).getConstructorType()->getParameterTypes();
+	if (parameterTypes.size() != m_arguments.size())
+		BOOST_THROW_EXCEPTION(createTypeError("Wrong argument count for constructor call."));
+	for (size_t i = 0; i < m_arguments.size(); ++i)
+		if (!m_arguments[i]->getType()->isImplicitlyConvertibleTo(*parameterTypes[i]))
+			BOOST_THROW_EXCEPTION(createTypeError("Invalid type for argument in constructer call."));
 }
 
 void StructDefinition::checkMemberTypes() const
@@ -346,7 +392,8 @@ void MemberAccess::checkTypeRequirements()
 	Type const& type = *m_expression->getType();
 	m_type = type.getMemberType(*m_memberName);
 	if (!m_type)
-		BOOST_THROW_EXCEPTION(createTypeError("Member \"" + *m_memberName + "\" not found in " + type.toString()));
+		BOOST_THROW_EXCEPTION(createTypeError("Member \"" + *m_memberName + "\" not found or not "
+											  "visible in " + type.toString()));
 	//@todo later, this will not always be STORAGE
 	m_lvalue = type.getCategory() == Type::Category::STRUCT ? LValueType::STORAGE : LValueType::NONE;
 }
@@ -396,7 +443,7 @@ void Identifier::checkTypeRequirements()
 	ContractDefinition const* contractDef = dynamic_cast<ContractDefinition const*>(m_referencedDeclaration);
 	if (contractDef)
 	{
-		m_type = make_shared<TypeType>(make_shared<ContractType>(*contractDef));
+		m_type = make_shared<TypeType>(make_shared<ContractType>(*contractDef), m_currentContract);
 		return;
 	}
 	MagicVariableDeclaration const* magicVariable = dynamic_cast<MagicVariableDeclaration const*>(m_referencedDeclaration);

libsolidity/AST.h

@@ -158,10 +158,12 @@ public:
 	ContractDefinition(Location const& _location,
 					   ASTPointer<ASTString> const& _name,
 					   ASTPointer<ASTString> const& _documentation,
+					   std::vector<ASTPointer<InheritanceSpecifier>> const& _baseContracts,
 					   std::vector<ASTPointer<StructDefinition>> const& _definedStructs,
 					   std::vector<ASTPointer<VariableDeclaration>> const& _stateVariables,
 					   std::vector<ASTPointer<FunctionDefinition>> const& _definedFunctions):
 		Declaration(_location, _name),
+		m_baseContracts(_baseContracts),
 		m_definedStructs(_definedStructs),
 		m_stateVariables(_stateVariables),
 		m_definedFunctions(_definedFunctions),
@@ -171,12 +173,13 @@ public:
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
+	std::vector<ASTPointer<InheritanceSpecifier>> const& getBaseContracts() const { return m_baseContracts; }
 	std::vector<ASTPointer<StructDefinition>> const& getDefinedStructs() const { return m_definedStructs; }
 	std::vector<ASTPointer<VariableDeclaration>> const& getStateVariables() const { return m_stateVariables; }
 	std::vector<ASTPointer<FunctionDefinition>> const& getDefinedFunctions() const { return m_definedFunctions; }
 
-	/// Checks that the constructor does not have a "returns" statement and calls
+	/// Checks that there are no illegal overrides, that the constructor does not have a "returns"
-	/// checkTypeRequirements on all its functions.
+	/// and calls checkTypeRequirements on all its functions.
 	void checkTypeRequirements();
 
 	/// @return A shared pointer of an ASTString.
@@ -187,16 +190,47 @@ public:
 	/// as intended for use by the ABI.
 	std::map<FixedHash<4>, FunctionDefinition const*> getInterfaceFunctions() const;
 
+	/// List of all (direct and indirect) base contracts in order from derived to base, including
+	/// the contract itself. Available after name resolution
+	std::vector<ContractDefinition const*> const& getLinearizedBaseContracts() const { return m_linearizedBaseContracts; }
+	void setLinearizedBaseContracts(std::vector<ContractDefinition const*> const& _bases) { m_linearizedBaseContracts = _bases; }
+
 	/// Returns the constructor or nullptr if no constructor was specified
 	FunctionDefinition const* getConstructor() const;
 
 private:
-	std::vector<std::pair<FixedHash<4>, FunctionDefinition const*>> getInterfaceFunctionList() const;
+	void checkIllegalOverrides() const;
+
+	std::vector<std::pair<FixedHash<4>, FunctionDefinition const*>> const& getInterfaceFunctionList() const;
 
+	std::vector<ASTPointer<InheritanceSpecifier>> m_baseContracts;
 	std::vector<ASTPointer<StructDefinition>> m_definedStructs;
 	std::vector<ASTPointer<VariableDeclaration>> m_stateVariables;
 	std::vector<ASTPointer<FunctionDefinition>> m_definedFunctions;
 	ASTPointer<ASTString> m_documentation;
+
+	std::vector<ContractDefinition const*> m_linearizedBaseContracts;
+	mutable std::unique_ptr<std::vector<std::pair<FixedHash<4>, FunctionDefinition const*>>> m_interfaceFunctionList;
+};
+
+class InheritanceSpecifier: public ASTNode
+{
+public:
+	InheritanceSpecifier(Location const& _location, ASTPointer<Identifier> const& _baseName,
+						 std::vector<ASTPointer<Expression>> _arguments):
+		ASTNode(_location), m_baseName(_baseName), m_arguments(_arguments) {}
+
+	virtual void accept(ASTVisitor& _visitor) override;
+	virtual void accept(ASTConstVisitor& _visitor) const override;
+
+	ASTPointer<Identifier> const& getName() const { return m_baseName; }
+	std::vector<ASTPointer<Expression>> const& getArguments() const { return m_arguments; }
+
+	void checkTypeRequirements();
+
+private:
+	ASTPointer<Identifier> m_baseName;
+	std::vector<ASTPointer<Expression>> m_arguments;
 };
 
 class StructDefinition: public Declaration
@@ -581,7 +615,7 @@ public:
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 	virtual void checkTypeRequirements() override;
 
-	void setFunctionReturnParameters(ParameterList& _parameters) { m_returnParameters = &_parameters; }
+	void setFunctionReturnParameters(ParameterList const& _parameters) { m_returnParameters = &_parameters; }
 	ParameterList const& getFunctionReturnParameters() const
 	{
 		solAssert(m_returnParameters, "");
@@ -593,7 +627,7 @@ private:
 	ASTPointer<Expression> m_expression; ///< value to return, optional
 
 	/// Pointer to the parameter list of the function, filled by the @ref NameAndTypeResolver.
-	ParameterList* m_returnParameters;
+	ParameterList const* m_returnParameters;
 };
 
 /**
@@ -870,21 +904,30 @@ class Identifier: public PrimaryExpression
 {
 public:
 	Identifier(Location const& _location, ASTPointer<ASTString> const& _name):
-		PrimaryExpression(_location), m_name(_name), m_referencedDeclaration(nullptr) {}
+		PrimaryExpression(_location), m_name(_name) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 	virtual void checkTypeRequirements() override;
 
 	ASTString const& getName() const { return *m_name; }
 
-	void setReferencedDeclaration(Declaration const& _referencedDeclaration) { m_referencedDeclaration = &_referencedDeclaration; }
+	void setReferencedDeclaration(Declaration const& _referencedDeclaration,
+								  ContractDefinition const* _currentContract = nullptr)
+	{
+		m_referencedDeclaration = &_referencedDeclaration;
+		m_currentContract = _currentContract;
+	}
 	Declaration const* getReferencedDeclaration() const { return m_referencedDeclaration; }
+	ContractDefinition const* getCurrentContract() const { return m_currentContract; }
 
 private:
 	ASTPointer<ASTString> m_name;
 
 	/// Declaration the name refers to.
-	Declaration const* m_referencedDeclaration;
+	Declaration const* m_referencedDeclaration = nullptr;
+	/// Stores a reference to the current contract. This is needed because types of base contracts
+	/// change depending on the context.
+	ContractDefinition const* m_currentContract = nullptr;
 };
 
 /**

libsolidity/ASTForward.h

@@ -38,6 +38,7 @@ class SourceUnit;
 class ImportDirective;
 class Declaration;
 class ContractDefinition;
+class InheritanceSpecifier;
 class StructDefinition;
 class ParameterList;
 class FunctionDefinition;

libsolidity/AST_accept.h

@@ -61,6 +61,7 @@ void ContractDefinition::accept(ASTVisitor& _visitor)
 {
 	if (_visitor.visit(*this))
 	{
+		listAccept(m_baseContracts, _visitor);
 		listAccept(m_definedStructs, _visitor);
 		listAccept(m_stateVariables, _visitor);
 		listAccept(m_definedFunctions, _visitor);
@@ -72,6 +73,7 @@ void ContractDefinition::accept(ASTConstVisitor& _visitor) const
 {
 	if (_visitor.visit(*this))
 	{
+		listAccept(m_baseContracts, _visitor);
 		listAccept(m_definedStructs, _visitor);
 		listAccept(m_stateVariables, _visitor);
 		listAccept(m_definedFunctions, _visitor);
@@ -79,6 +81,26 @@ void ContractDefinition::accept(ASTConstVisitor& _visitor) const
 	_visitor.endVisit(*this);
 }
 
+void InheritanceSpecifier::accept(ASTVisitor& _visitor)
+{
+	if (_visitor.visit(*this))
+	{
+		m_baseName->accept(_visitor);
+		listAccept(m_arguments, _visitor);
+	}
+	_visitor.endVisit(*this);
+}
+
+void InheritanceSpecifier::accept(ASTConstVisitor& _visitor) const
+{
+	if (_visitor.visit(*this))
+	{
+		m_baseName->accept(_visitor);
+		listAccept(m_arguments, _visitor);
+	}
+	_visitor.endVisit(*this);
+}
+
 void StructDefinition::accept(ASTVisitor& _visitor)
 {
 	if (_visitor.visit(*this))

libsolidity/CallGraph.cpp

@@ -31,13 +31,9 @@ namespace dev
 namespace solidity
 {
 
-void CallGraph::addFunction(FunctionDefinition const& _function)
+void CallGraph::addNode(ASTNode const& _node)
 {
-	if (!m_functionsSeen.count(&_function))
+	_node.accept(*this);
-	{
-		m_functionsSeen.insert(&_function);
-		m_workQueue.push(&_function);
-	}
 }
 
 set<FunctionDefinition const*> const& CallGraph::getCalls()
@@ -63,5 +59,41 @@ bool CallGraph::visit(Identifier const& _identifier)
 	return true;
 }
 
+bool CallGraph::visit(FunctionDefinition const& _function)
+{
+	addFunction(_function);
+	return true;
+}
+
+bool CallGraph::visit(MemberAccess const& _memberAccess)
+{
+	// used for "BaseContract.baseContractFunction"
+	if (_memberAccess.getExpression().getType()->getCategory() == Type::Category::TYPE)
+	{
+		TypeType const& type = dynamic_cast<TypeType const&>(*_memberAccess.getExpression().getType());
+		if (type.getMembers().getMemberType(_memberAccess.getMemberName()))
+		{
+			ContractDefinition const& contract = dynamic_cast<ContractType const&>(*type.getActualType())
+													.getContractDefinition();
+			for (ASTPointer<FunctionDefinition> const& function: contract.getDefinedFunctions())
+				if (function->getName() == _memberAccess.getMemberName())
+				{
+					addFunction(*function);
+					return true;
+				}
+		}
+	}
+	return true;
+}
+
+void CallGraph::addFunction(FunctionDefinition const& _function)
+{
+	if (!m_functionsSeen.count(&_function))
+	{
+		m_functionsSeen.insert(&_function);
+		m_workQueue.push(&_function);
+	}
+}
+
 }
 }

libsolidity/CallGraph.h

@@ -38,14 +38,17 @@ namespace solidity
 class CallGraph: private ASTConstVisitor
 {
 public:
-	void addFunction(FunctionDefinition const& _function);
+	void addNode(ASTNode const& _node);
 	void computeCallGraph();
 
 	std::set<FunctionDefinition const*> const& getCalls();
 
 private:
-	void addFunctionToQueue(FunctionDefinition const& _function);
+	virtual bool visit(FunctionDefinition const& _function) override;
 	virtual bool visit(Identifier const& _identifier) override;
+	virtual bool visit(MemberAccess const& _memberAccess) override;
+
+	void addFunction(FunctionDefinition const& _function);
 
 	std::set<FunctionDefinition const*> m_functionsSeen;
 	std::queue<FunctionDefinition const*> m_workQueue;

libsolidity/Compiler.cpp

@@ -21,6 +21,7 @@
  */
 
 #include <algorithm>
+#include <boost/range/adaptor/reversed.hpp>
 #include <libevmcore/Instruction.h>
 #include <libevmcore/Assembly.h>
 #include <libsolidity/AST.h>
@@ -34,48 +35,84 @@ using namespace std;
 namespace dev {
 namespace solidity {
 
-void Compiler::compileContract(ContractDefinition const& _contract, vector<MagicVariableDeclaration const*> const& _magicGlobals,
+void Compiler::compileContract(ContractDefinition const& _contract,
 							   map<ContractDefinition const*, bytes const*> const& _contracts)
 {
 	m_context = CompilerContext(); // clear it just in case
-	initializeContext(_contract, _magicGlobals, _contracts);
+	initializeContext(_contract, _contracts);
 
-	for (ASTPointer<FunctionDefinition> const& function: _contract.getDefinedFunctions())
+	for (ContractDefinition const* contract: _contract.getLinearizedBaseContracts())
-		if (function->getName() != _contract.getName()) // don't add the constructor here
+		for (ASTPointer<FunctionDefinition> const& function: contract->getDefinedFunctions())
+			if (function->getName() != contract->getName()) // don't add the constructor here
 				m_context.addFunction(*function);
 
 	appendFunctionSelector(_contract);
-	for (ASTPointer<FunctionDefinition> const& function: _contract.getDefinedFunctions())
+	for (ContractDefinition const* contract: _contract.getLinearizedBaseContracts())
-		if (function->getName() != _contract.getName()) // don't add the constructor here
+		for (ASTPointer<FunctionDefinition> const& function: contract->getDefinedFunctions())
+			if (function->getName() != contract->getName()) // don't add the constructor here
 				function->accept(*this);
 
 	// Swap the runtime context with the creation-time context
 	swap(m_context, m_runtimeContext);
-	initializeContext(_contract, _magicGlobals, _contracts);
+	initializeContext(_contract, _contracts);
 	packIntoContractCreator(_contract, m_runtimeContext);
 }
 
-void Compiler::initializeContext(ContractDefinition const& _contract, vector<MagicVariableDeclaration const*> const& _magicGlobals,
+void Compiler::initializeContext(ContractDefinition const& _contract,
 								 map<ContractDefinition const*, bytes const*> const& _contracts)
 {
 	m_context.setCompiledContracts(_contracts);
-	for (MagicVariableDeclaration const* variable: _magicGlobals)
-		m_context.addMagicGlobal(*variable);
 	registerStateVariables(_contract);
 }
 
 void Compiler::packIntoContractCreator(ContractDefinition const& _contract, CompilerContext const& _runtimeContext)
 {
+	// arguments for base constructors, filled in derived-to-base order
+	map<ContractDefinition const*, vector<ASTPointer<Expression>> const*> baseArguments;
 	set<FunctionDefinition const*> neededFunctions;
-	FunctionDefinition const* constructor = _contract.getConstructor();
+	set<ASTNode const*> nodesUsedInConstructors;
-	if (constructor)
+
-		neededFunctions = getFunctionsNeededByConstructor(*constructor);
+	// Determine the arguments that are used for the base constructors and also which functions
+	// are needed at compile time.
+	std::vector<ContractDefinition const*> const& bases = _contract.getLinearizedBaseContracts();
+	for (ContractDefinition const* contract: bases)
+	{
+		if (FunctionDefinition const* constructor = contract->getConstructor())
+			nodesUsedInConstructors.insert(constructor);
+		for (ASTPointer<InheritanceSpecifier> const& base: contract->getBaseContracts())
+		{
+			ContractDefinition const* baseContract = dynamic_cast<ContractDefinition const*>(
+													base->getName()->getReferencedDeclaration());
+			solAssert(baseContract, "");
+			if (baseArguments.count(baseContract) == 0)
+			{
+				baseArguments[baseContract] = &base->getArguments();
+				for (ASTPointer<Expression> const& arg: base->getArguments())
+					nodesUsedInConstructors.insert(arg.get());
+			}
+		}
+	}
+
+	//@TODO add virtual functions
+	neededFunctions = getFunctionsCalled(nodesUsedInConstructors);
 
 	for (FunctionDefinition const* fun: neededFunctions)
 		m_context.addFunction(*fun);
 
-	if (constructor)
+	// Call constructors in base-to-derived order.
-		appendConstructorCall(*constructor);
+	// The Constructor for the most derived contract is called later.
+	for (unsigned i = 1; i < bases.size(); i++)
+	{
+		ContractDefinition const* base = bases[bases.size() - i];
+		solAssert(base, "");
+		FunctionDefinition const* baseConstructor = base->getConstructor();
+		if (!baseConstructor)
+			continue;
+		solAssert(baseArguments[base], "");
+		appendBaseConstructorCall(*baseConstructor, *baseArguments[base]);
+	}
+	if (_contract.getConstructor())
+		appendConstructorCall(*_contract.getConstructor());
 
 	eth::AssemblyItem sub = m_context.addSubroutine(_runtimeContext.getAssembly());
 	// stack contains sub size
@@ -88,6 +125,21 @@ void Compiler::packIntoContractCreator(ContractDefinition const& _contract, Comp
 		fun->accept(*this);
 }
 
+void Compiler::appendBaseConstructorCall(FunctionDefinition const& _constructor,
+										 vector<ASTPointer<Expression>> const& _arguments)
+{
+	FunctionType constructorType(_constructor);
+	eth::AssemblyItem returnLabel = m_context.pushNewTag();
+	for (unsigned i = 0; i < _arguments.size(); ++i)
+	{
+		compileExpression(*_arguments[i]);
+		ExpressionCompiler::appendTypeConversion(m_context, *_arguments[i]->getType(),
+												 *constructorType.getParameterTypes()[i]);
+	}
+	m_context.appendJumpTo(m_context.getFunctionEntryLabel(_constructor));
+	m_context << returnLabel;
+}
+
 void Compiler::appendConstructorCall(FunctionDefinition const& _constructor)
 {
 	eth::AssemblyItem returnTag = m_context.pushNewTag();
@@ -107,11 +159,12 @@ void Compiler::appendConstructorCall(FunctionDefinition const& _constructor)
 	m_context << returnTag;
 }
 
-set<FunctionDefinition const*> Compiler::getFunctionsNeededByConstructor(FunctionDefinition const& _constructor)
+set<FunctionDefinition const*> Compiler::getFunctionsCalled(set<ASTNode const*> const& _nodes)
 {
+	// TODO this does not add virtual functions
 	CallGraph callgraph;
-	callgraph.addFunction(_constructor);
+	for (ASTNode const* node: _nodes)
-	callgraph.computeCallGraph();
+		callgraph.addNode(*node);
 	return callgraph.getCalls();
 }
 
@@ -193,8 +246,8 @@ void Compiler::appendReturnValuePacker(FunctionDefinition const& _function)
 
 void Compiler::registerStateVariables(ContractDefinition const& _contract)
 {
-	//@todo sort them?
+	for (ContractDefinition const* contract: boost::adaptors::reverse(_contract.getLinearizedBaseContracts()))
-	for (ASTPointer<VariableDeclaration> const& variable: _contract.getStateVariables())
+		for (ASTPointer<VariableDeclaration> const& variable: contract->getStateVariables())
 			m_context.addStateVariable(*variable);
 }
 

libsolidity/Compiler.h

@@ -32,23 +32,24 @@ class Compiler: private ASTConstVisitor
 public:
 	explicit Compiler(bool _optimize = false): m_optimize(_optimize), m_context(), m_returnTag(m_context.newTag()) {}
 
-	void compileContract(ContractDefinition const& _contract, std::vector<MagicVariableDeclaration const*> const& _magicGlobals,
+	void compileContract(ContractDefinition const& _contract,
 						 std::map<ContractDefinition const*, bytes const*> const& _contracts);
 	bytes getAssembledBytecode() { return m_context.getAssembledBytecode(m_optimize); }
 	bytes getRuntimeBytecode() { return m_runtimeContext.getAssembledBytecode(m_optimize);}
 	void streamAssembly(std::ostream& _stream) const { m_context.streamAssembly(_stream); }
 
 private:
-	/// Registers the global objects and the non-function objects inside the contract with the context.
+	/// Registers the non-function objects inside the contract with the context.
-	void initializeContext(ContractDefinition const& _contract, std::vector<MagicVariableDeclaration const*> const& _magicGlobals,
+	void initializeContext(ContractDefinition const& _contract,
 						   std::map<ContractDefinition const*, bytes const*> const& _contracts);
 	/// Adds the code that is run at creation time. Should be run after exchanging the run-time context
-	/// with a new and initialized context.
+	/// with a new and initialized context. Adds the constructor code.
-	/// adds the constructor code.
 	void packIntoContractCreator(ContractDefinition const& _contract, CompilerContext const& _runtimeContext);
+	void appendBaseConstructorCall(FunctionDefinition const& _constructor,
+								   std::vector<ASTPointer<Expression>> const& _arguments);
 	void appendConstructorCall(FunctionDefinition const& _constructor);
-	/// Recursively searches the call graph and returns all functions needed by the constructor (including itself).
+	/// Recursively searches the call graph and returns all functions referenced inside _nodes.
-	std::set<FunctionDefinition const*> getFunctionsNeededByConstructor(FunctionDefinition const& _constructor);
+	std::set<FunctionDefinition const*> getFunctionsCalled(std::set<ASTNode const*> const& _nodes);
 	void appendFunctionSelector(ContractDefinition const& _contract);
 	/// Creates code that unpacks the arguments for the given function, from memory if
 	/// @a _fromMemory is true, otherwise from call data. @returns the size of the data in bytes.

libsolidity/CompilerContext.cpp

@@ -61,7 +61,9 @@ void CompilerContext::addAndInitializeVariable(VariableDeclaration const& _decla
 
 void CompilerContext::addFunction(FunctionDefinition const& _function)
 {
-	m_functionEntryLabels.insert(std::make_pair(&_function, m_asm.newTag()));
+	eth::AssemblyItem tag(m_asm.newTag());
+	m_functionEntryLabels.insert(make_pair(&_function, tag));
+	m_virtualFunctionEntryLabels.insert(make_pair(_function.getName(), tag));
 }
 
 bytes const& CompilerContext::getCompiledContract(const ContractDefinition& _contract) const
@@ -83,6 +85,13 @@ eth::AssemblyItem CompilerContext::getFunctionEntryLabel(FunctionDefinition cons
 	return res->second.tag();
 }
 
+eth::AssemblyItem CompilerContext::getVirtualFunctionEntryLabel(FunctionDefinition const& _function) const
+{
+	auto res = m_virtualFunctionEntryLabels.find(_function.getName());
+	solAssert(res != m_virtualFunctionEntryLabels.end(), "Function entry label not found.");
+	return res->second.tag();
+}
+
 unsigned CompilerContext::getBaseStackOffsetOfVariable(Declaration const& _declaration) const
 {
 	auto res = m_localVariables.find(&_declaration);

libsolidity/CompilerContext.h

@@ -57,6 +57,8 @@ public:
 	bool isStateVariable(Declaration const* _declaration) const { return m_stateVariables.count(_declaration) != 0; }
 
 	eth::AssemblyItem getFunctionEntryLabel(FunctionDefinition const& _function) const;
+	/// @returns the entry label of the given function and takes overrides into account.
+	eth::AssemblyItem getVirtualFunctionEntryLabel(FunctionDefinition const& _function) const;
 	/// Returns the distance of the given local variable from the top of the local variable stack.
 	unsigned getBaseStackOffsetOfVariable(Declaration const& _declaration) const;
 	/// If supplied by a value returned by @ref getBaseStackOffsetOfVariable(variable), returns
@@ -116,6 +118,8 @@ private:
 	unsigned m_localVariablesSize;
 	/// Labels pointing to the entry points of funcitons.
 	std::map<Declaration const*, eth::AssemblyItem> m_functionEntryLabels;
+	/// Labels pointing to the entry points of function overrides.
+	std::map<std::string, eth::AssemblyItem> m_virtualFunctionEntryLabels;
 };
 
 }

libsolidity/CompilerStack.cpp

@@ -113,10 +113,8 @@ void CompilerStack::compile(bool _optimize)
 		for (ASTPointer<ASTNode> const& node: source->ast->getNodes())
 			if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
 			{
-				m_globalContext->setCurrentContract(*contract);
 				shared_ptr<Compiler> compiler = make_shared<Compiler>(_optimize);
-				compiler->compileContract(*contract, m_globalContext->getMagicVariables(),
+				compiler->compileContract(*contract, contractBytecode);
-										  contractBytecode);
 				Contract& compiledContract = m_contracts[contract->getName()];
 				compiledContract.bytecode = compiler->getAssembledBytecode();
 				compiledContract.runtimeBytecode = compiler->getRuntimeBytecode();

libsolidity/DeclarationContainer.h

@@ -42,11 +42,12 @@ public:
 	explicit DeclarationContainer(Declaration const* _enclosingDeclaration = nullptr,
 								  DeclarationContainer const* _enclosingContainer = nullptr):
 		m_enclosingDeclaration(_enclosingDeclaration), m_enclosingContainer(_enclosingContainer) {}
-	/// Registers the declaration in the scope unless its name is already declared. Returns true iff
+	/// Registers the declaration in the scope unless its name is already declared.
-	/// it was not yet declared.
+	/// @returns true iff it was not yet declared.
 	bool registerDeclaration(Declaration const& _declaration, bool _update = false);
 	Declaration const* resolveName(ASTString const& _name, bool _recursive = false) const;
 	Declaration const* getEnclosingDeclaration() const { return m_enclosingDeclaration; }
+	std::map<ASTString, Declaration const*> const& getDeclarations() const { return m_declarations; }
 
 private:
 	Declaration const* m_enclosingDeclaration;

libsolidity/ExpressionCompiler.cpp

@@ -419,6 +419,22 @@ void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
 		m_currentLValue.retrieveValueIfLValueNotRequested(_memberAccess);
 		break;
 	}
+	case Type::Category::TYPE:
+	{
+		TypeType const& type = dynamic_cast<TypeType const&>(*_memberAccess.getExpression().getType());
+		if (type.getMembers().getMemberType(member))
+		{
+			ContractDefinition const& contract = dynamic_cast<ContractType const&>(*type.getActualType())
+													.getContractDefinition();
+			for (ASTPointer<FunctionDefinition> const& function: contract.getDefinedFunctions())
+				if (function->getName() == member)
+				{
+					m_context << m_context.getFunctionEntryLabel(*function).pushTag();
+					return;
+				}
+		}
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid member access to " + type.toString()));
+	}
 	default:
 		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Member access to unknown type."));
 	}
@@ -449,20 +465,22 @@ void ExpressionCompiler::endVisit(Identifier const& _identifier)
 	{
 		if (magicVar->getType()->getCategory() == Type::Category::CONTRACT) // must be "this"
 			m_context << eth::Instruction::ADDRESS;
-		return;
 	}
-	if (FunctionDefinition const* functionDef = dynamic_cast<FunctionDefinition const*>(declaration))
+	else if (FunctionDefinition const* functionDef = dynamic_cast<FunctionDefinition const*>(declaration))
-	{
+		m_context << m_context.getVirtualFunctionEntryLabel(*functionDef).pushTag();
-		m_context << m_context.getFunctionEntryLabel(*functionDef).pushTag();
+	else if (dynamic_cast<VariableDeclaration const*>(declaration))
-		return;
-	}
-	if (dynamic_cast<VariableDeclaration const*>(declaration))
 	{
 		m_currentLValue.fromIdentifier(_identifier, *declaration);
 		m_currentLValue.retrieveValueIfLValueNotRequested(_identifier);
-		return;
 	}
+	else if (dynamic_cast<ContractDefinition const*>(declaration))
+	{
+		// no-op
+	}
+	else
+	{
 		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Identifier type not expected in expression context."));
+	}
 }
 
 void ExpressionCompiler::endVisit(Literal const& _literal)

libsolidity/GlobalContext.cpp

@@ -68,7 +68,7 @@ void GlobalContext::setCurrentContract(ContractDefinition const& _contract)
 vector<Declaration const*> GlobalContext::getDeclarations() const
 {
 	vector<Declaration const*> declarations;
-	declarations.reserve(m_magicVariables.size() + 1);
+	declarations.reserve(m_magicVariables.size());
 	for (ASTPointer<Declaration const> const& variable: m_magicVariables)
 		declarations.push_back(variable.get());
 	return declarations;
@@ -83,15 +83,5 @@ MagicVariableDeclaration const* GlobalContext::getCurrentThis() const
 
 }
 
-vector<MagicVariableDeclaration const*> GlobalContext::getMagicVariables() const
-{
-	vector<MagicVariableDeclaration const*> declarations;
-	declarations.reserve(m_magicVariables.size() + 1);
-	for (ASTPointer<MagicVariableDeclaration const> const& variable: m_magicVariables)
-		declarations.push_back(variable.get());
-	declarations.push_back(getCurrentThis());
-	return declarations;
-}
-
 }
 }

libsolidity/GlobalContext.h

@@ -49,8 +49,6 @@ public:
 	void setCurrentContract(ContractDefinition const& _contract);
 	MagicVariableDeclaration const* getCurrentThis() const;
 
-	/// @returns all magic variables.
-	std::vector<MagicVariableDeclaration const*> getMagicVariables() const;
 	/// @returns a vector of all implicit global declarations excluding "this".
 	std::vector<Declaration const*> getDeclarations() const;
 

libsolidity/NameAndTypeResolver.cpp

@@ -31,7 +31,6 @@ namespace dev
 namespace solidity
 {
 
-
 NameAndTypeResolver::NameAndTypeResolver(std::vector<Declaration const*> const& _globals)
 {
 	for (Declaration const* declaration: _globals)
@@ -46,18 +45,27 @@ void NameAndTypeResolver::registerDeclarations(SourceUnit& _sourceUnit)
 
 void NameAndTypeResolver::resolveNamesAndTypes(ContractDefinition& _contract)
 {
+	m_currentScope = &m_scopes[nullptr];
+
+	for (ASTPointer<InheritanceSpecifier> const& baseContract: _contract.getBaseContracts())
+		ReferencesResolver resolver(*baseContract, *this, &_contract, nullptr);
+
 	m_currentScope = &m_scopes[&_contract];
+
+	linearizeBaseContracts(_contract);
+	for (ContractDefinition const* base: _contract.getLinearizedBaseContracts())
+		importInheritedScope(*base);
+
 	for (ASTPointer<StructDefinition> const& structDef: _contract.getDefinedStructs())
-		ReferencesResolver resolver(*structDef, *this, nullptr);
+		ReferencesResolver resolver(*structDef, *this, &_contract, nullptr);
 	for (ASTPointer<VariableDeclaration> const& variable: _contract.getStateVariables())
-		ReferencesResolver resolver(*variable, *this, nullptr);
+		ReferencesResolver resolver(*variable, *this, &_contract, nullptr);
 	for (ASTPointer<FunctionDefinition> const& function: _contract.getDefinedFunctions())
 	{
 		m_currentScope = &m_scopes[function.get()];
-		ReferencesResolver referencesResolver(*function, *this,
+		ReferencesResolver referencesResolver(*function, *this, &_contract,
 											  function->getReturnParameterList().get());
 	}
-	m_currentScope = &m_scopes[nullptr];
 }
 
 void NameAndTypeResolver::checkTypeRequirements(ContractDefinition& _contract)
@@ -86,6 +94,96 @@ Declaration const* NameAndTypeResolver::getNameFromCurrentScope(ASTString const&
 	return m_currentScope->resolveName(_name, _recursive);
 }
 
+void NameAndTypeResolver::importInheritedScope(ContractDefinition const& _base)
+{
+	auto iterator = m_scopes.find(&_base);
+	solAssert(iterator != end(m_scopes), "");
+	for (auto const& nameAndDeclaration: iterator->second.getDeclarations())
+	{
+		Declaration const* declaration = nameAndDeclaration.second;
+		// Import if it was declared in the base and is not the constructor
+		if (declaration->getScope() == &_base && declaration->getName() != _base.getName())
+			m_currentScope->registerDeclaration(*declaration);
+	}
+}
+
+void NameAndTypeResolver::linearizeBaseContracts(ContractDefinition& _contract) const
+{
+	// order in the lists is from derived to base
+	// list of lists to linearize, the last element is the list of direct bases
+	list<list<ContractDefinition const*>> input(1, {&_contract});
+	for (ASTPointer<InheritanceSpecifier> const& baseSpecifier: _contract.getBaseContracts())
+	{
+		ASTPointer<Identifier> baseName = baseSpecifier->getName();
+		ContractDefinition const* base = dynamic_cast<ContractDefinition const*>(
+														baseName->getReferencedDeclaration());
+		if (!base)
+			BOOST_THROW_EXCEPTION(baseName->createTypeError("Contract expected."));
+		// "push_back" has the effect that bases mentioned earlier can overwrite members of bases
+		// mentioned later
+		input.back().push_back(base);
+		vector<ContractDefinition const*> const& basesBases = base->getLinearizedBaseContracts();
+		if (basesBases.empty())
+			BOOST_THROW_EXCEPTION(baseName->createTypeError("Definition of base has to precede definition of derived contract"));
+		input.push_front(list<ContractDefinition const*>(basesBases.begin(), basesBases.end()));
+	}
+	vector<ContractDefinition const*> result = cThreeMerge(input);
+	if (result.empty())
+		BOOST_THROW_EXCEPTION(_contract.createTypeError("Linearization of inheritance graph impossible"));
+	_contract.setLinearizedBaseContracts(result);
+}
+
+template <class _T>
+vector<_T const*> NameAndTypeResolver::cThreeMerge(list<list<_T const*>>& _toMerge)
+{
+	// returns true iff _candidate appears only as last element of the lists
+	auto appearsOnlyAtHead = [&](_T const* _candidate) -> bool
+	{
+		for (list<_T const*> const& bases: _toMerge)
+		{
+			solAssert(!bases.empty(), "");
+			if (find(++bases.begin(), bases.end(), _candidate) != bases.end())
+				return false;
+		}
+		return true;
+	};
+	// returns the next candidate to append to the linearized list or nullptr on failure
+	auto nextCandidate = [&]() -> _T const*
+	{
+		for (list<_T const*> const& bases: _toMerge)
+		{
+			solAssert(!bases.empty(), "");
+			if (appearsOnlyAtHead(bases.front()))
+				return bases.front();
+		}
+		return nullptr;
+	};
+	// removes the given contract from all lists
+	auto removeCandidate = [&](_T const* _candidate)
+	{
+		for (auto it = _toMerge.begin(); it != _toMerge.end();)
+		{
+			it->remove(_candidate);
+			if (it->empty())
+				it = _toMerge.erase(it);
+			else
+				++it;
+		}
+	};
+
+	_toMerge.remove_if([](list<_T const*> const& _bases) { return _bases.empty(); });
+	vector<_T const*> result;
+	while (!_toMerge.empty())
+	{
+		_T const* candidate = nextCandidate();
+		if (!candidate)
+			return vector<_T const*>();
+		result.push_back(candidate);
+		removeCandidate(candidate);
+	}
+	return result;
+}
+
 DeclarationRegistrationHelper::DeclarationRegistrationHelper(map<ASTNode const*, DeclarationContainer>& _scopes,
 															 ASTNode& _astRoot):
 	m_scopes(_scopes), m_currentScope(nullptr)
@@ -169,8 +267,10 @@ void DeclarationRegistrationHelper::registerDeclaration(Declaration& _declaratio
 }
 
 ReferencesResolver::ReferencesResolver(ASTNode& _root, NameAndTypeResolver& _resolver,
-									   ParameterList* _returnParameters, bool _allowLazyTypes):
+									   ContractDefinition const* _currentContract,
-	m_resolver(_resolver), m_returnParameters(_returnParameters), m_allowLazyTypes(_allowLazyTypes)
+									   ParameterList const* _returnParameters, bool _allowLazyTypes):
+	m_resolver(_resolver), m_currentContract(_currentContract),
+	m_returnParameters(_returnParameters), m_allowLazyTypes(_allowLazyTypes)
 {
 	_root.accept(*this);
 }
@@ -218,7 +318,7 @@ bool ReferencesResolver::visit(Identifier& _identifier)
 	if (!declaration)
 		BOOST_THROW_EXCEPTION(DeclarationError() << errinfo_sourceLocation(_identifier.getLocation())
 												 << errinfo_comment("Undeclared identifier."));
-	_identifier.setReferencedDeclaration(*declaration);
+	_identifier.setReferencedDeclaration(*declaration, m_currentContract);
 	return false;
 }
 

libsolidity/NameAndTypeResolver.h

@@ -23,6 +23,7 @@
 #pragma once
 
 #include <map>
+#include <list>
 #include <boost/noncopyable.hpp>
 
 #include <libsolidity/DeclarationContainer.h>
@@ -64,6 +65,17 @@ public:
 private:
 	void reset();
 
+	/// Imports all members declared directly in the given contract (i.e. does not import inherited
+	/// members) into the current scope if they are not present already.
+	void importInheritedScope(ContractDefinition const& _base);
+
+	/// Computes "C3-Linearization" of base contracts and stores it inside the contract.
+	void linearizeBaseContracts(ContractDefinition& _contract) const;
+	/// Computes the C3-merge of the given list of lists of bases.
+	/// @returns the linearized vector or an empty vector if linearization is not possible.
+	template <class _T>
+	static std::vector<_T const*> cThreeMerge(std::list<std::list<_T const*>>& _toMerge);
+
 	/// Maps nodes declaring a scope to scopes, i.e. ContractDefinition and FunctionDeclaration,
 	/// where nullptr denotes the global scope. Note that structs are not scope since they do
 	/// not contain code.
@@ -108,7 +120,9 @@ class ReferencesResolver: private ASTVisitor
 {
 public:
 	ReferencesResolver(ASTNode& _root, NameAndTypeResolver& _resolver,
-					   ParameterList* _returnParameters, bool _allowLazyTypes = true);
+					   ContractDefinition const* _currentContract,
+					   ParameterList const* _returnParameters,
+					   bool _allowLazyTypes = true);
 
 private:
 	virtual void endVisit(VariableDeclaration& _variable) override;
@@ -118,7 +132,8 @@ private:
 	virtual bool visit(Return& _return) override;
 
 	NameAndTypeResolver& m_resolver;
-	ParameterList* m_returnParameters;
+	ContractDefinition const* m_currentContract;
+	ParameterList const* m_returnParameters;
 	bool m_allowLazyTypes;
 };
 

libsolidity/Parser.cpp

@@ -117,10 +117,18 @@ ASTPointer<ContractDefinition> Parser::parseContractDefinition()
 		docstring = make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());
 	expectToken(Token::CONTRACT);
 	ASTPointer<ASTString> name = expectIdentifierToken();
-	expectToken(Token::LBRACE);
+	vector<ASTPointer<InheritanceSpecifier>> baseContracts;
 	vector<ASTPointer<StructDefinition>> structs;
 	vector<ASTPointer<VariableDeclaration>> stateVariables;
 	vector<ASTPointer<FunctionDefinition>> functions;
+	if (m_scanner->getCurrentToken() == Token::IS)
+		do
+		{
+			m_scanner->next();
+			baseContracts.push_back(parseInheritanceSpecifier());
+		}
+		while (m_scanner->getCurrentToken() == Token::COMMA);
+	expectToken(Token::LBRACE);
 	bool visibilityIsPublic = true;
 	while (true)
 	{
@@ -149,7 +157,25 @@ ASTPointer<ContractDefinition> Parser::parseContractDefinition()
 	}
 	nodeFactory.markEndPosition();
 	expectToken(Token::RBRACE);
-	return nodeFactory.createNode<ContractDefinition>(name, docstring, structs, stateVariables, functions);
+	return nodeFactory.createNode<ContractDefinition>(name, docstring, baseContracts, structs,
+													  stateVariables, functions);
+}
+
+ASTPointer<InheritanceSpecifier> Parser::parseInheritanceSpecifier()
+{
+	ASTNodeFactory nodeFactory(*this);
+	ASTPointer<Identifier> name = ASTNodeFactory(*this).createNode<Identifier>(expectIdentifierToken());
+	vector<ASTPointer<Expression>> arguments;
+	if (m_scanner->getCurrentToken() == Token::LPAREN)
+	{
+		m_scanner->next();
+		arguments = parseFunctionCallArguments();
+		nodeFactory.markEndPosition();
+		expectToken(Token::RPAREN);
+	}
+	else
+		nodeFactory.setEndPositionFromNode(name);
+	return nodeFactory.createNode<InheritanceSpecifier>(name, arguments);
 }
 
 ASTPointer<FunctionDefinition> Parser::parseFunctionDefinition(bool _isPublic)

libsolidity/Parser.h

@@ -49,6 +49,7 @@ private:
 	///@name Parsing functions for the AST nodes
 	ASTPointer<ImportDirective> parseImportDirective();
 	ASTPointer<ContractDefinition> parseContractDefinition();
+	ASTPointer<InheritanceSpecifier> parseInheritanceSpecifier();
 	ASTPointer<FunctionDefinition> parseFunctionDefinition(bool _isPublic);
 	ASTPointer<StructDefinition> parseStructDefinition();
 	ASTPointer<VariableDeclaration> parseVariableDeclaration(bool _allowVar);

libsolidity/Token.h

@@ -153,7 +153,7 @@ namespace solidity
 	K(DEFAULT, "default", 0)                                           \
 	K(DO, "do", 0)                                                     \
 	K(ELSE, "else", 0)                                                 \
-	K(EXTENDS, "extends", 0)                                           \
+	K(IS, "is", 0)                                                     \
 	K(FOR, "for", 0)                                                   \
 	K(FUNCTION, "function", 0)                                         \
 	K(IF, "if", 0)                                                     \

libsolidity/Types.cpp

@@ -431,12 +431,19 @@ bool ContractType::isImplicitlyConvertibleTo(Type const& _convertTo) const
 		return true;
 	if (_convertTo.getCategory() == Category::INTEGER)
 		return dynamic_cast<IntegerType const&>(_convertTo).isAddress();
+	if (_convertTo.getCategory() == Category::CONTRACT)
+	{
+		auto const& bases = getContractDefinition().getLinearizedBaseContracts();
+		return find(bases.begin(), bases.end(),
+					&dynamic_cast<ContractType const&>(_convertTo).getContractDefinition()) != bases.end();
+	}
 	return false;
 }
 
 bool ContractType::isExplicitlyConvertibleTo(Type const& _convertTo) const
 {
-	return isImplicitlyConvertibleTo(_convertTo) || _convertTo.getCategory() == Category::INTEGER;
+	return isImplicitlyConvertibleTo(_convertTo) || _convertTo.getCategory() == Category::INTEGER ||
+			_convertTo.getCategory() == Category::CONTRACT;
 }
 
 TypePointer ContractType::unaryOperatorResult(Token::Value _operator) const
@@ -695,6 +702,29 @@ bool TypeType::operator==(Type const& _other) const
 	return *getActualType() == *other.getActualType();
 }
 
+MemberList const& TypeType::getMembers() const
+{
+	// We need to lazy-initialize it because of recursive references.
+	if (!m_members)
+	{
+		map<string, TypePointer> members;
+		if (m_actualType->getCategory() == Category::CONTRACT && m_currentContract != nullptr)
+		{
+			ContractDefinition const& contract = dynamic_cast<ContractType const&>(*m_actualType).getContractDefinition();
+			vector<ContractDefinition const*> currentBases = m_currentContract->getLinearizedBaseContracts();
+			if (find(currentBases.begin(), currentBases.end(), &contract) != currentBases.end())
+				// We are accessing the type of a base contract, so add all public and private
+				// functions. Note that this does not add inherited functions on purpose.
+				for (ASTPointer<FunctionDefinition> const& f: contract.getDefinedFunctions())
+					if (f->getName() != contract.getName())
+						members[f->getName()] = make_shared<FunctionType>(*f);
+		}
+		m_members.reset(new MemberList(members));
+	}
+	return *m_members;
+}
+
+
 MagicType::MagicType(MagicType::Kind _kind):
 	m_kind(_kind)
 {

libsolidity/Types.h

@@ -442,7 +442,8 @@ class TypeType: public Type
 {
 public:
 	virtual Category getCategory() const override { return Category::TYPE; }
-	TypeType(TypePointer const& _actualType): m_actualType(_actualType) {}
+	TypeType(TypePointer const& _actualType, ContractDefinition const* _currentContract = nullptr):
+		m_actualType(_actualType), m_currentContract(_currentContract) {}
 	TypePointer const& getActualType() const { return m_actualType; }
 
 	virtual TypePointer binaryOperatorResult(Token::Value, TypePointer const&) const override { return TypePointer(); }
@@ -451,9 +452,14 @@ public:
 	virtual u256 getStorageSize() const override { BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Storage size of non-storable type type requested.")); }
 	virtual bool canLiveOutsideStorage() const override { return false; }
 	virtual std::string toString() const override { return "type(" + m_actualType->toString() + ")"; }
+	virtual MemberList const& getMembers() const override;
 
 private:
 	TypePointer m_actualType;
+	/// Context in which this type is used (influences visibility etc.), can be nullptr.
+	ContractDefinition const* m_currentContract;
+	/// List of member types, will be lazy-initialized because of recursive references.
+	mutable std::unique_ptr<MemberList> m_members;
 };
 
 

libsolidity/grammar.txt

@@ -1,7 +1,10 @@
-ContractDefinition = 'contract' Identifier '{' ContractPart* '}'
+ContractDefinition = 'contract' Identifier
+                     ( 'is' InheritanceSpecifier (',' InheritanceSpecifier )* )?
+                     '{' ContractPart* '}'
 ContractPart = VariableDeclaration ';' | StructDefinition |
                FunctionDefinition | 'public:' | 'private:'
 
+InheritanceSpecifier = Identifier ( '(' Expression ( ',' Expression )* ')' )?
 StructDefinition = 'struct' Identifier '{'
                      ( VariableDeclaration (';' VariableDeclaration)* )? '}
 

test/SolidityCompiler.cpp

@@ -64,7 +64,7 @@ bytes compileContract(const string& _sourceCode)
 		if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
 		{
 			Compiler compiler;
-			compiler.compileContract(*contract, {}, map<ContractDefinition const*, bytes const*>{});
+			compiler.compileContract(*contract, map<ContractDefinition const*, bytes const*>{});
 
 			// debug
 			//compiler.streamAssembly(cout);

test/SolidityEndToEndTest.cpp

@@ -1493,6 +1493,141 @@ BOOST_AUTO_TEST_CASE(value_for_constructor)
 	BOOST_REQUIRE(callContractFunction("getBalances()") == encodeArgs(12, 10));
 }
 
+BOOST_AUTO_TEST_CASE(virtual_function_calls)
+{
+	char const* sourceCode = R"(
+		contract Base {
+			function f() returns (uint i) { return g(); }
+			function g() returns (uint i) { return 1; }
+		}
+		contract Derived is Base {
+			function g() returns (uint i) { return 2; }
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("g()") == encodeArgs(2));
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(2));
+}
+
+BOOST_AUTO_TEST_CASE(access_base_storage)
+{
+	char const* sourceCode = R"(
+		contract Base {
+			uint dataBase;
+			function getViaBase() returns (uint i) { return dataBase; }
+		}
+		contract Derived is Base {
+			uint dataDerived;
+			function setData(uint base, uint derived) returns (bool r) {
+				dataBase = base;
+				dataDerived = derived;
+				return true;
+			}
+			function getViaDerived() returns (uint base, uint derived) {
+				base = dataBase;
+				derived = dataDerived;
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("setData(uint256,uint256)", 1, 2) == encodeArgs(true));
+	BOOST_CHECK(callContractFunction("getViaBase()") == encodeArgs(1));
+	BOOST_CHECK(callContractFunction("getViaDerived()") == encodeArgs(1, 2));
+}
+
+BOOST_AUTO_TEST_CASE(single_copy_with_multiple_inheritance)
+{
+	char const* sourceCode = R"(
+		contract Base {
+			uint data;
+			function setData(uint i) { data = i; }
+			function getViaBase() returns (uint i) { return data; }
+		}
+		contract A is Base { function setViaA(uint i) { setData(i); } }
+		contract B is Base { function getViaB() returns (uint i) { return getViaBase(); } }
+		contract Derived is A, B, Base { }
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("getViaB()") == encodeArgs(0));
+	BOOST_CHECK(callContractFunction("setViaA(uint256)", 23) == encodeArgs());
+	BOOST_CHECK(callContractFunction("getViaB()") == encodeArgs(23));
+}
+
+BOOST_AUTO_TEST_CASE(explicit_base_cass)
+{
+	char const* sourceCode = R"(
+		contract BaseBase { function g() returns (uint r) { return 1; } }
+		contract Base is BaseBase { function g() returns (uint r) { return 2; } }
+		contract Derived is Base {
+			function f() returns (uint r) { return BaseBase.g(); }
+			function g() returns (uint r) { return 3; }
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("g()") == encodeArgs(3));
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(1));
+}
+
+BOOST_AUTO_TEST_CASE(base_constructor_arguments)
+{
+	char const* sourceCode = R"(
+		contract BaseBase {
+			uint m_a;
+			function BaseBase(uint a) {
+				m_a = a;
+			}
+		}
+		contract Base is BaseBase(7) {
+			function Base() {
+				m_a *= m_a;
+			}
+		}
+		contract Derived is Base() {
+			function getA() returns (uint r) { return m_a; }
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("getA()") == encodeArgs(7 * 7));
+}
+
+BOOST_AUTO_TEST_CASE(function_usage_in_constructor_arguments)
+{
+	char const* sourceCode = R"(
+		contract BaseBase {
+			uint m_a;
+			function BaseBase(uint a) {
+				m_a = a;
+			}
+			function g() returns (uint r) { return 2; }
+		}
+		contract Base is BaseBase(BaseBase.g()) {
+		}
+		contract Derived is Base() {
+			function getA() returns (uint r) { return m_a; }
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("getA()") == encodeArgs(2));
+}
+
+BOOST_AUTO_TEST_CASE(constructor_argument_overriding)
+{
+	char const* sourceCode = R"(
+		contract BaseBase {
+			uint m_a;
+			function BaseBase(uint a) {
+				m_a = a;
+			}
+		}
+		contract Base is BaseBase(2) { }
+		contract Derived is Base, BaseBase(3) {
+			function getA() returns (uint r) { return m_a; }
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Derived");
+	BOOST_CHECK(callContractFunction("getA()") == encodeArgs(3));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }

test/SolidityNameAndTypeResolution.cpp

@@ -357,7 +357,6 @@ BOOST_AUTO_TEST_CASE(function_canonical_signature_type_aliases)
 		}
 }
 
-
 BOOST_AUTO_TEST_CASE(hash_collision_in_interface)
 {
 	char const* text = "contract test {\n"
@@ -369,6 +368,128 @@ BOOST_AUTO_TEST_CASE(hash_collision_in_interface)
 	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
 }
 
+BOOST_AUTO_TEST_CASE(inheritance_basic)
+{
+	char const* text = R"(
+		contract base { uint baseMember; struct BaseType { uint element; } }
+		contract derived is base {
+			BaseType data;
+			function f() { baseMember = 7; }
+		}
+	)";
+	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
+}
+
+BOOST_AUTO_TEST_CASE(inheritance_diamond_basic)
+{
+	char const* text = R"(
+		contract root { function rootFunction() {} }
+		contract inter1 is root { function f() {} }
+		contract inter2 is root { function f() {} }
+		contract derived is inter1, inter2, root {
+			function g() { f(); rootFunction(); }
+		}
+	)";
+	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
+}
+
+BOOST_AUTO_TEST_CASE(cyclic_inheritance)
+{
+	char const* text = R"(
+		contract A is B { }
+		contract B is A { }
+	)";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
+BOOST_AUTO_TEST_CASE(illegal_override_direct)
+{
+	char const* text = R"(
+		contract B { function f() {} }
+		contract C is B { function f(uint i) {} }
+	)";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
+BOOST_AUTO_TEST_CASE(illegal_override_indirect)
+{
+	char const* text = R"(
+		contract A { function f(uint a) {} }
+		contract B { function f() {} }
+		contract C is A, B { }
+	)";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
+BOOST_AUTO_TEST_CASE(complex_inheritance)
+{
+	char const* text = R"(
+		contract A { function f() { uint8 x = C(0).g(); } }
+		contract B { function f() {} function g() returns (uint8 r) {} }
+		contract C is A, B { }
+	)";
+	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
+}
+
+BOOST_AUTO_TEST_CASE(constructor_visibility)
+{
+	// The constructor of a base class should not be visible in the derived class
+	char const* text = R"(
+		contract A { function A() { } }
+		contract B is A { function f() { A x = A(0); } }
+	)";
+	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
+}
+
+BOOST_AUTO_TEST_CASE(overriding_constructor)
+{
+	// It is fine to "override" constructor of a base class since it is invisible
+	char const* text = R"(
+		contract A { function A() { } }
+		contract B is A { function A() returns (uint8 r) {} }
+	)";
+	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
+}
+
+BOOST_AUTO_TEST_CASE(missing_base_constructor_arguments)
+{
+	char const* text = R"(
+		contract A { function A(uint a) { } }
+		contract B is A { }
+	)";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
+BOOST_AUTO_TEST_CASE(base_constructor_arguments_override)
+{
+	char const* text = R"(
+		contract A { function A(uint a) { } }
+		contract B is A { }
+	)";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
+BOOST_AUTO_TEST_CASE(implicit_derived_to_base_conversion)
+{
+	char const* text = R"(
+		contract A { }
+		contract B is A {
+			function f() { A a = B(1); }
+		}
+	)";
+	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
+}
+BOOST_AUTO_TEST_CASE(implicit_base_to_derived_conversion)
+{
+	char const* text = R"(
+		contract A { }
+		contract B is A {
+			function f() { B b = A(1); }
+		}
+	)";
+	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }

test/SolidityParser.cpp

@@ -495,6 +495,51 @@ BOOST_AUTO_TEST_CASE(multiple_contracts_and_imports)
 	BOOST_CHECK_NO_THROW(parseText(text));
 }
 
+BOOST_AUTO_TEST_CASE(contract_inheritance)
+{
+	char const* text = "contract base {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n"
+					   "contract derived is base {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_NO_THROW(parseText(text));
+}
+
+BOOST_AUTO_TEST_CASE(contract_multiple_inheritance)
+{
+	char const* text = "contract base {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n"
+					   "contract derived is base, nonExisting {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_NO_THROW(parseText(text));
+}
+
+BOOST_AUTO_TEST_CASE(contract_multiple_inheritance_with_arguments)
+{
+	char const* text = "contract base {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n"
+					   "contract derived is base(2), nonExisting(\"abc\", \"def\", base.fun()) {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_NO_THROW(parseText(text));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }