Implement address.transfer()

4 files changed, 20 insertions, 5 deletions

diff --git a/Changelog.md b/Changelog.md
index 45aaf04a..37f20c71 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -2,6 +2,7 @@
 
 Features:
  * Add ``assert(condition)``, which throws if condition is false.
+ * Introduce ``.transfer(value)`` for sending Ether.
  * Code generator: Support ``revert()`` to abort with rolling back, but not consuming all gas.
  * Inline assembly: Support ``revert`` (EIP140) as an opcode.
  * Type system: Support explicit conversion of external function to address.
diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index 96b3ed17..7fccccbc 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -464,7 +464,8 @@ MemberList::MemberMap IntegerType::nativeMembers(ContractDefinition const*) cons
 			{"call", make_shared<FunctionType>(strings(), strings{"bool"}, FunctionType::Location::Bare, true, false, true)},
 			{"callcode", make_shared<FunctionType>(strings(), strings{"bool"}, FunctionType::Location::BareCallCode, true, false, true)},
 			{"delegatecall", make_shared<FunctionType>(strings(), strings{"bool"}, FunctionType::Location::BareDelegateCall, true)},
-			{"send", make_shared<FunctionType>(strings{"uint"}, strings{"bool"}, FunctionType::Location::Send)}
+			{"send", make_shared<FunctionType>(strings{"uint"}, strings{"bool"}, FunctionType::Location::Send)},
+			{"transfer", make_shared<FunctionType>(strings{"uint"}, strings(), FunctionType::Location::Transfer)}
 		};
 	else
 		return MemberList::MemberMap();
@@ -2097,6 +2098,7 @@ string FunctionType::identifier() const
 	case Location::BareDelegateCall: id += "baredelegatecall"; break;
 	case Location::Creation: id += "creation"; break;
 	case Location::Send: id += "send"; break;
+	case Location::Transfer: id += "transfer"; break;
 	case Location::SHA3: id += "sha3"; break;
 	case Location::Selfdestruct: id += "selfdestruct"; break;
 	case Location::Revert: id += "revert"; break;
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 3546e522..022b67c4 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -826,6 +826,7 @@ public:
 		BareDelegateCall, ///< DELEGATECALL without function hash
 		Creation, ///< external call using CREATE
 		Send, ///< CALL, but without data and gas
+		Transfer, ///< CALL, but without data and throws on error
 		SHA3, ///< SHA3
 		Selfdestruct, ///< SELFDESTRUCT
 		Revert, ///< REVERT
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index 2ed19a83..b0031513 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -616,6 +616,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			arguments.front()->accept(*this);
 			break;
 		case Location::Send:
+		case Location::Transfer:
 			_functionCall.expression().accept(*this);
 			// Provide the gas stipend manually at first because we may send zero ether.
 			// Will be zeroed if we send more than zero ether.
@@ -625,9 +626,12 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 				*arguments.front()->annotation().type,
 				*function.parameterTypes().front(), true
 			);
-			// gas <- gas * !value
-			m_context << Instruction::SWAP1 << Instruction::DUP2;
-			m_context << Instruction::ISZERO << Instruction::MUL << Instruction::SWAP1;
+			if (function.location() != Location::Transfer)
+			{
+				// gas <- gas * !value
+				m_context << Instruction::SWAP1 << Instruction::DUP2;
+				m_context << Instruction::ISZERO << Instruction::MUL << Instruction::SWAP1;
+			}
 			appendExternalFunctionCall(
 				FunctionType(
 					TypePointers{},
@@ -644,6 +648,12 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 				),
 				{}
 			);
+			if (function.location() == Location::Transfer)
+			{
+				// Check if zero (out of stack or not enough balance).
+				m_context << Instruction::ISZERO;
+				m_context.appendConditionalInvalid();
+			}
 			break;
 		case Location::Selfdestruct:
 			arguments.front()->accept(*this);
@@ -960,6 +970,7 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 				case FunctionType::Location::Bare:
 				case FunctionType::Location::BareCallCode:
 				case FunctionType::Location::BareDelegateCall:
+				case FunctionType::Location::Transfer:
 					_memberAccess.expression().accept(*this);
 					m_context << funType->externalIdentifier();
 					break;
@@ -1041,7 +1052,7 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 			);
 			m_context << Instruction::BALANCE;
 		}
-		else if ((set<string>{"send", "call", "callcode", "delegatecall"}).count(member))
+		else if ((set<string>{"send", "transfer", "call", "callcode", "delegatecall"}).count(member))
 			utils().convertType(
 				*_memberAccess.expression().annotation().type,
 				IntegerType(0, IntegerType::Modifier::Address),