Merge pull request #4321 from ethereum/contractConversion

[BREAKING] Disallow conversion between unrelated contract types.

Changelog.md

@@ -40,6 +40,7 @@ Breaking Changes:
  * Type Checker: Disallow arithmetic operations for boolean variables.
  * Type Checker: Disallow tight packing of literals. This was already the case in the experimental 0.5.0 mode.
  * Type Checker: Disallow conversions between ``bytesX`` and ``uintY`` of different size.
+ * Type Checker: Disallow conversions between unrelated contract types. Explicit conversion via ``address`` can still achieve it.
  * Type Checker: Disallow empty tuple components. This was partly already the case in the experimental 0.5.0 mode.
  * Type Checker: Disallow multi-variable declarations with mismatching number of values. This was already the case in the experimental 0.5.0 mode.
  * Type Checker: Disallow specifying base constructor arguments multiple times in the same inheritance hierarchy. This was already the case in the experimental 0.5.0 mode.

docs/contracts.rst

@@ -1,5 +1,7 @@
 .. index:: ! contract
 
+.. _contracts:
+
 ##########
 Contracts
 ##########

docs/frequently-asked-questions.rst

@@ -379,7 +379,7 @@ In this example::
     }
 
     contract A {
-        address child;
+        B child;
 
         function test() public {
             child = (new B).value(10)(); //construct a new B with 10 wei

docs/types.rst

@@ -192,6 +192,23 @@ The ``.gas()`` option is available on all three methods, while the ``.value()``
 .. note::
     The use of ``callcode`` is discouraged and will be removed in the future.
 
+Contract Types
+--------------
+
+Every :ref:`contract<contracts>` defines its own type. Contracts can be implicitly converted
+to contracts they inherit from. They can be explicitly converted from and to ``address`` types.
+
+The data representation of a contract is identical to that of the ``address`` type and
+this type is also used in the :ref:`ABI<ABI>`.
+
+Contracts do not support any operators.
+
+The members of contract types are the external functions of the contract including
+public state variables.
+
+.. note::
+    Starting with version 0.5.0 contracts do not derive from the address type, but can still be explicitly converted to address.
+
 .. index:: byte array, bytes32
 
 
@@ -884,7 +901,7 @@ for each ``_KeyType``, recursively.
         function f() public returns (uint) {
             MappingExample m = new MappingExample();
             m.update(100);
-            return m.balances(this);
+            return m.balances(address(this));
         }
     }
 

libsolidity/ast/Types.cpp

@@ -1403,15 +1403,15 @@ bool ContractType::isImplicitlyConvertibleTo(Type const& _convertTo) const
 {
 	if (*this == _convertTo)
 		return true;
-	if (_convertTo.category() == Category::Integer)
-		return dynamic_cast<IntegerType const&>(_convertTo).isAddress();
 	if (_convertTo.category() == Category::Contract)
 	{
 		auto const& bases = contractDefinition().annotation().linearizedBaseContracts;
 		if (m_super && bases.size() <= 1)
 			return false;
-		return find(m_super ? ++bases.begin() : bases.begin(), bases.end(),
+		return find(
-					&dynamic_cast<ContractType const&>(_convertTo).contractDefinition()) != bases.end();
+			m_super ? ++bases.begin() : bases.begin(), bases.end(),
+			&dynamic_cast<ContractType const&>(_convertTo).contractDefinition()
+		) != bases.end();
 	}
 	return false;
 }
@@ -1420,8 +1420,7 @@ bool ContractType::isExplicitlyConvertibleTo(Type const& _convertTo) const
 {
 	return
 		isImplicitlyConvertibleTo(_convertTo) ||
-		_convertTo.category() == Category::Integer ||
+		_convertTo == IntegerType(160, IntegerType::Modifier::Address);
-		_convertTo.category() == Category::Contract;
 }
 
 bool ContractType::isPayable() const

libsolidity/ast/Types.h

@@ -692,9 +692,9 @@ public:
 	virtual Category category() const override { return Category::Contract; }
 	explicit ContractType(ContractDefinition const& _contract, bool _super = false):
 		m_contract(_contract), m_super(_super) {}
-	/// Contracts can be implicitly converted to super classes and to addresses.
+	/// Contracts can be implicitly converted only to base contracts.
 	virtual bool isImplicitlyConvertibleTo(Type const& _convertTo) const override;
-	/// Contracts can be converted to themselves and to integers.
+	/// Contracts can only be explicitly converted to address types and base contracts.
 	virtual bool isExplicitlyConvertibleTo(Type const& _convertTo) const override;
 	virtual TypePointer unaryOperatorResult(Token::Value _operator) const override;
 	virtual std::string richIdentifier() const override;

test/compilationTests/MultiSigWallet/MultiSigWalletFactory.sol

@@ -15,7 +15,7 @@ contract MultiSigWalletFactory is Factory {
         public
         returns (address wallet)
     {
-        wallet = new MultiSigWallet(_owners, _required);
+        wallet = address(new MultiSigWallet(_owners, _required));
         register(wallet);
     }
 }

test/compilationTests/MultiSigWallet/MultiSigWalletWithDailyLimitFactory.sol

@@ -16,7 +16,7 @@ contract MultiSigWalletWithDailyLimitFactory is Factory {
         public
         returns (address wallet)
     {
-        wallet = new MultiSigWalletWithDailyLimit(_owners, _required, _dailyLimit);
+        wallet = address(new MultiSigWalletWithDailyLimit(_owners, _required, _dailyLimit));
         register(wallet);
     }
 }

test/compilationTests/corion/premium.sol

@@ -56,7 +56,7 @@ contract premium is module, safeMath {
         require( dbAddress != address(0x00) );
         db = ptokenDB(dbAddress);
         if ( ! forReplace ) {
-            require( db.replaceOwner(this) );
+            require( db.replaceOwner(address(this)) );
             isICO = true;
             icoAddr = icoContractAddr;
             assert( genesisAddr.length == genesisValue.length );

test/compilationTests/corion/schelling.sol

@@ -259,7 +259,7 @@ contract schelling is module, announcementTypes, schellingVars {
         db = schellingDB(_db);
         super.registerModuleHandler(_moduleHandler);
         if ( ! _forReplace ) {
-            require( db.replaceOwner(this) );
+            require( db.replaceOwner(address(this)) );
         }
     }
     function configure(announcementType a, uint256 b) external returns(bool) {

test/compilationTests/corion/token.sol

@@ -71,7 +71,7 @@ contract token is safeMath, module, announcementTypes {
         exchangeAddress = exchangeContractAddress;
         isICO = ! forReplace;
         if ( ! forReplace ) {
-            require( db.replaceOwner(this) );
+            require( db.replaceOwner(address(this)) );
             assert( genesisAddr.length == genesisValue.length );
             require( address(this).balance >= genesisAddr.length * 0.2 ether );
             for ( uint256 a=0 ; a<genesisAddr.length ; a++ ) {

test/compilationTests/gnosis/Events/Event.sol

@@ -54,7 +54,7 @@ contract Event {
         public
     {
         // Transfer collateral tokens to events contract
-        require(collateralToken.transferFrom(msg.sender, this, collateralTokenCount));
+        require(collateralToken.transferFrom(msg.sender, address(this), collateralTokenCount));
         // Issue new outcome tokens to sender
         for (uint8 i = 0; i < outcomeTokens.length; i++)
             outcomeTokens[i].issue(msg.sender, collateralTokenCount);

test/compilationTests/gnosis/Markets/Campaign.sol

@@ -102,12 +102,12 @@ contract Campaign {
         timedTransitions
         atStage(Stages.AuctionStarted)
     {
-        uint raisedAmount = eventContract.collateralToken().balanceOf(this);
+        uint raisedAmount = eventContract.collateralToken().balanceOf(address(this));
         uint maxAmount = funding.sub(raisedAmount);
         if (maxAmount < amount)
             amount = maxAmount;
         // Collect collateral tokens
-        require(eventContract.collateralToken().transferFrom(msg.sender, this, amount));
+        require(eventContract.collateralToken().transferFrom(msg.sender, address(this), amount));
         contributions[msg.sender] = contributions[msg.sender].add(amount);
         if (amount == maxAmount)
             stage = Stages.AuctionSuccessful;
@@ -138,7 +138,7 @@ contract Campaign {
         returns (Market)
     {
         market = marketFactory.createMarket(eventContract, marketMaker, fee);
-        require(eventContract.collateralToken().approve(market, funding));
+        require(eventContract.collateralToken().approve(address(market), funding));
         market.fund(funding);
         stage = Stages.MarketCreated;
         emit MarketCreation(market);
@@ -156,7 +156,7 @@ contract Campaign {
         market.close();
         market.withdrawFees();
         eventContract.redeemWinnings();
-        finalBalance = eventContract.collateralToken().balanceOf(this);
+        finalBalance = eventContract.collateralToken().balanceOf(address(this));
         stage = Stages.MarketClosed;
         emit MarketClosing();
     }

test/compilationTests/gnosis/Markets/StandardMarket.sol

@@ -60,8 +60,8 @@ contract StandardMarket is Market {
         atStage(Stages.MarketCreated)
     {
         // Request collateral tokens and allow event contract to transfer them to buy all outcomes
-        require(   eventContract.collateralToken().transferFrom(msg.sender, this, _funding)
+        require(   eventContract.collateralToken().transferFrom(msg.sender, address(this), _funding)
-                && eventContract.collateralToken().approve(eventContract, _funding));
+                && eventContract.collateralToken().approve(address(eventContract), _funding));
         eventContract.buyAllOutcomes(_funding);
         funding = _funding;
         stage = Stages.MarketFunded;
@@ -76,7 +76,7 @@ contract StandardMarket is Market {
     {
         uint8 outcomeCount = eventContract.getOutcomeCount();
         for (uint8 i = 0; i < outcomeCount; i++)
-            require(eventContract.outcomeTokens(i).transfer(creator, eventContract.outcomeTokens(i).balanceOf(this)));
+            require(eventContract.outcomeTokens(i).transfer(creator, eventContract.outcomeTokens(i).balanceOf(address(this))));
         stage = Stages.MarketClosed;
         emit MarketClosing();
     }
@@ -88,7 +88,7 @@ contract StandardMarket is Market {
         isCreator
         returns (uint fees)
     {
-        fees = eventContract.collateralToken().balanceOf(this);
+        fees = eventContract.collateralToken().balanceOf(address(this));
         // Transfer fees
         require(eventContract.collateralToken().transfer(creator, fees));
         emit FeeWithdrawal(fees);
@@ -112,8 +112,8 @@ contract StandardMarket is Market {
         // Check cost doesn't exceed max cost
         require(cost > 0 && cost <= maxCost);
         // Transfer tokens to markets contract and buy all outcomes
-        require(   eventContract.collateralToken().transferFrom(msg.sender, this, cost)
+        require(   eventContract.collateralToken().transferFrom(msg.sender, address(this), cost)
-                && eventContract.collateralToken().approve(eventContract, outcomeTokenCost));
+                && eventContract.collateralToken().approve(address(eventContract), outcomeTokenCost));
         // Buy all outcomes
         eventContract.buyAllOutcomes(outcomeTokenCost);
         // Transfer outcome tokens to buyer
@@ -142,7 +142,7 @@ contract StandardMarket is Market {
         // Check profit is not too low
         require(profit > 0 && profit >= minProfit);
         // Transfer outcome tokens to markets contract to sell all outcomes
-        require(eventContract.outcomeTokens(outcomeTokenIndex).transferFrom(msg.sender, this, outcomeTokenCount));
+        require(eventContract.outcomeTokens(outcomeTokenIndex).transferFrom(msg.sender, address(this), outcomeTokenCount));
         // Sell all outcomes
         eventContract.sellAllOutcomes(outcomeTokenProfit);
         // Transfer profit to seller
@@ -164,11 +164,11 @@ contract StandardMarket is Market {
         returns (uint cost)
     {
         // Buy all outcomes
-        require(   eventContract.collateralToken().transferFrom(msg.sender, this, outcomeTokenCount)
+        require(   eventContract.collateralToken().transferFrom(msg.sender, address(this), outcomeTokenCount)
-                && eventContract.collateralToken().approve(eventContract, outcomeTokenCount));
+                && eventContract.collateralToken().approve(address(eventContract), outcomeTokenCount));
         eventContract.buyAllOutcomes(outcomeTokenCount);
         // Short sell selected outcome
-        eventContract.outcomeTokens(outcomeTokenIndex).approve(this, outcomeTokenCount);
+        eventContract.outcomeTokens(outcomeTokenIndex).approve(address(this), outcomeTokenCount);
         uint profit = this.sell(outcomeTokenIndex, outcomeTokenCount, minProfit);
         cost = outcomeTokenCount - profit;
         // Transfer outcome tokens to buyer

test/compilationTests/gnosis/Oracles/FutarchyOracle.sol

@@ -95,14 +95,14 @@ contract FutarchyOracle is Oracle {
         isCreator
     {
         // Buy all outcomes
-        require(   categoricalEvent.collateralToken().transferFrom(creator, this, funding)
+        require(   categoricalEvent.collateralToken().transferFrom(creator, address(this), funding)
-                && categoricalEvent.collateralToken().approve(categoricalEvent, funding));
+                && categoricalEvent.collateralToken().approve(address(categoricalEvent), funding));
         categoricalEvent.buyAllOutcomes(funding);
         // Fund each market with outcome tokens from categorical event
         for (uint8 i = 0; i < markets.length; i++) {
             Market market = markets[i];
             // Approve funding for market
-            require(market.eventContract().collateralToken().approve(market, funding));
+            require(market.eventContract().collateralToken().approve(address(market), funding));
             market.fund(funding);
         }
         emit FutarchyFunding(funding);
@@ -122,7 +122,7 @@ contract FutarchyOracle is Oracle {
         market.withdrawFees();
         // Redeem collateral token for winning outcome tokens and transfer collateral tokens to creator
         categoricalEvent.redeemWinnings();
-        require(categoricalEvent.collateralToken().transfer(creator, categoricalEvent.collateralToken().balanceOf(this)));
+        require(categoricalEvent.collateralToken().transfer(creator, categoricalEvent.collateralToken().balanceOf(address(this))));
         emit FutarchyClosing();
     }
 

test/compilationTests/gnosis/Oracles/UltimateOracle.sol

@@ -92,7 +92,7 @@ contract UltimateOracle is Oracle {
         // There was no challenge yet or the challenge period expired
         require(   !isChallenged()
                 && !isChallengePeriodOver()
-                && collateralToken.transferFrom(msg.sender, this, challengeAmount));
+                && collateralToken.transferFrom(msg.sender, address(this), challengeAmount));
         outcomeAmounts[msg.sender][_outcome] = challengeAmount;
         totalOutcomeAmounts[_outcome] = challengeAmount;
         totalAmount = challengeAmount;
@@ -113,7 +113,7 @@ contract UltimateOracle is Oracle {
         // Outcome is challenged and front runner period is not over yet and tokens can be transferred
         require(   isChallenged()
                 && !isFrontRunnerPeriodOver()
-                && collateralToken.transferFrom(msg.sender, this, amount));
+                && collateralToken.transferFrom(msg.sender, address(this), amount));
         outcomeAmounts[msg.sender][_outcome] = outcomeAmounts[msg.sender][_outcome].add(amount);
         totalOutcomeAmounts[_outcome] = totalOutcomeAmounts[_outcome].add(amount);
         totalAmount = totalAmount.add(amount);

test/compilationTests/zeppelin/Bounty.sol

@@ -31,8 +31,8 @@ contract Bounty is PullPayment, Destructible {
    */
   function createTarget() public returns(Target) {
     Target target = Target(deployContract());
-    researchers[target] = msg.sender;
+    researchers[address(target)] = msg.sender;
-    emit TargetCreated(target);
+    emit TargetCreated(address(target));
     return target;
   }
 
@@ -47,7 +47,7 @@ contract Bounty is PullPayment, Destructible {
    * @param target contract
    */
   function claim(Target target) public {
-    address researcher = researchers[target];
+    address researcher = researchers[address(target)];
     if (researcher == address(0)) {
       revert();
     }

test/compilationTests/zeppelin/lifecycle/TokenDestructible.sol

@@ -26,7 +26,7 @@ contract TokenDestructible is Ownable {
     // Transfer tokens to owner
     for(uint256 i = 0; i < tokens.length; i++) {
       ERC20Basic token = ERC20Basic(tokens[i]);
-      uint256 balance = token.balanceOf(this);
+      uint256 balance = token.balanceOf(address(this));
       token.transfer(owner, balance);
     }
 

test/compilationTests/zeppelin/ownership/HasNoTokens.sol

@@ -28,7 +28,7 @@ contract HasNoTokens is Ownable {
    */
   function reclaimToken(address tokenAddr) external onlyOwner {
     ERC20Basic tokenInst = ERC20Basic(tokenAddr);
-    uint256 balance = tokenInst.balanceOf(this);
+    uint256 balance = tokenInst.balanceOf(address(this));
     tokenInst.transfer(owner, balance);
   }
 }

test/compilationTests/zeppelin/token/TokenTimelock.sol

@@ -33,7 +33,7 @@ contract TokenTimelock {
     require(msg.sender == beneficiary);
     require(now >= releaseTime);
 
-    uint amount = token.balanceOf(this);
+    uint amount = token.balanceOf(address(this));
     require(amount > 0);
 
     token.transfer(beneficiary, amount);

test/libsolidity/SolidityEndToEndTest.cpp

@@ -9420,7 +9420,7 @@ BOOST_AUTO_TEST_CASE(failed_create)
 		contract C {
 			uint public x;
 			constructor() public payable {}
-			function f(uint amount) public returns (address) {
+			function f(uint amount) public returns (D) {
 				x++;
 				return (new D).value(amount)();
 			}
@@ -9428,7 +9428,7 @@ BOOST_AUTO_TEST_CASE(failed_create)
 				if (depth < 1024)
 					return this.stack(depth - 1);
 				else
-					return f(0);
+					return address(f(0));
 			}
 		}
 	)";
@@ -12524,10 +12524,10 @@ BOOST_AUTO_TEST_CASE(staticcall_for_view_and_pure)
 				return (new C()).f();
 			}
 			function fview() public returns (uint) {
-				return (CView(new C())).f();
+				return (CView(address(new C()))).f();
 			}
 			function fpure() public returns (uint) {
-				return (CPure(new C())).f();
+				return (CPure(address(new C()))).f();
 			}
 		}
 	)";

test/libsolidity/syntaxTests/constructor/inconstructible_internal_constructor_inverted.sol

@@ -3,11 +3,11 @@
 contract B {
 	A a;
 	constructor() public {
-		a = new A(this);
+		a = new A(address(this));
 	}
 }
 contract A {
-	constructor(address a) internal {}
+	constructor(address) internal {}
 }
 // ----
 // TypeError: (141-146): Contract with internal constructor cannot be created directly.

test/libsolidity/syntaxTests/parsing/constructor_allowed_this.sol

@@ -3,9 +3,9 @@ contract A {
     }
 }
 contract B {
-    constructor(address) public {
+    constructor(C) public {
     }
-    function b(address) public returns (A) {
+    function b(C) public returns (A) {
         return new A();
     }
 }

test/libsolidity/syntaxTests/types/address_to_contract.sol

@@ -0,0 +1,6 @@
+contract C {
+  function f() public pure returns (C c) {
+    c = C(address(2));
+  }
+}
+// ----

test/libsolidity/syntaxTests/types/address_to_contract_implicitly.sol

@@ -0,0 +1,7 @@
+contract C {
+  function f() public view {
+    C c = address(2);
+  }
+}
+// ----
+// TypeError: (46-62): Type address is not implicitly convertible to expected type contract C.

test/libsolidity/syntaxTests/types/contract_to_address.sol

@@ -0,0 +1,7 @@
+contract C {
+  function f() public view {
+    address a = address(this);
+    a;
+  }
+}
+// ----

test/libsolidity/syntaxTests/types/contract_to_address_implicitly.sol

@@ -0,0 +1,8 @@
+contract C {
+  function f() public view {
+    address a = this;
+    a;
+  }
+}
+// ----
+// TypeError: (46-62): Type contract C is not implicitly convertible to expected type address.

test/libsolidity/syntaxTests/types/contract_to_base.sol

@@ -0,0 +1,9 @@
+contract A {}
+contract B is A {}
+contract C {
+  function f() public {
+    A a = new B();
+    a;
+  }
+}
+// ----

test/libsolidity/syntaxTests/types/contract_to_base_base.sol

@@ -0,0 +1,10 @@
+contract A {}
+contract B is A {}
+contract C is B {}
+contract D {
+  function f() public {
+    A a = new C();
+    a;
+  }
+}
+// ----

test/libsolidity/syntaxTests/types/contract_to_derived.sol

@@ -0,0 +1,9 @@
+contract B {}
+contract A is B {}
+contract C {
+  function f() public pure {
+    A a = A(new B());
+  }
+}
+// ----
+// TypeError: (85-95): Explicit type conversion not allowed from "contract B" to "contract A".

test/libsolidity/syntaxTests/types/contract_to_unrelated_contract.sol

@@ -0,0 +1,9 @@
+contract A {}
+contract B {}
+contract C {
+  function f() public pure {
+    B b = B(new A());
+  }
+}
+// ----
+// TypeError: (80-90): Explicit type conversion not allowed from "contract A" to "contract B".