Public state variables are implementing external functions.

7 files changed, 66 insertions, 21 deletions

diff --git a/Changelog.md b/Changelog.md
index 630801e4..7aa5a6be 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -27,6 +27,7 @@ Bugfixes:
  * Type Checker: Fixed internal error when trying to create abstract contract in some cases.
  * Type Checker: Fixed internal error related to double declaration of events.
  * Type Checker: Disallow inline arrays of mapping type.
+ * Type Checker: Consider abstract function to be implemented by public state variable.
 
 Build System:
  * Emscripten: Upgrade to Emscripten SDK 1.37.21 and boost 1.67.
diff --git a/libsolidity/analysis/ContractLevelChecker.cpp b/libsolidity/analysis/ContractLevelChecker.cpp
index 58dcfe4d..6dc564de 100644
--- a/libsolidity/analysis/ContractLevelChecker.cpp
+++ b/libsolidity/analysis/ContractLevelChecker.cpp
@@ -219,29 +219,40 @@ void ContractLevelChecker::checkAbstractFunctions(ContractDefinition const& _con
 	using FunTypeAndFlag = std::pair<FunctionTypePointer, bool>;
 	map<string, vector<FunTypeAndFlag>> functions;
 
-	// Search from base to derived
-	for (ContractDefinition const* contract: boost::adaptors::reverse(_contract.annotation().linearizedBaseContracts))
-		for (FunctionDefinition const* function: contract->definedFunctions())
+	auto registerFunction = [&](Declaration const& _declaration, FunctionTypePointer const& _type, bool _implemented)
+	{
+		auto& overloads = functions[_declaration.name()];
+		auto it = find_if(overloads.begin(), overloads.end(), [&](FunTypeAndFlag const& _funAndFlag)
 		{
-			// Take constructors out of overload hierarchy
-			if (function->isConstructor())
-				continue;
-			auto& overloads = functions[function->name()];
-			FunctionTypePointer funType = make_shared<FunctionType>(*function)->asCallableFunction(false);
-			auto it = find_if(overloads.begin(), overloads.end(), [&](FunTypeAndFlag const& _funAndFlag)
-			{
-				return funType->hasEqualParameterTypes(*_funAndFlag.first);
-			});
-			if (it == overloads.end())
-				overloads.push_back(make_pair(funType, function->isImplemented()));
-			else if (it->second)
-			{
-				if (!function->isImplemented())
-					m_errorReporter.typeError(function->location(), "Redeclaring an already implemented function as abstract");
-			}
-			else if (function->isImplemented())
-				it->second = true;
+			return _type->hasEqualParameterTypes(*_funAndFlag.first);
+		});
+		if (it == overloads.end())
+			overloads.push_back(make_pair(_type, _implemented));
+		else if (it->second)
+		{
+			if (!_implemented)
+				m_errorReporter.typeError(_declaration.location(), "Redeclaring an already implemented function as abstract");
 		}
+		else if (_implemented)
+			it->second = true;
+	};
+
+	// Search from base to derived, collect all functions and update
+	// the 'implemented' flag.
+	for (ContractDefinition const* contract: boost::adaptors::reverse(_contract.annotation().linearizedBaseContracts))
+	{
+		for (VariableDeclaration const* v: contract->stateVariables())
+			if (v->isPartOfExternalInterface())
+				registerFunction(*v, make_shared<FunctionType>(*v), true);
+
+		for (FunctionDefinition const* function: contract->definedFunctions())
+			if (!function->isConstructor())
+				registerFunction(
+					*function,
+					make_shared<FunctionType>(*function)->asCallableFunction(false),
+					function->isImplemented()
+				);
+	}
 
 	// Set to not fully implemented if at least one flag is false.
 	for (auto const& it: functions)
diff --git a/test/libsolidity/syntaxTests/inheritance/override/implement_interface_by_public_variable.sol b/test/libsolidity/syntaxTests/inheritance/override/implement_interface_by_public_variable.sol
new file mode 100644
index 00000000..49f7c33b
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inheritance/override/implement_interface_by_public_variable.sol
@@ -0,0 +1,7 @@
+interface X { function test() external returns (uint256); }
+contract Y is X {
+    uint256 public test = 42;
+}
+contract T {
+    constructor() public { new Y(); }
+}
diff --git a/test/libsolidity/syntaxTests/inheritance/override/implement_internal_function_by_public_variable.sol b/test/libsolidity/syntaxTests/inheritance/override/implement_internal_function_by_public_variable.sol
new file mode 100644
index 00000000..32fac25c
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inheritance/override/implement_internal_function_by_public_variable.sol
@@ -0,0 +1,9 @@
+contract X { function test() internal returns (uint256); }
+contract Y is X {
+    uint256 public test = 42;
+}
+contract T {
+    constructor() public { new Y(); }
+}
+// ----
+// DeclarationError: (81-105): Identifier already declared.
diff --git a/test/libsolidity/syntaxTests/inheritance/override/implement_private_function_by_public_variable.sol b/test/libsolidity/syntaxTests/inheritance/override/implement_private_function_by_public_variable.sol
new file mode 100644
index 00000000..c58e24b6
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inheritance/override/implement_private_function_by_public_variable.sol
@@ -0,0 +1,7 @@
+contract X { function test() private returns (uint256); }
+contract Y is X {
+    uint256 public test = 42;
+}
+contract T {
+    constructor() public { new Y(); }
+}
diff --git a/test/libsolidity/syntaxTests/inheritance/override/implement_public_function_by_public_variable.sol b/test/libsolidity/syntaxTests/inheritance/override/implement_public_function_by_public_variable.sol
new file mode 100644
index 00000000..7a59c137
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inheritance/override/implement_public_function_by_public_variable.sol
@@ -0,0 +1,9 @@
+contract X { function test() public returns (uint256); }
+contract Y is X {
+    uint256 public test = 42;
+}
+contract T {
+    constructor() public { new Y(); }
+}
+// ----
+// DeclarationError: (79-103): Identifier already declared.
diff --git a/test/libsolidity/syntaxTests/inheritance/override/state_variable_function.sol b/test/libsolidity/syntaxTests/inheritance/override/state_variable_function.sol
index 0f05cc8e..fb7f3fbd 100644
--- a/test/libsolidity/syntaxTests/inheritance/override/state_variable_function.sol
+++ b/test/libsolidity/syntaxTests/inheritance/override/state_variable_function.sol
@@ -6,3 +6,4 @@ contract C is A {
 }
 // ----
 // DeclarationError: (50-85): Identifier already declared.
+// TypeError: (50-85): Redeclaring an already implemented function as abstract