Merge pull request #4671 from ethereum/mappingTupleAssignment

Disallow assignments to mappings within tuple assignments; allow for local variables.

Changelog.md

@@ -80,6 +80,8 @@ Bugfixes:
  * Fix NatSpec json output for `@notice` and `@dev` tags on contract definitions.
  * References Resolver: Enforce ``storage`` as data location for mappings.
  * References Resolver: Report error instead of assertion fail when FunctionType has an undeclared type as parameter.
+ * Type Checker: Disallow assignments to mappings within tuple assignments as well.
+ * Type Checker: Allow assignments to local variables of mapping types.
  * Type Checker: Consider fixed size arrays when checking for recursive structs.
  * Type Checker: Report error when using structs in events without experimental ABIEncoderV2. This used to crash or log the wrong values.
  * Type System: Allow arbitrary exponents for literals with a mantissa of zero.

libsolidity/analysis/TypeChecker.cpp

@@ -1330,11 +1330,41 @@ bool TypeChecker::visit(Conditional const& _conditional)
 	return false;
 }
 
+void TypeChecker::checkExpressionAssignment(Type const& _type, Expression const& _expression)
+{
+	if (auto const* tupleExpression = dynamic_cast<TupleExpression const*>(&_expression))
+	{
+		auto const* tupleType = dynamic_cast<TupleType const*>(&_type);
+		auto const& types = tupleType ? tupleType->components() : vector<TypePointer> { _type.shared_from_this() };
+
+		solAssert(tupleExpression->components().size() == types.size(), "");
+		for (size_t i = 0; i < types.size(); i++)
+			if (types[i])
+			{
+				solAssert(!!tupleExpression->components()[i], "");
+				checkExpressionAssignment(*types[i], *tupleExpression->components()[i]);
+			}
+	}
+	else if (_type.category() == Type::Category::Mapping)
+	{
+		bool isLocalOrReturn = false;
+		if (auto const* identifier = dynamic_cast<Identifier const*>(&_expression))
+			if (auto const *variableDeclaration = dynamic_cast<VariableDeclaration const*>(identifier->annotation().referencedDeclaration))
+				if (variableDeclaration->isLocalOrReturn())
+					isLocalOrReturn = true;
+		if (!isLocalOrReturn)
+			m_errorReporter.typeError(_expression.location(), "Mappings cannot be assigned to.");
+	}
+}
+
 bool TypeChecker::visit(Assignment const& _assignment)
 {
 	requireLValue(_assignment.leftHandSide());
 	TypePointer t = type(_assignment.leftHandSide());
 	_assignment.annotation().type = t;
+
+	checkExpressionAssignment(*t, _assignment.leftHandSide());
+
 	if (TupleType const* tupleType = dynamic_cast<TupleType const*>(t.get()))
 	{
 		if (_assignment.assignmentOperator() != Token::Assign)
@@ -1351,11 +1381,6 @@ bool TypeChecker::visit(Assignment const& _assignment)
 		if (dynamic_cast<TupleType const*>(type(_assignment.rightHandSide()).get()))
 			checkDoubleStorageAssignment(_assignment);
 	}
-	else if (t->category() == Type::Category::Mapping)
-	{
-		m_errorReporter.typeError(_assignment.location(), "Mappings cannot be assigned to.");
-		_assignment.rightHandSide().accept(*this);
-	}
 	else if (_assignment.assignmentOperator() == Token::Assign)
 		expectType(_assignment.rightHandSide(), *t);
 	else

libsolidity/analysis/TypeChecker.h

@@ -87,6 +87,9 @@ private:
 	/// Checks (and warns) if a tuple assignment might cause unexpected overwrites in storage.
 	/// Should only be called if the left hand side is tuple-typed.
 	void checkDoubleStorageAssignment(Assignment const& _assignment);
+	// Checks whether the expression @arg _expression can be assigned from type @arg _type
+	// and reports an error, if not.
+	void checkExpressionAssignment(Type const& _type, Expression const& _expression);
 
 	virtual void endVisit(InheritanceSpecifier const& _inheritance) override;
 	virtual void endVisit(UsingForDirective const& _usingFor) override;

test/libsolidity/SolidityEndToEndTest.cpp

@@ -1478,6 +1478,73 @@ BOOST_AUTO_TEST_CASE(multi_level_mapping)
 	testContractAgainstCpp("f(uint256,uint256,uint256)", f, u256(5), u256(4), u256(0));
 }
 
+BOOST_AUTO_TEST_CASE(mapping_local_assignment)
+{
+	char const* sourceCode = R"(
+		contract test {
+			mapping(uint8 => uint8) m1;
+			mapping(uint8 => uint8) m2;
+			function f() public returns (uint8, uint8, uint8, uint8) {
+				mapping(uint8 => uint8) storage m = m1;
+				m[1] = 42;
+
+				m = m2;
+				m[2] = 21;
+
+				return (m1[1], m1[2], m2[1], m2[2]);
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(byte(42), byte(0), byte(0), byte(21)));
+}
+
+BOOST_AUTO_TEST_CASE(mapping_local_tuple_assignment)
+{
+	char const* sourceCode = R"(
+		contract test {
+			mapping(uint8 => uint8) m1;
+			mapping(uint8 => uint8) m2;
+			function f() public returns (uint8, uint8, uint8, uint8) {
+				mapping(uint8 => uint8) storage m = m1;
+				m[1] = 42;
+
+				uint8 v;
+				(m, v) = (m2, 21);
+				m[2] = v;
+
+				return (m1[1], m1[2], m2[1], m2[2]);
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(byte(42), byte(0), byte(0), byte(21)));
+}
+
+BOOST_AUTO_TEST_CASE(mapping_local_compound_assignment)
+{
+	char const* sourceCode = R"(
+		contract test {
+			mapping(uint8 => uint8) m1;
+			mapping(uint8 => uint8) m2;
+			function f() public returns (uint8, uint8, uint8, uint8) {
+				mapping(uint8 => uint8) storage m = m1;
+				m[1] = 42;
+
+				(m = m2)[2] = 21;
+
+				return (m1[1], m1[2], m2[1], m2[2]);
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(byte(42), byte(0), byte(0), byte(21)));
+}
+
+
 BOOST_AUTO_TEST_CASE(structs)
 {
 	char const* sourceCode = R"(

test/libsolidity/syntaxTests/nameAndTypeResolution/016_assignment_to_mapping.sol

@@ -1,12 +0,0 @@
-contract test {
-    struct str {
-        mapping(uint=>uint) map;
-    }
-    str data;
-    function fun() public {
-        mapping(uint=>uint) storage a = data.map;
-        data.map = a;
-    }
-}
-// ----
-// TypeError: (172-184): Mappings cannot be assigned to.

test/libsolidity/syntaxTests/types/mapping/assignment_local.sol

@@ -0,0 +1,11 @@
+contract test {
+    mapping(uint=>uint) map;
+    function fun() public view {
+        mapping(uint=>uint) storage a = map;
+        mapping(uint=>uint) storage b = map;
+        b = a;
+        (b) = a;
+        (b, b) = (a, a);
+    }
+}
+// ----

test/libsolidity/syntaxTests/types/mapping/assignment_state_variable.sol

@@ -0,0 +1,14 @@
+contract test {
+    mapping(uint=>uint) map;
+    function fun() public {
+        mapping(uint=>uint) storage a = map;
+        map = a;
+        (map) = a;
+        (map, map) = (a, a);
+    }
+}
+// ----
+// TypeError: (126-129): Mappings cannot be assigned to.
+// TypeError: (144-147): Mappings cannot be assigned to.
+// TypeError: (163-166): Mappings cannot be assigned to.
+// TypeError: (168-171): Mappings cannot be assigned to.

test/libsolidity/syntaxTests/types/mapping/assignment_struct.sol

@@ -0,0 +1,17 @@
+contract test {
+    struct str {
+        mapping(uint=>uint) map;
+    }
+    str data;
+    function fun() public {
+        mapping(uint=>uint) storage a = data.map;
+        data.map = a;
+        (data.map) = a;
+        (data.map, data.map) = (a, a);
+    }
+}
+// ----
+// TypeError: (172-180): Mappings cannot be assigned to.
+// TypeError: (195-203): Mappings cannot be assigned to.
+// TypeError: (219-227): Mappings cannot be assigned to.
+// TypeError: (229-237): Mappings cannot be assigned to.

test/libsolidity/syntaxTests/types/mapping/mapping_return_external.sol

@@ -0,0 +1,7 @@
+contract C {
+    function f() external pure returns (mapping(uint=>uint) storage m) {
+    }
+}
+// ----
+// TypeError: (53-82): Type is required to live outside storage.
+// TypeError: (53-82): Internal or recursive type is not allowed for public or external functions.

test/libsolidity/syntaxTests/types/mapping/mapping_return_internal.sol

@@ -0,0 +1,21 @@
+// This should be allowed in a future release.
+contract C {
+    mapping(uint=>uint) m;
+    function f() internal view returns (mapping(uint=>uint) storage) {
+        return m;
+    }
+    function g() private view returns (mapping(uint=>uint) storage) {
+        return m;
+    }
+    function h() internal view returns (mapping(uint=>uint) storage r) {
+        r = m;
+    }
+    function i() private view returns (mapping(uint=>uint) storage r) {
+        (r,r) = (m,m);
+    }
+}
+// ----
+// TypeError: (127-146): Type is required to live outside storage.
+// TypeError: (221-240): Type is required to live outside storage.
+// TypeError: (316-345): Type is required to live outside storage.
+// TypeError: (409-438): Type is required to live outside storage.

test/libsolidity/syntaxTests/types/mapping/mapping_return_public.sol

@@ -0,0 +1,7 @@
+contract C {
+    function f() public pure returns (mapping(uint=>uint) storage m) {
+    }
+}
+// ----
+// TypeError: (51-80): Type is required to live outside storage.
+// TypeError: (51-80): Internal or recursive type is not allowed for public or external functions.