Disallow assignments to mappings within tuple assignments.

Changelog.md

@@ -79,6 +79,7 @@ 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: Consider fixed size arrays when checking for recursive structs.
  * Type System: Allow arbitrary exponents for literals with a mantissa of zero.
 

libsolidity/analysis/TypeChecker.cpp

@@ -1318,11 +1318,31 @@ 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))
+	{
+		if (auto const* tupleType = dynamic_cast<TupleType const*>(&_type))
+		{
+			for (size_t i = 0; i < min(tupleExpression->components().size(), tupleType->components().size()); i++)
+				if (tupleType->components()[i] && tupleExpression->components()[i])
+					checkExpressionAssignment(*tupleType->components()[i], *tupleExpression->components()[i]);
+		}
+		else if (!tupleExpression->components().empty())
+			checkExpressionAssignment(_type, *tupleExpression->components().front());
+	}
+	else if (_type.category() == Type::Category::Mapping)
+		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)
@@ -1339,11 +1359,6 @@ 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/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 +1,15 @@
+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);
+    }
+}
+// ----
+// TypeError: (176-177): Mappings cannot be assigned to.
+// TypeError: (192-193): Mappings cannot be assigned to.
+// TypeError: (209-210): Mappings cannot be assigned to.
+// TypeError: (212-213): Mappings cannot be assigned to.

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.