Merge pull request #8977 from ethereum/mapping-type-error

Error when Mapping type in (non-local) storage is assigned to

Changelog.md

@@ -11,6 +11,7 @@ Compiler Features:
 
 Bugfixes:
  * Optimizer: Fixed a bug in BlockDeDuplicator.
+ * Type Checker: Disallow assignments to storage variables of type ``mapping``.
 
 
 ### 0.6.8 (2020-05-14)

libsolidity/analysis/TypeChecker.cpp

@@ -453,7 +453,15 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
 		if (contractType->contractDefinition().isLibrary())
 			m_errorReporter.typeError(1273_error, _variable.location(), "The type of a variable cannot be a library.");
 	if (_variable.value())
-		expectType(*_variable.value(), *varType);
+	{
+		if (_variable.isStateVariable() && dynamic_cast<MappingType const*>(varType))
+		{
+			m_errorReporter.typeError(6280_error, _variable.location(), "Mappings cannot be assigned to.");
+			_variable.value()->accept(*this);
+		}
+		else
+			expectType(*_variable.value(), *varType);
+	}
 	if (_variable.isConstant())
 	{
 		if (!_variable.type()->isValueType())

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

@@ -0,0 +1,10 @@
+contract D {
+    mapping (uint => uint) a;
+    mapping (uint => uint) b;
+    function foo() public view {
+        mapping (uint => uint) storage c = b;
+        b = c;
+    }
+}
+// ----
+// TypeError: (160-161): Mappings cannot be assigned to.

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

@@ -0,0 +1,27 @@
+contract C {
+    mapping (uint => address payable [ ]) public a = a ;
+}
+
+contract D {
+    mapping (uint => uint) a;
+    mapping (uint => uint) b = a;
+}
+
+contract F {
+    mapping (uint => uint) a;
+    mapping (uint => uint) b;
+
+    function foo() public {
+        a = b;
+    }
+}
+
+contract G {
+    uint x = 1;
+    mapping (uint => uint) b = x;
+}
+// ----
+// TypeError: (17-67): Mappings cannot be assigned to.
+// TypeError: (120-148): Mappings cannot be assigned to.
+// TypeError: (263-264): Mappings cannot be assigned to.
+// TypeError: (312-340): Mappings cannot be assigned to.

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

@@ -0,0 +1,8 @@
+contract D {
+    mapping (uint => uint) a;
+    function foo() public view {
+        mapping (uint => int) storage c = a;
+    }
+}
+// ----
+// TypeError: (84-119): Type mapping(uint256 => uint256) is not implicitly convertible to expected type mapping(uint256 => int256).