Moved a check related to constants to TypeChecker

And added a proper error message when constant types containing (nested) mapping types are used.

libsolidity/analysis/DeclarationTypeChecker.cpp

@@ -437,14 +437,16 @@ void DeclarationTypeChecker::endVisit(VariableDeclaration const& _variable)
 		type = TypeProvider::withLocation(ref, typeLoc, isPointer);
 	}
 
-	if (_variable.isConstant() && !type->isValueType())
-	{
-		bool allowed = false;
-		if (auto arrayType = dynamic_cast<ArrayType const*>(type))
-			allowed = arrayType->isByteArray();
-		if (!allowed)
-			m_errorReporter.fatalDeclarationError(9259_error, _variable.location(), "Constants of non-value type not yet implemented.");
-	}
+	if (
+		_variable.isConstant() &&
+		!dynamic_cast<UserDefinedValueType const*>(type) &&
+		type->containsNestedMapping()
+	)
+		m_errorReporter.fatalDeclarationError(
+			3530_error,
+			_variable.location(),
+			"The type contains a (nested) mapping and therefore cannot be a constant."
+		);
 
 	_variable.annotation().type = type;
 }

libsolidity/analysis/TypeChecker.cpp

@@ -530,6 +530,15 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
 	}
 	if (_variable.isConstant())
 	{
+		if (!varType->isValueType())
+		{
+			bool allowed = false;
+			if (auto arrayType = dynamic_cast<ArrayType const*>(varType))
+				allowed = arrayType->isByteArray();
+			if (!allowed)
+				m_errorReporter.fatalTypeError(9259_error, _variable.location(), "Constants of non-value type not yet implemented.");
+		}
+
 		if (!_variable.value())
 			m_errorReporter.typeError(4266_error, _variable.location(), "Uninitialized \"constant\" variable.");
 		else if (!*_variable.value()->annotation().isPure)

libsolidity/ast/Types.h

@@ -1124,6 +1124,8 @@ public:
 	bool containsNestedMapping() const override
 	{
 		solAssert(nameable(), "Called for a non nameable type.");
+		// DeclarationTypeChecker::endVisit(VariableDeclaration const&)
+		// assumes that this will never be true.
 		solAssert(!underlyingType().containsNestedMapping(), "");
 		return false;
 	}

test/libsolidity/syntaxTests/constantEvaluator/type_reference.sol

@@ -1,4 +1,3 @@
 int[L] constant L = 6;
 // ----
 // TypeError 5462: (4-5): Invalid array length, expected integer literal or constant expression.
-// DeclarationError 9259: (0-21): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/constantEvaluator/type_reference_in_contract.sol

@@ -3,4 +3,3 @@ contract C {
 }
 // ----
 // TypeError 5462: (21-22): Invalid array length, expected integer literal or constant expression.
-// DeclarationError 9259: (17-38): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/constants/mapping_constant.sol

@@ -1,3 +1,3 @@
 mapping(uint => uint) constant b = b;
 // ----
-// DeclarationError 9259: (0-36): Constants of non-value type not yet implemented.
+// DeclarationError 3530: (0-36): The type contains a (nested) mapping and therefore cannot be a constant.

test/libsolidity/syntaxTests/constants/struct_constant.sol

@@ -1,4 +1,4 @@
 struct S { uint x; }
 S constant s;
 // ----
-// DeclarationError 9259: (21-33): Constants of non-value type not yet implemented.
+// TypeError 9259: (21-33): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/iceRegressionTests/const_struct_with_mapping.sol

@@ -5,4 +5,4 @@ contract C {
     S public constant e = 0x1212121212121212121212121212121212121212;
 }
 // ----
-// DeclarationError 9259: (71-135): Constants of non-value type not yet implemented.
+// DeclarationError 3530: (71-135): The type contains a (nested) mapping and therefore cannot be a constant.

test/libsolidity/syntaxTests/nameAndTypeResolution/105_constant_input_parameter.sol

@@ -3,4 +3,3 @@ contract test {
 }
 // ----
 // DeclarationError 1788: (31-55): The "constant" keyword can only be used for state variables or variables at file level.
-// DeclarationError 9259: (31-55): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/nameAndTypeResolution/171_assignment_to_const_array_vars.sol

@@ -2,4 +2,4 @@ contract C {
     uint[3] constant x = [uint(1), 2, 3];
 }
 // ----
-// DeclarationError 9259: (17-53): Constants of non-value type not yet implemented.
+// TypeError 9259: (17-53): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/nameAndTypeResolution/173_constant_struct.sol

@@ -3,4 +3,4 @@ contract C {
     S constant x = S(5, new uint[](4));
 }
 // ----
-// DeclarationError 9259: (52-86): Constants of non-value type not yet implemented.
+// TypeError 9259: (52-86): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/nameAndTypeResolution/constant_mapping.sol

@@ -1,7 +1,5 @@
 contract C {
-    // This should probably have a better error message at some point.
-    // Constant mappings should not be possible in general.
     mapping(uint => uint) constant x;
 }
 // ----
-// DeclarationError 9259: (148-180): Constants of non-value type not yet implemented.
+// DeclarationError 3530: (17-49): The type contains a (nested) mapping and therefore cannot be a constant.

test/libsolidity/syntaxTests/nameAndTypeResolution/constant_nested_mapping.sol

@@ -5,4 +5,4 @@ contract C {
     S public constant c;
 }
 // ----
-// DeclarationError 9259: (71-90): Constants of non-value type not yet implemented.
+// DeclarationError 3530: (71-90): The type contains a (nested) mapping and therefore cannot be a constant.

test/libsolidity/syntaxTests/parsing/location_specifiers_for_params.sol

@@ -3,4 +3,3 @@ contract Foo {
 }
 // ----
 // DeclarationError 1788: (30-55): The "constant" keyword can only be used for state variables or variables at file level.
-// DeclarationError 9259: (30-55): Constants of non-value type not yet implemented.

test/libsolidity/syntaxTests/userDefinedValueType/forward_reference_constant_variable_declaration.sol

@@ -0,0 +1,2 @@
+MyInt constant x = MyInt.wrap(20);
+type MyInt is int;