Allow UserDefinedValueType.uwrap (and wrap) as RHS of constant decl

Needed to make `MyType.unwrap` and `MyType.unwrap` as pure in the process. This change affected some
existing tests ("statement has no effect").

libsolidity/analysis/TypeChecker.cpp

@@ -2916,7 +2916,10 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
 	// TODO some members might be pure, but for example `address(0x123).balance` is not pure
 	// although every subexpression is, so leaving this limited for now.
 	if (auto tt = dynamic_cast<TypeType const*>(exprType))
-		if (tt->actualType()->category() == Type::Category::Enum)
+		if (
+			tt->actualType()->category() == Type::Category::Enum ||
+			tt->actualType()->category() == Type::Category::UserDefinedValueType
+		)
 			annotation.isPure = true;
 	if (
 		auto const* functionType = dynamic_cast<FunctionType const*>(exprType);

libsolidity/ast/Types.cpp

@@ -3499,7 +3499,9 @@ bool FunctionType::isPure() const
 		m_kind == Kind::ABIEncodeWithSelector ||
 		m_kind == Kind::ABIEncodeWithSignature ||
 		m_kind == Kind::ABIDecode ||
-		m_kind == Kind::MetaType;
+		m_kind == Kind::MetaType ||
+		m_kind == Kind::Wrap ||
+		m_kind == Kind::Unwrap;
 }
 
 TypePointers FunctionType::parseElementaryTypeVector(strings const& _types)