Cherry-pick changes from main

src/forest.cpp

@@ -76,7 +76,6 @@ Constructs a forest with *n* nodes, that is initialised so that the
                           parents,
                       std::vector<int_or_unsigned_constant<node_type>> const&
                           labels) {
-            using node_type = node_type;
             return make<Forest>(to_ints<node_type>(parents),
                                 to_ints<node_type>(labels));
           }),
@@ -156,10 +155,7 @@ the same state as if it had just been constructed as ``Forest(n)``.
           "label",
           [](Forest const& self,
              node_type     i) -> int_or_unsigned_constant<node_type> {
-            if (self.label(i) != UNDEFINED) {
-              return {self.label(i)};
-            }
-            return {UNDEFINED};
+            return from_int(self.label(i));
           },
           py::arg("i"),
           R"pbdoc(

src/main.hpp

@@ -100,7 +100,7 @@ namespace libsemigroups {
                                              int_or_unsigned_constant<Int>>;
 
   template <typename Int>
-  Int to_int(int_or_constant<Int> val) {
+  Int to_int(int_or_constant<Int> const& val) {
     if (std::holds_alternative<Int>(val)) {
       return std::get<0>(val);
     } else if (std::holds_alternative<Undefined>(val)) {

src/transf.cpp

@@ -112,6 +112,8 @@ the image of the point ``i`` under the {0} is ``imgs[i]``.
             // work.
             try {
               auto result = a.at(b);
+              // Don't use from_int here, because that will incorrectly convert
+              // things to LIMIT_MAX and POSITIVE_INFINITY.
               if (result != UNDEFINED) {
                 return {result};
               }
@@ -170,6 +172,9 @@ definition, which is equal to the size of :any:`{0}.images`.
           [](PTransfSubclass& self) {
             auto r = rx::iterator_range(self.begin(), self.end())
                      | rx::transform(
+                         // Don't use from_int here, because that will
+                         // incorrectly convert things to LIMIT_MAX and
+                         // POSITIVE_INFINITY.
                          [](auto val) -> int_or_unsigned_constant<Scalar> {
                            if (val != UNDEFINED) {
                              return {val};