Fix: assert when converting between incompatible field types

This results in a compile time error now which hopefully prevents
this specific kind of mistake in the future.

source/blender/functions/FN_field.hh

@@ -193,6 +193,16 @@ template<typename T> class Field : public GField, detail::TypedFieldBase {
     BLI_assert(this->cpp_type().template is<T>());
   }
 
+  /**
+   * Generally, the constructor above would be sufficient, but this additional constructor ensures
+   * that trying to create e.g. a `Field<int>` from a `Field<float>` does not compile (instead of
+   * only failing at run-time).
+   */
+  template<typename U> Field(Field<U> field) : GField(std::move(field))
+  {
+    static_assert(std::is_same_v<T, U>);
+  }
+
   Field(std::shared_ptr<FieldNode> node, const int node_output_index = 0)
       : Field(GField(std::move(node), node_output_index))
   {

source/blender/nodes/geometry/nodes/node_geo_curve_topology_points_of_curve.cc

@@ -237,7 +237,7 @@ static void node_geo_exec(GeoNodeExecParams params)
   }
   if (params.output_is_required("Point Index")) {
     Field<int> sort_index = params.extract_input<Field<int>>("Sort Index");
-    Field<int> sort_weight = params.extract_input<Field<float>>("Weights");
+    Field<float> sort_weight = params.extract_input<Field<float>>("Weights");
     if (use_start_point_special_case(curve_index, sort_index, sort_weight)) {
       params.set_output("Point Index", Field<int>(std::make_shared<CurveStartPointInput>()));
     }