Fix problem where rtepack types were not parsable (nor probably binary compatible)

doc/arts/dev.xml.rst

@@ -39,8 +39,8 @@ There are two structs defined in ``xml_io_struct.h``:
     static void read(std::istream&, T&, bifstream* = nullptr) = delete;
 
     // Binary streaming IO (optional)
-    static void get(std::span<const T>, bofstream*) = delete;
-    static void put(std::span<T>, bifstream*)       = delete;
+    static void get(std::span<T>, bifstream*)       = delete;
+    static void put(std::span<const T>, bofstream*) = delete;
 
     // Text streaming (optional)
     static void parse(std::span<T>, std::istream&) = delete;

src/core/rtepack/rtepack_mueller_matrix.h

@@ -275,8 +275,8 @@ Array<muelmat_vector> forward_cumulative_transmission(
 }  // namespace rtepack
 
 template <>
-
 struct std::formatter<rtepack::muelmat> : std::formatter<Matrix44> {};
 
 template <>
-struct xml_io_stream<rtepack::muelmat> : xml_io_stream<Matrix44> {};
+struct xml_io_stream<rtepack::muelmat>
+    : xml_io_stream_inherit<Matrix44, rtepack::muelmat> {};

src/core/rtepack/rtepack_propagation_matrix.h

@@ -127,8 +127,8 @@ propmat_vector operator*(Numeric x, const propmat_vector_const_view &y);
 }  // namespace rtepack
 
 template <>
-
 struct std::formatter<rtepack::propmat> : std::formatter<Vector7> {};
 
 template <>
-struct xml_io_stream<rtepack::propmat> : xml_io_stream<Vector7> {};
+struct xml_io_stream<rtepack::propmat>
+    : xml_io_stream_inherit<Vector7, rtepack::propmat> {};

src/core/rtepack/rtepack_spectral_matrix.h

@@ -271,8 +271,8 @@ using specmat_tensor3_const_view = matpack::view_t<const specmat, 3>;
 }  // namespace rtepack
 
 template <>
-
 struct std::formatter<rtepack::specmat> : std::formatter<ComplexMatrix44> {};
 
 template <>
-struct xml_io_stream<rtepack::specmat> : xml_io_stream<ComplexMatrix44> {};
+struct xml_io_stream<rtepack::specmat>
+    : xml_io_stream_inherit<ComplexMatrix44, rtepack::specmat> {};

src/core/rtepack/rtepack_stokes_vector.h

@@ -160,8 +160,8 @@ using stokvec_tensor6_const_view = matpack::view_t<const stokvec, 6>;
 }  // namespace rtepack
 
 template <>
-
 struct std::formatter<rtepack::stokvec> : std::formatter<Vector4> {};
 
 template <>
-struct xml_io_stream<rtepack::stokvec> : xml_io_stream<Vector4> {};
+struct xml_io_stream<rtepack::stokvec>
+    : xml_io_stream_inherit<Vector4, rtepack::stokvec> {};

src/core/xml/xml_io_stream.h

@@ -39,8 +39,8 @@ struct xml_io_stream {
   static void read(std::istream&, T&, bifstream* = nullptr) = delete;
 
   // Binary streaming IO (optional)
-  static void get(std::span<const T>, bofstream*) = delete;
-  static void put(std::span<T>, bifstream*)       = delete;
+  static void get(std::span<T>, bifstream*)       = delete;
+  static void put(std::span<const T>, bofstream*) = delete;
 
   // Text streaming (optional)
   static void parse(std::span<T>, std::istream&) = delete;
@@ -103,3 +103,28 @@ template <typename T>
 concept xml_io_parseable = requires(std::span<T> b, std::istream& is) {
   xml_io_stream<T>::parse(b, is);
 };
+
+//! Explicitly inherit and cast between spans
+template <arts_xml_ioable U, std::derived_from<U> T>
+struct xml_io_stream_inherit : xml_io_stream<U> {
+  static void get(std::span<T> b, bifstream* pbifs)
+    requires(xml_io_binary<U>)
+  {
+    xml_io_stream<U>::get(std::span{reinterpret_cast<U*>(b.data()), b.size()},
+                          pbifs);
+  }
+
+  static void put(std::span<const T> b, bofstream* pbofs)
+    requires(xml_io_binary<U>)
+  {
+    xml_io_stream<U>::put(
+        std::span{reinterpret_cast<const U*>(b.data()), b.size()}, pbofs);
+  }
+
+  static void parse(std::span<T> b, std::istream& is)
+    requires(xml_io_parseable<U>)
+  {
+    xml_io_stream<U>::parse(std::span{reinterpret_cast<U*>(b.data()), b.size()},
+                            is);
+  }
+};

src/core/xml/xml_io_stream_array.h

@@ -153,16 +153,16 @@ struct xml_io_stream<std::array<T, N>> {
   }
   ARTS_METHOD_ERROR_CATCH
 
-  static void put(std::span<const std::array<T, N>> v, bifstream* pbifs)
+  static void put(std::span<const std::array<T, N>> v, bofstream* pbofs)
     requires(xml_io_binary<T>)
   {
-    inner::put(std::span(reinterpret_cast<const T*>(v.data()), N), pbifs);
+    inner::put(std::span(reinterpret_cast<const T*>(v.data()), N), pbofs);
   }
 
-  static void get(std::span<std::array<T, N>> v, bofstream* pbofs)
+  static void get(std::span<std::array<T, N>> v, bifstream* pbifs)
     requires(xml_io_binary<T>)
   {
-    inner::get(std::span(reinterpret_cast<T*>(v.data()), N), pbofs);
+    inner::get(std::span(reinterpret_cast<T*>(v.data()), N), pbifs);
   }
 
   static void parse(std::span<std::array<T, N>> v, std::istream& is)