🩹 Relax message_base range constructor constraints

Accept a range of T as a constructor argument for `message_base`, where T is
convertible to `std::uint32_t`.

This unblocks issue #315.

TODO: properly relax the value type of `message_base`'s storage, as discussed
with @mjcaisse-intel.

include/msg/message.hpp

@@ -19,6 +19,13 @@ concept range = requires(T &t) {
  std::begin(t);
  std::end(t);
  };
+
+template <typename T>
+using iterator_t = decltype(std::begin(std::declval<T &>()));
+
+template <typename T, typename V>
+concept convertible_range_of =
+ range<T> and std::convertible_to<std::iter_value_t<iterator_t<T>>, V>;
 } // namespace detail
 
 template <std::uint32_t MaxNumDWords>
@@ -96,8 +103,8 @@ struct message_base : public message_data<MaxNumDWords> {
  (set(FieldsT{}), ...);
  }
 
- template <detail::range R> explicit constexpr message_base(R const &r) {
-  static_assert(std::is_same_v<typename R::value_type, std::uint32_t>);
+ template <detail::convertible_range_of<std::uint32_t> R>
+ explicit constexpr message_base(R const &r) {
  resize_and_overwrite(*this, [&](std::uint32_t *dest,
  std::size_t max_size) {
  std::copy_n(std::begin(r), std::min(std::size(r), max_size), dest);

test/msg/message.cpp

@@ -75,6 +75,18 @@ TEST_CASE("TestMessageDataPartialRangeConstruction", "[message]") {
  CHECK(0x0042d00d == msg[1]);
 }
 
+TEST_CASE("TestMessageDataConvertibleRangeConstruction", "[message]") {
+ TestMsg msg{std::array<std::uint16_t, 2>{0xba11, 0xd00d}};
+
+ CHECK(0xba11 == msg.get<TestField1>());
+ CHECK(0x0 == msg.get<TestField2>());
+ CHECK(0xd00d == msg.get<TestField3>());
+
+ REQUIRE(msg.size() == 2u);
+ CHECK(0x0000ba11 == msg[0]);
+ CHECK(0x0000d00d == msg[1]);
+}
+
 TEST_CASE("EqualToMatcher", "[message]") {
  TestMsg msg{std::array<uint32_t, 2>{0x8000ba11, 0x0042d00d}};