raise priority of optional and variant above sequence

Author: grisumbras

CHANGELOG.adoc

@@ -8,6 +8,7 @@ include::doc/pages/definitions.adoc[]
 == Boost 1.89.0
 
 .API Changes
+* {issue}1050[#1050] Optionals that are ranges are categorised as optionals.
 * {issue}1086[#1086] Described class support is enabled for types with bases.
 
 == Boost 1.87.0

doc/pages/conversion/overview.adoc

@@ -70,6 +70,20 @@ a| The result is a number equal to input and has the type
 |The result is a <<ref_string>>.
 |The result is constructed from a <<ref_string_view>>.
 
+|Type satisfying <<ref_is_variant_like>>.
+|`std::variant` and similar types, e.g. `boost::variant2::variant`.
+|The result is equal to the result of conversion of the active variant
+    alternative.
+|The result holds the first alternative for which a conversion succeeds.
+
+|Type satisfying <<ref_is_optional_like>>
+|
+|If the input value is empty, the result is a `null`. Otherwise it is
+    equivalent to conversion of the object stored inside of optional.
+|The result is default constructed if the input value is `null`. Otherwise the
+    result is constructed from the result of conversion of the input to the
+    type stored in optional.
+
 |Type satisfying <<ref_is_map_like>>.
 |A one-to-one mapping (e.g. `std::map`) with string-like keys.
 |The result is an <<ref_object>>.
@@ -99,20 +113,6 @@ a| The result is a number equal to input and has the type
 |The result is the described enumerator, corresponding to the input
     <<ref_string>>.
 
-|Type satisfying <<ref_is_variant_like>>.
-|`std::variant` and similar types, e.g. `boost::variant2::variant`.
-|The result is equal to the result of conversion of the active variant
-    alternative.
-|The result holds the first alternative for which a conversion succeeds.
-
-|Type satisfying <<ref_is_optional_like>>
-|
-|If the input value is empty, the result is a `null`. Otherwise it is
-    equivalent to conversion of the object stored inside of optional.
-|The result is default constructed if the input value is `null`. Otherwise the
-    result is constructed from the result of conversion of the input to the
-    type stored in optional.
-
 |Type satisfying <<ref_is_path_like>>.
 |`std::filesystem::path` and similar types, e.g. `boost::filesystem::path`.
 |The result is equal to the result of `path::generic_string`.

include/boost/json/impl/conversion.hpp

@@ -363,13 +363,13 @@ using generic_conversion_category = mp11::mp_cond<
     std::is_floating_point<T>, floating_point_conversion_tag,
     is_null_like<T>,           null_like_conversion_tag,
     is_string_like<T>,         string_like_conversion_tag,
+    is_variant_like<T>,        variant_conversion_tag,
+    is_optional_like<T>,       optional_conversion_tag,
     is_map_like<T>,            map_like_conversion_tag,
     is_sequence_like<T>,       sequence_conversion_tag,
     is_tuple_like<T>,          tuple_conversion_tag,
     is_described_class<T>,     described_class_conversion_tag,
     is_described_enum<T>,      described_enum_conversion_tag,
-    is_variant_like<T>,        variant_conversion_tag,
-    is_optional_like<T>,       optional_conversion_tag,
     is_path_like<T>,           path_conversion_tag,
     // failed to find a suitable implementation
     mp11::mp_true,             no_conversion_tag>;