LWG3541 indirectly_readable_traits should be SFINAE-friendly for all types

Author: jensmaurer

source/iterators.tex

@@ -773,6 +773,10 @@
 struct indirectly_readable_traits<T>
   : @\placeholder{cond-value-type}@<typename T::element_type> { };
 
+template<@\exposconcept{has-member-value-type}@ T>
+  requires @\exposconcept{has-member-element-type}@<T>
+struct indirectly_readable_traits<T> { };
+
 template<@\exposconcept{has-member-value-type}@ T>
   requires @\exposconcept{has-member-element-type}@<T> &&
            @\libconcept{same_as}@<remove_cv_t<typename T::element_type>, remove_cv_t<typename T::value_type>>