Merge 2025-06 LWG Motion 16

P3748R0 Inspecting exception_ptr should be constexpr

Author: tkoeppe

source/support.tex

@@ -3865,7 +3865,7 @@
   constexpr exception_ptr current_exception() noexcept;
   [[noreturn]] constexpr void rethrow_exception(exception_ptr p);
   template<class E> constexpr exception_ptr make_exception_ptr(E e) noexcept;
-  template<class E> const E* exception_ptr_cast(const exception_ptr& p) noexcept;
+  template<class E> constexpr const E* exception_ptr_cast(const exception_ptr& p) noexcept;
   template<class E> void exception_ptr_cast(const exception_ptr&&) = delete;
 
   template<class T> [[noreturn]] constexpr void throw_with_nested(T&& t);
@@ -4246,7 +4246,7 @@
 
 \indexlibraryglobal{exception_ptr_cast}%
 \begin{itemdecl}
-template<class E> const E* exception_ptr_cast(const exception_ptr& p) noexcept;
+template<class E> constexpr const E* exception_ptr_cast(const exception_ptr& p) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}