[PATCH] D128745: [c++] implements DR692, DR1395 and tentatively DR1432, about partial ordering of variadic template partial specialization or function template

[Alex Brachet via Phabricator via cfe-commits]

abrachet added subscribers: mcgrathr, abrachet.
abrachet added a comment.

This is breaking us.

  template <typename T, typename... Ts> struct S; // #1
  
  template <typename T> struct S<T> {}; // #2

The following compiled before but is now broken, (we use `-fclang-abi-compat=13.0`). We get a warning from `-Winvalid-partial-specialization`

This change _does_ make https://eel.is/c++draft/temp.func.order#example-5 work, ie for function overload resolution but regresses the type deduction example above.

There seem to be examples in the standard that suggest #2 is more specialized. @mcgrathr found https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1432 and https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1395 among others. WDYT?


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