c++: Implement part of CWG3044

The following patch implements part of CWG3044 resolution.
Small part of it has been implemented already earlier (using ptrdiff_t
as the type of i rather than leaving that unspecified), part of it
can't be implemented until constexpr references are supported
(removal of static keywords), but the final CWG3044 resolution
wording states that it is begin + decltype(begin - begin){i}
rather than just begin + i.

The following patch implements that.

It broke a bunch of tests because I haven't implemented operator -
for those. fixed that too (plus added a testcase expected to fail
now with operator - not implemented).

2026-01-28  Jakub Jelinek  <jakub@redhat.com>

	* pt.cc (finish_expansion_stmt): Implement part of CWG3044.
	Add to begin decltype(begin - begin){i} with std::ptrdiff_t
	i instead of just i.

	* g++.dg/cpp26/expansion-stmt1.C (A::operator -, C::operator -): New.
	* g++.dg/cpp26/expansion-stmt2.C (A::operator -, C::operator -): New.
	* g++.dg/cpp26/expansion-stmt3.C (A::operator -, C::operator -): New.
	* g++.dg/cpp26/expansion-stmt18.C  (A::operator -): New.
	* g++.dg/cpp26/expansion-stmt25.C: New test.

0 files changed, 0 insertions, 0 deletions