[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 Jason Merrill changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #7 from Jason Merrill --- Fixed for 8.2.
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 --- Comment #6 from Jason Merrill --- Author: jason Date: Mon Jun 11 22:02:13 2018 New Revision: 261463 URL: https://gcc.gnu.org/viewcvs?rev=261463=gcc=rev Log: PR c++/85765 - SFINAE and non-type default template arg. * pt.c (type_unification_real): Do full semantic processing if substituting a partial args list replaces all template parms. Added: branches/gcc-8-branch/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg10.C Modified: branches/gcc-8-branch/gcc/cp/ChangeLog branches/gcc-8-branch/gcc/cp/pt.c
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 --- Comment #5 from Jason Merrill --- Author: jason Date: Mon Jun 4 13:22:52 2018 New Revision: 261146 URL: https://gcc.gnu.org/viewcvs?rev=261146=gcc=rev Log: PR c++/85765 - SFINAE and non-type default template arg. * pt.c (type_unification_real): Do full semantic processing if substituting a partial args list replaces all template parms. Added: trunk/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg10.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/pt.c
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 Jason Merrill changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |jason at gcc dot gnu.org
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 Richard Biener changed: What|Removed |Added Target Milestone|--- |8.2
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765
--- Comment #4 from Casey Carter ---
Narrowing the error down:
template())), decltype(*U(),0) =
0>
U g(T& t, long) { return begin(t); } // #1
prog.cc: In instantiation of 'U g(T&, long int) [with T = volatile il; U =
int*; decltype (((* U()), 0)) = 0]'
The "U = int*" is particularly damning here: it tells us the compiler
substituted `volatile il` into `decltype(begin(declval()))` to get
`begin(declval())`. `int* begin(il);` is a *candidate* for
overload resolution - it has the right name and number of parameters - and it's
a viable candidate because the ICS from lvalue `volatile il` to `il` is an
identity conversion per [over.best.ics]/6: "Any difference in top-level
cv-qualification is subsumed by the initialization itself and does not
constitute a conversion. ... When the parameter has a class type and the
argument expression has the same type, the implicit conversion sequence is an
identity conversion." Since it's the *only* viable function, it is
unambiguously the *best* viable function.
So the only question here is why the compiler omits the final analysis that
would determine that initialization of an `il` from a `volatile il&` is
ill-formed - making the entire function call expression ill-formed - but only
does so when the following `decltype(*U(),0) = 0` is present in the template
parameter list.
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 --- Comment #3 from Jonathan Wakely --- But that patch is also on gcc-7-branch and the testcases work with gcc version 7.3.1 20180419, so there must have been something latent on trunk that was revealed by that change.
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 --- Comment #2 from Jonathan Wakely --- Those volatile overloads in std::bind are a constant source of problems (most recently PR 85118). The regression happened with r258407: PR c++/84785 - ICE with alias template and default targs. * pt.c (type_unification_real): Set processing_template_decl if saw_undeduced == 1.
[Bug c++/85765] [8/9 Regression] Missing SFINAE in default template argument
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85765 Jonathan Wakely changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2018-05-13 Known to work||7.3.1 Summary|Missing SFINAE in default |[8/9 Regression] Missing |template argument |SFINAE in default template ||argument Ever confirmed|0 |1 Known to fail||8.1.0, 9.0
