[Bug c++/64970] New: Hard error instead of SFINAE for expression in nested template alias

[Bug c++/64970] New: Hard error instead of SFINAE for expression in nested template alias

[eric.niebler at gmail dot com]

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64970

            Bug ID: 64970
           Summary: Hard error instead of SFINAE for expression in nested
                    template alias
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eric.niebler at gmail dot com

The following code gives a hard error. I believe it should not.


template<typename T>
T && declval();

template<typename T>
struct void_ { using type = void; };

template<typename T>
using void_t = typename void_<T>::type;

template<class A, class B>
struct Outer
{
    template<class C, class D>
    using Inner = decltype(true ? declval<C>() : declval<D>());
};

template<class A, class B, typename Enable = void>
struct S
{};

template<class A, class B>
struct S<A, B, void_t<typename Outer<A, B>::template Inner<A, B>>>
{};

struct A{};
struct B{};
int main()
{
    S<A, B> s;
}


The error:

test.cpp: In substitution of ‘template<class A, class B> template<class C,
class D> using Inner = decltype ((true ?  declval<C>() : declval<D>())) [with C
= A; D = B; A = A; B = B]’:
test.cpp:32:13:   required from here
test.cpp:15:33: error: no match for ternary ‘operator?:’ (operand types are
‘bool’, ‘A’, and ‘B’)
     using Inner = decltype(true ? declval<C>() : declval<D>());
                                 ^
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Subject: [Bug preprocessor/64965] __FILE__ doesn't work if the filename contains newline
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd965

--- Comment #1 from Rasmus Villemoes <rv at rasmusvillemoes dot dk> ---
Created attachment 34693
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id4693&actioníit
Make __FILE__ work for filenames containing newline

[Bug c++/64970] Hard error instead of SFINAE for expression in nested template alias

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64970

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-02-08
                 CC|                            |ville.voutilainen at gmail dot com
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.2, 4.9.1, 5.0

--- Comment #1 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Clang accepts the code without a hard error.

[Bug c++/64970] Hard error instead of SFINAE for expression in nested template alias

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64970

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Mine.

[Bug c++/64970] Hard error instead of SFINAE for expression in nested template alias

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64970

--- Comment #3 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Fri Feb 13 14:54:48 2015
New Revision: 220684

URL: https://gcc.gnu.org/viewcvs?rev=220684&root=gcc&view=rev
Log:
/cp
2015-02-13  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/64970
    * decl.c (make_typename_type): Pass tsubst_flags_t argument
    to lookup_template_class.

/testsuite
2015-02-13  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/64970
    * g++.dg/cpp0x/sfinae55.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/sfinae55.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/decl.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/64970] Hard error instead of SFINAE for expression in nested template alias

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64970

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
           Assignee|paolo.carlini at oracle dot com    |unassigned at gcc dot gnu.org
   Target Milestone|---                         |5.0
      Known to fail|5.0                         |

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed for 5.0.