[Bug c++/52422] New: [C++11][SFINAE] Hard errors with void or arithmetic expressions

[Bug c++/52422] New: [C++11][SFINAE] Hard errors with void or arithmetic expressions

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52422

             Bug #: 52422
           Summary: [C++11][SFINAE] Hard errors with void or arithmetic
                    expressions
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: daniel.kruegler@googlemail.com


gcc 4.7.0 20120225 (experimental) in C++11 mode produces a hard compiler error
during a sfinae-conforming situation involving function-like or pointer-like
expressions:

//---
template<class T>
struct add_rval_ref
{
  typedef T&& type;
};

template<>
struct add_rval_ref<void>
{
  typedef void type;
};

template<class T>
typename add_rval_ref<T>::type create();

template<class T, 
  class = decltype(create<T>()()) // line 17
>
auto f(int) -> char(&)[1];

template<class>
auto f(...) -> char(&)[2];

static_assert(sizeof(f<void>(0)) != 1, "");
//---

"16|error: void value not ignored as it ought to be"

Here some further variations of the theme:

a) Replace line 17 by

class = decltype(*create<T>()) // line 17

b) Replace above test by

//---
template<class T>
struct add_rval_ref
{
  typedef T&& type;
};

template<>
struct add_rval_ref<void>
{
  typedef void type;
};

template<class T>
typename add_rval_ref<T>::type create();

template<class T, class U,
  class = decltype( (create<T>().*create<U>())() ) // line 17
>
auto f(int) -> char(&)[1];

template<class, class>
auto f(...) -> char(&)[2];

static_assert(sizeof(f<void, void>(0)) != 1, ""); // line 24
//---

"17|error: 'create<void>()' cannot be used as a member pointer, since it is of
type 'add_rval_ref<void>::type {aka void}'"

c) Replace in the test (b) line 24 by the following line:

static_assert(sizeof(f<int, int>(0)) != 1, ""); // line 24

"17|error: 'create<int>()' cannot be used as a member pointer, since it is of
type 'int'"

d) Replace line 17 in the test (b) by the following line and use either of
"void, void" or "int, int" as template arguments in line 24:

class = decltype( create<T>().*create<U>() )

"17|error: 'create<void>()' cannot be used as a member pointer, since it is of
type 'add_rval_ref<void>::type {aka void}'"

or

"17|error: 'create<int>()' cannot be used as a member pointer, since it is of
type 'int'"

respectively.

[Bug c++/52422] [C++11][SFINAE] Hard errors with void or arithmetic expressions

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52422

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-02-28
     Ever Confirmed|0                           |1

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-02-28 20:38:06 UTC ---
Ok. Likely simple to fix, I'll have a look.

[Bug c++/52422] [C++11][SFINAE] Hard errors with void or arithmetic expressions

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52422

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |paolo.carlini at oracle dot
                   |gnu.org                     |com
   Target Milestone|---                         |4.8.0

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-02-28 23:18:42 UTC ---
As expected pretty straightforward, essentially matter of propagating complain
to decay_conversion and build_m_component_ref.

[Bug c++/52422] [C++11][SFINAE] Hard errors with void or arithmetic expressions

[paolo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52422

--- Comment #3 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> 2012-04-18 10:21:52 UTC ---
Author: paolo
Date: Wed Apr 18 10:21:43 2012
New Revision: 186565

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186565
Log:
/cp
2012-04-18  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/52422
    * cp-tree.h (build_addr_func, decay_conversion,
    get_member_function_from_ptrfunc,
    build_m_component_ref, convert_member_func_to_ptr):
    Add tsubst_flags_t parameter.
    * typeck.c (cp_default_conversion): Add.
    (decay_conversion, default_conversion,
    get_member_function_from_ptrfunc, convert_member_func_to_ptr):
    Add tsubst_flags_t parameter and use it throughout.
    (cp_build_indirect_ref, cp_build_array_ref,
    cp_build_function_call_vec, convert_arguments, build_x_binary_op,
    cp_build_binary_op, cp_build_unary_op, build_reinterpret_cast_1,
    build_const_cast_1, expand_ptrmemfunc_cst,
    convert_for_initialization): Adjust.
    * init.c (build_vec_init): Adjust.
    * decl.c (grok_reference_init, get_atexit_node): Likewise.
    * rtti.c (build_dynamic_cast_1, tinfo_base_init): Likewise.
    * except.c (build_throw): Likewise.
    * typeck2.c (build_x_arrow): Likewise.
    (build_m_component_ref): Add tsubst_flags_t parameter and
    use it throughout.
    * pt.c (convert_nontype_argument): Adjust.
    * semantics.c (finish_asm_stmt, maybe_add_lambda_conv_op): Likewise.
    * decl2.c (build_offset_ref_call_from_tree): Likewise.
    * call.c (build_addr_func): Add tsubst_flags_t parameter and
    use it throughout.
    (build_call_a, build_conditional_expr_1, build_new_op_1,
    convert_like_real, convert_arg_to_ellipsis, build_over_call,
    build_special_member_call): Adjust.
    * cvt.c (cp_convert_to_pointer, force_rvalue,
    build_expr_type_conversion): Likewise.

/testsuite
2012-04-18  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/52422
    * g++.dg/cpp0x/sfinae33.C: New.
    * g++.dg/cpp0x/sfinae34.C: Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/sfinae33.C
    trunk/gcc/testsuite/g++.dg/cpp0x/sfinae34.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/cvt.c
    trunk/gcc/cp/decl.c
    trunk/gcc/cp/decl2.c
    trunk/gcc/cp/except.c
    trunk/gcc/cp/init.c
    trunk/gcc/cp/pt.c
    trunk/gcc/cp/rtti.c
    trunk/gcc/cp/semantics.c
    trunk/gcc/cp/typeck.c
    trunk/gcc/cp/typeck2.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/52422] [C++11][SFINAE] Hard errors with void or arithmetic expressions

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52422

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
              Alias|jason at gcc dot gnu.org    |

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-18 10:23:56 UTC ---
Fixed for 4.8.0.