[Bug c++/104548] New: parser rejects alias template id of lambda in unevaluated-context and accepts when no alias is used

[Bug c++/104548] New: parser rejects alias template id of lambda in unevaluated-context and accepts when no alias is used

[nickhuang99 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104548

            Bug ID: 104548
           Summary: parser rejects alias template id of lambda in
                    unevaluated-context and accepts when no alias is used
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nickhuang99 at hotmail dot com
  Target Milestone: ---

I feel this issue is related with PR104537 and PR104358 
Parser rejects following code with alias of template id:
https://www.godbolt.org/z/eec3T5ebj


template<typename T>
using FunPtr=decltype(+[](T t)->T{return t+1;});

template<typename T>
auto foo(T t, FunPtr<T> funPtr){
        return funPtr(t);
}

void test(){
    // parser rejects when using alias
        foo<int>(5, [](int t){return t+1;});
}
<source>:14:21: error: invalid user-defined conversion from
'test()::<lambda(int)>' to 'int' [-fpermissive]
   14 |         foo<int>(5, [](int t){return t+1;});
      |                     ^~~~~~~~~~~~~~~~~~~~~~



And accepts exact same code when NO alias is used:

template<typename T>
auto foo(T t, decltype(+[](T t)->T{return t+1;}) lam){
        return lam(t);
}
void test(){
    // parser accepts when no alias is used
        foo<int>(5, [](int t){return t+1;});
}

[Bug c++/104548] parser rejects alias template id of lambda in unevaluated-context and accepts when no alias is used

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104548

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=90533
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-02-16
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, very much related to PR 90533.

[Bug c++/104548] parser rejects alias template id of lambda in unevaluated-context and accepts when no alias is used

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104548

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |14.0
                 CC|                            |ppalka at gcc dot gnu.org
             Status|NEW                         |RESOLVED

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 14 by the PR114393 fixes.