[Bug c++/115198] Class template argument deduction fails for copy ctor when used with an alias template if the aliased class template has explicitly defaulted copy ctor

[s.murthy at outlook dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115198

--- Comment #3 from Sean Murthy <s.murthy at outlook dot com> ---
For everyone's convenience, attaching here the compiler's error message. The
notes the compiler attached to the error indicate the issue might be with a
possibly erroneous/superfluous deduction guide the compiler itself generates. 

At least that is my speculation based on the first note attached to the error
message.


<source>:57:13: error: class template argument deduction failed:
   57 |     A1 a1(c1);
      |             ^
<source>:57:13: error: call of overloaded 'C1(C1<false, int>&)' is ambiguous
<source>:5:7: note: candidate: 'C1(C1<false, T>)-> C1<false, T> [with T = int]'
    5 | class C1
      |       ^~
<source>:9:5: note: candidate: 'C1(const C1<false, T>&)-> C1<false, T> [with T
= int]'
    9 |     C1(const C1& other) = default;