[Bug c++/83644] New: ICE using type alias from recursive decltype in noexcept or return type

[gccbugbjorn at fahller dot se]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83644

            Bug ID: 83644
           Summary: ICE using type alias from recursive decltype in
                    noexcept or return type
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gccbugbjorn at fahller dot se
  Target Milestone: ---

Created attachment 42996
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42996&action=edit
Source of failing program

The program (attached, and on https://godbolt.org/g/N6nHKk) ICEs as follows:

bf@rahonavis /tmp> g++ -std=c++17 t.cpp
t.cpp: In instantiation of 'compose(F&&, Fs&& ...)::<lambda(auto:1&& ...)>
[with auto:1 = {int}; F = f()::<lambda(auto:2)>; Fs =
{f()::<lambda(auto:3)>}]':
t.cpp:32:72:   required from here
t.cpp:20:39: internal compiler error: Segmentation fault
     using tail_type = decltype(compose(std::forward<Fs>(fs)...));
                                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions.


To make it not fail, use the macro instead of the type alias, or comment out
both the trailing return type and the noexcept.