[Bug c++/95878] New: ICE when compiling code that mixes an empty class, [[no_unique_address]] and non-trivial default and copy constructors

[boris.staletic at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95878

            Bug ID: 95878
           Summary: ICE when compiling code that mixes an empty class,
                    [[no_unique_address]] and non-trivial default and copy
                    constructors
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: boris.staletic at gmail dot com
  Target Milestone: ---

Hello,

first, apologies for a bad title. I was unsure how to make it more descriptive.

My repro case looks suspiciously like
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90432

However, the bug in 90432 has been fixed in 10.1 and 9.3. I've encountered a
similar code that still triggers an ICE. Just like 90432, gcc 8 works fine.
I've encountered a non-minimal version of this bug while working on the
nanorange library.

The minimal code that causes ICE:

struct istream_iterator {
        istream_iterator() {}
        istream_iterator(const istream_iterator&) {}
};

istream_iterator next(istream_iterator&& bound) {
        return static_cast<istream_iterator>(bound);
}

struct copy_result {
        [[no_unique_address]] istream_iterator in;
};

int main() {
        copy_result result{next(istream_iterator{})};
}


during RTL pass: expand
<source>: In function 'int main()':
<source>:15:45: internal compiler error: in assign_temp, at function.c:982
   15 |  copy_result result{next(istream_iterator{})};
      |                                             ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1