[Bug c++/84075] Template parameter not resolved: invalid application of ‘sizeof’ to incomplete type ‘boost::serialization::U’

[schmitt.marc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84075

--- Comment #7 from Marc Schmitt <schmitt.marc at gmail dot com> ---
Created attachment 45619
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45619&action=edit
Preprocessed test case with eigen-only dependency