https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94583
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
We crash on the assert in get_defaulted_eh_spec:
2417 if (sfk == sfk_comparison)
2418 {
2419 /* We're in synthesize_method. Start with NULL_TREE,
build_comparison_op
2420 will adjust as needed. */
2421 gcc_assert (decl == current_function_decl);
2422 return NULL_TREE;
2423 }
https://eel.is/c++draft/class.compare#default-5 seems to be relevant:
If the three-way comparison operator function has no noexcept-specifier, the
implicitly-declared == operator function has an implicit exception
specification ([except.spec]) that may differ from the implicit exception
specification of the three-way comparison operator function.
[except.spec]/11 The exception specification for a comparison operator function
([over.binary]) without a noexcept-specifier that is defaulted on its first
declaration is potentially-throwing if and only if any expression in the
implicit definition is potentially-throwing.
The implicit operator== has noexcept_deferred_spec, and unfortunately
synthesized_method_walk doesn't seem to work on sfk_comparison.
