https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119844
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Nathaniel Shead <nsh...@gcc.gnu.org>: https://gcc.gnu.org/g:10418a6cbd34e0a4081f6dcdf8c36a9592aaf318 commit r16-3433-g10418a6cbd34e0a4081f6dcdf8c36a9592aaf318 Author: Nathaniel Shead <nathanielosh...@gmail.com> Date: Wed Aug 27 22:24:43 2025 +1000 c++/modules: Add explanatory note for incomplete types with definition in different module [PR119844] The confusion in the PR arose because the definition of 'User' in a separate named module did not provide an implementation for the forward-declaration in the global module. This seems likely to be a common mistake while people are transitioning to modules, so this patch adds an explanatory note. While I was looking at this I also noticed that the existing handling of partial specialisations for this note was wrong (we pointed at the primary template declaration rather than the relevant partial spec), so this patch fixes that up, and also gives a more precise error message for using a template other than by self-reference while it's being defined. PR c++/119844 gcc/cp/ChangeLog: * typeck2.cc (cxx_incomplete_type_inform): Add explanation when a similar type is complete but attached to a different module. Also fix handling of partial specs and templates. gcc/testsuite/ChangeLog: * g++.dg/modules/pr119844_a.C: New test. * g++.dg/modules/pr119844_b.C: New test. Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
