https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120644
--- Comment #13 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:98fd493db6216cff11142c9dc477a3ff8e4269fa commit r16-1759-g98fd493db6216cff11142c9dc477a3ff8e4269fa Author: Nathaniel Shead <nathanielosh...@gmail.com> Date: Mon Jun 23 22:24:22 2025 +1000 c++/modules: Ensure type of partial spec VAR_DECL is consistent with its template [PR120644] We were erroring because the TEMPLATE_DECL of the existing partial specialisation has an undeduced return type, but the imported declaration did not. The root cause is similar to what was fixed in r13-2744-g4fac53d6522189, where modules streaming code assumes that a TEMPLATE_DECL and its DECL_TEMPLATE_RESULT will always have the same TREE_TYPE. That commit fixed the issue by ensuring that when the type of a variable is deduced the TEMPLATE_DECL is updated as well, but missed handling partial specialisations. This patch ensures that the same adjustment is made there as well. PR c++/120644 gcc/cp/ChangeLog: * decl.cc (cp_finish_decl): Also propagate type to partial templates. * module.cc (trees_out::decl_value): Add assertion that the TREE_TYPE of a streamed template decl matches its inner. (trees_in::is_matching_decl): Clarify function return type deduction should only occur for non-TEMPLATE_DECL. * pt.cc (template_for_substitution): Handle partial specs. gcc/testsuite/ChangeLog: * g++.dg/modules/auto-7.h: New test. * g++.dg/modules/auto-7_a.H: New test. * g++.dg/modules/auto-7_b.C: New test. Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com> Reviewed-by: Jason Merrill <ja...@redhat.com> Reviewed-by: Patrick Palka <ppa...@redhat.com>
