https://gcc.gnu.org/g:a423c594989e10be8dabe3d7175dfda3aac49d20
commit r15-10789-ga423c594989e10be8dabe3d7175dfda3aac49d20 Author: Patrick Palka <[email protected]> Date: Thu Feb 5 09:13:42 2026 -0500 c++: cv-qualified pack index propagation [PR122169] Since type pack indexes can be cv-qualified, we need to propagate their qualifiers when substituting them. PR c++/122169 gcc/cp/ChangeLog: * pt.cc (tsubst_pack_index): Propagate cv-qualifiers of PACK_INDEX_TYPE. gcc/testsuite/ChangeLog: * g++.dg/cpp26/pack-indexing19.C: New test. Reviewed-by: Marek Polacek <[email protected]> Reviewed-by: Jason Merrill <[email protected]> (cherry picked from commit 6385a3582c0b6b30479bc68f7d2b74e327ec44d7) Diff: --- gcc/cp/pt.cc | 9 ++++++-- gcc/testsuite/g++.dg/cpp26/pack-indexing19.C | 32 ++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 2 deletions(-) diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 05018a98dac8..883f7bbac7c5 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -14141,10 +14141,15 @@ tsubst_pack_index (tree t, tree args, tsubst_flags_t complain, tree in_decl) tree index = tsubst_expr (PACK_INDEX_INDEX (t), args, complain, in_decl); const bool parenthesized_p = (TREE_CODE (t) == PACK_INDEX_EXPR && PACK_INDEX_PARENTHESIZED_P (t)); + tree r; if (!value_dependent_expression_p (index) && TREE_CODE (pack) == TREE_VEC) - return pack_index_element (index, pack, parenthesized_p, complain); + r = pack_index_element (index, pack, parenthesized_p, complain); else - return make_pack_index (pack, index); + r = make_pack_index (pack, index); + if (TREE_CODE (t) == PACK_INDEX_TYPE) + r = cp_build_qualified_type (r, cp_type_quals (t) | cp_type_quals (r), + complain | tf_ignore_bad_quals); + return r; } /* Make an argument pack out of the TREE_VEC VEC. */ diff --git a/gcc/testsuite/g++.dg/cpp26/pack-indexing19.C b/gcc/testsuite/g++.dg/cpp26/pack-indexing19.C new file mode 100644 index 000000000000..cd9370579080 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp26/pack-indexing19.C @@ -0,0 +1,32 @@ +// PR c++/122169 +// { dg-do compile { target c++26 } } + +template<class T, class U> +concept same_as = __is_same(T, U); + +template<class... Ts> +void f() { + using T = Ts...[0]; + static_assert(same_as<const T, const int>); + + []<int I>() { + using U = Ts...[I]; + static_assert(same_as<const U, const int>); + }.template operator()<0>(); +} + +template void f<int>(); + + +template<class... Ts> +void g() { + using T = Ts...[0]; + static_assert(same_as<const T, const volatile int>); + + []<int I>() { + using U = Ts...[I]; + static_assert(same_as<const U, const volatile int>); + }.template operator()<0>(); +} + +template void g<volatile int>();
