From 93ec7bf22530610ef697fd3a64a28bebd589c790 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Tue, 26 Apr 2022 00:19:40 -0400 Subject: [PATCH] c++: pack init-capture of unresolved overload [PR102629] Here we were failing to diagnose that the initializer for the capture pack is an unresolved overload. It turns out that the reason we didn't recognize the deduction failure in do_auto_deduction was that the individual 'auto' in the expansion of the capture pack was still marked as a parameter pack, so we were deducing it to an empty pack instead of failing. PR c++/102629 gcc/cp/ChangeLog: * pt.c (gen_elem_of_pack_expansion_instantiation): Clear TEMPLATE_TYPE_PARAMETER_PACK on auto. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/lambda-pack-init7.C: New test. --- gcc/cp/pt.c | 8 +++++++- gcc/testsuite/g++.dg/cpp2a/lambda-pack-init7.C | 18 ++++++++++++++++++ 2 files changed, 25 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-pack-init7.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 7ce9ac234f8c..fb214e8f8c93 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -12435,7 +12435,13 @@ gen_elem_of_pack_expansion_instantiation (tree pattern, t = tsubst_expr (pattern, args, complain, in_decl, /*integral_constant_expression_p=*/false); else - t = tsubst (pattern, args, complain, in_decl); + { + t = tsubst (pattern, args, complain, in_decl); + if (is_auto (t) && !ith_elem_is_expansion) + /* When expanding the fake auto... pack expansion from add_capture, we + need to mark that the expansion is no longer a pack. */ + TEMPLATE_TYPE_PARAMETER_PACK (t) = false; + } /* If the Ith argument pack element is a pack expansion, then the Ith element resulting from the substituting is going to diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-pack-init7.C b/gcc/testsuite/g++.dg/cpp2a/lambda-pack-init7.C new file mode 100644 index 000000000000..f3c3899e97a1 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-pack-init7.C @@ -0,0 +1,18 @@ +// PR c++/102629 +// { dg-do compile { target c++20 } } + +template T&& forward(T&); +template T&& forward(T&&); + +struct S {}; + +template +void foo(Args&&... args) { + [...args = forward /*(args)*/] { // { dg-error "" } + [](auto...) { } (forward(args)...); + }; +} + +void bar( ) { + foo(S{}); +} -- 2.47.2