From cafcfcb5840b62d9fc80c12192189351e995a4f2 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Wed, 20 Jan 2021 09:44:33 -0500 Subject: [PATCH] c++: Fix tsubsting CLASS_PLACEHOLDER_TEMPLATE [PR95434] Here, during partial instantiation of the generic lambda, we do tsubst_copy on the CLASS_PLACEHOLDER_TEMPLATE for U{0} which yields a (level-lowered) TEMPLATE_TEMPLATE_PARM rather than the corresponding TEMPLATE_DECL. This later confuses do_class_deduction which expects that a CLASS_PLACEHOLDER_TEMPLATE is always a TEMPLATE_DECL. gcc/cp/ChangeLog: PR c++/95434 * pt.c (tsubst) : If tsubsting CLASS_PLACEHOLDER_TEMPLATE yields a TEMPLATE_TEMPLATE_PARM, adjust to its TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL. gcc/testsuite/ChangeLog: PR c++/95434 * g++.dg/cpp2a/lambda-generic9.C: New test. --- gcc/cp/pt.c | 2 ++ gcc/testsuite/g++.dg/cpp2a/lambda-generic9.C | 9 +++++++++ 2 files changed, 11 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-generic9.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index bcf4c6efe11..373f8279604 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -15688,6 +15688,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl) else if (tree pl = CLASS_PLACEHOLDER_TEMPLATE (t)) { pl = tsubst_copy (pl, args, complain, in_decl); + if (TREE_CODE (pl) == TEMPLATE_TEMPLATE_PARM) + pl = TEMPLATE_TEMPLATE_PARM_TEMPLATE_DECL (pl); CLASS_PLACEHOLDER_TEMPLATE (r) = pl; } } diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-generic9.C b/gcc/testsuite/g++.dg/cpp2a/lambda-generic9.C new file mode 100644 index 00000000000..20ceb370c38 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-generic9.C @@ -0,0 +1,9 @@ +// PR c++/95434 +// { dg-do compile { target c++20 } } + +template +void f() { + []