Hi! The r13-2965-g73d9b0e5947e16 change changed the line touched in this patch from return RECUR (tmp, want_rval); to return RECUR (DECL_INITIAL (tmp), want_rval); This is on DECL_EXPR handling code, where tmp can be lots of different trees and DECL_INITIAL unfortunately also means different things on different trees. It is the initializer on VAR_DECL, DECL_ARG_TYPE on PARM_DECLs (though those are unlikely to have DECL_EXPRs), for FUNCTION_DECLs the body, ..., USING_DECL_DECLS on USING_DECLs and DECL_FRIENDLIST on TYPE_DECLs.
The testcase below ICEs because we have a DECL_EXPR for TYPE_DECL which has non-NULL DECL_FRIENDLIST and we certainly can't recurse on the friend list. The following patch is a conditional partial reversion of r13-2965, it will recurse on DECL_INITIAL only for VAR_DECLs and for anything else keep previous behavior. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2023-02-22 Jakub Jelinek <ja...@redhat.com> PR c++/108606 * constexpr.cc (potential_constant_expression_1) <case DECL_EXPR>: Only recurse on DECL_INITIAL (tmp) if tmp is a VAR_DECL, otherwise recurse on tmp. * g++.dg/cpp1y/pr108606.C: New test. --- gcc/cp/constexpr.cc.jj 2023-02-20 22:06:36.000000000 +0100 +++ gcc/cp/constexpr.cc 2023-02-21 14:40:39.366910531 +0100 @@ -9699,7 +9699,9 @@ potential_constant_expression_1 (tree t, (tmp, /*constexpr_context_p=*/true, flags)) return false; } - return RECUR (DECL_INITIAL (tmp), want_rval); + if (VAR_P (tmp)) + return RECUR (DECL_INITIAL (tmp), want_rval); + return RECUR (tmp, want_rval); case TRY_FINALLY_EXPR: return (RECUR (TREE_OPERAND (t, 0), want_rval) --- gcc/testsuite/g++.dg/cpp1y/pr108606.C.jj 2023-02-21 14:44:41.292380973 +0100 +++ gcc/testsuite/g++.dg/cpp1y/pr108606.C 2023-02-21 14:44:15.622755459 +0100 @@ -0,0 +1,11 @@ +// PR c++/108606 +// { dg-do compile { target c++14 } } + +template <typename T> +void bar (T) {} + +void +foo () +{ + bar ([&] (auto x) { class C { friend void baz (); }; }); +} Jakub