[Bug c++/90448] [8/9 Regression] decltype-based lambda parameter pack is rejected

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90448

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The testcase ICEs on powerpc64-linux with -m32:
lambda-generic-variadic20.C:5:12: internal compiler error: in
expand_expr_addr_expr_1, at expr.c:8075
    5 |   auto L = [](auto ... a) {
      |            ^~~~~~~~~~~~~~~~
    6 |     auto M = [](decltype(a) ... b) -> void {
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    7 |     };
      |     ~~      
    8 |     return M;
      |     ~~~~~~~~~
    9 |   };
      |   ~         
0xd9422a expand_expr_addr_expr_1
        ../../gcc/expr.c:8075
0xd94817 expand_expr_addr_expr
        ../../gcc/expr.c:8188
0xda0a68 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        ../../gcc/expr.c:11363
0xd94bcd expand_expr_real(tree_node*, rtx_def*, machine_mode, expand_modifier,
rtx_def**, bool)
        ../../gcc/expr.c:8358
0xc050ff expand_normal
        ../../gcc/expr.h:288
0xc0686f precompute_register_parameters
        ../../gcc/calls.c:982
0xc0fc27 expand_call(tree_node*, rtx_def*, int)
        ../../gcc/calls.c:4398
0xd9f9cb expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        ../../gcc/expr.c:11135
0xd94bcd expand_expr_real(tree_node*, rtx_def*, machine_mode, expand_modifier,
rtx_def**, bool)
        ../../gcc/expr.c:8358
0xd8cef5 store_expr(tree_node*, rtx_def*, int, bool, bool)
        ../../gcc/expr.c:5752
0xd8c194 expand_assignment(tree_node*, tree_node*, bool)
        ../../gcc/expr.c:5514
0xc2860b expand_call_stmt
        ../../gcc/cfgexpand.c:2701
0xc2b6b5 expand_gimple_stmt_1
        ../../gcc/cfgexpand.c:3682
0xc2bc49 expand_gimple_stmt
        ../../gcc/cfgexpand.c:3847
0xc32a16 expand_gimple_basic_block
        ../../gcc/cfgexpand.c:5887
0xc3401a execute
        ../../gcc/cfgexpand.c:6542
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