https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105931
--- Comment #2 from Sam James <sam at gentoo dot org> ---
Interesting!
The minimised version of this is:
```
$ cat test.cxx
template <unsigned ElemSize> decltype(0 % ElemSize == 0)
```
```
$ g++ -o test.o -c -O2 test.cxx
new.cxx:1:52: internal compiler error: unexpected expression ‘ElemSize’ of kind
template_parm_index
1 | template <unsigned ElemSize> decltype(0 % ElemSize == 0)
| ~~~~~~~~~~~~~^~~~
0x6def33 cxx_eval_constant_expression
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:7587
0x6df310 cxx_eval_outermost_constant_expr
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:7824
0x6e154d potential_constant_expression_1
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:9274
0x6e1ef5 potential_constant_expression_1(tree_node*, bool, bool, bool, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:9550
0x6e1ef5 is_constant_expression(tree_node*)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:9607
0x6e1ef5 is_nondependent_constant_expression(tree_node*)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:9644
0x6e2b04 maybe_constant_value(tree_node*, tree_node*, bool)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/constexpr.cc:8071
0x74e35b fold_for_warn(tree_node*)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/expr.cc:416
0x8c9552 shorten_compare(unsigned int, tree_node**, tree_node**, tree_node**,
tree_code*)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/c-family/c-common.cc:3237
0x889d72 cp_build_binary_op(op_location_t const&, tree_code, tree_node*,
tree_node*, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/typeck.cc:6158
0x6bd96c build_new_op(op_location_t const&, tree_code, int, tree_node*,
tree_node*, tree_node*, tree_node*, tree_node**, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/call.cc:6935
0x88041b build_x_binary_op(op_location_t const&, tree_code, tree_node*,
tree_code, tree_node*, tree_code, tree_node*, tree_node**, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/typeck.cc:4563
0x81f7e7 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/pt.cc:20369
0x82337a instantiate_non_dependent_expr_internal(tree_node*, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/pt.cc:6367
0x82337a instantiate_non_dependent_expr_sfinae(tree_node*, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/pt.cc:6388
0x85eec3 finish_decltype_type(tree_node*, bool, int)
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/semantics.cc:11255
0x7e183f cp_parser_decltype
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/parser.cc:16540
0x7fa3e7 cp_parser_simple_type_specifier
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/parser.cc:19647
0x7d6cbd cp_parser_type_specifier
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/parser.cc:19424
0x7d7d81 cp_parser_decl_specifier_seq
/usr/src/debug/sys-devel/gcc-12.1.1_p20220611/gcc-12-20220611/gcc/cp/parser.cc:15905
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://bugs.gentoo.org/> for instructions.
```
This minimised version is only slightly different to the one in the original
bug.
