[Bug c++/126870] New: ICE segfault on reference initialized to extracted reflection of itself

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126870

            Bug ID: 126870
           Summary: ICE segfault on reference initialized to extracted
                    reflection of itself
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eczbek.void at gmail dot com
  Target Milestone: ---

https://godbolt.org/z/d1e4c3s4e

```
#include <meta>

constexpr const int& r = std::meta::extract<const int&>(^^r);
```

```
<source>:3:56: internal compiler error: Segmentation fault
    3 | constexpr const int& r = std::meta::extract<const int&>(^^r);
      |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
0x2bb9ec8 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x2baeb0b internal_error(char const*, ...)
        ???:0
0xe2489c process_metafunction(constexpr_ctx const*, tree_node*, tree_node*,
bool*, bool*, tree_node**)
        ???:0
0xbb2321 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbb18b2 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbb18b2 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbcb379 maybe_constant_value(tree_node*, tree_node*, mce_value)
        ???:0
0xeaacc7 store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xc56656 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int,
cp_decomp*)
        ???:0
0xd9a313 c_parse_file()
        ???:0
0xf2d8a9 c_common_parse_file()
        ???:0
/cefs/05/0541330772b8b6bab5825a2a_gcc-trunk-20260814/bin/../libexec/gcc/x86_64-linux-gnu/17.0.0/cc1plus
-quiet -imultiarch x86_64-linux-gnu -iprefix
/cefs/05/0541330772b8b6bab5825a2a_gcc-trunk-20260814/bin/../lib/gcc/x86_64-linux-gnu/17.0.0/
-D_GNU_SOURCE <source> -quiet -dumpdir /app/ -dumpbase output.cpp -dumpbase-ext
.cpp -masm=intel -mtune=generic -march=x86-64 -g -Wpedantic -Wall -Wextra
-Wconversion -Wsign-conversion -std=c++26 -fdiagnostics-color=always
-fno-verbose-asm -freflection -o /app/output.s
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
```