[Bug c++/123684] New: [14/15/16 Regression] ICE in check_abi_tag_args (tree check: expected tree_list, have error_mark) with empty abi_tag on namespace

[jirehguo at tju dot edu.cn via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123684

            Bug ID: 123684
           Summary: [14/15/16 Regression] ICE in check_abi_tag_args (tree
                    check: expected tree_list, have error_mark) with empty
                    abi_tag on namespace
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jirehguo at tju dot edu.cn
  Target Milestone: ---

Compiler Explorer: https://godbolt.org/z/nPrvs151j
The following c++ code crash gcc trunk.
Goes back to 14.1 with checking.

Code:
```cpp
inline namespace __cxx11 [[__abi_tag__()]] {}
```

Stack dump:
```
<source>:1:42: internal compiler error: tree check: expected tree_list, have
error_mark in check_abi_tag_args, at cp/tree.cc:5749
    1 | inline namespace __cxx11 [[__abi_tag__()]] {}
      |                                          ^
0x2950b58 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x294591b internal_error(char const*, ...)
        ???:0
0xa2350f tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ???:0
0xce0532 handle_namespace_attrs(tree_node*, tree_node*)
        ???:0
0xd64c43 c_parse_file()
        ???:0
0xeeed69 c_common_parse_file()
        ???:0
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.
Compiler returned: 1
```