[Bug c++/128526] New: internal compiler error: tree check: expected class 'type', have 'exceptional' (tree_list) in comp_type_attributes, at attribs.cc

[0599jiangyc at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128526

            Bug ID: 128526
           Summary: internal compiler error: tree check: expected class
                    'type', have 'exceptional' (tree_list) in
                    comp_type_attributes, at attribs.cc
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 0599jiangyc at gmail dot com
  Target Milestone: ---

The following code:
```cpp
template<class T> struct A;
template<class T> void f() { using V [[gnu::vector_size(16)]] = T; A<V> *p; }
template<class T> void g() { using V [[gnu::vector_size(16)]] = T; A<V> *p; }
```

Resulted in this output:
```
<source>:3:71: internal compiler error: tree check: expected class 'type', have
'exceptional' (tree_list) in comp_type_attributes, at attribs.cc:1509
```

Trunk reproducer: https://godbolt.org/z/jrbr38d3b