[Bug c++/84655] internal compiler error: unexpected expression 'a' of kind template_parm_index

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84655

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Before that we printed a boatload of errors:

q.cc: In lambda function:
q.cc:4:26: error: parameter packs not expanded with ‘...’:
   int d[] = [] { auto f(a); };
                          ^
q.cc:4:26: note:         ‘a’
q.cc: At global scope:
q.cc:5:33: error: array must be initialized with a brace-enclosed initializer
 } const __attribute__((noinline(b<>())));
                                 ^~~~~
q.cc:5:33: error: use of deleted function ‘b<>::b()’
q.cc:2:8: error: array must be initialized with a brace-enclosed initializer
 struct b {
        ^
q.cc:2:8: note: ‘b<>::b()’ is implicitly deleted because the default definition
would be ill-formed:
q.cc:2:8: error: uninitialized reference member in ‘struct b<>’
q.cc:3:9: note: ‘int&& b<>::c’ should be initialized
   int &&c;
         ^
q.cc:5:3: error: ‘const’ can only be specified for objects and functions
 } const __attribute__((noinline(b<>())));
   ^~~~~
q.cc:2:8: warning: attribute ignored in declaration of ‘struct b<a>’
[-Wattributes]
 struct b {
        ^
q.cc:2:8: note: attribute for ‘struct b<a>’ must follow the ‘struct’ keyword