When writing something like the expression `|_: ...| {}`, we now detect the `...` during parsing explicitly instead of relying on the detection in `parse_ty_common` so that we don't talk about "nested `...` are not supported".
```
error: unexpected `...`
--> $DIR/no-closure.rs:6:35
|
LL | const F: extern "C" fn(...) = |_: ...| {};
| ^^^
|
= note: only `extern "C"` and `extern "C-unwind"` functions may have a C variable argument list
```
