Rollup merge of #144616 - Zalathar:try-in-macro, r=jieyouxu

coverage: Regression test for "function name is empty" bug

Regression test for rust-lang/rust#141577, which was triggered by rust-lang/rust#144298.

The bug was triggered by a particular usage of the `?` try operator in a proc-macro expansion.

Thanks to lqd for the minimization at https://github.com/rust-lang/rust/pull/144571#issuecomment-3127534223.

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I have manually verified that reverting the relevant follow-up fixes (rust-lang/rust#144480 and rust-lang/rust#144530) causes this test to reproduce the bug:

```sh
git revert -m1 8aa3d41b8527f9f78e0f2459b50a6e13aea35144 c462895a6f0b463ff0c1c1db2a3a654d7e5976c7
```

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r? compiler