[Issue 21918] segfault in getParameterStorageClasses on auto function with error

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21918

--- Comment #3 from Dlang Bot <dlang-bot at dlang.rocks> ---
dlang/dmd pull request #12600 "merge stable" was merged into master:

- 3b02dc18411a49bd5e9ec43892bec61d4ec0a51c by MoonlightSentinel:
  Fix 21918 - Segfault for getParameterStorageClasses for invalid functions

  The type of a `FuncDeclaration` is set to `TypeError` if the `auto`
  inference fails. So `getParameters` has to check that the type is
  actually a `TypeFunction`.

  The additional check in `traits.d` prevents the invalid error message:
  ```
  Error: parameter index must be in range 0..0 not 0
  ```

https://github.com/dlang/dmd/pull/12600

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