auto allowed with a type in C++

[shafik]

We currently allow something like this in C++: https://godbolt.org/z/7fabbGfe6

void f() {
  auto int x = 1;
}

It looks like this was allowed as an extension in C++ because it was valid C but I don't think it makes sense to support this anymore.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Shafik Yaghmour (shafik)

We currently allow something like this in C++: https://godbolt.org/z/7fabbGfe6

void f() {
  auto int x = 1;
}

It looks like this was allowed as an extension in C++ because it was valid C but I don't think it makes sense to support this anymore.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor is working on this issue. If someone is assigned to the issue or claimed to be working on it, ping the person. After one week without a response, the assignee may be changed.
2. Leave a comment indicating that you are working on the issue, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Shafik Yaghmour (shafik)

We currently allow something like this in C++: https://godbolt.org/z/7fabbGfe6

void f() {
  auto int x = 1;
}

It looks like this was allowed as an extension in C++ because it was valid C but I don't think it makes sense to support this anymore.

[zygoloid]

It looks like this was allowed as an extension in C++ because it was valid C but I don't think it makes sense to support this anymore.

That's not exactly the history here as I recall it: we allow it as an extension in C++11 onwards primarily because it's valid C++98, and we were trying to make as much code as possible from earlier standards modes continue to compile in later modes in order to ease the transition between language standards. But nonetheless, our diagnostic has said "will not be supported in future releases" since Clang 2.9; it seems like we should finally get around to removing the extension (or stop saying that in the diagnostic 😄)

[moar55]

I would like to take this one :)