rustc panic with manual Fn implementation

I was attempting to implement Fn manually, possibly incorrectly!

I tried this code:
Playground URL: https://play.rust-lang.org/?gist=0c4c814bd6fe031a33f6673c27de9239&version=nightly&backtrace=0
Gist URL: https://gist.github.com/0c4c814bd6fe031a33f6673c27de9239

Meta

error: internal compiler error: /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_trans/abi.rs:374: argument to function with "rust-call" ABI is not a tuple

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

thread 'rustc' panicked at 'Box', /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_errors/lib.rs:423
note: Run with RUST_BACKTRACE=1 for a backtrace.

[durka]

It is incorrect, you need to use a tuple: https://is.gd/0lhHva

That said it should not ICE.

Thanks, I have added the tuples since posting. I've also found that this is probably a duplicate of #21139 and #22565.

[durka]

Yes, dupe of #22565.

[Mark-Simulacrum]

Closing in favor of #22565.