bug#42991: Rust support

[Richard Stallman]

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  > > There are two Emacs modes for Rust already (rust-mode and
  > > rustic). Neither are under GPL and both have a lot of contributors, so
  > > getting those into the Emacs distribution would be an uphill struggle.

  > And rust-mode is on Melpa, so users can just install it via M-x
  > list-packages, if they want to.

They can do that if they enable MELPA.  But we want to have a good
Rust mode included in the Emacs core.

-- 
Dr Richard Stallman
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)