Installing pinned rust version for build in formula

[dariaguy]

Output of brew config

HOMEBREW_VERSION: 5.0.6-46-g528de97
ORIGIN: https://github.com/Homebrew/brew
HEAD: 528de976d061d2b38669c8e37c48cc44cb5aea94
Last commit: 6 hours ago
Branch: main
Core tap HEAD: a94104b2a6cc5c0ea91f96a4842772cc75f72937
Core tap last commit: 26 hours ago
Core tap JSON: 18 Dec 13:56 UTC
Core cask tap JSON: 18 Dec 13:56 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DOWNLOAD_CONCURRENCY: 28
HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set
HOMEBREW_MAKE_JOBS: 14
HOMEBREW_SORBET_RUNTIME: set
Homebrew Ruby: 3.4.8 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.4.8/bin/ruby
CPU: 14-core 64-bit arm_brava
Clang: 17.0.0 build 1700
Git: 2.39.5 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 15.6.1-arm64
CLT: 16.4.0.0.1.1747106510
Xcode: N/A
Rosetta 2: false

Output of brew doctor

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Warning: No Cask quarantine support available: Swift compilation failed.
This is usually due to a broken or incompatible Command Line Tools installation.
Install the Command Line Tools:
  xcode-select --install

If that doesn't resolve your issues, run:
  sudo rm -rf /Library/Developer/CommandLineTools
  sudo xcode-select --install

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You should download the Command Line Tools for Xcode 16.4.

Description of issue

Hi, I'm trying to create a formula for redisjson that will be used in homebrew-core. Redisjson is using a pinned rust version in rust-toolchain.toml. I tried adding rustup dependency for build and got this error in brew audit --formula redisjson --online --new:

  * line 21, col 3: Formulae in homebrew/core should use `depends_on "rust" => build` instead of `depends_on "rustup" => :build`.

I can't use rust formula build dependency since it's the latest stable version. How can I install the pinned rust version?
Thanks!

[carlocab]

You can't do this for a formula in Homebrew/core, unfortunately. If you must use a specific version of Rust, you can host your formula in an external tap.