celeste: fix rustc 1.85.0 errors (#461968)

pkgs/by-name/ce/celeste/missing-unsafe-block.patch

@@ -0,0 +1,25 @@
+From 96ec13b49ee2fcb2869f87b1f9e8c6cfc92275df Mon Sep 17 00:00:00 2001
+From: Tom van Dijk <18gatenmaker6@gmail.com>
+Date: Fri, 14 Nov 2025 18:55:40 +0100
+Subject: [PATCH] rust 2024 fixes
+
+---
+ src/main.rs | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/main.rs b/src/main.rs
+index 127f649..5ef526e 100644
+--- a/src/main.rs
++++ b/src/main.rs
+@@ -103,7 +103,7 @@ fn main() {
+         }
+     } else {
+         // Set `RUST_BACKTRACE` so we get a better backtrace for reporting.
+-        env::set_var("RUST_BACKTRACE", "1");
++        unsafe { env::set_var("RUST_BACKTRACE", "1"); }
+ 
+         // Run the command and get the stderr, checking for a backtrace.
+         let mut args = vec!["run-gui"];
+-- 
+2.51.0
+

pkgs/by-name/ce/celeste/package.nix

@@ -31,6 +31,9 @@ rustPlatform.buildRustPackage rec {
 
   cargoHash = "sha256-OBGDnhpVLOPdYhofWfeaueklt7KBkLhM02JNvuvUQ2Q=";
 
+  # rust 2024 requires that you put an unsafe block around std::env::set_var
+  patches = [ ./missing-unsafe-block.patch ];
+
   postPatch = ''
     pushd $cargoDepsCopy/librclone-sys-*
     oldHash=$(sha256sum build.rs | cut -d " " -f 1)
@@ -45,6 +48,10 @@ rustPlatform.buildRustPackage rec {
       --replace "{{ env_var('DESTDIR') }}/usr" "${placeholder "out"}"
     # buildRustPackage takes care of installing the binary
     sed -i "#/bin/celeste#d" justfile
+
+    # fix: as of rust 1.85, it is required that you specify edition 2024 for let chains
+    substituteInPlace Cargo.toml \
+      --replace-warn 'edition = "2021"' 'edition = "2024"'
   '';
 
   RUSTC_BOOTSTRAP = 1;