Remove no longer needed unsafeDiscardStringContext workaround

Fixed in: NixOS/nix#7260

Author: Kranzes

crate2nix/templates/crate2nix-sources.nix.tera

@@ -18,8 +18,7 @@
 , crate2nixJson ? ./crate2nix.json
 }:
 
-# unsafeDiscardStringContext is a workaround for https://github.com/NixOS/nix/issues/6647
-let config = builtins.fromJSON (builtins.unsafeDiscardStringContext (builtins.readFile crate2nixJson));
+let config = lib.importJSON crate2nixJson;
     sources = config.sources or (builtins.throw "no sources in ${crate2nixJson}");
 in
 rec {
@@ -108,4 +107,4 @@ rec {
                 tar -xzf ${archive} --strip-components=1 -C $out
             '';
     };
-}
+}

tools.nix

@@ -249,8 +249,7 @@ rec {
 
         locked =
           let
-            # unsafeDiscardStringContext is a workaround for https://github.com/NixOS/nix/issues/6647
-            parseFile = cargoLock: builtins.fromTOML (builtins.unsafeDiscardStringContext (builtins.readFile cargoLock));
+            parseFile = cargoLock: lib.importTOML cargoLock;
             allParsedFiles = builtins.map parseFile lockFiles;
             merge = merged: lock:
               {