use subcommand candidate

Author: nooma-42

src/bin/cargo/cli.rs

@@ -691,26 +691,20 @@ See '<cyan,bold>cargo help</> <cyan><<command>></>' for more information on a sp
                 }))
             }).collect()
         })))
-                .arg( Arg::new("toolchain")
-            .help("Specifies the toolchain to use for this command")
-            .value_name("TOOLCHAIN")
-            .action(ArgAction::Set)
-        .add(clap_complete::engine::ArgValueCompleter::new(|partial: &OsStr| {
-            let toolchains = get_toolchains_from_rustup();
-
-            toolchains
+        .add(clap_complete::engine::SubcommandCandidates::new(|| {
+            get_toolchains_from_rustup()
                 .into_iter()
-                .filter(|t| OsStr::new(t).as_encoded_bytes().starts_with(partial.as_encoded_bytes()))
                 .map(|t| clap_complete::CompletionCandidate::new(t))
                 .collect()
-        })))
+        }))
         .subcommands(commands::builtin())
 }
 
 fn get_toolchains_from_rustup() -> Vec<String> {
     let output = std::process::Command::new("rustup")
         .arg("toolchain")
         .arg("list")
+        .arg("-q")
         .output()
         .unwrap();