refactor(config): clean up dist_root_server()

Author: rami3l

src/config.rs

@@ -302,7 +302,7 @@ impl<'a> Cfg<'a> {
         let notify_clone = notify_handler.clone();
         let tmp_cx = temp::Context::new(
             rustup_dir.join("tmp"),
-            dist_root_server.as_str(),
+            &dist_root_server,
             Box::new(move |n| (notify_clone)(n.into())),
         );
         let dist_root = dist_root_server + "/dist";
@@ -319,7 +319,7 @@ impl<'a> Cfg<'a> {
             notify_handler,
             toolchain_override: None,
             env_override,
-            dist_root_url: dist_root,
+            dist_root_url: dist_root.to_string(),
             current_dir,
             process,
         };
@@ -940,25 +940,22 @@ impl<'a> Cfg<'a> {
     }
 }
 
-fn dist_root_server(process: &Process) -> String {
-    match process.var("RUSTUP_DIST_SERVER") {
-        Ok(s) if !s.is_empty() => {
-            trace!("`RUSTUP_DIST_SERVER` has been set to `{s}`");
-            s
-        }
-        _ => {
+fn dist_root_server(process: &Process) -> Cow<'static, str> {
+    process
+        .var("RUSTUP_DIST_SERVER")
+        .ok()
+        .and_then(utils::if_not_empty)
+        .inspect(|s| trace!("`RUSTUP_DIST_SERVER` has been set to `{s}`"))
+        .or_else(|| {
             // For backward compatibility
             process
                 .var("RUSTUP_DIST_ROOT")
                 .ok()
                 .and_then(utils::if_not_empty)
                 .inspect(|url| trace!("`RUSTUP_DIST_ROOT` has been set to `{url}`"))
-                .map_or(Cow::Borrowed(dist::DEFAULT_DIST_ROOT), Cow::Owned)
-                .as_ref()
-                .trim_end_matches("/dist")
-                .to_owned()
-        }
-    }
+                .map(|s| s.trim_end_matches("/dist").to_owned())
+        })
+        .map_or(Cow::Borrowed(dist::DEFAULT_DIST_SERVER), Cow::Owned)
 }
 
 impl<'a> Debug for Cfg<'a> {

src/dist/mod.rs

@@ -42,9 +42,6 @@ pub(crate) use triple::*;
 
 pub static DEFAULT_DIST_SERVER: &str = "https://static.rust-lang.org";
 
-// Deprecated
-pub(crate) static DEFAULT_DIST_ROOT: &str = "https://static.rust-lang.org/dist";
-
 const TOOLSTATE_MSG: &str =
     "If you require these components, please install and use the latest successful build version,\n\
      which you can find at <https://rust-lang.github.io/rustup-components-history>.\n\nAfter determining \