fix: exit code 0 when installing an already-installed toolchain

CHANGELOG.md

@@ -1,5 +1,6 @@
 # Unreleased
 
+- `elan install`/`elan toolchain install` now report an already-installed toolchain as such and exit with code 0 instead of failing with `'...' is already installed`.
 - Fix panic in `elan toolchain gc` when a toolchain directory listed in `~/.elan/toolchains` does not resolve to an existing directory, e.g. after deleting a toolchain manually.
 
 # 4.2.3 - 2026-06-08

src/elan-cli/elan_mode.rs

@@ -264,11 +264,14 @@ fn install(cfg: &Cfg, m: &ArgMatches<'_>) -> Result<()> {
         let desc = lookup_toolchain_desc(cfg, name)?;
         let toolchain = cfg.get_toolchain(&desc, false)?;
 
-        if !toolchain.exists() || !toolchain.is_custom() {
-            toolchain.install_from_dist()?;
-            println!();
-            common::show_channel_update(cfg, &toolchain.desc)?;
+        if toolchain.exists() {
+            info!("toolchain '{}' is already installed", toolchain.desc);
+            continue;
         }
+
+        toolchain.install_from_dist()?;
+        println!();
+        common::show_channel_update(cfg, &toolchain.desc)?;
     }
 
     Ok(())