feat(cli): warn when removing the default/active toolchain

Author: rami3l

src/cli/rustup_mode.rs

@@ -1281,8 +1281,25 @@ async fn toolchain_link(
 }
 
 fn toolchain_remove(cfg: &mut Cfg<'_>, opts: UninstallOpts) -> Result<utils::ExitCode> {
+    let default_toolchain = cfg.get_default().ok().flatten();
+    let active_toolchain = cfg.find_active_toolchain().ok().flatten().map(|(it, _)| it);
+
     for toolchain_name in &opts.toolchain {
         let toolchain_name = toolchain_name.resolve(&cfg.get_default_host_triple()?)?;
+
+        if active_toolchain
+            .as_ref()
+            .is_some_and(|n| n == &toolchain_name)
+        {
+            warn!("removing the active toolchain; a toolchain override will be required for running Rust tools");
+        }
+        if default_toolchain
+            .as_ref()
+            .is_some_and(|n| n == &toolchain_name)
+        {
+            warn!("removing the default toolchain; proc-macros and build scripts might no longer build");
+        }
+
         Toolchain::ensure_removed(cfg, (&toolchain_name).into())?;
     }
     Ok(utils::ExitCode(0))

src/toolchain/names.rs

@@ -359,6 +359,15 @@ from_variant!(
     LocalToolchainName::Path
 );
 
+impl PartialEq<ToolchainName> for LocalToolchainName {
+    fn eq(&self, other: &ToolchainName) -> bool {
+        match self {
+            LocalToolchainName::Named(n) => n == other,
+            _ => false,
+        }
+    }
+}
+
 impl Display for LocalToolchainName {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {

tests/suite/cli_v2.rs

@@ -212,18 +212,39 @@ async fn list_toolchains_with_none() {
 }
 
 #[tokio::test]
-async fn remove_toolchain() {
+async fn remove_toolchain_default() {
     let mut cx = CliTestContext::new(Scenario::SimpleV2).await;
     cx.config.expect_ok(&["rustup", "update", "nightly"]).await;
     cx.config
-        .expect_ok(&["rustup", "toolchain", "remove", "nightly"])
+        .expect_stderr_ok(
+            &["rustup", "toolchain", "remove", "nightly"],
+            "removing the default toolchain; proc-macros and build scripts might no longer build",
+        )
         .await;
     cx.config.expect_ok(&["rustup", "toolchain", "list"]).await;
     cx.config
         .expect_stdout_ok(&["rustup", "toolchain", "list"], "no installed toolchains")
         .await;
 }
 
+#[tokio::test]
+async fn remove_toolchain_active() {
+    let mut cx = CliTestContext::new(Scenario::SimpleV2).await;
+    cx.config.expect_ok(&["rustup", "default", "nightly"]).await;
+    cx.config
+        .expect_ok(&["rustup", "override", "set", "stable"])
+        .await;
+    cx.config
+        .expect_stderr_ok(
+            &["rustup", "toolchain", "remove", "stable"],
+            "removing the active toolchain; a toolchain override will be required for running Rust tools",
+        )
+        .await;
+    cx.config
+        .expect_stdout_ok(&["rustup", "toolchain", "list"], "nightly")
+        .await;
+}
+
 // Issue #2873
 #[tokio::test]
 async fn remove_toolchain_ignore_trailing_slash() {