fix(config): call warn_if_host_is_incompatible() in ensure_install()

src/config.rs

@@ -11,8 +11,11 @@ use tokio_stream::StreamExt;
 use tracing::trace;
 
 use crate::{
-    cli::self_update::SelfUpdateMode,
-    dist::{self, download::DownloadCfg, temp, PartialToolchainDesc, Profile, ToolchainDesc},
+    cli::{common, self_update::SelfUpdateMode},
+    dist::{
+        self, download::DownloadCfg, temp, PartialToolchainDesc, Profile, TargetTriple,
+        ToolchainDesc,
+    },
     errors::RustupError,
     fallback_settings::FallbackSettings,
     install::UpdateStatus,
@@ -788,6 +791,12 @@ impl<'a> Cfg<'a> {
         profile: Option<Profile>,
         verbose: bool,
     ) -> Result<(UpdateStatus, Toolchain<'_>)> {
+        common::warn_if_host_is_incompatible(
+            toolchain,
+            &TargetTriple::from_host_or_build(self.process),
+            &toolchain.target,
+            false,
+        )?;
         if verbose {
             (self.notify_handler)(Notification::LookingForToolchain(toolchain));
         }

tests/suite/cli_rustup.rs

@@ -2725,6 +2725,19 @@ warn: If you meant to build software to target that platform, perhaps try `rustu
     ).await;
 }
 
+#[tokio::test]
+async fn warn_on_unmatch_build_default() {
+    let cx = CliTestContext::new(Scenario::MultiHost).await;
+    let arch = clitools::MULTI_ARCH1;
+    cx.config.expect_stderr_ok(
+        &["rustup", "default", &format!("nightly-{arch}")],
+        &format!(
+            r"warn: toolchain 'nightly-{arch}' may not be able to run on this system.
+warn: If you meant to build software to target that platform, perhaps try `rustup target add {arch}` instead?",
+        ),
+    ).await;
+}
+
 #[tokio::test]
 async fn dont_warn_on_partial_build() {
     let cx = CliTestContext::new(Scenario::SimpleV2).await;