warn toolchain

src/cli/rustup_mode.rs

@@ -15,7 +15,9 @@ use super::self_update;
 use super::term2;
 use super::term2::Terminal;
 use super::topical_doc;
-use crate::dist::dist::{PartialTargetTriple, PartialToolchainDesc, Profile, TargetTriple};
+use crate::dist::dist::{
+    PartialTargetTriple, PartialToolchainDesc, Profile, TargetTriple, ToolchainDesc,
+};
 use crate::dist::manifest::Component;
 use crate::process;
 use crate::toolchain::{CustomToolchain, DistributableToolchain};
@@ -904,6 +906,32 @@ fn update(cfg: &mut Cfg, m: &ArgMatches<'_>) -> Result<utils::ExitCode> {
     if let Some(names) = m.values_of("toolchain") {
         for name in names {
             update_bare_triple_check(cfg, name)?;
+
+            let toolchain_has_triple = match PartialToolchainDesc::from_str(name) {
+                Ok(x) => x.has_triple(),
+                _ => false,
+            };
+
+            if toolchain_has_triple {
+                let host_arch = TargetTriple::from_host_or_build();
+                match ToolchainDesc::from_str(name) {
+                    Ok(toolchain_desc) => {
+                        let target_triple = toolchain_desc.target.clone();
+                        if host_arch.ne(&target_triple) {
+                            warn!(
+                                "toolchain '{}' may not be able to run on this system.",
+                                name
+                            );
+                            warn!(
+                                "If you meant to build software to target that platform, perhaps try `rustup target add {}` instead?",
+                                target_triple.to_string()
+                            );
+                        }
+                    }
+                    _ => (),
+                }
+            }
+
             let toolchain = cfg.get_toolchain(name, false)?;
 
             let status = if !toolchain.is_custom() {

tests/cli-rustup.rs

@@ -1940,3 +1940,25 @@ fn check_host_goes_away() {
         );
     })
 }
+
+#[test]
+fn warn_on_unmatch_build() {
+    clitools::setup(Scenario::MultiHost, &|config| {
+        let arch = clitools::MULTI_ARCH1;
+        expect_stderr_ok(
+            config,
+            &[
+                "rustup",
+                "toolchain",
+                "install",
+                &format!("nightly-{}", arch),
+                "--no-self-update",
+            ],
+            &format!(
+                r"warning: toolchain 'nightly-{0}' may not be able to run on this system.
+warning: If you meant to build software to target that platform, perhaps try `rustup target add {0}` instead?",
+                arch,
+            ),
+        );
+    });
+}