feat(toolchain): notify the user when proxy fallback is activated

Author: rami3l

src/toolchain.rs

@@ -333,8 +333,12 @@ impl<'a> Toolchain<'a> {
         // Should push the cargo fallback into a custom toolchain type? And then
         // perhaps a trait that create command layers on?
         if let Some(cmd) = self.maybe_do_cargo_fallback(binary)? {
+            info!("`cargo` is unavailable for the active toolchain");
+            info!("falling back to {:?}", cmd.get_program());
             return Ok(cmd);
         } else if let Some(cmd) = self.maybe_do_rust_analyzer_fallback(binary)? {
+            info!("`rust-analyzer` is unavailable for the active toolchain");
+            info!("falling back to {:?}", cmd.get_program());
             return Ok(cmd);
         }
 

tests/suite/cli_misc.rs

@@ -1343,7 +1343,10 @@ async fn rust_analyzer_proxy_falls_back_external() {
             &["rust-analyzer", "--echo-current-exe"],
             &[("PATH", &extern_dir.to_string_lossy())],
             "",
-            &format!("{}\n", extern_path.display()),
+            &format!(
+                "info: `rust-analyzer` is unavailable for the active toolchain\ninfo: falling back to {:?}\n{}\n",
+                extern_path.as_os_str(), extern_path.display()
+            ),
         )
         .await;
 }