Display warning message if Cargo.toml is missing

src/extension.ts

@@ -155,6 +155,8 @@ export function activate(context: ExtensionContext) {
 
 function startLanguageClient(context: ExtensionContext)
 {
+    warnOnMissingCargoToml();
+
     window.setStatusBarMessage('RLS: starting up');
 
     // FIXME(#66): Hack around stderr not being output to the window if ServerOptions is a function
@@ -192,6 +194,14 @@ export function deactivate(): Promise<void> {
     return Promise.resolve();
 }
 
+function warnOnMissingCargoToml() {
+    workspace.findFiles('Cargo.toml').then(files => {
+        if (files.length < 1) {
+            window.showWarningMessage('Cargo.toml must be in the workspace in order to support all features');
+        }
+    });
+}
+
 function warnOnRlsToml() {
     const tomlPath = workspace.rootPath + '/rls.toml';
     fs.access(tomlPath, fs.constants.F_OK, (err) => {