fix(cursor): throw error in ChangeStream constructor if `changeStream…

…Thunk()` throws a sync error

lib/cursor/changeStream.js

@@ -33,19 +33,34 @@ class ChangeStream extends EventEmitter {
       );
     }
 
+    let syncError = null;
     this.$driverChangeStreamPromise = new Promise((resolve, reject) => {
       // This wrapper is necessary because of buffering.
-      changeStreamThunk((err, driverChangeStream) => {
-        if (err != null) {
-          this.emit('error', err);
-          return reject(err);
-        }
+      try {
+        changeStreamThunk((err, driverChangeStream) => {
+          if (err != null) {
+            this.emit('error', err);
+            return reject(err);
+          }
 
-        this.driverChangeStream = driverChangeStream;
-        this.emit('ready');
-        resolve();
-      });
+          this.driverChangeStream = driverChangeStream;
+          this.emit('ready');
+          resolve();
+        });
+      } catch (err) {
+        syncError = err;
+        this.emit('error', err);
+        reject(err);
+      }
     });
+
+    // Because a ChangeStream is an event emitter, there's no way to register an 'error' handler
+    // that catches errors which occur in the constructor, unless we force sync errors into async
+    // errors with setImmediate(). For cleaner stack trace, we just immediately throw any synchronous
+    // errors that occurred with changeStreamThunk().
+    if (syncError != null) {
+      throw syncError;
+    }
   }
 
   _bindEvents() {