fix

Author: mluukkai

src/content/9/en/part9c.md

@@ -270,6 +270,17 @@ For this set of exercises, you will be developing a backend for an existing proj
 
 The [frontend](https://github.com/fullstack-hy2020/patientor) has already been built by outsider experts and your task is to create a backend to support the existing code.
 
+#### WARNING
+
+Quite often VS code looses track what is really happening in the code and it shows type or style related warnings despite the code has been fixed. If this happens (to me it has happened quite often), just restart the editor. It is also good to doublecheck that everything really works by running the compiler and the eslint from the command line with commands:
+
+```
+npm run tsc
+npm run lint
+```
+
+When run in command line you get the "real result" for sure. So, never trust the editor too much!
+
 #### 9.8: Patientor backend, step1
 
 Initialize a new backend project that will work with the frontend. Configure eslint and tsconfig with the same configurations as proposed in the material. Define an endpoint that answers HTTP GET requests for route */api/ping*.