Let's enter a random code and see what can be done:
Invoking Show Type Info Action
If you select Show type info on mouse hover after, ms check box in Settings | Languages and Frameworks | Scala, then in the Editor, you can simply navigate with the mouse to a value to see its type information.
To invoke Show Type Info action in Editor, navigate to the value and press N/A:
You can also see the type information on a value definition. Simply put the caret on a value definition and press N/A:
Adding Type Annotation
To add a type annotation, highlight the value and press Alt+Enter: As a result, the type annotation is added:
You can also use Adjust types action to shorten types with full qualified names. In this case the necessary imports are added.
Removing Type Annotation
You can also remove the type annotation the same way you have added it, by pressing Alt+Enter:
Seeing Type Annotation on Expression
To see the type information on an expression, simply navigate to the expression, highlight it and press N/A:
