In the ABAP class where you want to create the empty implementation part of a method, the declaration of the method must exist in the definition part.
The ABAP class must be free of syntax errors, other than those for the missing method implementation(s).
In an ABAP class, you can generate the implementation part of a method from an existing declaration in the definition part. The added implementation part is empty and can be edited for development activities.
ABAP Development Tools inserts the corresponding (empty) implementation part of the method into the existing implementation of the ABAP class.