Accessing TYPES through instance variables

[larshp]

For a section in the guide suggest adding "Don't access TYPES through instance variables"

Background: same story as https://github.com/SAP/styleguides/blob/main/clean-abap/CleanABAP.md#dont-call-static-methods-through-instance-variables

anti pattern example,

CLASS lcl DEFINITION.
  PUBLIC SECTION.
    TYPES foo TYPE i.
ENDCLASS.
CLASS lcl IMPLEMENTATION.
ENDCLASS.

INTERFACE lif.
  DATA ref TYPE REF TO lcl.
  TYPES blah TYPE ref->foo.   " <- this is bad
ENDINTERFACE.

instead do,

CLASS lcl DEFINITION.
  PUBLIC SECTION.
    TYPES foo TYPE i.
ENDCLASS.
CLASS lcl IMPLEMENTATION.
ENDCLASS.

INTERFACE lif.
  DATA ref TYPE REF TO lcl.
  TYPES blah TYPE lcl=>foo.   " <- this is good
ENDINTERFACE.

any thoughts/comments?

[nununo]

Agree!

[N2oB6n-SAP]

I agree, even though (this holds true for the referenced section on instance variables as well)

[...] is a potential source of confusion [...]

feels like a rather soft and/or incomplete argument to me.

I would prefer to actually name the confusion (the accessed type not being instance-specific/dependent) and possibly argue that refactoring of the instance variable [name] would misleadingly touch a piece of code that is unrelated to the type definition.

@larshp Would you like to open a PR yourself?

[bjoern-jueliger-sap]

Merged with #305