So I think you're talking about TYPES.

  TYPE PERSON
    AGE AS INTEGER
    FIRSTNAME AS STRING * 12
  END TYPE

  DIM KURTZ AS PERSON


  PRINT KURTZ._

However you are right that if you hit F1 on KURTZ it would then show User defined PERSON, and then you could hit F1 again and it would show built-in help of user defined TYPE with AGE/FIRSTNAME properties. Sort of like context-sensitive help I guess.

As far as subroutines/functions go, if you tried to pass data into a subroutine where the data couldn’t be coerced, it would just give you a generic type mismatch.

  DIM Y AS SINGLE
  Y = 10.5

  PRINTIT  Y   ' Throws parameter type mismatch
  PRINTIT (Y) ' Succeeds through a self-evaluated expression which is effectively BYVAL because Microsoft takes pain in your suffering.

  SUB PRINTIT (X%)
    PRINT X%
  END SUB

I've spent the last 6 months building a similar 1:1 faithful recreation of QBASIC and QuickBasic 4.5 that runs natively in the browser [1] - so I know way more about this than anyone should by right.

[1] - https://mordenstar.com/share/qbasic-core-demos