VAL INT MSIZE IS 32 :
DATA TYPE COLUMN IS [MSIZE]REAL32:
DATA TYPE MATRIX IS [MSIZE]COLUMN:

PROC main()
  CHAN COLUMN c:
  PAR
    MATRIX a:
    c ! a[0]

    -- Change this to FALSE to get rid of the error.
    #IF TRUE
    DATA TYPE BLOCK IS MATRIX:
    BLOCK a:
    #ELSE
    MATRIX a:
    #ENDIF
    c ? a[0]
:
