Allocate Source= question

Dear all,

I have a question regarding the following code snippet:

MODULE TestModule !{
TYPE X0Type

	  REAL(KIND=8), DIMENSION(:),ALLOCATABLE :: X

	ENDTYPE

	 

	TYPE SL_DataStrucType

	  REAL(KIND=8), DIMENSION(:), POINTER :: X

	  TYPE(X0Type), DIMENSION(:), POINTER :: StoredX0    => null()

	ENDTYPE SL_DataStrucType
TYPE(SL_DataStrucType),             POINTER :: DB_MMxSL_Data       => null()

	TYPE(X0Type),        DIMENSION(:),  POINTER :: StoredX0    => null()
  CONTAINS

	 

	  SUBROUTINE Test()

	    ALLOCATE(DB_MMxSL_Data%StoredX0(1))

	    ALLOCATE(DB_MMxSL_Data%X, SOURCE=StoredX0(1)%X)

	    ALLOCATE(DB_MMxSL_Data%X, SOURCE=DB_MMxSL_Data%StoredX0(1)%X)

	  END SUBROUTINE
ENDMODULE TestModule !}

There seems not to be any problem with the upper allocate statement, but when the allocate option Source= is encompassed in a structure, I get the following compiler diagnostic:

error #8152: Neither the ERRMSG= variable nor any part of the source expression in SOURCE= or MOLD= specifiers may be allocated in the ALLOCATE statement in which it appears.   [DB_MMXSL_DATA]

Can anyone explain the fundamental difference between the two allocate statements, that is causing in this error.

Dirk