Yet more ABAP fails

The following methods gives different results based upon indentation of source code:

PROGRAM test.

CLASS cl_test DEFINITION.
  PUBLIC SECTION.
    CLASS-METHODS bug1 RETURNING VALUE(r_string) TYPE string.
    CLASS-METHODS bug2 RETURNING VALUE(r_string) TYPE string.
ENDCLASS.

CLASS cl_test IMPLEMENTATION.

  METHOD bug1.
    CONCATENATE '______________________________________________________'
'______________________________________________________________________' " not indented
                '______________' INTO r_string.
  ENDMETHOD.

  METHOD bug2.
    CONCATENATE '______________________________________________________'
                '______________________________________________________________________' " indented
                '______________' INTO r_string.
  ENDMETHOD.

ENDCLASS.

START-OF-SELECTION.
  WRITE: / 'Exact same code, only differ in indent:',
         / `bug1: `, cl_test=>bug1( ),
         / `bug2: `, cl_test=>bug2( ).

Results:

Exact same code, only differ in indent:

bug1: ______________________________________________________'____...____
bug2: ___________________________________________________________...___