:unset +s
:unset +t
-- first, clean up:
:! rm -f *.hi *.o *~
:! cp A1.hs A.hs

:load D

-- compile A & reload
:! $HC $HC_OPTS -no-recomp -c A.hs
:reload

B.g 42
B.g 42
B.g 42

-- swap A2 for A, compile & reload
:! cp A2.hs A.hs
:! $HC $HC_OPTS -no-recomp -c A.hs
:reload
-- the system should ignore the compiled version and compile its own.

B.g 42
B.g 42
B.g 42

-- pick up newly compiled A
:load D

B.g 42
B.g 42
B.g 42

-- remove A.o: system should recompile A
:! rm A.o
:reload

B.g 42
B.g 42
B.g 42