all: bar baz

.DELETE_ON_ERROR:

.PRECIOUS: %.g

.SECONDEXPANSION:

%: %.g
	# updating $@
	# the error occurs HERE!  do we delete $@?
	$(info echo bing\
	echo bong)
	false

%.g: %.in
	# updating $@
	touch $*.g
	touch $*

%: %.in2
	# updating baz
	touch $@
	false