-include completely turns off errors

[Noel Yap]

I have the following makefile:

-include foo.mk

.PHONY: all
all: foo.mk
        @echo all


Since there's no rule to create foo.mk, I'd expect the build to fail since all 
is dependent on foo.mk, but it seems that the -include turns off this error.  
Is this a bug?

Thanks,
Noel

PS
This throws a kink into the "delayed error message" workaround for "include" 
that I had proposed.