#       clear the source var so we can't inherit the value twice
#
# $(1): context prefix
# $(2): name of this node
# $(3): list of variable names
#
define _expand-inherited-values
  $(foreach v,$(3), \
    $(eval ### "Shorthand for the name of the target variable") \
    $(eval _eiv_tv := $(1).$(2).$(v)) \
    $(eval ### "Get the list of nodes that this variable inherits") \
    $(eval _eiv_i := \
        $(sort \
            $(patsubst $(INHERIT_TAG)%,%, \
                $(filter $(INHERIT_TAG)%, $($(_eiv_tv)) \
     )))) \
    $(foreach i,$(_eiv_i), \
      $(eval ### "Make sure that this inherit appears only once") \
      $(eval $(_eiv_tv) := \
          $(call uniq-word,$($(_eiv_tv)),$(INHERIT_TAG)$(i))) \
      $(eval ### "Expand the inherit tag") \
      $(eval $(_eiv_tv) := \
          $(strip \
              $(patsubst $(INHERIT_TAG)$(i),$($(1).$(i).$(v)), \
                  $($(_eiv_tv))))) \
      $(eval ### "Clear the child so DAGs don't create duplicate entries" ) \
      $(eval $(1).$(i).$(v) :=) \
      $(eval ### "If we just inherited ourselves, it's a cycle.") \
      $(if $(filter $(INHERIT_TAG)$(2),$($(_eiv_tv))), \
        $(warning Cycle detected between "$(2)" and "$(i)" for context "$(1)") \
        $(error import of "$(2)" failed) \
      ) \
     ) \
   ) \
   $(eval _eiv_tv :=) \
   $(eval _eiv_i :=)
endef

#
# $(1): context prefix
# $(2): makefile representing this node
# $(3): list of node variable names
#
# _include_stack contains the list of included files, with the most recent files first.
define _import-node