lib.mergeEqualOption

The following is the current implementation of this function.

mergeEqualOption =
    loc: defs:
    if defs == [ ] then
      abort "This case should never happen."
    # Return early if we only have one element
    # This also makes it work for functions, because the foldl' below would try
    # to compare the first element with itself, which is false for functions
    else if length defs == 1 then
      (head defs).value
    else
      (foldl' (
        first: def:
        if def.value != first.value then
          throw "The option `${showOption loc}' has conflicting definition values:${
            showDefs [
              first
              def
            ]
          }\n${prioritySuggestion}"
        else
          first
      ) (head defs) (tail defs)).value;