Error in `Stack.Build.Source.splitComponents`?

[mpilgrem]

In #3955

splitComponents :: [NamedComponent]
                -> (Set Text, Set Text, Set Text)
splitComponents =
    go id id id
  where
    go a b c [] = (Set.fromList $ a [], Set.fromList $ b [], Set.fromList $ c [])
    go a b c (CLib:xs) = go a b c xs
    go a b c (CExe x:xs) = go (a . (x:)) b c xs
    go a b c (CTest x:xs) = go a (b . (x:)) c xs
    go a b c (CBench x:xs) = go a b (c . (x:)) xs

became:

splitComponents :: [NamedComponent]
                -> (Set Text, Set Text, Set Text)
splitComponents =
    go id id id
  where
    go a b c [] = (Set.fromList $ a [], Set.fromList $ b [], Set.fromList $ c [])
    go a b c (CLib:xs) = go a b c xs
    go a b c (CInternalLib x:xs) = go (a . (x:)) b c xs -- <<<< Added line
    go a b c (CExe x:xs) = go (a . (x:)) b c xs
    go a b c (CTest x:xs) = go a (b . (x:)) c xs
    go a b c (CBench x:xs) = go a b (c . (x:)) xs

It appears to me that that may be an error, as I can't see why the names of named library components would be added to the set of the names of executable components.

[mpilgrem]

The reason that this has not manifested to date is that splitComponents is used only in one place:

Just (TargetComps comps) -> splitComponents $ Set.toList comps

and, to date, it has not been possible to specify a named library component of a package as a target component.