A few things:

- We now have a proper pre-mixin-linking pass which computes
  just the set of requirements we expect to see after mixin
  linking is done.  That lets us precompute the unit id
  for locally defined modules.

- Since we now know the correct module identities, we can
  make shapes for exposed-modules/other-modules and make
  them participate in mix-in linking.

- But we don't actually want to instantiate a requirement with
  a locally defined module, because GHC can't compile that!
  We want to error in this case.  Previously, we didn't notice
  that this had occurred at all; now it is caught, fixing #4447.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

 - Existing test `InternalLibrary4` was deleted because it relied on the old
   behavior.

 - New tests added are:
    - InternalVersions/BuildDependsBad
    - InternalVersions/BuildDependsExtra
    - InternalVersions/BuildToolsBad
    - InternalVersions/BuildToolsExtra
    - InternalVersions/BuildToolDependsBad
    - InternalVersions/BuildToolDependsExtra
    - ToolDependsInternalMissing

Edward Z. Yang authored 8 years ago and Edward Z. Yang committed 8 years ago

The key idea is that once we put PackageTests in its own package, we can
ensure that its Setup.hs is compiled with the same version of Cabal
library as package-tests is compiled with.  This means that LBI reading
will *always succeed* which is quite nice.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>