We test both for single and multiple exe/package.

`new-run` must halt on ambiguities or no compatible exes,
and must run the exe if one can be uniquely selected between
packages and components.

This reverts commit aa682f9e.

Move Distribution.Client.Compat.Prelude to Distribution.Compat.Prelude

The idea here is to break the dependency that has crept in from the
"Solver" into the "Client". (If there's ever going to be a separate
solver then the dependency would become a big problem.)

Fixes #4566.

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

Solver: Refactor Validate.hs.

Refactor goal sorting in the solver DSL.

This just moves some functions and types into Validate.hs in preparation for
#4391.

Now DSL.exResolve takes a goal-ordering function, which is more flexible
than a list of sorted goals.

[ci skip]

This reverts commit 8b563d4c.

Herbert Valerio Riedel authored 7 years ago and Mikhail Glushenkov committed 7 years ago

GHC 8.2.1 appears to take significantly longer to compile the code
and pushes us over the Travis job time limit.

[ci skip]

Fix test suite wobbliness on GHC 8.2.

Here were the root causes:

- Some tests involving Custom setpu showed MORE output
  (UseLocalPackageForSetup) when run on GHC 8.2.  This is because GHC
  8.2 ships a recent enough version of Cabal to know how to emit
  markers, which means we have started picking up the output.  I hacked
  up these tests to not accept this output, but a more correct thing to
  do is figure out how to NOT request marking of a Setup script which is
  not the inplace install.  This was a little tricky so I bailed.

- GHC 8.2 no longer emits "It is a member of the hidden package".
  This broke CustomWithoutCabalDefaultMain.  Not sure if this
  is a GHC regression but it's pretty harmless.

- While I was at it, I fixed an inexhaustive pattern match in
  cabal-testsuite (though perhaps poorly; I couldn't figure out
  what the new constructor does.)

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