`stack solver` creates a build plan that `stack build` can't follow.

[danielwaterworth]

Steps to reproduce

For example:

1. git clone https://github.com/DanielWaterworth/editor.git&& cd editor&& git checkout stack_bug
2. Run command stack solver.
3. Run command stack build.

Expected

A successful build, or at least successful dependency resolution.

Actual

https://gist.github.com/DanielWaterworth/e83cded59a6d7f4a3335f4ffb3d177ca

Stack version

$ stack --version
Version 1.1.2, Git revision cebe10e845fed4420b6224d97dcabf20477bbd4b (3646 commits) x86_64 hpack-0.14.0

Method of installation

• Installed via curl command.

[danielwaterworth]

It looks like stack solver doesn't take into account dependencies that are forced by the ghc version. In this case template-haskell.

[harendra-kumar]

In the second retry phase when it relaxes the hard constraints to soft preferences it treats even the ghc wired-in packages as preferences. ghc packages should still remain as hard constraints only other packages should be relaxed. I am fixing it.