stack init fails for packages that depend on Win32

[ndmitchell]

If I have a package that depends on Win32, stack init doesn't work.

Steps to reproduce

Using stack-1.9.3 on Windows, via stack upgrade.

1. stack init foo && cd foo
2. Edit package.yaml to include Win32 as a dependency of the library (line 24)
3. stack build works fine
4. stack init --force should find the resolver it was already using (lts-13.3 in my case), but:

C:\Neil\temp\stack-win32\foo>stack init --force --resolver=lts-13.3
Looking for .cabal or package.yaml files to use to init the project.
Using cabal packages:
- .\

Selected resolver: lts-13.3
Resolver 'lts-13.3' does not have all the packages to match your requirements.
    Win32 not found
        - foo requires -any

This may be resolved by:
    - Using '--solver' to ask cabal-install to generate extra-deps, atop the chosen snapshot.
    - Using '--omit-packages to exclude mismatching package(s).
    - Using '--resolver' to specify a matching snapshot/resolver

I expect it would generate an initial stack.yaml which roughly matches what stack new did. I imagine because Win32 is built in and platform conditional it needs to be ignored when searching for suitable resolvers.

CC @shayne-fletcher-da who is also suffering with the same issue.

[snoyberg]

I think this is fixed on master, where we've set up a global-hints.yaml file which includes Win32 (thanks to @sgraf812 in commercialhaskell/stackage-content#59).

[ndmitchell]

Perfect! I confirm this works on HEAD.