See this StackOverflow question. In short, the following fails with an error about base not being in the build plan on a fresh 64-bit Windows 7/8 MinGHC 2015-08-13 installation:

stack new stack-test new-template
cd stack-test
stack haddock

Changing "stack haddock" to "stack haddock --install-ghc --no-system-ghc" makes it work.