stack's ghci command breaks importing from the current directory.
~/code/stack-bug $ ghci
GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help
λ> :l Foo
[1 of 2] Compiling Bar ( Bar.hs, interpreted )
[2 of 2] Compiling Foo ( Foo.hs, interpreted )
Ok, modules loaded: Foo, Bar.
λ>
Leaving GHCi.
~/code/stack-bug $ stack ghci
Configuring GHCi with the following packages:
GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help
λ> :l Foo
Foo.hs:3:8:
Could not find module ‘Bar’
Perhaps you meant
Bag (needs flag -package-key ghc-7.10.3)
Var (needs flag -package-key ghc-7.10.3)
Failed, modules loaded: none.
λ>
Thanks to Christopher Allen for pointing the way towards a fix.
You can work around the bug by re-including the current directory:
$ stack ghci --ghci-options -i.