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In some cases, stack says that precompiled packages are broken. This problem will solve following steps.

1. unregister package by ghc-pkg
2. delete precompiled package files of stack

In following instruction, the target package name will denote as “package”. In stack message, the pakcage name is denote with version number, like “package-1.0.1”.

delete package

stack exec -- ghc-pkg unregister --force package

check deletion

stack exec -- ghc-pkg list | grep package

When there are several version of GHC, these commands may not work well. Then do below.

1. find ghc-pkg manageing the target pakcage
   • ex : ~/.stack/programs/x86_64-osx/ghc-7.10.2/bin/ghc-pkg
   • $$ $$
2. find database file
   • ex : ~/.stack/snapshots/x86_64-osx/lts-3.1/7.10.2/pkgdb
   • $$ $$
3. delete package
   • do > $$ghcpkg –package-db $$pkgdb unregister –force package
4. check deletion
   • do > $$ghcpkg –package-db $$pkgdb list | grep package

find ~/.stack/precompiled -type d -name package-* | xargs rm -rf

Do “stack build”, “stack install …” or something. You may see that stack recompile the target pakcages.

• Force stack to rebuild an installed package