Upgrading packages/Updating to GHC 7

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A list of common problems upgrading packages to GHC 7.

If you maintain packages, this is for you.


If you use -XGADTs or -XTypeFamilies you get -XMonoLocalBinds, which says that local let/where bindings are not auto-generalised. There's a blog post that explains the change, and what do to about it:

base 3 goes away

There is no base 3 now, after being deprecated for several years, so dependencies on base 3 won't compile with GHC 7.

-fglasgow-exts is deprecated

-fglasgow-exts is deprecated, and enables fewer extensions than in previous releases. Use individual language flags (or better yet, pragmas) instead.

Quasiquotation data constructor modified

The QuasiQuoter constructor now takes four arguments instead of 2. (quoteType and quoteDec were added). One solution: use record syntax to set only the quoters you provide. This allows code to remain backwards compatible.

Quasiquotation: [$foo|...|] -> [foo|...|]

Quasiquoter invocation no longer requires/allows a leading dollar sign.

The binary library shipped with the compiler is renamed ghc-binary

If your package expects to see binary, the correct thing is to build and install an external version. However, you will need a version newer than, which was the current version in hackage when this was written.

Required library versions

A list of libraries and their earliest (known) GHC 7 ready version:

  • network >=
  • mtl >=
  • quickcheck >=
  • stringsearch >= 0.3.2