When were GADTs introduced in GHC?
gadt, ghc, haskell
Solution
GADTs were first supported in ghc-6.4, which was released in March 2005.
They are still a language extension, the latest standard, Haskell2010, has not adopted them (since it was a GHC-only extension, afaik).
Problem
When were GADTs introduced in GHC? (version + date) Also, are they still considered a language extension or are they now part of the Haskell standard proper?