Use transformers 0.2. This will be selected by cabal picking the appropriate version.

Use transformers 0.3. This will be selected by cabal picking the appropriate version.

Use transformers 0.4. This will be selected by cabal picking the appropriate version.

Use transformers 0.5 up until (but not including) 0.5.3. This will be selected by cabal picking the appropriate version.

• f-mtl Disables support for mtl for transformers 0.2 and 0.3. That is an unsupported configuration, and results in missing instances for ExceptT.

• f-generic-deriving prevents generic-deriving from being built as a dependency. This disables certain aspects of generics for older versions of GHC. In particular, Generic(1) instances will not be backported prior to GHC 7.2, and generic operations over unlifted types will not be backported prior to GHC 8.0. This is an unsupported configuration.