B: MonoPatBinds is no longer the default

languageExtensions (Just Haskell98)
    = [Opt_ImplicitPrelude,
       Opt_MonomorphismRestriction,
       Opt_NPlusKPatterns,
       Opt_DatatypeContexts,
       Opt_TraditionalRecordSyntax,
       Opt_NondecreasingIndentation
           -- strictly speaking non-standard, but we always had this
           -- on implicitly before the option was added in 7.1, and
           -- turning it off breaks code, so we're keeping it on for
           -- backwards compatibility.  Cabal uses -XHaskell98 by
           -- default unless you specify another language.
      ]

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languageExtensions (Just Haskell98)
    = [Opt_ImplicitPrelude,
       Opt_MonomorphismRestriction,
       Opt_NPlusKPatterns,
       Opt_DatatypeContexts,
       Opt_TraditionalRecordSyntax,
       Opt_NondecreasingIndentation
           -- strictly speaking non-standard, but we always had this
           -- on implicitly before the option was added in 7.1, and
           -- turning it off breaks code, so we're keeping it on for
           -- backwards compatibility.  Cabal uses -XHaskell98 by
           -- default unless you specify another language.
      ]
languageExtensions (Just Haskell98)
    = [Opt_ImplicitPrelude,
       Opt_MonomorphismRestriction,
       Opt_NPlusKPatterns,
       Opt_DatatypeContexts,
       Opt_TraditionalRecordSyntax,
       Opt_NondecreasingIndentation
           -- strictly speaking non-standard, but we always had this
           -- on implicitly before the option was added in 7.1, and
           -- turning it off breaks code, so we're keeping it on for
           -- backwards compatibility.  Cabal uses -XHaskell98 by
           -- default unless you specify another language.
      ]