Add 30281

message-index/messages/GHC-30281/deriving-strategies/after/DerivingStrategies.hs

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+{-# LANGUAGE DerivingStrategies #-}
+
+module DerivingStrategies where
+
+data Foo = Foo
+  deriving Eq
+  deriving Ord

message-index/messages/GHC-30281/deriving-strategies/before/DerivingStrategies.hs

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+module Deriving-DerivingStrategies where
+
+data Foo = Foo
+  deriving Eq
+  deriving Ord

message-index/messages/GHC-30281/deriving-strategies/index.md

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+---
+title: Resolve by using the `DerivingStrategies` language extension
+order: 2
+---

message-index/messages/GHC-30281/deriving-tuple/after/Tuple.hs

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+module Tuple where
+
+data Foo = Foo
+  deriving (Eq, Show)

message-index/messages/GHC-30281/deriving-tuple/before/Tuple.hs

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+module Tuple where
+
+data Foo = Foo
+  deriving Eq
+  deriving Show

message-index/messages/GHC-30281/deriving-tuple/index.md

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+---
+title: Resolve by `deriving` a tuple of type classes
+order: 1
+---

message-index/messages/GHC-30281/index.md

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+---
+title: Multiple `deriving` clauses
+summary: Multiple `deriving` clauses are not allowed.
+severity: error
+introduced: 9.6.1
+---
+
+Using the `deriving` clause multiple times on the same `data` or `newtype` definition is illegal.
+
+Can be resolved by either:
+
+- Using deriving with a tuple (`deriving (Eq, Ord)`)
+- Using the `DerivingStrategies` language extension
+