Add GHC-24922 (#501)

Author: frasertweedale

message-index/messages/GHC-24922/example/after/CannotReifyOutOfScopeThing.hs

@@ -0,0 +1,10 @@
+{-# LANGUAGE TemplateHaskell #-}
+
+module CannotReifyOutOfScopeThing where
+
+import Language.Haskell.TH
+
+doesn'tExist = "I do so!"
+
+do  t <- reifyType (mkName "doesn'tExist")
+    return []

message-index/messages/GHC-24922/example/before/CannotReifyOutOfScopeThing.hs

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+{-# LANGUAGE TemplateHaskell #-}
+
+module CannotReifyOutOfScopeThing where
+
+import Language.Haskell.TH
+
+do  t <- reifyType (mkName "doesn'tExist")
+    return []

message-index/messages/GHC-24922/example/index.md

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+---
+title: Cannot reify type because name is not in scope
+---
+
+GHC fails with an error because the requested name is not in scope.
+
+## Error Message
+
+```haskell
+CannotReifyOutOfScopeThing.hs:7:1: error: [GHC-24922]
+    ‘doesn'tExist’ is not in scope at a reify
+  |
+7 | do  t <- reifyType (mkName "doesn'tExist")
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
+```

message-index/messages/GHC-24922/index.md

@@ -0,0 +1,20 @@
+---
+title: Cannot reify type because name is not in scope
+summary: A Template Haskell error indicating that the given name is not in scope and therefore cannot be reified.
+severity: error
+introduced: 9.6.1
+---
+
+The [Template Haskell] [`reifyType`][haddock-reifyType] function
+returns the type or kind of a given name:
+
+```haskell
+reifyType :: Name -> Q Type
+```
+
+If the name is not in scope, GHC fails with error **GHC-24922**.
+The name has possibly been misspelled, or needs to be defined or
+brought into scope.
+
+[Template Haskell]: https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/template_haskell.html
+[haddock-reifyType]: https://hackage.haskell.org/package/template-haskell-2.22.0.0/docs/Language-Haskell-TH.html#v:reifyType