Merge pull request #446 from jhrcek/GHC-42044

Document GHC-42044

Author: BinderDavid

message-index/messages/GHC-42044/example1/after/UnrecognisedPragmas.hs

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+{-# LANGUAGE BangPatterns #-}
+{-# OPTIONS_HUGS #-}
+module UnrecognisedPragmas where
+
+x :: Int
+x = 42
+{-# INLINE x #-}

message-index/messages/GHC-42044/example1/before/UnrecognisedPragmas.hs

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+{-# LANGUGE BangPatterns #-}
+--       ^ missing A
+{-# OPTION_HUGS #-}
+--        ^ missing S
+module UnrecognisedPragmas where
+
+x :: Int
+x = 42
+{-# INLNE x #-}
+--     ^ missing I
+

message-index/messages/GHC-42044/example1/index.md

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+---
+title: Misspelled pragmas
+---
+
+Typos in pragma names leads to warnings being emitted. Fixing the typos makes the warnings go away.
+
+## Error Message
+```
+UnrecognisedPragmas.hs:1:1: warning: [GHC-42044] [-Wunrecognised-pragmas]
+    Unrecognised pragma: LANGUGE
+    Suggested fix: Perhaps you meant ‘LANGUAGE’
+  |
+1 | {-# LANGUGE BangPatterns #-}
+  | ^^^^^^^^^^^
+
+UnrecognisedPragmas.hs:3:1: warning: [GHC-42044] [-Wunrecognised-pragmas]
+    Unrecognised pragma: OPTION_HUGS
+    Suggested fix: Perhaps you meant ‘OPTIONS_HUGS’
+  |
+3 | {-# OPTION_HUGS #-}
+  | ^^^^^^^^^^^^^^^
+
+UnrecognisedPragmas.hs:9:1: warning: [GHC-42044] [-Wunrecognised-pragmas]
+    Unrecognised pragma: INLNE
+    Suggested fix: Perhaps you meant ‘INLINE’
+  |
+9 | {-# INLNE x #-}
+  | ^^^^^^^^^
+```

message-index/messages/GHC-42044/index.md

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+---
+title: Unrecognised pragma
+summary: GHC didn't recognize pragma and will thus ignore it
+severity: warning
+flag: -Wunrecognised-pragmas
+introduced: 9.6.1
+---
+
+GHC emits a warning whenever it encounters a pragma which it doesn't recognize. In these cases it just ignores the pragma, which might not be what you want.
+
+This can indicate a typo in the name of the pragma, in which case fixing the typo should make the warning go away. See the GHC User Guide for a list of [supported pragmas](https://downloads.haskell.org/ghc/latest/docs/users_guide/exts/pragmas.html).