1 patch for repository http://code.haskell.org/parsec3:

Thu May 31 01:38:09 EEST 2012  Roman Cheplyaka <roma@ro-che.info>
  * When merging error messages, prefer known messages to unknown ones
  
  This fixes a regression introduced by:
  
  Sun Feb 20 18:24:22 EET 2011  Roman Cheplyaka <roma@ro-che.info>
    * Choose the longest match when merging error messages
  
  The source of the regression is that parsec sometimes generates dummy (aka
  "unknown") error messages when no actual error has occurred.
  
  So, when merging errors, before simply looking at the positions we should check
  if one of them is unknown and just ignore it.
  
  Reported by Matthias Hörmann.

New patches:

[When merging error messages, prefer known messages to unknown ones
Roman Cheplyaka <roma@ro-che.info>**20120530223809
 Ignore-this: 1cfcc0a8d1cbfd183a3897e79c320c22
 
 This fixes a regression introduced by:
 
 Sun Feb 20 18:24:22 EET 2011  Roman Cheplyaka <roma@ro-che.info>
   * Choose the longest match when merging error messages
 
 The source of the regression is that parsec sometimes generates dummy (aka
 "unknown") error messages when no actual error has occurred.
 
 So, when merging errors, before simply looking at the positions we should check
 if one of them is unknown and just ignore it.
 
 Reported by Matthias Hörmann.
] {
hunk ./Text/Parsec/Error.hs 137
     = ParseError pos (msg : filter (msg /=) msgs)
 
 mergeError :: ParseError -> ParseError -> ParseError
-mergeError (ParseError pos1 msgs1) (ParseError pos2 msgs2)
+mergeError e1@(ParseError pos1 msgs1) e2@(ParseError pos2 msgs2)
+    -- prefer meaningful errors
+    | null msgs2 && not (null msgs1) = e1
+    | null msgs1 && not (null msgs2) = e2
+    | otherwise
     = case pos1 `compare` pos2 of
         -- select the longest match
         EQ -> ParseError pos1 (msgs1 ++ msgs2)
hunk ./Text/Parsec/Error.hs 145
-        GT -> ParseError pos1 msgs1
-        LT -> ParseError pos2 msgs2
+        GT -> e1
+        LT -> e2
 
 instance Show ParseError where
     show err
}

Context:

[TAG 3.1.2
Antoine Latter <aslatter@gmail.com>**20111008182138
 Ignore-this: 96361fd74cad3d51b4213e0bcd91cdf3
] 
[version bump for release
Antoine Latter <aslatter@gmail.com>**20111008181844
 Ignore-this: 9c28994644744eaf375d9c5d75d2b201
] 
[add Stream Text instances
Antoine Latter <aslatter@gmail.com>**20111008181718
 Ignore-this: fcf1bc6a54bae9936669e28047c4f736
] 
[Fix reserved name recognition for case-insensitive languages.
Antoine Latter <aslatter@gmail.com>**20111008180454
 Ignore-this: aed4027b1f273913f7586208e5a6f82c
] 
[Documentation fix
Roman Cheplyaka <roma@ro-che.info>**20111228222953
 Ignore-this: 2d226ed7cde7a8322be04f5188957eb2
] 
[lookAhead: do not consume input on success; update documentation
Roman Cheplyaka <roma@ro-che.info>**20110220162920
 Ignore-this: e884771490209b93e9fec044543a18ef
] 
[try: do not reset the error position
Roman Cheplyaka <roma@ro-che.info>**20110220162449
 Ignore-this: 8508bc41fc6dcd9b7c06aac762f12c71
] 
[Choose the longest match when merging error messages
Roman Cheplyaka <roma@ro-che.info>**20110220162422
 Ignore-this: 54e2733159a1574abb229e09ff6935c1
] 
[TAG 3.1.1
Antoine Latter <aslatter@gmail.com>**20110129160030
 Ignore-this: 42ddc9e7316d68945c2c1260c2acd403
] 
Patch bundle hash:
09fc71cdc9e86dc672f19bc8fb939103cae782bb