Markdown reader: don't parse links or bracketed spans as citations.

Previously pandoc would parse

    [link to (@a)](url)

as a citation; similarly

    [(@a)]{#ident}

This is undesirable.  One should be able to use example references
in citations, and even if `@a` is not defined as an example
reference, `[@a](url)` should be a link containing an author-in-text
citation rather than a normal citation followed by literal `(url)`.

Closes #7632.

src/Text/Pandoc/Readers/Markdown.hs

@@ -327,6 +327,7 @@ referenceKey :: PandocMonad m => MarkdownParser m (F Blocks)
 referenceKey = try $ do
   pos <- getPosition
   skipNonindentSpaces
+  notFollowedBy (void cite)
   (_,raw) <- reference
   char ':'
   skipSpaces >> optional newline >> skipSpaces >> notFollowedBy (char '[')
@@ -1781,8 +1782,8 @@ endline = try $ do
 -- a reference label for a link
 reference :: PandocMonad m => MarkdownParser m (F Inlines, Text)
 reference = do
-  guardDisabled Ext_footnotes <|> notFollowedBy' (string "[^")
-  guardDisabled Ext_citations <|> notFollowedBy' (string "[@")
+  -- guardDisabled Ext_footnotes <|> notFollowedBy' (string "[^")
+  -- guardDisabled Ext_citations <|> notFollowedBy' (string "[@")
   withRaw $ trimInlinesF <$> inlinesInBalancedBrackets
 
 parenthesizedChars :: PandocMonad m => MarkdownParser m Text
@@ -2201,6 +2202,7 @@ normalCite = try $ do
   citations <- citeList
   spnl
   char ']'
+  notFollowedBy (oneOf "{([")  -- not a link or a bracketed span
   return citations
 
 suffix :: PandocMonad m => MarkdownParser m (F Inlines)

test/command/7632.md

@@ -0,0 +1,66 @@
+```
+% pandoc -t native
+(@a) First case
+
+[link to (@a)](url)
+^D
+[ OrderedList
+    ( 1 , Example , TwoParens )
+    [ [ Plain [ Str "First" , Space , Str "case" ] ] ]
+, Para
+    [ Link
+        ( "" , [] , [] )
+        [ Str "link" , Space , Str "to" , Space , Str "(1)" ]
+        ( "url" , "" )
+    ]
+]
+```
+
+```
+% pandoc -t native
+[@a]{.class}
+^D
+[ Para
+    [ Span
+        ( "" , [ "class" ] , [] )
+        [ Cite
+            [ Citation
+                { citationId = "a"
+                , citationPrefix = []
+                , citationSuffix = []
+                , citationMode = AuthorInText
+                , citationNoteNum = 1
+                , citationHash = 0
+                }
+            ]
+            [ Str "@a" ]
+        ]
+    ]
+]
+
+```
+
+```
+% pandoc -t native
+[@a](url)
+^D
+[ Para
+    [ Link
+        ( "" , [] , [] )
+        [ Cite
+            [ Citation
+                { citationId = "a"
+                , citationPrefix = []
+                , citationSuffix = []
+                , citationMode = AuthorInText
+                , citationNoteNum = 1
+                , citationHash = 0
+                }
+            ]
+            [ Str "@a" ]
+        ]
+        ( "url" , "" )
+    ]
+]
+
+```