[clang] [Clang][Comments] Support for parsing headers in Doxygen \par commands (PR #91100)

[Aaron Ballman via cfe-commits]

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@@ -149,6 +149,63 @@ class TextTokenRetokenizer {
     addToken();
   }
 
+  /// Check if this line starts with @par or \par
+  bool startsWithParCommand() {
+    unsigned Offset = 1;
+
+    /// Skip all whitespace characters at the beginning.
+    /// This needs to backtrack because Pos has already advanced past the
+    /// actual \par or @par command by the time this function is called.
+    while (isWhitespace(*(Pos.BufferPtr - Offset)))
+      Offset++;
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AaronBallman wrote:

Rather than backtracking, can't we still do a peek ahead? e.g., once we've seen `@par`, we can do a peek to see if the next token is a newline or not (or do a scan through the buffer to see if there is a non-whitespace character or only whitespace ending with a newline/eof)?

https://github.com/llvm/llvm-project/pull/91100