Index: docs/InternalsManual.html
===================================================================
--- docs/InternalsManual.html	(revision 157874)
+++ docs/InternalsManual.html	(working copy)
@@ -441,6 +441,12 @@
 to render the code differently (e.g., as markup inline) or even give
 the user the ability to automatically fix the problem.</p>
 
+<p>Fix-it hints on errors and warnings are automatically applied if
+<code>-Xclang -fixit</code> is passed to the driver, which means that errors
+and warnings should only have fix-its that very likely match the user's intent.
+Fix-its on notes are not applied automatically, so if the input is ambiguous
+put the fix-it on a note.</p>
+
 <p>All fix-it hints are described by the <code>FixItHint</code> class,
 instances of which should be attached to the diagnostic using the
 &lt;&lt; operator in the same way that highlighted source ranges and