Ignore code block annotations in docstrings

Improves #66.

racer.el

@@ -415,6 +415,8 @@ the user to choose."
        ((and (not in-code) (string-match-p (rx bol "[`" (+? anything) "`]: ") line)))
        ;; Skip repeated blank lines (caused by skipping cross references).
        ((and (equal line "") (equal (-first-item current-section-lines) "")))
+       ;; Skip lines in code blocks that are rustdoc annotations, e.g. # #[allow(dead_code)]
+       ((and in-code (s-starts-with-p "# " line)))
        ;; Otherwise, just keep appending the line to the current
        ;; section.
        (t

test/racer-test.el

@@ -63,6 +63,27 @@ bar.
     2
 ")))
 
+(defun racer--remove-properties (text)
+  "Remove all the properties on TEXT.
+Tests that use `equal' ignore properties, but
+this makes the ert failure descriptions clearer."
+  (with-temp-buffer
+    (insert text)
+    (buffer-substring-no-properties (point-min) (point-max))))
+
+(ert-deftest racer--propertize-docstring-code-annotations ()
+  "Ignore '# foo' lines in code sections in docstrings."
+  (should
+   (equal
+    (racer--remove-properties
+     (racer--propertize-docstring "```
+# #[allow(dead_code)]
+#[derive(Debug)]
+struct Foo {}
+```"))
+    "    #[derive(Debug)]
+    struct Foo {}")))
+
 (ert-deftest racer--propertize-docstring-newlines ()
   "Ensure we still handle links that have been split over two lines."
   (should