Problem:

When pressing alt-s to save a method with a compile error, the current
contents of the method pane may be reverted to the last saved contents.
This problem is new in 3.7.

This can be reproduced in a 3.7alpha #5657 image as follows:

1) alt-b (brings up a system browser) 
2) left-click on Kernel-Objects
3) left-click on Boolean
4) left-click on method &
5) left-click in method pane
6) alt-a (highlights method pane contents)
7) press a
8) press space
9) press b   (ie, method 'a' with undeclared var 'b') 
10) press alt-s

Now the the 'unknown variable' dialog is displayed and the method pane
contents reverts to the #& method. It should still show 'a b'. Pressing
cancel does not recover the changes. If the method is larger and the error
cannot be corrected via the dialog, significant work can be lost.

Note that restarting this procedure again from step 6 does NOT reproduce
the error.