form fields cannot have the name 'edit'

If a form field has the name 'edit'; e.g.:

$form['edit'] = array(
  '#type' => 'textfield',
  ...
);

then upon submitting the form we will be redirected to a "strange" URL: a URL which is the first letter typed into that form field. For example, if we type "rolex" into the field, then, after clicking the submit button, we will be redirected to http://example.com/r.

That's becaue drupal_goto(), which is used by FAPI, has the folowing code:

[...] if (isset($_REQUEST['edit']['destination'])) {

This condition will evaluate to TRUE. That's how string subscripts are handled in PHP. Another example:

$a['edit'] = 'rolex';
// the following statement prints 'r'
print $a['edit']['destination']; 

(Bug discovered while helping a user in the fourm.)