imenu-extract-index-name-function

imenu-extract-index-name-function is a variable defined in `imenu.el'.
Its value is

nil

• Automatically becomes buffer-local when set.
• This variable may be risky if used as a file-local variable.

Documentation:
Function for extracting the index item name, given a position.

This function is called after `imenu-prev-index-position-function'
finds a position for an index item, with point at that position.
It should return the name for that index item.