imenu--index-alist

imenu--index-alist 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:
The buffer index alist computed for this buffer in Imenu.

Simple elements in the alist look like (INDEX-NAME . POSITION).
POSITION is the buffer position of the item; to go to the item
is simply to move point to that position.
POSITION is passed to `imenu-default-goto-function', so it can be a non-number
if that variable has been changed (e.g. Semantic uses overlays for POSITIONs).

Special elements look like (INDEX-NAME POSITION FUNCTION ARGUMENTS...).
To "go to" a special element means applying FUNCTION
to INDEX-NAME, POSITION, and the ARGUMENTS.

A nested sub-alist element looks like (INDEX-NAME . SUB-ALIST).
The function `imenu--subalist-p' tests an element and returns t
if it is a sub-alist.

There is one simple element with negative POSITION; selecting that
element recalculates the buffer's index alist.