profiler-report seems to be missing data?

[Charlie Andrews]

I'm trying to profile the usually excellent `find-things-fast` package to
figure out why it's slow in my project.

I started profiling with `profiler-start`, executed the command that's slow
(`ftf-find-file`), then immediately ran `profiler-report`.

This generated the following report:

    Functions                                                 CPU samples  %
    - command-execute                                                1770
88%
     - call-interactively                                            1770
88%
      - apply                                                        1770
88%
       - call-interactively@ido-cr+-record-current-command
 1770  88%
        - apply                                                      1770
88%
         - #<subr call-interactively>                                1770
88%
          - funcall-interactively                                    1770
88%
           - ftf-find-file                                           1597
80%
            - ftf-project-files-alist                                1522
76%
             - ftf-project-files-hash                                1330
66%
              - let                                                  1330
66%
               - mapcar                                              1330
66%
                - #<lambda 0x5458e8e0>                               1024
51%
                 - let*                                              1008
50%
                    cons                                               24
 1%
                + split-string                                        282
14%
             + maphash                                                192
 9%
            + ido-completing-read                                      67
 3%
           + next-line                                                 75
 3%
           + ido-switch-buffer                                         41
 2%
           + ido-switch-buffer-other-window                            38
 1%
           + profiler-report                                           19
 0%
    + ...                                                             145
 7%
    + redisplay_internal (C function)                                  37
 1%
    + timer-event-handler                                              26
 1%
      undefined                                                         5
 0%
    + gui-set-selection                                                 4
 0%
      internal-echo-keystrokes-prefix                                   2
 0%

The profiler report seems to blame the `let*` function within
`ftf-project-files-hash`.

However, looking at that function:

    (defun ftf-project-files-hash ()
      "Returns a hashtable filled with file names as the key and "
      (let ((default-directory (ftf-project-directory))
            (table (make-hash-table :test 'equal)))
        (mapcar (lambda (file)
                  (let* ((file-name (file-name-nondirectory file))
                         (full-path (expand-file-name file))
                         (pathlist (cons full-path (gethash file-name table
nil))))
                    (puthash file-name pathlist table)))
                (split-string (ftf-project-files-string)))
        table))

It seems incredibly unlikely that `let*` is the slow part, but rather one
of the functions called within that `let*`.

Why is `profiler-report` stopping at `let*` rather than telling me which
component of that `let*` is slow? How can I dig deeper to find which
exactly function is slow?

(FWIW, I've tried increasing profiler-max-stack-depth from 16 to 30 to no
avail.)