This happens with latest master, after make bootstrap:

1) emacs -Q
2) M-x eshell

eshell-mode: Symbol’s value as variable is void:
eshell-variable-aliases-list

Eshell starts, but the prompt cannot be seen (and by default, eshell-prompt
is enabled).

Bisecting points to 0d5e83611e5157800fd855fe8e3f60c8eff0af7c

Best regards,
Mauro.

In GNU Emacs 27.0.50 (build 1, i686-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2019-04-08 built on the-blackbeard
Repository revision: 3e5e097fdf056f4b3440993dd25ebdbad436abc3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 16.04.6 LTS

Recent messages:
Loading em-basic...done
Loading em-cmpl...done
Loading em-dirs...done
Loading em-glob...done
Loading em-hist...done
Loading em-ls...done
Loading em-prompt...done
Loading em-script...done
Loading em-term...done
Loading em-unix...done
eshell-mode: Symbol’s value as variable is void:
eshell-variable-aliases-list
Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB
NOTIFY INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF
XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: en_US.utf8
  value of $XMODIFIERS:
  locale-coding-system: utf-8-unix

Major mode: Eshell

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv dired dired-loaddefs format-spec rfc822 mml
mml-sec password-cache epa derived epg epg-config gnus-util rmail
rmail-loaddefs text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils em-unix em-term
term disp-table easymenu ehelp em-script em-prompt em-ls cl-loaddefs
cl-lib em-hist em-pred em-glob em-dirs em-cmpl pcomplete comint
ansi-color ring em-basic em-banner em-alias esh-mode eshell esh-cmd
esh-ext esh-opt esh-proc esh-io esh-arg esh-module esh-groups esh-util
elec-pair mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 8 59334 5566)
 (symbols 24 7470 1)
 (strings 16 19939 1418)
 (string-bytes 1 686848)
 (vectors 8 11799)
 (vector-slots 4 144802 10856)
 (floats 8 24 51)
 (intervals 28 205 0)
 (buffers 564 12)
 (heap 1024 7804 765))