elfeed and emacs 27: elfeed-db-load: Wrong type argument

Question

After upgrading to emacs 27 with

brew install emacs --HEAD

When starting elfeed with

C-x w

I get

elfeed-db-load: Wrong type argument: avl-tree-, [cl-struct-avl-tree- [[[[[[[[[[[[[nil nil ... 0] [nil nil ... 0]\
 ... 0] [[nil nil ... 0] [nil nil ... 0] ... 0] ... 0] [[[nil nil ... 0] [nil nil ... 0] ... 0] [nil [nil nil ..\
. 0] ... 1] ... 0] ... 0] [[[[nil nil ... 0] nil ... -1] [[nil nil ... 0] [nil nil ... 0] ... 0] ... 0] [[[nil n\
il ... 0] [nil nil ... 0] ... 0] [[nil nil ... 0]
...   -1] nil nil 0] elfeed-db-compare]

Any ideas how to make elfeed work? This used to work in emacs 25

Answer 1

Just do this

rm ~/.emacs.d/elpa/elfeed-20180115.2112/*.elc

Answer 2

It is problem with the elfeed-db after the emacs internals have changed in v. 26. See https://github.com/skeeto/elfeed/issues/207.

The database needs to be rebuild. I ran rm -rf ~/.elfeed/ and restarted emacs to purge memory.