Could you please point out where does pcase.el uses 'map' in its
source? The error message you quote doesn't reference pcase.el, only
org-bookmark-heading.el, which is not part of Emacs and is not on
ELPA, AFAICT.

Apology for the misleading title.

`pcase.el' itself doesn't depend on `map.el', nor does it contain `map' pattern
in its source. `pcase.el' itself successfully compiles.

I encountered the error while trying to byte-compile `org-bookmark-heading.el',
which contains a `map' pattern at the following location:

https://github.com/alphapapa/org-bookmark-heading/blob/f245c9023df28d6ee545dae4b96a1c237e6965ba/org-bookmark-heading.el#L176

The error vanishes if I add `(eval-when-compile (require 'map))' as in the
following PR:

https://github.com/alphapapa/org-bookmark-heading/pull/19/files

I encountered similar errors in other libraries that contain a `map' pattern
inside a `pcase' form. It didn't happen until recently, when I updated Emacs and
began to get those errors.

So I wonder where's the place in the core Emacs sources
which causes the problem, and I couldn't find it. I'm probably
missing something.

There are some other additional patterns for `pcase'. One of them is `rx'
pattern. There is an autoload cookie right above the definition of
`(pcase-defmacro rx ...' in `rx.el'. On the other hand, there is no autoload
above `(pcase-defmacro map ...' in `map.el'. I think this might be the cause.

Is there any reason for not autoloading the `pcase-defmacro` form?

Thanks.