Win10: ASDF can't load system (ASDF_OUTPUT_TRANSLATION error) - windows-10

Question

Update 2
I think #faré is right, it's an output translation problem.
So I declared the evironment variable ASDF_OUTPUT_TRANSLATIONS and set it to E:/. Now (asdf:require-system "my-system") yields a different error: Uneven number of components in source to destination mapping: "E:/" which led me to this SO-topic.
Unfortunately, his solution doesn't work for me. So I tried the other answer and set ASDF_OUTPUT_TRANSLATIONS to (:output-translations (t "E:/")). Now I get yet another error:
Invalid source registry (:OUTPUT-TRANSLATIONS (T "E:/")).
One and only one of
:INHERIT-CONFIGURATION or
:IGNORE-INHERITED-CONFIGURATION
is required.
(will be skipped)
Original Posting
I have a simple system definition but can't get ASDF to load it.
(asdf-version 3.1.5, sbcl 1.3.12 (upgraded to 1.3.18 AMD64), slime 2.19, Windows 10)
What I have tried so far
Following the ASDF manual: "4.1 Configuring ASDF to find your systems"
There it says:
For Windows users, and starting with ASDF 3.1.5, start from your
%LOCALAPPDATA%, which is usually ~/AppData/Local/ (but you can ask in
a CMD.EXE terminal echo %LOCALAPPDATA% to make sure) and underneath
create a subpath config/common-lisp/source-registry.conf.d/
That's exactly what I did:
Echoing %LOCALAPPDATA% which evaluates to C:\Users\my-username\AppData\Local
Underneath I created the subfolders config\common-lisp\source-registry.conf.d\ (In total: C:\Users\my-username\AppData\Local\config\common-lisp\source-registry.conf.d\
The manual continues:
there create a file with any name of your choice but with the type conf, for instance 50-luser-lisp.conf; in this file, add the following line to tell ASDF to recursively scan all the subdirectories under /home/luser/lisp/ for .asd files: (:tree "/home/luser/lisp/")
That’s enough. You may replace /home/luser/lisp/ by wherever you want to install your source code.
In the source-registry.conf.d folder I created the file my.conf and put in it (:tree "C:/Users/my-username/my-systems/"). This folder contains a my-system.asd.
And here comes the weird part:
If I now type (asdf:require-system "my-system") in the REPL I get the following error:
Can't create directory C:\Users\my-username\AppData\Local\common-lisp\sbcl-1.3.12-win-x86\C\Users\my-username\my-systems\C:\
So the problem is not that ASDF doesn't find the file, it does -- but (whatever the reason) it tries to create a really weird subfolder hierarchy which ultimately fails because at the end it tries to create the folder C: but Windows doesn't allow foldernames containing a colon.
Another approach: (push path asdf:*central-registry*)
If I try
> (push #P"C:/Users/my-username/my-systems/" asdf:*central-registry*)
(#P"C:/Users/my-username/my-systems/"
#P"C:/Users/my-username/AppData/Roaming/quicklisp/quicklisp/")
> (asdf:require-system "my-system")
I get the exact same error.
I don't know what to do.
Update
Because of the nature of the weird path ASDF was trying to create I thought maybe I could bypass the problem by specifying a relative path instead of an absolute one.
So I tried
  (:tree "\\Users\\my-username\\my-systems")
in my conf file. Still the same error.

Answer 1

Ahem. It looks like an output-translations problem.
I don't have a Windows machine right now, but this all used to work last time I tried.
Can you setup some ad hoc output-translations for now that will make it work?