In srfi-0 document, the example section shows cond-expand with no else clause and says

"Note that an error will be signaled at macro-expansion time if this feature is not present."

In R[57]RS, "an error is signaled" indicates that implementations must detect and report the error

(as opposed to more lenient "... is an error", to which implementations can choose what to do.)

On Mon, Mar 2, 2020 at 11:17 PM Lassi Kortela <xxxxxx@lassi.io> wrote:

Chibi -- returns #t
Cyclone -- returns #t
Gambit -- error
Gauche -- error
Gerbil -- returns no values
Guile -- error
Kawa -- returns no values
Larceny -- returns no values
Sagittarius -- error

Not sure which of these Schemes claim their cond-expand is SRFI 0
-compliant.