The type isn't illegal.

Pike v7.6 release 112 running Hilfe v3.5 (Incremental Pike Frontend)

1[""];

Indexing the integer 1 with unknown method "". HilfeInput:1: HilfeInput()->___HilfeWrapper()

1["sgn"]();

(1) Result: 1

But the error in your example seems wrong, yes.

of course, ideally, i'd like to see something like:

can not index a function [*]

but i'd be happy with anything that at least gives a hint that there is an indexing error.

greetings, martin. [*] actually, i wish any type was indexable with the members of the respective type modules, as we discussed at the last conference, but that's a different topic.

Well, you do get e.g.

fun[5];

Cannot index function with 5. HilfeInput:1: HilfeInput()->___HilfeWrapper()

which seems to indicate that functions can be indexed by _something_. I don't know what, or what it would mean, though...