How can I test a signature violation without calling a perl function?

Question

Let's say I have,

use experimental 'signatures';
sub foo ($bar) { return 0 };

Now if I call it without the right arity, I'll get an error.

# Too few arguments for subroutine 'main::foo'
foo()
# Too many arguments for subroutine 'main::foo'
foo(1,2);

However, how can I test that. Let's say I want to make sure that someone implements a package Bar such that its function foo requires one argument. Is there a way to do this without running that code.

---

I see this question as different from my other question because even if I can't read the signature through some kind of Perl API, there may be a way to test that a subroutine is declared with a specific signature? An answer to that question can be used to answer this one. But an answer to this question may not answer that one.

Answer 1

From irc.freenode.net/#perl,

15:06 < Grinnz> EvanCarroll: yes, there's no way to do that either

He's speaking in reference to an earlier question about getting the signature of a function with an API.

Answer 2

The best you can do is try to call it in a string-eval:

$ perl -E 'sub foo ($bar) { return $bar } eval "foo()"; print "error: $@"'
error: Not enough arguments for main::foo at (eval 1) line 1, near "()
"

It needs to be a string-eval, not a block-eval, as you need to catch a compile-time error.