Bug #80550 for Function-Parameters: Introspection API

I agree that this would be a good thing to have in principle. I'm less sure about what the API should actually look like. For asking about the parameter list, there would probably be a function in Function::Parameters:: that returns an object with methods that return information about the parameters ... but in what form? Need to design an interface here. Suggestions? Next: How to actually implement this? Storing metadata during parsing/code generation is probably not hard, but how does the lookup work? Closures return a new subroutine each time they're evaluated at runtime, so the set of coderefs is not static. There's probably an internal associated code pointer that remains the same (CV?). Need to investigate perl internals. "Declared as a method" is a fuzzy concept. Function::Parameters has 3 orthogonal options that can be switched on/off for each keyword: 1) 'shift' - is $_[0] automatically shifted off and assigned to a variable (typically $self)? 2) 'invocant' - can individual function declarations override autoshifting (whether on or off) with an '$invocant:' parameter? 3) 'attributes' - what are the default attributes for subroutines declared with this keyword? The default method declarator includes ':method' here. #3 is the easiest to detect because you can already check whether attributes::get(\&foo) includes 'method'. In other words, if you don't use custom keywords, you can already detect methods declared with Function::Parameters right now. #1 and #2 would probably be covered by the proposed "parameter list" object - you'd check whether Function::Parameters::meta(\&foo)->invocant returns true (or something like that).

For completeness, it would be nice if the Function::Parameters::Info object had the following additional methods, unless they'd be a pain to implement... * name - the name of the sub, or undef * body - the coderef * attributes - the attributes declared if any. Not sure what level of parsing I'd expect Function::Parameters::Info to have done. The minimal probably. * prototype - the prototype for the function. Yes, Perl has a built-in for this... but for completeness. :-) A "keyword" method telling you what keyword was used to declare the sub also seems obvious, but actually I think that should be deliberately omitted. It's an implementation detail. If people want to use different keywords to classify different types of subs, they can give each keyword an attribute.