Name of lambda parameters

[Dan Smith]

On Jan 7, 2013, at 11:04 AM, Remi Forax <forax at univ-mlv.fr> wrote:

> (CC Alex Buckley)
> 
> As noticed recently on lambda-dev mailing list,
> there is no way to get the parameter names of a lambda because
> there is no way to do reflection on a lambda (an object implementing a functional interface) to get the corresponding declared method.

Note that it _is_ possible to get to the function descriptor:

Method descriptor = lambdaObj.getClass().getInterfaces()[0].getDeclaredMethods()[0]; // horribly oversimplified

What you want, I gather, is to get to the "method" that corresponds to the "lambda object" itself.  But note that there need not exist any such method in general.

Block<String> b1 = (String arg1) -> {};
Block<String> b2 = (String arg2) -> {};
assert b1 == b2; // this assertion might succeed

// possible implementation: class EmptyBlock implements Block<String> { void run(String arg3) {} }

Here, what is the "parameter name of" b2?

That fact that the current javac implementation has a one-to-one mapping between lambda expressions and compiled methods is an implementation detail.

(High-level point which is getting muddled here: lambdas are not objects that get converted to functional interface types.  Lambdas are expressions that evaluate to instances of functional interfaces.)

—Dan