The new Function API (
PUP-1799) does not specify a mechanism to handle a Lambda as the last argument.
This issue is blocked by
PUP-2026 (adding a lambda type).
There also needs to be smart handling of a lambda given to a function; if it should be included in the dispatched set of parameters or not, and how it is delivered to a method (like a Ruby block / on the side), or as an explicit parameter.
There are also issues regarding if the function API should help with typical processing of lambda arguments (the behavior of the function may differ based on the number of arguments given etc. This makes it more complex than just a "accepts Lambda taking these number of args and of these types" kind of declaration.
Right now, there is 0 support - at least it must be possible to handle an explicit Lambda among the parameters.