Function conversion (SAM) and ambiguity

[Mahmood Ali]

Greetings,

I was just wondering how the function conversion semantics interacts
with method overloading, where overloaded methods accept difference
SAMs.  Should there be a mechanism to explicitly state which interface
the closure should be converted to?

For example, suppose you have the following declaration

  interface ThrowingRunnable { void run() throws Throwable; }
  interface Executor {
    void execute(Runnable r);
    void execute(ThrowingRunnable r);
  }

  Executor e = ...
  e.execute(#() { doSomething(); })   // ambiguous conversion
  e.execute(#() { throw new RuntimeException(); }) // still ambiguous

I would propose resolving this ambiguity by:
 1. Issuing an error where an ambigiouty is found, and
 2. permitting the abstract class/interface name to appear between #
and parameters:

    e.execute(#Runnable() { doSomething(); });
    e.execute(#ThrowingRunnable() { throw new RuntimeException(); });

I realize that that space is reserved for return types in function
type declarations.

- Mahmood