Project Lambda: Java Language Specification draft

[Alex Buckley]

Alex Blewitt wrote:
> On 22 Jan 2010, at 22:55, Alex Buckley <Alex.Buckley at Sun.COM> wrote:
> 
>> * Exceptions
>>
>> [11.2.1 Exception Analysis of Expressions]
>>
>> A lambda invocation expression on a lambda expression of type
>> #T(S1..Sm)(X1..Xn) can throw an exception type E iff either:
>>
>> - some expression of the argument list can throw E, or
>> - there exists an i in 1..n such that Xi is E.
> 
> Does that mean the only way to throw a RuntimeException is if it is 
> explicitly declared in the type?

No. The body of the lambda expression is able to throw whatever 
unchecked exceptions it likes, akin to the body of a method. For the 
purpose of exception checking, it is not the case that a method 
invocation "can throw" a RuntimeException even if the method's body 
contains 'throw new RuntimeException()'. Same for lambda invocation.

> Does it also prevent throwing an EOFException if you've only declared 
> IOException in the list?

It shouldn't prevent it, but technically it does. I am reminded of some 
changes to 11.2 that Neal raised years ago; time to sync them up.

Alex