Proposal: single-expression method bodies

[Brian Goetz]

As a reminder, the spec-comments list is not for ongoing discussions; it is for self-contained comment submissions which are guaranteed to get to the attention of the Expert Group.  Discussions can happen on amber-dev or amber-spec-observers.  

> On Nov 24, 2017, at 10:58 PM, Daniel Trebbien <dtrebbien at gmail.com> wrote:
> 
> Hello Zheka,
> 
> I personally like your idea of supporting expression lambda syntax with
> methods.  Being able to write simple getters as public int getSomeField()
> -> someField; would be very useful, in my opinion.
> 
> I don't like the idea of expression lambda syntax support for switch cases,
> though, because I think that it wouldn't work well with fall-through
> support.  By way of example, consider:
> 
> String s = switch (o) {
>    case Integer n:
>    case Double n:
>        return n.toString();
> }
> 
> (I believe that reusing bound variable names like this is anticipated to be
> supported, but I could be wrong.)
> 
> Allowing expression lambda syntax with that might look like:
> 
> String s = switch (o) {
>    case Integer n ->
>    case Double n -> n.toString();
> }
> 
> Or maybe:
> 
> String s = switch (o) {
>    case Integer n,
>    case Double n -> n.toString();
> }
> 
> Or:
> 
> String s = switch (o) {
>    case Integer n, Double n -> n.toString();
> }
> 
> All three seem a bit strange and potentially confusing to me.
> 
> Daniel
> 
> On Wed, Nov 22, 2017 at 11:24 PM, Zheka Kozlov <orionllmain at gmail.com>
> wrote:
> 
>> Sorry if I'm repeating what was already discussed before. I didn't find
>> anything about this in the old threads.
>> 
>> Currently, lambdas support two forms of bodies:
>> 
>> 1. Function<Integer, String> func = (Integer i) -> i.toString();
>> 2. Function<Integer, String> func = (Integer i) -> {
>>    return i.toString();
>> };
>> 
>> But for methods only the second form is supported:
>> 
>> public String func(Integer i) {
>>    return i.toString();
>> }
>> 
>> This seems unfair to me, and I think the first form should be supported
>> too:
>> 
>> public String func(Integer i) -> i.toString()
>> 
>> 
>> Single-expression method bodies can reduce the amount of boilerplate:
>> 
>> public static int square(int x) -> x * x
>> 
>> // Simple getter
>> public int getSomeField() -> someField;
>> 
>> 
>> This will also be consistent with the two forms of switch (regular switch
>> and expression switch):
>> 
>> switch (o) {
>>    case Integer i: return i.toString();
>> }
>> 
>> vs.
>> 
>> String s = switch (o) {
>>    case Integer i -> i.toString();
>> }
>> 
>> What do you think?
>>