Guards

[Guy Steele]

> On Mar 5, 2021, at 6:32 PM, John Rose <john.r.rose at oracle.com> wrote:
> 
> On Mar 5, 2021, at 3:11 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
>> 
>> 
>> Or:
>> 
>>    case &&e:
> 
> Yes, I was reticent about that, but perhaps
> unary “&&” is a reasonable marker for
> “go into expression land”.  It could also
> help to mark in-args for deconstructor
> methods.

Ah, you have put your finger on what bothers me about using the specific symbol `&&` in this specific way: it looks like a unary operator, and unary operators bind tight.

	case && x > 0:

looks like it ought to mean

	case ((&& x) > 0):

Now,

	case var _ && x > 0:

clearly does the job, and the abbreviated form

	case _ && x > 0:

I could get behind.  But even that is beginning to be a lot of noise to introduce the guard.

Maybe we are just trying too hard.  Maybe we should use && to introduce guards, but

	case var _ && x > 0:

can be abbreviated as

	when x > 0:

?