Record construction

[Brian Goetz]

> Minor tweak, but class names can get quite long. A keyword would be preferable:

Yes, that's also a realistic option, and reminiscent of instance 
initializers (but has the advantage of _not_ being an instance 
initializer, which already means something.)  From a readability 
perspective, I have a subjective preference for something that looks 
like a constructor, but I'd not rule this out.  (Remember, reading code 
is more important than writing code, so I don't think the length of the 
name is really the primary consideration.)


> Wild idea - is there a way for the library method to obtain the
> variable name and type used at the call site?:
>
>   public static void isTrue(CallsiteBooleanExpression expr) {
>     if (expr.isFalse()) {
>       throw new IllegalArgumentExpression(expr.expressionString() + "
> must be true");
>     }
>   }
>

Putting it in terms of a variable name and type doesn't make sense, 
because there might be multiple variable names and types:

     Preconditions.require(x < y);

Doing so would require something like expression trees, a major project.

A less intrusive path (but still not trivial) would be to factor out the 
dual "evaluate and textify" behavior of assert into a language feature, 
so that assert()-style methods could be written as ordinary library 
methods, and the method could receive, somehow, both the value and the 
text of a condition:

     MyLibrary.require( x < y )

Not crazy, but you've got to go a long way for it, so "wild" sounds 
about right.