Evaluation of subexpressions in Any.of

[usaoc]

I have two questions:

1. Should the subexpressions be evaluated whenever matching happens?
2. If yes, should Any.of have a short-circuiting behavior?

The following program showcases the difference in behavior.

def bx :: Box.later_of(Any.of(block:
                                println("one")
                                1,
                              block:
                                println("two")
                                2)):
  Box(1)
bx.value
bx.value := 2
bx.value

• If no to 1, then “one” and “two” will be printed;
• If yes to 1,
  • If yes to 2, then “one”, “one”, “two” will be printed;
  • If no to 2, then “one”, “two”, “one”, “two” will be printed.

[usaoc]

Somewhat relatedly: evaluation of subexpressions in Real.{at_least,above,below,at_most} and {Real,Int}.in.

[mflatt]

My first impression is that the answer to 1 should be "no", and the expressions should be evaluated when the definition is evaluated.

But that would implement that the environment of a function argument's annotation doesn't include earlier arguments. I can't remember whether that feature of the current implementaation is important and intentional for some purpose, or if it's just an artifact of the current expansion:

fun f(a, b :: Real.in(a, 10)):
  "ok"

f(1, 9)
f(1, 20) // => does not satisfy annotation

[mflatt]

After looking into this, I concluded that the answer to 1 needs to be "no". Supporting that answer required a refinement to the low-level binding protocol, which is implemented in 9864aef. The intended behavior is now documented to a useful degree, but more precision is needed (probably in the new "Rhombus Language Model" document as it fills out).