Typestate too strict for multi-var let

[marijnh]

I'd like this to work:

let x = 10, y = x;

Currently, the initializer for y is checked in an environment where neither variable has been defined, so typestate rejects this line.

[catamorphism]

For simplicity, I actually prefer the current behavior.

What's the static semantics of let x = y, y = x; -- should it be rejected by typestate, or should it compile but diverge at runtime?

[marijnh]

The (recently revised) resolver will reject this. Variables can no longer be used before they are initialized, and series of variables in a single let behave as if they are defined one after the other (i.e Common Lisp's let* form, not let). To do a name swap, you can do 'let (x, y) = (y, x);' (where x and y were previously bound).

[catamorphism]

Ah, ok. As long as the resolver checks for obviously non-well-founded definitions, I guess I'm ok with implementing your original suggestion.