Typestate doesn't track initialization through closures

[jdm]

fn foo(bl: block(int)) {
    let val = 5;
    bl(val);
}

fn main() {
    let val;
    foo({|new_val| val = new_val;});
    log_err val;
}

yields this error:

/Users/jdm/src/closure.rs:8:8: 8:34 error: Unsatisfied precondition constraint (for example, init(val [/Users/jdm/src/closure.rs:7:8: 7:11])) for expression:
{|new_val| val = new_val; }
Precondition:
init(val [/Users/jdm/src/closure.rs:7:8: 7:11])
Prestate:
!init(val [/Users/jdm/src/closure.rs:7:8: 7:11]), !init(main [/Users/jdm/src/closure.rs:6:0: 10:0]), !init(main! [/Users/jdm/src/closure.rs:6:0: 10:0])
/Users/jdm/src/closure.rs:8     foo({|new_val| val = new_val;});
                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
rust: upcall fail 'explicit failure', ../src/comp/driver/session.rs:66
rust: domain main @0x10202c400 root task failed

[graydon]

The type state system has no idea that the block gets run. It sees you using an uninitialized value in the log statement.

[marijnh]

Right. Calling a block zero times is valid, so the error message is correct in the above case.