Prusti encounters unexpected internal error about prusti-dev

[vakaras]

Based on the stack trace, the crash happens during the encoding of specifications or pure functions. It is illegal to use quantifiers inside pure functions, so I suspect that the crash is caused by is_square:

#[pure]
fn is_square(y: i32) -> bool {
    exists(|z: i32| y == sqr(z), y) // Illegal syntax.
}

By the way:

1. Existentials are typically hard for SMT solvers. Therefore, it is recommended to use a concrete witness instead.
2. x * x is an example of non-linear integer arithmetic, which is undecidable.

[Aurel300]

In addition to @vakaras comment, if you do want to wrap specification-only code into a "function", you can do so with a predicate. Predicates can only be called from specifications, such as pre- and postconditions, so your assert! would also have to be changed to a prusti_assert!.

[lpnaunau]

Thank you for your help, I'll have a look! Thx !