[BUG] Top-level code isn't enforcing ownership and mutability

[modularml]

[BUG] Top-level code isn't enforcing ownership and mutability

[Mogball]

Thanks for the bug report! This seems specifically like a notebook environment bug, as it is occurring in top-level code (trying to do the same inside a function definition will cause a compilation error). @River707 I guess we need to track liveliness?

[lattner]

Yep, this is workbook toplevel code specific, thanks for reporting it!

[gabrieldemarmiesse]

Doing some triaging here, with Mojo 2024.1.0. I updated the example to reproduce the bug to the latest syntax:

struct Foo:
    var x: String
    fn __init__(inout self, owned x: String):
        self.x = x
    fn __moveinit__(inout self, owned existing: Self):
        self.x = existing.x

fn bar(owned foo: Foo) -> Int:
    return 2

var foo = Foo(String("test"))
print(bar(foo^))
print(bar(foo^))

We now get this output:

error: Expression [1]:12:14: cannot consume indirect references to values
print(bar(foo^))
             ^

error: Expression [1]:13:14: cannot consume indirect references to values
print(bar(foo^))
             ^

2
2

So we're getting errors in the output, but the notebook cell is still considered successful and the code is still executed. That's a different bug, but still a bug.