"Cannot pass a mutable reference" error when returning an enum from an unconstrained function

[jfecher]

Aim

fn main() {
    let x = unsafe { foo() };
}

fn foo() -> Enum {
    Enum::A
}

enum Enum { A }

Expected Behavior

The program to either work or issue an error explaining that enums cannot cross the constrained <-> unconstrained boundary.

Bug

error: Cannot pass a mutable reference from a unconstrained runtime to an constrained runtime
  ┌─ src/main.nr:6:22
  │
6 │     let x = unsafe { foo() };
  │                      -----
  │

To Reproduce

Workaround

None

Workaround Description

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Additional Context

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Project Impact

None

Blocker Context

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Nargo Version

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NoirJS Version

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Proving Backend Tooling & Version

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