repro:

using import Box
using import testing

# I use Box here, but seems to happen with any lifetime checked type.
let T = (Box i32)

fn A ()
    label l
        do
            merge l (T)

fn B ()
    label l
        merge l (T)

fn C ()
    label l
        T;

C;
B;
# cannot access value of type (uniqueof <Box i32> 1000) because it has been moved
test-compiler-error
    A;
none