Compiler panics when using `--dump-impls`

Running:

```
forc build -p test/src/e2e_vm_tests/test_programs/should_pass/return_into/ --dump-impls=Bytes
```

results in:

```
thread 'main' (3440458) panicked at sway-types/src/span.rs:279:9:
Spans from different files cannot be joined.
```