We have a few ui tests to ensure we emit an error if we encounter too
big arrays. Before this fix, compiling the tests with `-Cdebuginfo=2`
would not include the spans of the instantiation sites, because the
error is then emitted from a different code path that does not include
the span.
Propagate the span to the error also in the debuginfo case, so the tests
passes regardless of debuginfo level.
