These tests deliberately use non-standard formatting, so that the line
execution counts reported by `llvm-cov` reveal additional information about
where code regions begin and end.
When MIR is built for an if-not expression, the `!` part of the condition
doesn't correspond to any MIR statement, so coverage instrumentation normally
can't see it.
We can fix that by deliberately injecting a dummy statement whose sole purpose
is to associate that span with its enclosing block.
