Macro to enforce static code regions.
```
function my_hot_function(args...)
# ...setup...
x,y = 1, 2 # ...
z = 0
# hot regions must stay performant
@enforce_stable begin
for i in 1:1000
# ...
z = x + y + z
# ...
i % 100 == 0 && @allow_unstable @info "computed $z"
end
end
return z
end
```
