Improve Structure (subclass) construction performance.
#797
| Job | Run time |
|---|---|
| 1m 38s | |
| 8m 2s | |
| 7m 25s | |
| 1m 24s | |
| 8m 21s | |
| 7m 32s | |
| 1m 24s | |
| 9m 27s | |
| 7m 28s | |
| 1m 23s | |
| 8m 30s | |
| 7m 28s | |
| 1m 26s | |
| 8m 40s | |
| 1h 20m 8s |