Save an allocation during inner observer creation in Switch.

[danielcweber]

No description provided.

[glennawatson]

Hey if it's possible, can you add benchmarks like you did in your other PR? That was useful to see the results. I understand that's a bit of work so can understand if you decline to.

[danielcweber]

I added a benchmark that switches between 10000 observables.

Original:

               Method |     Mean |     Error |    StdDev |     Gen 0 | Allocated |
--------------------- |---------:|----------:|----------:|----------:|----------:|
 Switch_10000_Sources | 17.54 ms | 0.3283 ms | 0.3224 ms | 3656.2500 |   7.34 MB |


Less allocations:

               Method |     Mean |     Error |    StdDev |     Gen 0 | Allocated |
--------------------- |---------:|----------:|----------:|----------:|----------:|
 Switch_10000_Sources | 18.09 ms | 0.3541 ms | 0.5916 ms | 3531.2500 |   7.09 MB |

[glennawatson]

The bench marks show that you have more fluctations with the increase in the standard deviation, with only a very slight decrease in terms of performance. I think it's good enough with the improvement to allocations.