the first example works fine the second one throws an error
| extend bucket1=1s
| summarize any(x) by bin(TimeGenerated,bucket)
| extend bucket =(iff(true,1s,1s))| summarize any(x) by bin(TimeGenerated,bucket)
the error:
bin(): failed to cast argument 2 to scalar constant Support id: acaf1907-d613-4238-a4c7-f77033167916
