Wrong return type for subtract between DateTime and Timespan

[faridmehrhesam]

Consider writing following KQL

print datetime('2025-01-01 00:05:00') - dynamic(3m)
| extend  type = gettype(print_0)

the result is:

but using KustoCode.ParseAndAnalyze will result in ResultType of the last QueryOperator to be:

Which is wrong as print_0 column needs to be of timespan type, looking into the code found issue to be return type of the Subtract in Kusto.Language.Operators:

[faridmehrhesam]

it’s actually the last signature that gets picked as the ReferencedSignature. The signature’s return type is DateTime, but what we get is a TimeSpan. So the language and the engine aren’t behaving the same way.

[mattwar]

This has been fixed in the source. It is not published on nuget yet.