Tailcall parameter in Expression.Lambda

What is the reason behind giving a parameter for tailcall optimization in

Expression.Lambda(Expression body,bool tailcall,
IEnumerable<ParameterExpression> Parameters)

As long 开发者_StackOverflowas it is not going affect the result why do we explicitly need to specify a value for it.And i feel it is always better to have tailcall optimization. Do you have different thought on this

The design is kinda funny.

Passing true for the tailcall parameter, will attempt to call method in a tail position as a tail call within the body of the lambda.

A tail position is where a method call is the expression being returned.

As for better, that is subjective.

• Tail calls tend to be always slower
• There are certain rules to follow (return types must match or be references)
• You have no stacktrace for debugging