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

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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