Posted 2015-June-14, 03:50
Not specifically discussed, but if double of 2♠ is take-out, then 3♠ sounds like a game forcing club raise. Partner may be able to infer the spade length from failure to double and the overcall/raise.
You are right that 2♠ takes away two calls, but in return: (i) Responder gets back one extra positive call (double); (ii) you've told the opponents about the spade fit; (iii) you've told partner about the spade fit so there's a significant possibility that he'll now over-compete the hand. Even worse (iv) in the future on hands where you raise to 2♠ he'll think twice before competing, fearing that you have a completely useless hand like this.