Funny. I see just about everyone has his own opinion as to what the bidding shows
But I think the problem simply boils down to whether South holds
KQJxxx
x
xxx
Kxx
(A spade negative free bid)
or
KQxxx
x
xx
AKxxx
(A game forcing 55)
Now.. playing natural (no fancy competitive stuff like equality, NFBs or whatever), we would all agree that the auction
1C....1S....X...pass
2C..pass..2H
obviously shows a heart negative free bid: 5-6 cards, not enough hcp for a direct 2H. The point is up to what level should this philosophy hold? Let's look at a few examples:
1D....1H....X...pass
2D..pass..3C
The 3C probably shows a hand close to a NFB, since pard can pass or correct to 3D.
1D....2H....X...pass
3D..pass..3S
Now, does it still make sense that 3S is a NFB? Not really. To force to the 3 level, pard cannot have less than 11-12 points. With those 11-12 he might as well have bid a direct 2S. But he didn't do so. So he must have some interest in clubs, thus pard's bidding shows a 5-5 in the blacks. Since responder gave finding a club fit as much importance as finding a spade fit, I'd even dare to say 3S is slammish.
1H....3D....X...pass
3H..pass..3S
Finally, our example is the borderline case: on the one hand South couldn't have bid 2S. On the other hand he's forcing the 3 level. The first argument points at a NFB with very nice spades (after all, it's the 3 level...), the second at a game forcing black 55. Since with a nice spade holding South might have streched to bid 3/4S the first round, I am inclined to place South with the forcing 55.
In this case, the correct bidding is clear:
1H....3D....X...pass
3H..pass..3S...pass
4C..pass..5C (or RKCB)
North's 4S on the 5-2 fit is passable, but after the double, I think bidding 5C is somewhat safer.
Anyway, at table both players interpreted 3S as the 55. In the end the "correct" meaning to 3S depends on what you agree with pard. But what I claim is that bidding "rules" (in this case dbl + suit = NFB) only apply up to a point. In a practical situation one should put prejudice aside and think. Things aren't always what they seem...
See below for auction.