nan := math.NaN()
		for i := 0; i < n; i++ {
			m[nan] = 1
		}
		if len(m) != n {
			panic("wrong size map after nan insertion")
		}
	})

	// ~6ms on a 1.6GHz Zeon.
	checkLinear("eface", 10000, func(n int) {
		m := map[interface{}]int{}
		for i := 0; i < n; i++ {
			m[i] = 1
		}
	})

	// ~7ms on a 1.6GHz Zeon.
	// Regression test for CL 119360043.
	checkLinear("iface", 10000, func(n int) {

	base.AssertfAt(dst.IsInterface(), n.Pos(), "want interface type, have %L", n)
	if hasRType(n, n.TypeWord, "TypeWord") {
		return n.TypeWord
	}
	if dst.IsEmptyInterface() {
		return concreteRType(pos, src) // direct eface construction
	}
	if !src.IsInterface() {
		return ITabAddrAt(pos, src, dst) // direct iface construction
	}
	return TypePtrAt(pos, dst) // convI2I
}

// ConvIfaceSrcRType asserts that n is a conversion from