func heapSetType(x, dataSize uintptr, typ *_type, header **_type, span *mspan) (scanSize uintptr) {
	const doubleCheck = false

	gctyp := typ
	if header == nil {
		if doubleCheck && (!heapBitsInSpan(dataSize) || !heapBitsInSpan(span.elemsize)) {
			throw("tried to write heap bits, but no heap bits in span")
		}
		// Handle the case where we have no malloc header.
		scanSize = span.writeHeapBitsSmall(x, dataSize, typ)
	} else {

				// Note: disabled when race detector is on, see comment near end of this function.
				c.tiny = uintptr(x)
				c.tinyoffset = size
			}
			size = maxTinySize
		} else {
			hasHeader := !noscan && !heapBitsInSpan(size)
			if hasHeader {
				size += mallocHeaderSize
			}
			var sizeclass uint8
			if size <= smallSizeMax-8 {
				sizeclass = size_to_class8[divRoundUp(size, smallSizeDiv)]
			} else {

		if sizeclass := spanclass.sizeclass(); sizeclass == 0 {
			s.elemsize = nbytes
			s.nelems = 1
			s.divMul = 0
		} else {
			s.elemsize = uintptr(class_to_size[sizeclass])
			if !s.spanclass.noscan() && heapBitsInSpan(s.elemsize) {
				// Reserve space for the pointer/scan bitmap at the end.
				s.nelems = uint16((nbytes - (nbytes / goarch.PtrSize / 8)) / s.elemsize)
			} else {
				s.nelems = uint16(nbytes / s.elemsize)
			}