When investigating a coverity ticket for an unchecked return value in SERVER-50838 it was noticed that the return value was unchecked in 

• CountScan::doRestoreStateRequiresIndex()
• DistinctScan::doRestoreStateRequiresIndex()
• sbe::IndexScanStage::doRestoreState()
• SortedDataInterfaceThrottleCursor::restore()

Should we add uasserts to check the return values for these calls? We do check the return value in FetchStage.

uassert(50982, "could not restore cursor for FETCH stage", couldRestore)