code: func (d *Descriptions) IsStub(fn *ssa.Function) bool {
  	if len(fn.Blocks) == 0 {
  		return true
  	}
  	if len(fn.Blocks) > 1 {
  		return false
  	}
  	instrs := lintdsl.FilterDebug(fn.Blocks[0].Instrs)
  	if len(instrs) != 1 {
  		return false
  	}
  
  	switch instrs[0].(type) {
  	case *ssa.Return:
  		// Since this is the only instruction, the return value must
  		// be a constant. We consider all constants as stubs, not just
  		// the zero value. This does not, unfortunately, cover zero
  		// initialised structs, as these cause additional
  		// instructions.
  		return true
  	case *ssa.Panic:
  		return true
  	default:
  		return false
  	}
  }
docs: // IsStub reports whether a function is a stub. A function is
  // considered a stub if it has no instructions or exactly one
  // instruction, which must be either returning only constant values or
  // a panic.