// be true in any match. It returns ^EmptyOp(0) if no matches are possible.
func (p *Prog) StartCond() EmptyOp {
	var flag EmptyOp
	pc := uint32(p.Start)
	i := &p.Inst[pc]
Loop:
	for {
		switch i.Op {
		case InstEmptyWidth:
			flag |= EmptyOp(i.Arg)
		case InstFail:
			return ^EmptyOp(0)
		case InstCapture, InstNop:
			// skip
		default:
			break Loop
		}

					b.cap[inst.Arg] = pos
				}
				pc = inst.Out
				goto CheckAndLoop
			}

		case syntax.InstEmptyWidth:
			flag := i.context(pos)
			if !flag.match(syntax.EmptyOp(inst.Arg)) {
				continue
			}
			pc = inst.Out
			goto CheckAndLoop

		case syntax.InstNop:
			pc = inst.Out
			goto CheckAndLoop

		case syntax.InstMatch:

	}
	return c.loop(f1, nongreedy)
}

func (c *compiler) plus(f1 frag, nongreedy bool) frag {
	return frag{f1.i, c.loop(f1, nongreedy).out, f1.nullable}
}

func (c *compiler) empty(op EmptyOp) frag {
	f := c.inst(InstEmptyWidth)
	c.p.Inst[f.i].Arg = uint32(op)
	f.out = makePatchList(f.i << 1)
	return f
}

func (c *compiler) rune(r []rune, flags Flags) frag {
	f := c.inst(InstRune)

	structp    *Struct
	bigstructp *BigStruct
	emptyp     *Empty
	empty1p    *Empty1
)

func f1() {
	_ = *intp    // ERROR "nil check"
	_ = *arrayp  // ERROR "nil check"
	_ = *array0p // ERROR "nil check"
	_ = *array0p // ERROR "nil check"
	_ = *intp    // ERROR "nil check"
	_ = *arrayp  // ERROR "nil check"
	_ = *structp // ERROR "nil check"
	_ = *emptyp  // ERROR "nil check"
	_ = *arrayp  // ERROR "nil check"
}

	_ = *structp // ERROR "generated nil check"
	_ = *emptyp  // ERROR "generated nil check"
	_ = *arrayp  // ERROR "removed nil check"
}

func f2() {
	var (
		intp       *int
		arrayp     *[10]int
		array0p    *[0]int
		bigarrayp  *[1 << 20]int
		structp    *Struct
		bigstructp *BigStruct
		emptyp     *Empty
		empty1p    *Empty1
	)

	_ = *intp       // ERROR "generated nil check"