Range branch with label(break/continue/goto/return)

[JessonChan]

L:
for k, v := range [1,2,3] {
	if k < 2 {
		continue L
	}
	if k > 2{
                println("range break")
		break L
	}
	println(k, v)
}

[codecov-commenter]

Codecov Report

Merging #511 into master will increase coverage by 0.03%.
The diff coverage is 95.77%.

@@            Coverage Diff             @@
##           master     #511      +/-   ##
==========================================
+ Coverage   89.90%   89.93%   +0.03%     
==========================================
  Files          40       41       +1     
  Lines       10210    10295      +85     
==========================================
+ Hits         9179     9259      +80     
- Misses        752      754       +2     
- Partials      279      282       +3     

Impacted Files	Coverage Δ
cl/expr.go	86.51% <ø> (-0.07%)	⬇️
cl/ctx_check.go	76.40% <33.33%> (+0.09%)	⬆️
exec/golang/stmt.go	94.27% <53.33%> (-2.50%)	⬇️
cl/context.go	83.55% <100.00%> (+0.68%)	⬆️
cl/stmt.go	93.59% <100.00%> (-0.02%)	⬇️
exec/bytecode/code.go	100.00% <100.00%> (ø)
exec/bytecode/context.go	94.44% <100.00%> (-0.11%)	⬇️
exec/bytecode/flow.go	97.01% <100.00%> (+0.68%)	⬆️
exec/bytecode/func.go	93.65% <100.00%> (-0.08%)	⬇️
exec/bytecode/goinstr_lstcompr.go	94.22% <100.00%> (+0.81%)	⬆️
... and 6 more

---

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[xushiwei]

It seems too complex to implement this feature.
Let's discuss how to improve it.

[JessonChan]

Let's discuss how to improve it.

Glad to discuss this.

[xushiwei]

In cl package we can introduce ContainerTrait and container Iterator:

func TraitContainer(containerTy reflect.Type) ContainerTrait

type ContainerTrait struct {
    Key, Value reflect.Type // Key can be nil, and it means the Iterator only has Value(), not has Key()
    Iter interface{} // func(c interface{}) Iterator or func(c interface{}) ValueIterator
}

type Iterator interface {
     Next() bool
     Key() interface{}
     Value() interface{}
}

type ValueIterator interface {
     Next() bool
     Key() reflect.Value
     Value() reflect.Value
}

And then

for k, v = range container {
     ...
}

can become:

trait := TraitContainer(reflect.TypeOf(container))
for __iter := trait.Iter(container); __iter.Next(); {
    k, v = __iter.Key().(trait.Key), __iter.Value().(trait.Value)
    ...
}

[xushiwei]

#563

[liyue201]

In cl package we can introduce ContainerTrait and container Iterator:

func TraitContainer(containerTy reflect.Type) ContainerTrait

type ContainerTrait struct {
    Key, Value reflect.Type // Key can be nil, and it means the Iterator only has Value(), not has Key()
    Iter interface{} // func(c interface{}) Iterator or func(c interface{}) ValueIterator
}

type Iterator interface {
     Next() bool
     Key() interface{}
     Value() interface{}
}

type ValueIterator interface {
     Next() bool
     Key() reflect.Value
     Value() reflect.Value
}

And then

for k, v = range container {
     ...
}

can become:

trait := TraitContainer(reflect.TypeOf(container))
for __iter := trait.Iter(container); __iter.Next(); {
    k, v = __iter.Key().(trait.Key), __iter.Value().(trait.Value)
    ...
}

这个转化很巧妙，没看到这个帖子之前，光看代码一脸懵逼