proposal: reflect: reflect.StructOf support for circular references

[Anthony-Dong]

Proposal Details

Currently, I'm facing an issue. I want to use reflect.StructOf to dynamically build a structure based on a DSL (Domain-Specific Language), but I found that it does not support circular references. I used an unsafe approach to handle this. May I ask if the official implementation supports this?

func UnsafeReplaceFieldType(_st reflect.Type, index int, _rst reflect.Type) {
	field := createStructField(_st, index, _rst)
	st := toStructType(_st)
	st.fields[index] = field
}

func createStructField(st reflect.Type, index int, _rst reflect.Type) structField {
	if _rst.Kind() != reflect.Struct {
		panic(`expected a struct type`)
	}
	fields := make([]reflect.StructField, st.NumField())
	for i := 0; i < st.NumField(); i++ {
		field := st.Field(i)
		if i != index {
			fields[i] = field
			continue
		}
		field.Type = reflect.New(_rst).Type()
		fields[i] = field
	}
	s := toStructType(reflect.StructOf(fields))
	return s.fields[index]
}

func toStructType(t reflect.Type) *structType {
	if t.Kind() != reflect.Struct {
		panic(`expected a struct type`)
	}
	s := (*rtype)(reflect.ValueOf(t).UnsafePointer())
	tt := (*structType)(unsafe.Pointer(s))
	return tt
}

[ianlancetaylor]

Thanks. Closing as a dup of #39717.

[gabyhelp]

Related Issues

• reflect: StructOf doesn't support recursive structs #20013 (closed)
• reflect: generate runtime [circle refrence] types similar to compile time. #70339 (closed)

Related Code Changes

• reflect: implement StructOf

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