https://issues.dlang.org/show_bug.cgi?id=20511

          Issue ID: 20511
           Summary: Can't format JSONValue to OutputRange due to @safe
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: default_357-line@yahoo.de

Consider the following code:

---
import std.format : formattedWrite;
import std.json : JSONValue;
import std.range : nullSink, OutputRange, outputRangeObject;

void main()
{
  outputRangeObject!(const(char)[])(nullSink)
    .formattedWrite!"%s"(JSONValue.init);
}
---

This should compile, but it instead produces an error. This is caused by std.json.toJson being `@safe`.

toJson can not be @safe, because it calls arbitrary output range code.

--