[Issue 19799] New: templated string formatting fails with const Nullable!string

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19799

          Issue ID: 19799
           Summary: templated string formatting fails with const
                    Nullable!string
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: default_357-line at yahoo.de

import std.stdio;
import std.typecons;

void main() { writefln!"%s"(const(Nullable!string)()); }

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Expected: "Nullable.null"
Got: horrible format template barf.

Come on guys. This code is too simple to fail so badly.

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