Piggyback: AK: Add formatter for std::nullptr_t.

Author: https://github.com/asynts
Commit: https://github.com/SerenityOS/serenity/commit/632ff01e174
Pull-request: https://github.com/SerenityOS/serenity/pull/4727

AK/Format.h

@@ -348,6 +348,17 @@ struct Formatter<double> : StandardFormatter {
 };
 #endif
 
+template<>
+struct Formatter<std::nullptr_t> : Formatter<FlatPtr> {
+    void format(FormatBuilder& builder, std::nullptr_t)
+    {
+        if (m_mode == Mode::Default)
+            m_mode = Mode::Pointer;
+
+        return Formatter<FlatPtr>::format(builder, 0);
+    }
+};
+
 void vformat(StringBuilder& builder, StringView fmtstr, TypeErasedFormatParams);
 void vformat(const LogStream& stream, StringView fmtstr, TypeErasedFormatParams);
 

AK/Tests/TestFormat.cpp

@@ -269,4 +269,9 @@ TEST_CASE(yay_this_implementation_sucks)
     EXPECT_EQ(String::formatted("{:.0}", .99999999999), "0.");
 }
 
+TEST_CASE(format_nullptr)
+{
+    EXPECT_EQ(String::formatted("{}", nullptr), String::formatted("{:p}", static_cast<FlatPtr>(0)));
+}
+
 TEST_MAIN(Format)