Strange behavior std.range.takeNone

[Dennis Ritchie via Digitalmars-d-learn]

Hi,
Is it OK?

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import std.stdio : writeln;
import std.range : takeNone;

void main() {

        auto s = takeNone("test");

        s ~= 5;

        writeln(s); // prints ♣
}
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Windows 8.1 x64, DMD 2.067.0