akePureMalloc cannot be interpreted at compile time

[Adnan]

The following program produces an error message and it is not 
clear exactly what line causes this error:

module maybe;

@nogc:
private import std.container : Array;

struct MayBe(T) {
	Array!T data;

	this(T datum) {
		data.reserve(1);
		data.insert(datum);
	}

	T unwrap() const {
		return data[0];
	}

	T unwrapOr(T alternateValue) const {
		return isSome() ? unwrap() : alternateValue;
	}

	bool isSome() const {
		return !data.empty();
	}

	bool isNone() const {
		return !isSome();
	}

	bool contains(T arg) const {
		return isSome() && unwrap() == arg;
	}

	T expect(lazy string msg) const {
		if (isNone()) {
			import core.stdc.stdio : puts;
			import core.stdc.stdlib : exit;

			puts(msg.ptr);
			exit(-1);
		}
		return unwrap();
	}

	void nullify() {
		data.clear();
	}

	void insert(T datum) {
		if (isNone())
			data.insert(datum);
		else
			data.front = datum;
	}
}

MayBe!T flatten(T)(MayBe!(MayBe!T) arg) {
	return isSome() ? arg.unwrap() : some!T();
}

MayBe!T some(T)(T arg) {
	return MayBe!T(arg);
}

MayBe!T none(T)() {
	return MayBe!T();
}

unittest {
	alias MB = MayBe;

	MB!int a;
	assert(a.isNone);

	auto b = none!int();
	assert(b.isNone);

	auto c = some!int(23);
	assert(c.contains(23));

	c.nullify();

	assert(a == c);

	a.insert(11);
	c.insert(11);
	assert(a == c);

	auto d = some!(some!int(9));
	assert(d.flatten() == some!int(9));
}

$ dub test
Generating test runner configuration 'maybe-test-library' for 
'library' (library).
Performing "unittest" build using dmd for x86_64.
maybe ~master: building configuration "maybe-test-library"...
/snap/dmd/99/bin/../import/phobos/std/internal/memory.d(31,33): 
Error: fakePureMalloc cannot be interpreted at compile time, 
because it has no available source code
dmd failed with exit code 1.

And what is the meaning of this error message?