import std.stdio;

template Test(A ...) {
    template Test(B) {
        void Test(A a, B b) { writefln(a, b); }
    }
}

void main() {
    alias Test!(char[], int) Temp;
    alias Temp!(float) T;
}

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Compiling the above code produces: "Error: error: forward reference of B".

B is quite obviously not forward-referenced in the code.