Fix Issue #17712 - Add test cases

test/compilable/b17712.d

@@ -0,0 +1,40 @@
+// REQUIRED_ARGS: -main
+// https://issues.dlang.org/show_bug.cgi?id=17712
+
+struct Bytecode
+{
+    uint data;
+}
+
+@trusted ctSub(U)(string format, U args)
+{
+    import std.conv : to;
+    foreach (i; format)
+        return  format~ to!string(args);
+    return format;
+}
+
+struct CtContext
+{
+    import std.uni : CodepointSet;
+
+    CodepointSet[] charsets;
+
+    string ctAtomCode(Bytecode[] ir)
+    {
+        string code;
+        switch (code)
+        {
+            OrChar:
+                code ~=  ``;
+                for (uint i ; i ;)
+                    code ~= ctSub(``, ir[i].data);
+                charsets[ir[0].data].toSourceCode;
+                break;
+
+            default:
+                assert(0);
+        }
+        return code;
+    }
+}

test/compilable/b17712_c13.d

@@ -0,0 +1,54 @@
+// https://issues.dlang.org/show_bug.cgi?id=17712#c13
+
+import std.datetime;
+import std.typecons;
+import std.variant;
+
+
+Y a()
+{
+    Y n = Y(Y[].init);
+
+    n.get!(X[]);
+    return n;
+}
+
+struct X
+{
+    Y key;
+}
+struct Y
+{
+    Algebraic!(Y[]) value_;
+    this(T)(T value)
+    {
+        value_ = value;
+    }
+    bool opEquals(T)(T rhs) const
+    {
+        static if(is(Unqual!T == Y))
+        {
+            return true;
+        }
+        else
+        {
+            return get!(T, No.x) == get!T;
+        }
+    }
+    T get(T, Flag!"x" x = Yes.x)() const
+    {
+        return this[""].get!(T, x);
+    }
+
+    Y opIndex(T)(T index) const
+    {
+        const X[] pairs;
+        if(pairs[0].key == index)
+        {
+            assert(0);
+        }
+        assert(0);
+    }
+}
+
+void main(){}