Detect recursive creation of generics #2366.

test/test_suite/generic/recursive_generic.c3

@@ -0,0 +1,14 @@
+module test;
+import test1;
+
+fn int main() => 0;
+
+Aa {int} a;
+
+module test1 {Type};
+import test2;
+alias Cc = Aa {Bb {Type}}; // #error: Generic resolution of this type has become deeply nested
+struct Aa {Type a;}
+
+module test2 {Type};
+struct Bb {Type b;}