add test for #3781

tests/misc/projects/Issue3781/Main.hx

@@ -0,0 +1,14 @@
+enum E {
+    E1<T:String>(v:T);
+}
+
+abstract Ab(String) to String {}
+
+class Main<T:Ab> {
+    static function main() {
+    }
+
+    function doStuff(v:T) {
+        E1(v);
+    }
+}

tests/misc/projects/Issue3781/compile-fail.hxml

@@ -0,0 +1 @@
+--run Main

tests/misc/projects/Issue3781/compile-fail.hxml.stderr

@@ -0,0 +1,2 @@
+Main.hx:12: characters 8-10 : Constraint check failure for E1.T
+Main.hx:12: characters 8-10 : Main.T should be String