diff --git a/src/protocol/tests/parser_validation.rs b/src/protocol/tests/parser_validation.rs
index 741203c921e0b370a23cc3cb94ebd22a5f41cd31..6a414915213d4489b8501aab995fefb260e97779 100644
--- a/src/protocol/tests/parser_validation.rs
+++ b/src/protocol/tests/parser_validation.rs
@@ -30,4 +30,59 @@ fn test_correct_struct_instance() {
         Foo<int> bar(int arg) { return Foo<int>{ field: arg }; }
         "
     );
+
+    Tester::new_single_source_expect_ok(
+        "single field, implicit polymorph",
+        "
+        struct Foo<T>{ T field }
+        int bar(int arg) {
+            auto thingo = Foo{ field: arg };
+            return arg;
+        }
+        "
+    );
+
+    Tester::new_single_source_expect_ok(
+        "multiple fields, same explicit polymorph",
+        "
+        struct Pair<T1, T2>{ T1 first, T2 second }
+        int bar(int arg) {
+            auto qux = Pair<int, int>{ first: arg, second: arg };
+            return arg;
+        }
+        "
+    );
+
+    Tester::new_single_source_expect_ok(
+        "multiple fields, same implicit polymorph", 
+        "
+        struct Pair<T1, T2>{ T1 first, T2 second }
+        int bar(int arg) {
+            auto wup = Pair{ first: arg, second: arg };
+            return arg;
+        }
+        "
+    );
+
+    Tester::new_single_source_expr_ok(
+        "multiple fields, different explicit polymorph",
+        "
+        struct Pair<T1, T2>{ T1 first, T2 second }
+        int bar(int arg1, byte arg2) {
+            auto shoo = Pair<int, byte>{ first: arg1, second: arg2 };
+            return arg1;
+        }
+        "
+    );
+
+    Tester::new_single_source_expect_ok(
+        "multiple fields, different implicit polymorph",
+        "
+        struct Pair<T1, T2>{ T1 first, T2 second }
+        int bar(int arg1, byte arg2) {
+            auto shrubbery = Pair{ first: arg1, second: arg2 };
+            return arg1;
+        }
+        "
+    );
 }
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