add test case

tests/ast-parsing/user_defined_value_type/top-level-0.8.8.sol

@@ -0,0 +1,27 @@
+type Operand is uint256;
+type StackTop is uint256;
+struct StorageOpcodesRange {
+    uint256 pointer;
+    uint256 length;
+}
+struct IntegrityState {
+    // Sources first as we read it in assembly.
+    bytes[] sources;
+    StorageOpcodesRange storageOpcodesRange;
+    uint256 constantsLength;
+    uint256 contextLength;
+    StackTop stackBottom;
+    StackTop stackMaxTop;
+    uint256 contextScratch;
+    function(IntegrityState memory, Operand, StackTop)
+        view
+        returns (StackTop)[] integrityFunctionPointers;
+}
+
+contract Test {
+    function set(StackTop stackTop_, uint256 a_) internal pure {
+        assembly {
+            mstore(stackTop_, a_)
+        }
+    }
+}