Suffix cleanup test

test/libsolidity/semanticTests/literalSuffixes/suffix_return_parameter_cleanup.sol

@@ -0,0 +1,29 @@
+function suffix(uint8) pure suffix returns (uint8 z) {
+    assembly {
+        // Return a value with dirty bytes outside of uint8
+        z := 0xffff
+    }
+}
+
+contract C {
+    function test() external pure returns (uint, uint) {
+        uint8 a;
+
+        // The exact literal used does not matter
+        uint8 suffixResult = 1 suffix;
+        uint8 functionResult = suffix(1);
+
+        // Get the whole slot, including bytes outside of uint8
+        uint suffixResultFull;
+        uint functionResultFull;
+        assembly {
+            suffixResultFull := suffixResult
+            functionResultFull := functionResult
+        }
+
+        // If the result is not 0xff, no cleanup was performed.
+        return (suffixResultFull, functionResultFull);
+    }
+}
+// ----
+// test() -> 0xffff, 0xffff