Fix control flow check for unary operators

test/libsolidity/syntaxTests/controlFlow/userDefinedTypeOperators/binary_operator.sol

@@ -0,0 +1,17 @@
+struct S { bool f; }
+
+using {add as +} for S;
+
+function add(S storage x, S storage) pure returns (S storage) { return x; }
+
+contract C {
+    S s;
+    function f() public {
+        S storage x = s;
+        S storage y;
+        x + y;
+    }
+}
+
+// ----
+// TypeError 3464: (230-231): This variable is of storage pointer type and can be accessed without prior assignment, which would lead to undefined behaviour.

test/libsolidity/syntaxTests/controlFlow/userDefinedTypeOperators/unary_operator.sol

@@ -0,0 +1,15 @@
+struct S { int f; }
+
+using {sub as -} for S;
+
+function sub(S storage x) pure returns (S storage) { return x; }
+
+contract C {
+    function f() public {
+        S storage y;
+        -y;
+    }
+}
+
+// ----
+// TypeError 3464: (181-182): This variable is of storage pointer type and can be accessed without prior assignment, which would lead to undefined behaviour.