Using for for operators.

test/libsolidity/syntaxTests/constants/constant_cyclic_via_user_operators.sol

@@ -0,0 +1,10 @@
+type Type is uint;
+using {f as +} for Type;
+function f(Type, Type) pure returns (Type) {}
+
+Type constant t = Type.wrap(1);
+Type constant u = v + t;
+Type constant v = u + t;
+// ----
+// TypeError 8349: (141-146): Initial value for constant variable has to be compile-time constant.
+// TypeError 8349: (166-171): Initial value for constant variable has to be compile-time constant.

test/libsolidity/syntaxTests/using/operator_for_builtin.sol

@@ -0,0 +1,4 @@
+using {f as +} for uint;
+function f(uint, uint) pure returns (uint) {}
+// ----
+// TypeError 5332: (7-8): Operators can only be implemented for user-defined types and not for contracts.