Type::userDefinedOperator takes return parameters into account

test/libsolidity/syntaxTests/operators/custom/operator_invalid_parameters.sol

@@ -0,0 +1,33 @@
+type Int is int256;
+
+using {
+    add as +, sub as -, div as /
+} for Int;
+
+function add(Int) pure returns (Int) {
+    return Int.wrap(0);
+}
+
+function sub(Int, Int, Int) pure returns (Int) {
+    return Int.wrap(1);
+}
+
+function div(int256, int256) pure returns (Int) {
+    return Int.wrap(2);
+}
+
+function f() pure {
+    Int.wrap(0) + Int.wrap(1);
+    Int.wrap(0) - Int.wrap(0);
+    Int.wrap(0) / Int.wrap(0);
+    Int.wrap(0) * Int.wrap(0);
+}
+
+// ----
+// TypeError 1884: (33-36): The function "add" needs to have two parameters of equal type to be used for the operator +.
+// TypeError 8112: (43-46): The function "sub" needs to have one or two parameters to be used for the operator -.
+// TypeError 3100: (53-56): The function "div" cannot be bound to the type "Int" because the type cannot be implicitly converted to the first argument of the function ("int256").
+// TypeError 2271: (317-342): Operator + not compatible with types Int and Int. No matching user-defined operator found.
+// TypeError 2271: (348-373): Operator - not compatible with types Int and Int. No matching user-defined operator found.
+// TypeError 2271: (379-404): Operator / not compatible with types Int and Int. No matching user-defined operator found.
+// TypeError 2271: (410-435): Operator * not compatible with types Int and Int. No matching user-defined operator found.

test/libsolidity/syntaxTests/operators/custom/operator_invalid_return_parameters.sol

@@ -0,0 +1,49 @@
+type Int is int256;
+
+using {
+    add as +,
+    div as /,
+    unsub as -,
+    gt as >,
+    lt as <
+} for Int;
+
+function add(Int x, Int y) pure returns (int256) {
+    return 0;
+}
+
+function div(Int x, Int y) pure {
+    x = y;
+}
+
+function unsub(Int) pure returns (Int, Int) {
+    return (Int.wrap(0), Int.wrap(1));
+}
+
+function gt(Int, Int) pure returns (Int) {
+    return Int.wrap(0);
+}
+
+function lt(Int, Int) pure returns (bool, Int) {
+    return (true, Int.wrap(1));
+}
+
+function f() pure {
+    Int.wrap(0) + Int.wrap(1);
+    Int.wrap(0) / Int.wrap(0);
+    -Int.wrap(0);
+    Int.wrap(0) < Int.wrap(0);
+    Int.wrap(0) > Int.wrap(0);
+}
+
+// ----
+// TypeError 7743: (33-36): The function "add" needs to return exactly one value of type Int to be used for the operator +.
+// TypeError 7743: (47-50): The function "div" needs to return exactly one value of type Int to be used for the operator /.
+// TypeError 7743: (61-66): The function "unsub" needs to return exactly one value of type Int to be used for the operator -.
+// TypeError 7995: (77-79): The function "gt" needs to return exactly one value of type bool to be used for the operator >.
+// TypeError 7995: (90-92): The function "lt" needs to return exactly one value of type bool to be used for the operator <.
+// TypeError 2271: (492-517): Operator + not compatible with types Int and Int. No matching user-defined operator found.
+// TypeError 2271: (523-548): Operator / not compatible with types Int and Int. No matching user-defined operator found.
+// TypeError 4907: (554-566): Unary operator - cannot be applied to type Int
+// TypeError 2271: (572-597): Operator < not compatible with types Int and Int. No matching user-defined operator found.
+// TypeError 2271: (603-628): Operator > not compatible with types Int and Int. No matching user-defined operator found.

test/libsolidity/syntaxTests/operators/custom/operator_wrong_number_params_return.sol

@@ -1,39 +0,0 @@
-type Int is int256;
-
-using {
-    add as +, sub as -,
-    mul as *, div as /,
-    gt as >, lt as <
-} for Int;
-
-function add(Int) pure returns (Int) {
-    return Int.wrap(0);
-}
-
-function sub(Int, Int, Int) pure returns (Int) {
-    return Int.wrap(1);
-}
-
-function mul(Int) pure returns (Int) {
-    return Int.wrap(2);
-}
-
-function div(Int x, Int y) pure {
-    x = y;
-}
-
-function gt(Int, Int) pure returns (Int) {
-    return Int.wrap(0);
-}
-
-function lt(Int, Int) pure returns (bool, Int) {
-    return (true, Int.wrap(1));
-}
-
-// ----
-// TypeError 1884: (33-36): The function "add" needs to have two parameters of equal type to be used for the operator +.
-// TypeError 8112: (43-46): The function "sub" needs to have one or two parameters to be used for the operator -.
-// TypeError 1884: (57-60): The function "mul" needs to have two parameters of equal type to be used for the operator *.
-// TypeError 7743: (67-70): The function "div" needs to return exactly one value of type Int to be used for the operator /.
-// TypeError 7995: (81-83): The function "gt" needs to return exactly one value of type bool to be used for the operator >.
-// TypeError 7995: (90-92): The function "lt" needs to return exactly one value of type bool to be used for the operator <.