[nfc] Add test for operators on address-only types.

Author: zoecarver

test/Interop/Cxx/operators/Inputs/member-inline.h

@@ -43,6 +43,10 @@ struct AddressOnlyIntWrapper {
   int operator()(int x, int y) {
     return value + x * y;
   }
+
+  AddressOnlyIntWrapper operator-(AddressOnlyIntWrapper rhs) const {
+    return AddressOnlyIntWrapper(value - rhs.value);
+  }
 };
 
 struct HasDeletedOperator {

test/Interop/Cxx/operators/member-inline.swift

@@ -231,6 +231,14 @@ OperatorsTestSuite.test("PtrToPtr.subscript (inline)") {
   expectEqual(23, arr[0]![0]![0])
 }
 
+OperatorsTestSuite.test("AddressOnlyIntWrapper.minus") {
+  let lhs = AddressOnlyIntWrapper(42)
+  let rhs = AddressOnlyIntWrapper(23)
+
+  let result = lhs - rhs
+  expectEqual(19, result.value)
+}
+
 // TODO: this causes a crash (does it also crash on main?)
 //OperatorsTestSuite.test("TemplatedSubscriptArrayByVal.subscript (inline)") {
 //  let ptr: UnsafeMutablePointer<Int32> =