allow comparing BorrowedReference to null

lostmsu · lostmsu · commit c3fc7f08a013 · 2021-02-23T23:25:01.000-08:00
diff --git a/src/runtime/BorrowedReference.cs b/src/runtime/BorrowedReference.cs
@@ -28,6 +28,14 @@ public BorrowedReference(IntPtr pointer)
             => a.pointer == b.pointer;
         public static bool operator !=(BorrowedReference a, BorrowedReference b)
             => a.pointer != b.pointer;
+        public static bool operator ==(BorrowedReference reference, NullOnly @null)
+            => reference.IsNull;
+        public static bool operator !=(BorrowedReference reference, NullOnly @null)
+            => !reference.IsNull;
+        public static bool operator ==(NullOnly @null, BorrowedReference reference)
+            => reference.IsNull;
+        public static bool operator !=(NullOnly @null, BorrowedReference reference)
+            => !reference.IsNull;
 
         public override bool Equals(object obj) {
             if (obj is IntPtr ptr)
diff --git a/src/runtime/importhook.cs b/src/runtime/importhook.cs
@@ -155,7 +155,7 @@ public static unsafe NewReference GetCLRModule(BorrowedReference fromList = defa
 
             // find any items from the from list and get them from the root if they're not
             // already in the module dictionary
-            if (fromList != null && fromList != default)
+            if (fromList != null)
             {
                 if (Runtime.PyTuple_Check(fromList))
                 {
@@ -224,7 +224,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)
             if (num_args >= 4)
             {
                 fromList = Runtime.PyTuple_GetItem(args, 3);
-                if (fromList != default &&
+                if (fromList != null &&
                     Runtime.PyObject_IsTrue(fromList) == 1)
                 {
                     fromlist = true;
@@ -297,7 +297,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)
             BorrowedReference modules = Runtime.PyImport_GetModuleDict();
             BorrowedReference module = Runtime.PyDict_GetItem(modules, py_mod_name);
 
-            if (module != default)
+            if (module != null)
             {
                 if (fromlist)
                 {
diff --git a/src/runtime/tricks/NullOnly.cs b/src/runtime/tricks/NullOnly.cs
@@ -0,0 +1,12 @@
+namespace Python.Runtime
+{
+    /// <summary>
+    /// An utility class, that can only have one value: <c>null</c>.
+    /// <para>Useful for overloading operators on structs,
+    /// that have meaningful concept of <c>null</c> value (e.g. pointers and references).</para>
+    /// </summary>
+    class NullOnly
+    {
+        private NullOnly() { }
+    }
+}

Original file line number	Diff line number	Diff line change
`@@ -155,7 +155,7 @@ public static unsafe NewReference GetCLRModule(BorrowedReference fromList = defa`
`155`	`155`
`156`	`156`	`// find any items from the from list and get them from the root if they're not`
`157`	`157`	`// already in the module dictionary`
`158`		`- if (fromList != null && fromList != default)`
	`158`	`+ if (fromList != null)`
`159`	`159`	`{`
`160`	`160`	`if (Runtime.PyTuple_Check(fromList))`
`161`	`161`	`{`
`@@ -224,7 +224,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)`
`224`	`224`	`if (num_args >= 4)`
`225`	`225`	`{`
`226`	`226`	`fromList = Runtime.PyTuple_GetItem(args, 3);`
`227`		`- if (fromList != default &&`
	`227`	`+ if (fromList != null &&`
`228`	`228`	`Runtime.PyObject_IsTrue(fromList) == 1)`
`229`	`229`	`{`
`230`	`230`	`fromlist = true;`
`@@ -297,7 +297,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)`
`297`	`297`	`BorrowedReference modules = Runtime.PyImport_GetModuleDict();`
`298`	`298`	`BorrowedReference module = Runtime.PyDict_GetItem(modules, py_mod_name);`
`299`	`299`
`300`		`- if (module != default)`
	`300`	`+ if (module != null)`
`301`	`301`	`{`
`302`	`302`	`if (fromlist)`
`303`	`303`	`{`