Merge pull request #419 from xamarin/lets-make-dispose-better

notify on use of disposed object

Author: stephen-hawley

SwiftReflector/NewClassCompiler.cs

@@ -3693,11 +3693,14 @@ void ImplementIDisposable (ClassDeclaration classDecl, ClassContents contents, C
 			// protected virtual void DisposeUnmanagedResources()
 			// {
 			//      SwiftCore.Release(SwiftObject);
+			//      SwiftObject = IntPtr.Zero;
 			// }
 			var disposeUnmanaged = new CSMethod (CSVisibility.Protected,
 							  CSMethodKind.Virtual, CSSimpleType.Void, disposeUnmanagedIdent, new CSParameterList (),
 							  new CSCodeBlock ()
-				.And (CSFunctionCall.FunctionCallLine ("SwiftCore.Release", false, kSwiftObjectGetter)));
+				.And (CSFunctionCall.FunctionCallLine ("SwiftCore.Release", false, kSwiftObjectGetter))
+				.And (CSAssignment.Assign (kSwiftObjectGetter, CSConstant.IntPtrZero))
+				);
 			cl.Methods.Add (disposeUnmanaged);
 
 			var destructor = new CSMethod (CSVisibility.None, CSMethodKind.None, null, csDestructorIdent, new CSParameterList (),

SwiftRuntimeLibrary/SwiftMarshal/StructMarshal.cs

@@ -25,6 +25,8 @@ public static unsafe IntPtr RetainSwiftObject (ISwiftObject obj)
 		{
 			if (obj == null)
 				return IntPtr.Zero;
+			if (obj.SwiftObject == IntPtr.Zero)
+				throw new SwiftRuntimeException ("SwiftObject handle is IntPtr.Zero, likely because it was disposed.");
 			byte* valueBuffer = stackalloc byte [3 * IntPtr.Size];
 			SwiftCore.swift_beginAccess (obj.SwiftObject, valueBuffer, (uint)SwiftExclusivityFlags.Track, IntPtr.Zero);
 			var result = SwiftCore.Retain (obj.SwiftObject);

tests/tom-swifty-test/SwiftReflector/NewClassCompilerTests.cs

@@ -1498,6 +1498,41 @@ public func reportIt (a: EasyToRepresent) -> Bool {
 
 			TestRunning.TestAndExecute (swiftCode, callingCode, "Here.Value cannot be null.\nParameter name: a\n");
 		}
+
+		[Test]
+		public void CheckOnDisposeThanks ()
+		{
+			var swiftCode = @"
+public class DisposeMeThanks {
+    public init () { }
+    public func doIt () -> Int {
+        return 77
+    }
+}
+public func tryMeHere (a:DisposeMeThanks ) -> Int {
+    return a.doIt ()
+}
+";
+			// try {
+			//    var p = new DisposeMeThanks ();
+			//    p.Dispose ();
+			//    TopLevelEntities.TryMeHere (p);
+			// } catch (Exception err) {
+			//    Console.WriteLine (err.Message);
+			// }
+
+			var pID = new CSIdentifier ("p");
+			var errID = new CSIdentifier ("err");
+			var pDecl = CSVariableDeclaration.VarLine (pID, new CSFunctionCall ("DisposeMeThanks", true));
+			var disposeCall = CSFunctionCall.FunctionCallLine ($"{pID.Name}.Dispose", false);
+			var tryItCall = CSFunctionCall.FunctionCallLine ("TopLevelEntities.TryMeHere", false, pID);
+			var catchPrinter = CSFunctionCall.ConsoleWriteLine (errID.Dot (new CSIdentifier ("Message")));
+			var tryCatch = new CSTryCatch (CSCodeBlock.Create (pDecl, disposeCall, tryItCall),
+				typeof (Exception), errID.Name, CSCodeBlock.Create (catchPrinter));
+			var callingCode = CSCodeBlock.Create (tryCatch);
+
+			TestRunning.TestAndExecute (swiftCode, callingCode, "SwiftObject handle is IntPtr.Zero, likely because it was disposed.\n");
+		}
 	}
 }