add some log msg to debug issue

src/vs/workbench/parts/files/common/editors/textFileEditorModelManager.ts

@@ -204,6 +204,9 @@ export class TextFileEditorModelManager implements ITextFileEditorModelManager {
 		this.mapResourceToPendingModelLoaders[resource.toString()] = modelPromise;
 
 		return modelPromise.then(model => {
+			if (model.isDisposed()) {
+				console.error('Adding disposed model into cache!!!'); // TODO@Ben remove me
+			}
 
 			// Make known to manager (if not already known)
 			this.add(resource, model);

src/vs/workbench/parts/files/test/browser/textFileEditorModelManager.test.ts

@@ -312,4 +312,18 @@ suite('Files - TextFileEditorModelManager', () => {
 			});
 		});
 	});
+
+	test('disposing model takes it out of the manager', function (done) {
+		const manager: TextFileEditorModelManager = instantiationService.createInstance(TextFileEditorModelManager);
+
+		const resource = toResource('/path/index_something.txt');
+
+		manager.loadOrCreate(resource, 'utf8').then(model => {
+			model.dispose();
+
+			assert.ok(!manager.get(resource));
+			manager.dispose();
+			done();
+		});
+	});
 });
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