[ Widget Preview ] TypeError: type 'DisposedAnalysisContextResult' is not a subtype of type 'ErrorsResult' in type cast #178472
Description
Crash detected via crashlytics for 3.38.0 release:
Thread 0 main thread_TypeError: type 'DisposedAnalysisContextResult' is not a subtype of type 'ErrorsResult' in type cast
at LibraryPreviewNode.populateErrors(dependency_graph.dart:219)
at <asynchronous gap>(async)
at PreviewDetector._findPreviewFunctions(preview_detector.dart:251)
at <asynchronous gap>(async)
at PreviewDetector.initialize(preview_detector.dart:73)
at <asynchronous gap>(async)
at WidgetPreviewStartCommand.runCommand(widget_preview.dart:340)
at <asynchronous gap>(async)
at FlutterCommand.run.<anonymous closure>(flutter_command.dart:1559)
at <asynchronous gap>(async)
at AppContext.run.<anonymous closure>(context.dart:154)
at <asynchronous gap>(async)
at CommandRunner.runCommand(command_runner.dart:212)
at <asynchronous gap>(async)
at FlutterCommandRunner.runCommand.<anonymous closure>(flutter_command_runner.dart:487)
at <asynchronous gap>(async)
at AppContext.run.<anonymous closure>(context.dart:154)
at <asynchronous gap>(async)
at FlutterCommandRunner.runCommand(flutter_command_runner.dart:422)
at <asynchronous gap>(async)
at run.<anonymous closure>.<anonymous closure>(runner.dart:101)
at <asynchronous gap>(async)
at AppContext.run.<anonymous closure>(context.dart:154)
at <asynchronous gap>(async)
at main(executable.dart:103)
at <asynchronous gap>(async)
We're making a bad assumption about the return type as errors can be returned once the analysis context is disposed while we're in the middle of updating the preview dependency graph.