src/vs/workbench/common/editor/diffEditorInput.ts/DiffEditorInput/asFileResources
class DiffEditorInput:	private asFileResources(): { original: URI, modified: URI } | undefined {
		if (
			this.originalInput instanceof AbstractTextResourceEditorInput &&
			this.modifiedInput instanceof AbstractTextResourceEditorInput &&
			this.fileService.canHandleResource(this.originalInput.preferredResource) &&
			this.fileService.canHandleResource(this.modifiedInput.preferredResource)
		) {
			return {
				original: this.originalInput.preferredResource,
				modified: this.modifiedInput.preferredResource
			};
		}

		return undefined;
	}