src/vs/workbench/common/editor/sideBySideEditorInput.ts/AbstractSideBySideEditorInputSerializer/canSerialize
class AbstractSideBySideEditorInputSerializer:	canSerialize(editorInput: EditorInput): boolean {
		const input = editorInput as SideBySideEditorInput | DiffEditorInput;

		if (input.primary && input.secondary) {
			const [secondaryInputSerializer, primaryInputSerializer] = this.getInputSerializers(input.secondary.typeId, input.primary.typeId);

			return !!(secondaryInputSerializer?.canSerialize(input.secondary) && primaryInputSerializer?.canSerialize(input.primary));
		}

		return false;
	}