src/vs/workbench/api/common/extHostDocumentData.ts/setWordDefinitionFor
export function setWordDefinitionFor(languageId: string, wordDefinition: RegExp | undefined): void {
	if (!wordDefinition) {
		_languageId2WordDefinition.delete(languageId);
	} else {
		_languageId2WordDefinition.set(languageId, wordDefinition);
	}
}