ParseHelper parse = new ParseHelper(defId.getStartPos());
Expression bodyExp = parse.checkResult(parseAssignExpression_toMissing(true, RULE_EXPRESSION));
SimpleLambdaDefUnit lambdaDefId = conclude(defId.nameSourceRange, new SimpleLambdaDefUnit(defId));
return parse.resultConclude(new ExpSimpleLambda(lambdaDefId, bodyExp));
}