walkArrowFunctionExpression(expression) {
		const wasTopLevel = this.scope.topLevelScope;
		this.scope.topLevelScope = wasTopLevel ? "arrow" : false;
		this.inFunctionScope(false, expression.params, () => {
			for (const param of expression.params) {
				this.walkPattern(param);
			}
			if (expression.body.type === "BlockStatement") {
				this.detectMode(expression.body.body);
				const prev = this.prevStatement;
				this.preWalkStatement(expression.body);
				this.prevStatement = prev;
				this.walkStatement(expression.body);
			} else {
				this.walkExpression(expression.body);
			}
		});
		this.scope.topLevelScope = wasTopLevel;
	}
@param {ArrowFunctionExpression} expression arrow function expression