src/vs/workbench/contrib/debug/common/debugViewModel.ts/ViewModel/setSelectedExpression
class ViewModel:	setSelectedExpression(expression: IExpression | undefined, settingWatch: boolean) {
		this.selectedExpression = expression ? { expression, settingWatch: settingWatch } : undefined;
		this.expressionSelectedContextKey.set(!!expression);
		this._onDidSelectExpression.fire(this.selectedExpression);
	}