Webstorm is reporting an AngularJS syntax error when using the word "as" in an expression?

Our team just moved a Typescript / AngularJS application from Visual Studio to WebStorm. 

Some of the code that was working before now gives an error as below:

     <div 
         ng-controller="authenticationHomeController"
         style="flex-direction: column;
                flex: 1;
                margin-left: 3rem;">
        
        <div >
            <div ></div>
            <div id="login" 
                 ng-class="{'enabled':as.authTab == AuthTabs.Login,
                            'disabled': as.authTab != AuthTabs.Login}"
                 ng-click="as.setAuthTab(AuthTabs.Login)">

WebStorm is showing a red syntax error and saying "Expecting an expression" for the code area `as.authTab`

Here's the controller:

    class AuthenticationHomeController {
        static $inject = [
            "$scope",
            "authService"
        ];
    
        constructor(
            public $scope,
            public as:IAuthService
        ) {
            $scope.as = as; 
            as.setAuthTab(AuthTabs.Login);
        }
    }

The error can be fixed by changing the $scope.as = as to $scope.bs = as  and then chaning the HTML to show bs.authTab

For some reason WebStorm does not like the word "as".

Can you let me know if this is a bug.  The issue was opened on Stack Overflow and one of the members there suggested this was probably a bug with WebStorm