Module build failed: Error: Debug Failure. Unexpected node. Node PrefixUnaryExpression was unexpected.

I was getting this error in an Angular 4 application in attempting to compile. A one operand operation is unary in nature, and in this particular case the problem was:

@Input() transactionId: string | -1;

 
 

I fixed the problem by revamping the line of code to look like this:

@Input() transactionId: string | number;