contextualExpressionTypecheckingDoesntBlowStack.types

=== tests/cases/compiler/contextualExpressionTypecheckingDoesntBlowStack.ts ===
// repro for: https://github.com/Microsoft/TypeScript/issues/23661
export interface IValidationError {
    message: string;
>message : string
}

export default class Operation {
>Operation : Operation

    validateParameters(parameterValues: any) : IValidationError[] | null {
>validateParameters : (parameterValues: any) => IValidationError[] | null
>parameterValues : any
>null : null

        let result: IValidationError[] | null = null;
>result : IValidationError[] | null
>null : null
>null : null

        for(const parameterLocation of Object.keys(parameterValues)) {
>parameterLocation : string
>Object.keys(parameterValues) : string[]
>Object.keys : { <K extends string>(o: Record<K, any>): K[]; (o: {}): string[]; }
>Object : ObjectConstructor
>keys : { <K extends string>(o: Record<K, any>): K[]; (o: {}): string[]; }
>parameterValues : any

            const parameter: any = (this as any).getParameter();;
>parameter : any
>(this as any).getParameter() : any
>(this as any).getParameter : any
>(this as any) : any
>this as any : any
>this : this
>getParameter : any

            const values = (this as any).getValues();
>values : any
>(this as any).getValues() : any
>(this as any).getValues : any
>(this as any) : any
>this as any : any
>this : this
>getValues : any

            const innerResult = parameter.validate(values[parameter.oaParameter.name]);
>innerResult : any
>parameter.validate(values[parameter.oaParameter.name]) : any
>parameter.validate : any
>parameter : any
>validate : any
>values[parameter.oaParameter.name] : any
>values : any
>parameter.oaParameter.name : any
>parameter.oaParameter : any
>parameter : any
>oaParameter : any
>name : any

            if(innerResult && innerResult.length > 0) {
>innerResult && innerResult.length > 0 : boolean
>innerResult : any
>innerResult.length > 0 : boolean
>innerResult.length : any
>innerResult : any
>length : any
>0 : 0

                // Commenting out this line will fix the problem.
                result = (result || []).concat(innerResult);
>result = (result || []).concat(innerResult) : IValidationError[]
>result : IValidationError[] | null
>(result || []).concat(innerResult) : IValidationError[]
>(result || []).concat : { (...items: ConcatArray<IValidationError>[]): IValidationError[]; (...items: (IValidationError | ConcatArray<IValidationError>)[]): IValidationError[]; }
>(result || []) : IValidationError[]
>result || [] : IValidationError[]
>result : IValidationError[] | null
>[] : never[]
>concat : { (...items: ConcatArray<IValidationError>[]): IValidationError[]; (...items: (IValidationError | ConcatArray<IValidationError>)[]): IValidationError[]; }
>innerResult : any
            }
        }

        return result;
>result : IValidationError[] | null
    }
}