Extended interfaces are not recognized by strict check

[rzinnatullin]

Suppose we have the following interfaces:

export interface FieldFilter {
  fieldName: string
  condition: FieldFilterCondition
}

export interface FieldFilterCondition {
  type: FieldFilterConditionType
  invert?: boolean
}

export enum FieldFilterConditionType {
  isNull = 'isNull',
  in = 'in'
}

export interface FieldFilterConditionIsNull extends FieldFilterCondition {
  type: FieldFilterConditionType.isNull
}

export interface FieldFilterConditionIn extends FieldFilterCondition {
  type: FieldFilterConditionType.in
  values: Value[]
}

Strict check on the following JSON will fail:

      {
         "fieldName":"SomeFieldName",
         "condition":{
            "type":"in",
            "values":[
               "Some value"
            ]
         }
      }

Error message:

...
value.condition.values is extraneous
...

[alexmojaki]

This sounds like a duplicate of #46

In pure TypeScript, this is also an error:

const cond: FieldFilterCondition = {
  type: FieldFilterConditionType.in,
  values: [1, 2]
}

That doesn't mean this issue should be dismissed, I even said myself:

this is all hypothetical until an actual user complains

and here we are.

[rzinnatullin]

Thank you @alexmojaki for the answer.
I think it is very clear why strict check fails - it simply does not know what exact derived type to use here.

The solution I can imagine is to allow defining a type selector for the checker.