There is no universal best common type that can cover all return expressions

Question

There is no universal best common type that can cover all return expressions

While implementing Collection2 in my angular2-meteor project, I noticed that the code snippets from the demo on GitHub always result in a warning message being displayed in the terminal:

"No best common type exists among return expressions."

Is there a way to enhance these codes and resolve this issue? Thank you

{
  createdAt: {
    type: Date,
    autoValue: function() {
      if (this.isInsert) {
        return new Date();
      } else if (this.isUpsert) {
        return {$setOnInsert: new Date()};
      } else {
        this.unset();
      }
    }
  }
}

meteor typescript angular meteor-collection2 angular2-meteor

Answer 1

Answer №1

Every return branch must provide a Date type, so you have two options: either return a Date type for every if/else branch, or create a union that returns two different types.

If the type is Date, it is valid to return null for the third condition in TypeScript.

autoValue: function() : Date|Object  {
    if (this.isInsert) {
        return new Date();
    } else if (this.isUpsert) {
        return {$setOnInsert: new Date()};
    } else {
        this.unset();
        return null;
    }
}

Answer 2

Every return branch must provide a Date type, so you have two options: either return a Date type for every if/else branch, or create a union that returns two different types.

If the type is Date, it is valid to return null for the third condition in TypeScript.

autoValue: function() : Date|Object  {
    if (this.isInsert) {
        return new Date();
    } else if (this.isUpsert) {
        return {$setOnInsert: new Date()};
    } else {
        this.unset();
        return null;
    }
}

There is no universal best common type that can cover all return expressions

Answer №1

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