Not able to infer type by checking existence of property in object

[egonm12]

TypeScript Version: 3.9.2

Search Terms:
object type inference
incorrect type inference

Expected behavior:
When I have two interfaces that extend from the same base interface I should be able to check for the existence of a property within a variable that only exists in one of the two interfaces. TypeScript will not give an error saying that the property doesn't exist on the other type when I first check for its existence.

Actual behavior:
When I have two interfaces that extend from the same base interface I am not able to check for the existence of a property within a variable that only exists in one of the two interfaces. TypeScript will give an error saying that the property doesn't exist on the other type.

Related Issues:

Code

export type ProductDescription =
  | BagDescription
  | BeltDescription
  | ClothingDescription
  | ShoeDescription;

export interface BaseDescription {
  brand: string;
  name: string;
  partner_catalogue_number: number;
  color: string;
}

export type BagDescription = BaseDescription;

export interface BeltDescription extends BaseDescription {
  length: string;
  length_manufacturer: string;
}

export interface ClothingDescription extends BaseDescription {
  clothing_size_eu: string;
  clothing_size_manufacturer: string;
}

export interface ShoeDescription extends BaseDescription {
  shoe_size_eu: string;
  shoe_size_manufacturer: string;
}

// a response from an API request
// unkown what description will be
const description: ProductDescription = {} as ProductDescription;

// ts error while I expect this to work
// Property 'shoe_size_eu' does not exist on type 'ProductDescription'.
//  Property 'shoe_size_eu' does not exist on type 'BagDescription'
if (description.shoe_size_eu) console.log(description.shoe_size_eu)

// not a ts error
if ("shoe_size_eu" in description) console.log(description.shoe_size_eu)

Output

// a response from an API request
// unkown what ProductDescription will be
const description = {};
if (description.shoe_size_eu)
    console.log(description.shoe_size_eu);
if ("shoe_size_eu" in description)
    console.log(description.shoe_size_eu);

Compiler Options

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

[RyanCavanaugh]

This is the intended behavior; see #34590, #37343, or others

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.