Changing property declaration order causes error

[ahejlsberg]

🔎 Search Terms

Variance

🕗 Version & Regression Information

This is the behavior in every version I tried.

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/JYOwLgpgTgZghgYwgAgCLWANwgEwCpwBGANhADwDKyEAHpCDgM7IDeyhcjEAXMnCAE8A3MhAQA7r34DkAXwB8rALAAoZOuQB6TcgCiUKAHsoyHMEZwADpYhwozcQAsIIZGGddklozahgZOBAIxHZwYMCGIMx2KFAQ2Pa4qhrIjAjOALZwvBQA2gBEHFz5ALrIAGTIefli4qXJGnFwOJHEAhTpEFm8AEq2LSBtlAVFEKUVVQW1pfKqsqqqoJCwiCgAQpwobKMACj68IACuGYTQIvMqS9DwSMgAchLqbLV7hpa8hIaGpPznCyqBYIxZAISKMMCpQyHKBIXjoKBYXAEEjkbabXgbLgAGlEEl4D3EclmKlBUQhgXBoDCERAcIw2HwRFIZDRXAxmxEtXxj0qmJQCmQAF5IdCkCJtHoDMZVEA

💻 Code

interface DerivedTable<S extends { base: any; new: any }> {
    // Error disappears when these property declarations are reversed
    schema: S["base"] & S["new"]
    readonlySchema: Readonly<S["base"] & S["new"]>
}

interface Base { baseProp: number; }
interface New  { newProp: boolean; }

declare const source: DerivedTable<{ base: Base, new: New }>
const destination: DerivedTable<{ base: Base; new: New & Base }> = source; // Error

🙁 Actual behavior

Error.

🙂 Expected behavior

No error.

Additional information about the issue

Investigation of cause here.