Object Properties Spread with Generic Object Types not allowed

[kitsonk]

TypeScript Version: 2.3.2

Code

Playground Example

class Foo<P> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

class Bar<P extends object> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

class Baz<P extends { [prop: string]: any; }> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

class Qat<P extends object = object> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

Expected behavior:

That properties are spread on class Bar, class Baz, and class Qat.

Actual behavior:

All three cases report that Spread types may only be created from object types. In all cases, the generic could be inferred to be of an object type, so the restriction seems to be arbitrary.

[mhegazy]

This is tracked by #10727 and fixed by #13288

[timocov]

@mhegazy but it works in 2.2.1 - it is blocker to updated to 2.3 for us :-(

[mhegazy]

@mhegazy but it works in 2.2.1 - it is blocker to updated to 2.3 for us :-(

Not sure what you mean by that, this has always been an error..

c:\test>type b.ts
class Foo<P> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

class Bar<P extends object> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

class Baz<P extends { [prop: string]: any; }> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

class Qat<P extends object> {
  setProperties(props: P) {
    const newProps = { ...props };
  }
}

c:\test>node c:\releases\2.2.1\tsc.js --version
Version 2.2.1

c:\test>node c:\releases\2.2.1\tsc.js b.ts
b.ts(3,24): error TS2698: Spread types may only be created from object types.
b.ts(9,24): error TS2698: Spread types may only be created from object types.
b.ts(15,24): error TS2698: Spread types may only be created from object types.
b.ts(21,24): error TS2698: Spread types may only be created from object types.

c:\test>node c:\releases\2.2.2\tsc.js --version
Version 2.2.2

c:\test>node c:\releases\2.2.2\tsc.js b.ts
b.ts(3,24): error TS2698: Spread types may only be created from object types.
b.ts(9,24): error TS2698: Spread types may only be created from object types.
b.ts(15,24): error TS2698: Spread types may only be created from object types.
b.ts(21,24): error TS2698: Spread types may only be created from object types.

c:\test>node c:\releases\2.3.2\tsc.js --version
Version 2.3.2

c:\test>node c:\releases\2.3.2\tsc.js b.ts
b.ts(3,24): error TS2698: Spread types may only be created from object types.
b.ts(9,24): error TS2698: Spread types may only be created from object types.
b.ts(15,24): error TS2698: Spread types may only be created from object types.
b.ts(21,24): error TS2698: Spread types may only be created from object types.

do you mean spread in JSX?

[timocov]

Oh, sorry - yes, we have this error in JSX. I just have decided that is the same errors - the symptoms is very similar :)

[mhegazy]

That is tracked by #15742, fixed by #15789, and should be in TS 2.3.3 (out next week).

The fix should be in typescript@next already, give it a try and let us know if you are still running into issues.

[timocov]

@mhegazy For 2.3.3-insiders.20170512 this problem is gone, thank you!