Compiler is forgetting the basetype of an extended type when that type is generic #28280

Also why is 'Proxy' in the ES2015 lib and not in the 'ES6' lib, and whats the difference between these libs?

ES2015 is es6. When es6 was published they formally started a by-year versioning scheme; so es6 and es2015 are synonymous.

Secondly: An interface cannot inherit from a variable type parameter. If you want similar behavior, you want to use intersection types, like so:

    type TExtObj = TObj & {
        newAttr: any
    }

Thirdly: Capital O Object refers to the global Object constructor base type. You probably don't want that - you probably want the object (lower case o) primitive instead.

Fourth: Spreads are currently limited to concrete types - you cannot spread a generic. This will change in 3.2, thanks to #28234.

ES2015 is es6. When es6 was published they formally started a by-year versioning scheme; so es6 and es2015 are synonymous.

Well, this is embarassing. Other than what you might think I am capable of performing a google search, so when i got an Cannot find name error on an Proxy keyword while having es6 in the libs variable of the tsconfig, I was really out of my depth. Even more so when I tried it with es2015 and it worked. But upon retry es6 works perfectly, so it mustve been an user error somewhere.

Secondly: An interface cannot inherit from a variable type parameter

Well yeah, thats more or less what I'm saying. Do you mean to say that this is by design? Why would you want to do that? Note that the variable type will always be an extension of object. The problem is that the compiler isnt smart enough to notice that, at least from what I think to see there.

Thanks for the hint with the intersection types. It could very well work, I'll try and report back.

Thirdly: Capital O Object refers to the global Object constructor base type. You probably don't want that - you probably want the object (lower case o) primitive instead.

Using object will throw Cannot find name at the reproduction with Interfaces below. {} Will throw a more understandable An object can only extend an identifier/qualified-name with optional type arguments, eventually I got to Object which worked. I guess cause its not a simple object. But true, its not really what i want here... didnt think any further about it after that worked.

Fourth: Spreads are currently limited to concrete types - you cannot spread a generic. This will change in 3.2, thanks to #28234.

Good to know, thanks. Hard to test though, as the issue described above is causing issues (Compiler specifically says that its not an object not only upon use of the spread operator but also the interface inheritance.), and here the Compiler of course already resolved it:

const genTypeFactory = <T>(param: T) => {
    return param;
}

const reWrapped = {...genTypeFactory({attr: "someVal"})}

EDIT: Actually I just tested it with the 3.2.0-dev.20181101. The spread-issue is gone indeed, the other issues remain. And the spread operation wasnt really a problem of mine, It was just something I tried to see if other operations I'd expect to work on an object worked.

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