Type error with .set() since TypeScript 3.6

[richard-viney]

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Which package(s) does this problem pertain to?

• @types/ember__object

Repro steps

The following code reports no typing errors in TypeScript 3.5.x, but gives errors as of TypeScript 3.6 that are still present in TypeScript 3.7.2.

import EmberObject, { set } from "@ember/object"

class Foo extends EmberObject {
  public version!: number
}

class Bar extends EmberObject {
  public version!: number
  public name!: string // Note: removing this line makes the error below go away
}

function test(a: Foo | Bar) {
  // Global set type checks correctly, no problems here
  set(a, "version", 1)

  // But using .set() gives `error TS2349: This expression is not callable.`
  a.set("version", 1)
}

Expected result would be for the above code to continue to be error-free when upgrading TypeScript. Something to do with the union type appears to be the issue.

Workaround is to use global set().

Thanks.

[chriskrycho]

Thanks for reporting! Looks like our chicanery to get EmberObject#set through the type system has taken another hit. :sad: One of us will try to get this fixed sometime soon!

[chriskrycho]

As far as I can tell, this may remain an issue on the TS side, but is largely irrelevant since every use of this.get() and this.set() in Ember can be safely replaced with a normal ES property access or assignment statement, including in Ember Data. Closing as “not planned” accordingly.