this subclass inference problem

[JonathanMEdwards]

• VSCode Version: Code 1.12.1 (f6868fc, 2017-05-04T21:18:32.269Z)
• OS Version: Darwin x64 16.5.0
• Extensions:

Extension	Author	Version
ExtensionUpdateCheck	HookyQR	0.0.2
vscode-npm-script	eg2	0.1.9
auto-close-tag	formulahendry	0.3.12
backspace-plusplus	jrieken	0.0.15
Theme-MaterialKit	ms-vscode	0.1.4
debugger-for-chrome	msjsdiag	3.1.1
theme-black-plus	none	0.0.1
theme-visualstudio black	none	0.0.1

---

Steps to Reproduce:

class A {
  foo = 0;
  method() {
    if (this instanceof B) {
      this.foo;
    } else {
      this.foo;
    }
  }
}
class B extends A {
}

Produces error:

'Property 'foo' does not exist on type 'never'.'

[mjbvz]

This issue was moved to microsoft/TypeScript#15615