Unexpected intersection type constraint error related to union, generic type and private field #38236

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1. DanielRosenwasser commented on Apr 29, 2020

   

   Daniel Rosenwasser (DanielRosenwasser)

   on Apr 29, 2020

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   I'm guessing related to #37762.
2. Daniel Rosenwasser (DanielRosenwasser)

   added

   BugA bug in TypeScriptA bug in TypeScript

   on Apr 29, 2020
3. Daniel Rosenwasser (DanielRosenwasser)

   added this to the TypeScript 3.9.2 milestone on Apr 29, 2020
4. Daniel Rosenwasser (DanielRosenwasser)

   assigned

   Anders Hejlsberg (ahejlsberg)

   on Apr 29, 2020
5. vilicvane (vilicvane)

   changed the title [-]Unexpected intersection type constraint error related to primitive union, generic type and private field[/-] [+]Unexpected intersection type constraint error related to union, generic type and private field[/+] on Apr 30, 2020
6. ahejlsberg commented on Apr 30, 2020

   

   Anders Hejlsberg (ahejlsberg)

   on Apr 30, 2020

   Last edited by ahejlsberg

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   Actually, looks to be caused by #37537. We currently say that unions of object types never contain private or protected members. But that isn't quite right. A union of object types should contain any private or protected member that is present in every constituent and originates in exactly the same declaration. This rarely matters, but in this particular case we end up structurally relating the union ISyncableObject & object | ISyncableObject & string to ISyncableObject, and that fails (but shouldn't) because of the private member.
7. Anders Hejlsberg (ahejlsberg)

   added

   Fix AvailableA PR has been opened for this issueA PR has been opened for this issue

   on Apr 30, 2020
8. Anders Hejlsberg (ahejlsberg)

   closed this as completedin #38277on May 4, 2020
9. microsoft

   locked as resolved and limited conversation to collaborators on Oct 21, 2025