Type discrimination bug with string literal tuple. about typescript HOT 4 CLOSED

The word is “tuple”, not “touple”. Could you edit so this issue can be found via searches on “tuple”?

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Config can be rewritten as type Config = (Base & AType) | (Base & BType) | (Base & AandBType) with the same result.
I looked at this and figured that when checking compatibility the checker could look for matching union members, then apply the Excess Property Check to each matching member, ruling out any that fail, or throw an EPC error if they all fail. But it doesn't seem to.

Changing array to a string, which TS seems to need to use it as a discriminator makes the EPC kick in. But I'm just not getting why an EPC check on a union needs a discriminator. I may be missing something, but seemed solvable to me.

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But I'm just not getting why an EPC check on a union needs a discriminator.

#20863

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This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.

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