"Expression produces a union type that is too complex to represent" when using interfaces with large number of params for filtering and narrowing down certain keys about typescript HOT 4 CLOSED

Since #56004 we reason more deeply (and correctly) about conditional type constraints, which definitely is a good thing. In this particular example it apparently causes us to materialize intersection types of the form ("foo" | Exclude<Q, "foo>) & ("bar | Exclude<Q, "bar">) & .... with 18 or so union types being intersected. This comes out to 2^18 possible constituents, which is above our 100,000 limit. Of course, the final intersection will actually only have 19 constituents because all of the literal types intersect to never. But we don't realize that.

Here's a simpler repro:

// Error: Expression produces a union type that is too complex to represent.
type Foo<T extends string> =
    & ("a" | T)
    & ("b" | T)
    & ("c" | T)
    & ("d" | T)
    & ("e" | T)
    & ("f" | T)
    & ("g" | T)
    & ("h" | T)
    & ("i" | T)
    & ("j" | T)
    & ("k" | T)
    & ("l" | T)
    & ("m" | T)
    & ("n" | T)
    & ("q" | T)
    & ("p" | T)
    & ("q" | T)
    & ("r" | T);

I'll think about ways to optimize this.

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I assume you mean "properties" instead of "parameters"? There are no function types in the Update interface, let alone ones with large numbers of parameters.

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Bisects to #56004

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@ahejlsberg seems like Not a Defect to me but wanted to double-check

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