「Bug」multiple candidates for the same type variable in contra-variant positions causes an intersection type to be inferred

[ghost]

According to the #21496 PR, there should be string & number expected results

type Bar<T> = T extends { a: (x: infer U) => void; b: (x: infer U) => void } ? U : never;
type T20 = Bar<{ a: (x: string) => void; b: (x: string) => void }>; // string
type T21 = Bar<{ a: (x: string) => void; b: (x: number) => void }>; // string & number

However, under ts version 3.6.4, the results are not as expected

[fatcerberus]

string & number is an empty intersection (there is no value that can satisfy that type) and now collapses to never eagerly per #31838. It still collapsed to never before that PR, but was lazy and didn't happen until the type was used in a distributive context. Now (as of TS 3.6) it happens immediately.

[IllusionMH]

Not a duplicate but related to #34684. This is expected behavior as described above