fix(scope-manager): correct analysis of inferred types in conditional types

[dinofx]

This fixes #2526
In a conditional type, the inferred types are not in scope in the "if false" type.

[typescript-eslint]

Thanks for the PR, @dinofx!

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[codecov]

Codecov Report

Merging #2537 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2537   +/-   ##
=======================================
  Coverage   92.82%   92.82%           
=======================================
  Files         290      290           
  Lines        9505     9506    +1     
  Branches     2664     2664           
=======================================
+ Hits         8823     8824    +1     
  Misses        323      323           
  Partials      359      359           

Flag	Coverage Δ
#unittest	92.82% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ckages/scope-manager/src/referencer/TypeVisitor.ts	89.13% <ø> (+0.11%)	⬆️

[bradzacher]

Fix itself LGTM!

---

To help prevent regressions, could you please add a new snapshot test into packages/scope-manager/tests/fixtures/type-declaration
Call it something like conditional-nested.ts

The test should be something like:

type Test<T> = T extends Array<infer U>
  ? U
  : T extends Set<infer U>
  ? U

Then you can cd pacakges/scope-manager && yarn test fixtures -u to update the snapshot.
What we're looking for here is a snapshot wherein there are two separate U variables created each with their own reference.

If you're not sure what to look for, just push the snapshot and I will be able to verify it.

[dinofx]

Added the new fixture and snapshot

[dinofx]

@bradzacher are any other changes needed?

[bradzacher]

LGTM - thanks for doing this!