Propagate nonInferrableType in &&, || and ?? operators

[Anders Hejlsberg (ahejlsberg)]

Fixes#37974.

[Anders Hejlsberg (ahejlsberg)]

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Heya Anders Hejlsberg (@ahejlsberg), I've started to run the extended test suite on this PR at ade45ee. You can monitor the build here.

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Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at ade45ee. You can monitor the build here.

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Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized community code test suite on this PR at ade45ee. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master.

[Anders Hejlsberg (ahejlsberg)]

Tests all look clean (DT errors are preexisting conditions).

[Wesley Wigham (weswigham)]

Do ternaries also need a fix at all? They union two branches, and a ? a : b scans a lot like a || b.

[Anders Hejlsberg (ahejlsberg)]

Thought about it some more and realized the real issue here is that getTypeFacts should return TypeFacts.None for never. Right now it returns TypeFacts.All, similar to what we return for any and unknown, and that's definitely not right. Once we return TypeFacts.None there is no need to modify the logic for the operators because never then propagates naturally.

[Anders Hejlsberg (ahejlsberg)]

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[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized community code test suite on this PR at 96f45ff. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at 96f45ff. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the extended test suite on this PR at 96f45ff. You can monitor the build here.

[Andrew Branch (andrewbranch)]

Thought about it some more and realized the real issue here is that getTypeFacts should return TypeFacts.None for never.

In one of my experiments, I actually tried doing this specifically for nonInferrableType instead of for all never. If I recall correctly, it caused a bunch of baseline errors, so I abandoned that approach. Nice to know I was on the right track after all.