Fixed a regression with discriminating unions based on a union property against undefined with strictNullChecks: false
#49648
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Andarist
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Jun 23, 2022
| // skip all the checks we don't need and just return `isSimpleTypeRelatedTo` result | ||
| if (originalSource.flags & TypeFlags.Object && originalTarget.flags & TypeFlags.Primitive) { | ||
| if (isSimpleTypeRelatedTo(originalSource, originalTarget, relation, reportErrors ? reportError : undefined)) { | ||
| if (relation === comparableRelation && !(originalTarget.flags & TypeFlags.Never) && isSimpleTypeRelatedTo(originalTarget, originalSource, relation) || |
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The condition was adjusted based on:
https://github.dev/microsoft/TypeScript/blob/8636adbbb9ab47bb377bd89a3390a13b66df34d2/src/compiler/checker.ts#L18248
and also the same~ thing being checked a few lines below in this very same function:
https://github.dev/microsoft/TypeScript/blob/8636adbbb9ab47bb377bd89a3390a13b66df34d2/src/compiler/checker.ts#L18709-L18710
…ty against `undefined` with `strictNullChecks: false`
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weswigham
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Nov 7, 2022
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fixes #49643
It's a regression from: 78ef3e7
Previously the first part of the condition was returning
truein theisTypeRelatedTohere (called fromnarrowTypeByDiscriminantbyisTypeComparableTo):https://github.dev/microsoft/TypeScript/blob/8636adbbb9ab47bb377bd89a3390a13b66df34d2/src/compiler/checker.ts#L18248-L18250
It was passing because unions were not ignored by this condition here:
78ef3e7#diff-d9ab6589e714c71e657f601cf30ff51dfc607fc98419bf72e04f6b0fa92cc4b8L17910
Since the mentioned commit explicitly started to ignore unions there and the comment was put in place about it the code followed along through this call:
https://github.dev/microsoft/TypeScript/blob/8636adbbb9ab47bb377bd89a3390a13b66df34d2/src/compiler/checker.ts#L18263-L18265
and a union member has started to be tested through the condition I've adjusted now. The fix was needed here because this condition was not checking the "reversed" relation (
isSimpleTypeRelatedTo(originalTarget, originalSource, relation)) in the case of thecomparableRelation.cc @nicolo-ribaudo