Narrow intersected classes using instanceof
#51032
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ahejlsberg
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Nov 23, 2022
| @@ -17775,7 +17775,7 @@ namespace ts { | |||
| target.flags & TypeFlags.Union ? some((target as UnionType).types, t => isTypeDerivedFrom(source, t)) : | |||
| source.flags & TypeFlags.InstantiableNonPrimitive ? isTypeDerivedFrom(getBaseConstraintOfType(source) || unknownType, target) : | |||
| target === globalObjectType ? !!(source.flags & (TypeFlags.Object | TypeFlags.NonPrimitive)) : | |||
| target === globalFunctionType ? !!(source.flags & TypeFlags.Object) && isFunctionObjectType(source as ObjectType) : | |||
| target === globalFunctionType ? isFunctionObjectType(source) : | |||
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The issue isn't just with x instanceof Function checks, it also extends to x instanceof Object checks. I have a more general solution to the problem in #51631.
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Closing as superseded by #51631 |
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fixes #50844
isTypeDerivedFromcheck here in thenarrowTypeByInstanceofisTypeDerivedFromwas not happy about thesourcestate because it wasn't an object type, it was an intersection. So I've adjusted the check hereisFunctionObjectTypeas that seemed cleaner to me.