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Make && operator properly reflect falsy types from constraints

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This commit is contained in:
Anders Hejlsberg
2018-09-14 10:47:13 -07:00
parent 932e14e661
commit 332b8f29b5
1 changed files with 2 additions and 1 deletions
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3
src/compiler/checker.ts
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@@ -12838,7 +12838,8 @@ namespace ts {
}
function getDefinitelyFalsyPartOfType(type: Type): Type {
return type.flags & TypeFlags.String ? emptyStringType :
return type.flags & TypeFlags.Instantiable ? extractDefinitelyFalsyTypes(getBaseConstraintOfType(type) || unknownType) :
type.flags & TypeFlags.String ? emptyStringType :
type.flags & TypeFlags.Number ? zeroType :
type.flags & TypeFlags.Boolean || type === falseType ? falseType :
type.flags & (TypeFlags.Void | TypeFlags.Undefined | TypeFlags.Null) ||