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Properly handle edge cases

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This commit is contained in:
Anders Hejlsberg 2018-05-16 16:26:37 -07:00
parent 8b6e85347d
commit 027829fbcd
1 changed files with 10 additions and 5 deletions
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15
src/compiler/checker.ts
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@ -8457,9 +8457,11 @@ namespace ts {
}
i--;
}
if (intersection !== unionType.types) {
types[unionIndex] = getUnionTypeFromSortedList(intersection, unionType.flags & TypeFlags.UnionOfUnitTypes);
if (intersection === unionType.types) {
return false;
}
types[unionIndex] = getUnionTypeFromSortedList(intersection, unionType.flags & TypeFlags.UnionOfUnitTypes);
return true;
}
// We normalize combinations of intersection and union types based on the distributive property of the '&'
@ -8489,9 +8491,6 @@ namespace ts {
includes & TypeFlags.ESSymbol && includes & TypeFlags.UniqueESSymbol) {
removeRedundantPrimitiveTypes(typeSet, includes);
}
if (includes & TypeFlags.UnionOfUnitTypes) {
intersectUnionsOfUnitTypes(typeSet);
}
if (includes & TypeFlags.EmptyObject && !(includes & TypeFlags.Object)) {
typeSet.push(emptyObjectType);
}
@ -8499,6 +8498,12 @@ namespace ts {
return typeSet[0];
}
if (includes & TypeFlags.Union) {
if (includes & TypeFlags.UnionOfUnitTypes && intersectUnionsOfUnitTypes(typeSet)) {
// When the intersection creates a reduced set (which might mean that *all* union types have
// disappeared), we restart the operation to get a new set of combined flags. Once we have
// reduced we'll never reduce again, so this occurs at most once.
return getIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
}
// We are attempting to construct a type of the form X & (A | B) & Y. Transform this into a type of
// the form X & A & Y | X & B & Y and recursively reduce until no union type constituents remain.
const unionIndex = findIndex(typeSet, t => (t.flags & TypeFlags.Union) !== 0);