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Fix bivariant checking of signatures returning type predicates

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This commit is contained in:
Anders Hejlsberg
2019-04-21 11:25:51 -07:00
parent df50477d31
commit 39c263b2f5
1 changed files with 2 additions and 2 deletions
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src/compiler/checker.ts
+2 -2
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@@ -11960,8 +11960,8 @@ namespace ts {
// The following block preserves behavior forbidding boolean returning functions from being assignable to type guard returning functions
const targetTypePredicate = getTypePredicateOfSignature(target);
if (targetTypePredicate) {
const sourceTypePredicate = getTypePredicateOfSignature(source);
const sourceTypePredicate = getTypePredicateOfSignature(source);
if (targetTypePredicate && (sourceTypePredicate || callbackCheck !== CallbackCheck.Bivariant)) {
if (sourceTypePredicate) {
result &= callbackCheck === CallbackCheck.Bivariant && compareTypePredicateRelatedTo(targetTypePredicate, sourceTypePredicate, /*reportErrors*/ false, /*errorReporter*/ undefined, compareTypes) ||
compareTypePredicateRelatedTo(sourceTypePredicate, targetTypePredicate, reportErrors, errorReporter, compareTypes);