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Don't use callback parameter code path when strictly checking functions

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This commit is contained in:
Anders Hejlsberg
2017-10-05 13:18:38 -07:00
parent 924460406e
commit c3d1b027dc
1 changed files with 2 additions and 2 deletions
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4
src/compiler/checker.ts
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@@ -8540,7 +8540,7 @@ namespace ts {
}
const kind = target.declaration ? target.declaration.kind : SyntaxKind.Unknown;
const strictVariance = strictFunctionTypes && kind !== SyntaxKind.MethodDeclaration &&
const strictVariance = !checkAsCallback && strictFunctionTypes && kind !== SyntaxKind.MethodDeclaration &&
kind !== SyntaxKind.MethodSignature && kind !== SyntaxKind.Constructor;
let result = Ternary.True;
@@ -8579,7 +8579,7 @@ namespace ts {
// similar to return values, callback parameters are output positions. This means that a Promise<T>,
// where T is used only in callback parameter positions, will be co-variant (as opposed to bi-variant)
// with respect to T.
const callbacks = sourceSig && targetSig && !sourceSig.typePredicate && !targetSig.typePredicate &&
const callbacks = !strictVariance && sourceSig && targetSig && !sourceSig.typePredicate && !targetSig.typePredicate &&
(getFalsyFlags(sourceType) & TypeFlags.Nullable) === (getFalsyFlags(targetType) & TypeFlags.Nullable);
const related = callbacks ?
compareSignaturesRelated(targetSig, sourceSig, /*checkAsCallback*/ true, /*ignoreReturnTypes*/ false, reportErrors, errorReporter, compareTypes) :