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Proper contravariance in type parameter promotion

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This commit is contained in:
Anders Hejlsberg 2019-03-13 06:51:05 -07:00
parent edf8954aae
commit 6656671536
1 changed files with 2 additions and 3 deletions
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5
src/compiler/checker.ts
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@ -14511,10 +14511,9 @@ namespace ts {
emptyObjectType;
}
function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0) {
function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0, contravariant = false) {
let symbolStack: Symbol[];
let visited: Map<boolean>;
let contravariant = false;
let bivariant = false;
let propagationType: Type;
let allowComplexConstraintInference = true;
@ -23474,7 +23473,7 @@ namespace ts {
// contextual signature starting with an empty set of inference candidates.
const inferences = map(context.inferences, info => createInferenceInfo(info.typeParameter));
applyToParameterTypes(instantiatedSignature, contextualSignature, (source, target) => {
inferTypes(inferences, source, target);
inferTypes(inferences, source, target, /*priority*/ 0, /*contravariant*/ true);
});
if (some(inferences, hasInferenceCandidates)) {
// We have inference candidates, indicating that one or more type parameters are referenced