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Stop inferring unions for disjoint callback parameter inferences

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This commit is contained in:
Anders Hejlsberg 2018-08-29 13:42:20 -07:00
parent d066e1e9e3
commit 529ed2d59d
2 changed files with 8 additions and 10 deletions
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13
src/compiler/checker.ts
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@ -13658,7 +13658,7 @@ namespace ts {
return inference.priority! & InferencePriority.PriorityImpliesCombination ? getIntersectionType(inference.contraCandidates!) : getCommonSubtype(inference.contraCandidates!);
}
function getCovariantInference(inference: InferenceInfo, context: InferenceContext, signature: Signature) {
function getCovariantInference(inference: InferenceInfo, signature: Signature) {
// Extract all object literal types and replace them with a single widened and normalized type.
const candidates = widenObjectLiteralCandidates(inference.candidates!);
// We widen inferred literal types if
@ -13671,10 +13671,9 @@ namespace ts {
const baseCandidates = primitiveConstraint ? sameMap(candidates, getRegularTypeOfLiteralType) :
widenLiteralTypes ? sameMap(candidates, getWidenedLiteralType) :
candidates;
// If all inferences were made from contravariant positions, infer a common subtype. Otherwise, if
// union types were requested or if all inferences were made from the return type position, infer a
// union type. Otherwise, infer a common supertype.
const unwidenedType = context.flags & InferenceFlags.InferUnionTypes || inference.priority! & InferencePriority.PriorityImpliesCombination ?
// If all inferences were made from a position that implies a combined result, infer a union type.
// Otherwise, infer a common supertype.
const unwidenedType = inference.priority! & InferencePriority.PriorityImpliesCombination ?
getUnionType(baseCandidates, UnionReduction.Subtype) :
getCommonSupertype(baseCandidates);
return getWidenedType(unwidenedType);
@ -13694,7 +13693,7 @@ namespace ts {
inference.contraCandidates = undefined;
}
if (inference.candidates) {
inferredType = getCovariantInference(inference, context, signature);
inferredType = getCovariantInference(inference, signature);
}
else if (context.flags & InferenceFlags.NoDefault) {
// We use silentNeverType as the wildcard that signals no inferences.
@ -18633,7 +18632,7 @@ namespace ts {
// Instantiate a generic signature in the context of a non-generic signature (section 3.8.5 in TypeScript spec)
function instantiateSignatureInContextOf(signature: Signature, contextualSignature: Signature, contextualMapper?: TypeMapper, compareTypes?: TypeComparer): Signature {
const context = createInferenceContext(signature.typeParameters!, signature, InferenceFlags.InferUnionTypes, compareTypes);
const context = createInferenceContext(signature.typeParameters!, signature, InferenceFlags.None, compareTypes);
const sourceSignature = contextualMapper ? instantiateSignature(contextualSignature, contextualMapper) : contextualSignature;
forEachMatchingParameterType(sourceSignature, signature, (source, target) => {
// Type parameters from outer context referenced by source type are fixed by instantiation of the source type

5
src/compiler/types.ts
View file

@ -4175,9 +4175,8 @@ namespace ts {
/* @internal */
export const enum InferenceFlags {
None = 0, // No special inference behaviors
InferUnionTypes = 1 << 0, // Infer union types for disjoint candidates (otherwise unknownType)
NoDefault = 1 << 1, // Infer unknownType for no inferences (otherwise anyType or emptyObjectType)
AnyDefault = 1 << 2, // Infer anyType for no inferences (otherwise emptyObjectType)
NoDefault = 1 << 0, // Infer unknownType for no inferences (otherwise anyType or emptyObjectType)
AnyDefault = 1 << 1, // Infer anyType for no inferences (otherwise emptyObjectType)
}
/**