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Clean up inference of type parameters, contravariant types #49915

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Merged
jakebailey merged 2 commits into from
Jul 19, 2022
Merged

Clean up inference of type parameters, contravariant types #49915

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01789d3
Clean up inference of type parameters, contravariant types
jakebailey Jul 15, 2022
4c5d4c1
Remove unintentional change
jakebailey Jul 19, 2022
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46 changes: 27 additions & 19 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22556,15 +22556,11 @@ namespace ts {
inferFromTypeArguments(getTypeArguments(source as TypeReference), getTypeArguments(target as TypeReference), getVariances((source as TypeReference).target));
}
else if (source.flags & TypeFlags.Index && target.flags & TypeFlags.Index) {
contravariant = !contravariant;
inferFromTypes((source as IndexType).type, (target as IndexType).type);
contravariant = !contravariant;
inferFromContravariantTypes((source as IndexType).type, (target as IndexType).type);
}
else if ((isLiteralType(source) || source.flags & TypeFlags.String) && target.flags & TypeFlags.Index) {
const empty = createEmptyObjectTypeFromStringLiteral(source);
contravariant = !contravariant;
inferWithPriority(empty, (target as IndexType).type, InferencePriority.LiteralKeyof);
contravariant = !contravariant;
inferFromContravariantTypesWithPriority(empty, (target as IndexType).type, InferencePriority.LiteralKeyof);
}
else if (source.flags & TypeFlags.IndexedAccess && target.flags & TypeFlags.IndexedAccess) {
inferFromTypes((source as IndexedAccessType).objectType, (target as IndexedAccessType).objectType);
Expand All @@ -22577,10 +22573,7 @@ namespace ts {
}
else if (source.flags & TypeFlags.Substitution) {
inferFromTypes((source as SubstitutionType).baseType, target);
const oldPriority = priority;
priority |= InferencePriority.SubstituteSource;
inferFromTypes((source as SubstitutionType).substitute, target); // Make substitute inference at a lower priority
priority = oldPriority;
inferWithPriority((source as SubstitutionType).substitute, target, InferencePriority.SubstituteSource); // Make substitute inference at a lower priority
}
else if (target.flags & TypeFlags.Conditional) {
invokeOnce(source, target, inferToConditionalType);
Expand Down Expand Up @@ -22631,6 +22624,20 @@ namespace ts {
priority = savePriority;
}

function inferFromContravariantTypesWithPriority(source: Type, target: Type, newPriority: InferencePriority) {
const savePriority = priority;
priority |= newPriority;
inferFromContravariantTypes(source, target);
priority = savePriority;
}

function inferToMultipleTypesWithPriority(source: Type, targets: Type[], targetFlags: TypeFlags, newPriority: InferencePriority) {
const savePriority = priority;
priority |= newPriority;
inferToMultipleTypes(source, targets, targetFlags);
priority = savePriority;
}

function invokeOnce(source: Type, target: Type, action: (source: Type, target: Type) => void) {
const key = source.id + "," + target.id;
const status = visited && visited.get(key);
Expand Down Expand Up @@ -22694,10 +22701,14 @@ namespace ts {
}

function inferFromContravariantTypes(source: Type, target: Type) {
contravariant = !contravariant;
inferFromTypes(source, target);
contravariant = !contravariant;
}

function inferFromContravariantTypesIfStrictFunctionTypes(source: Type, target: Type) {
if (strictFunctionTypes || priority & InferencePriority.AlwaysStrict) {
contravariant = !contravariant;
inferFromTypes(source, target);
contravariant = !contravariant;
inferFromContravariantTypes(source, target);
}
else {
inferFromTypes(source, target);
Expand Down Expand Up @@ -22860,11 +22871,8 @@ namespace ts {
inferFromTypes(getFalseTypeFromConditionalType(source as ConditionalType), getFalseTypeFromConditionalType(target));
}
else {
const savePriority = priority;
priority |= contravariant ? InferencePriority.ContravariantConditional : 0;
const targetTypes = [getTrueTypeFromConditionalType(target), getFalseTypeFromConditionalType(target)];
inferToMultipleTypes(source, targetTypes, target.flags);
priority = savePriority;
inferToMultipleTypesWithPriority(source, targetTypes, target.flags, contravariant ? InferencePriority.ContravariantConditional : 0);
}
}

Expand Down Expand Up @@ -23059,7 +23067,7 @@ namespace ts {
const kind = target.declaration ? target.declaration.kind : SyntaxKind.Unknown;
// Once we descend into a bivariant signature we remain bivariant for all nested inferences
bivariant = bivariant || kind === SyntaxKind.MethodDeclaration || kind === SyntaxKind.MethodSignature || kind === SyntaxKind.Constructor;
applyToParameterTypes(source, target, inferFromContravariantTypes);
applyToParameterTypes(source, target, inferFromContravariantTypesIfStrictFunctionTypes);
bivariant = saveBivariant;
applyToReturnTypes(source, target, inferFromTypes);
}
Expand Down Expand Up @@ -30072,7 +30080,7 @@ 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, inferenceContext?: InferenceContext, compareTypes?: TypeComparer): Signature {
const context = createInferenceContext(signature.typeParameters!, signature, InferenceFlags.None, compareTypes);
const context = createInferenceContext(signature.typeParameters!, signature, inferenceContext?.flags ?? InferenceFlags.None, compareTypes);

@jakebailey jakebailey Jul 19, 2022

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Uh, I think this is cruft from my other PR. Will remove and retest.

// We clone the inferenceContext to avoid fixing. For example, when the source signature is <T>(x: T) => T[] and
// the contextual signature is (...args: A) => B, we want to infer the element type of A's constraint (say 'any')
// for T but leave it possible to later infer '[any]' back to A.
Expand Down