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Consistently propagate 'any' and 'never' types in type inference

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This commit is contained in:
Anders Hejlsberg 2018-02-28 14:08:25 -08:00
parent c0c3f4aa12
commit e5b568f9f4
2 changed files with 12 additions and 17 deletions
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26
src/compiler/checker.ts
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@ -11490,20 +11490,21 @@ namespace ts {
let symbolStack: Symbol[];
let visited: Map<boolean>;
let contravariant = false;
let propagationType: Type;
inferFromTypes(originalSource, originalTarget);
function inferFromTypes(source: Type, target: Type) {
if (!couldContainTypeVariables(target)) {
return;
}
if (source === neverType || source === wildcardType) {
// We are inferring from 'never' or the wildcard type. We want to infer this
// type for every type parameter referenced in the target type, so we infer from
// target to itself with a flag we check when recording candidates.
const savePriority = priority;
priority |= source === neverType ? InferencePriority.Never : InferencePriority.Wildcard;
if (source.flags & (TypeFlags.Any | TypeFlags.Never) && source !== silentNeverType) {
// We are inferring from 'any' or 'never'. We want to infer this type for every type parameter
// referenced in the target type, so we record the propagation type and infer from the target
// to itself. Then, as we find candidates we substitute the propagation type.
const savePropagationType = propagationType;
propagationType = source;
inferFromTypes(target, target);
priority = savePriority;
propagationType = savePropagationType;
return;
}
if (source.aliasSymbol && source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol) {
@ -11567,16 +11568,13 @@ namespace ts {
const inference = getInferenceInfoForType(target);
if (inference) {
if (!inference.isFixed) {
const p = priority & InferencePriority.Mask;
if (inference.priority === undefined || p < inference.priority) {
if (inference.priority === undefined || priority < inference.priority) {
inference.candidates = undefined;
inference.contraCandidates = undefined;
inference.priority = p;
inference.priority = priority;
}
if (p === inference.priority) {
const candidate = priority & InferencePriority.Never ? neverType :
priority & InferencePriority.Wildcard ? wildcardType :
source;
if (priority === inference.priority) {
const candidate = propagationType || source;
if (contravariant) {
inference.contraCandidates = append(inference.contraCandidates, candidate);
}

3
src/compiler/types.ts
View File

@ -3915,9 +3915,6 @@ namespace ts {
ReturnType = 1 << 2, // Inference made from return type of generic function
NoConstraints = 1 << 3, // Don't infer from constraints of instantiable types
AlwaysStrict = 1 << 4, // Always use strict rules for contravariant inferences
Wildcard = 1 << 5, // Inferring from wildcard type
Never = 1 << 6, // Inferring from never type
Mask = NakedTypeVariable | MappedType | ReturnType,
}
/* @internal */