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Make lower priority inferences when inference process is blocked

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This commit is contained in:
Anders Hejlsberg 2019-07-20 09:57:10 -07:00
parent 8f020559fb
commit 2450c1947f
1 changed files with 10 additions and 3 deletions
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13
src/compiler/checker.ts
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@ -15459,6 +15459,7 @@ namespace ts {
let bivariant = false;
let propagationType: Type;
let inferenceCount = 0;
let inferenceBlocked = false;
let allowComplexConstraintInference = true;
inferFromTypes(originalSource, originalTarget);
@ -15655,6 +15656,7 @@ namespace ts {
if (source.flags & (TypeFlags.Object | TypeFlags.Intersection)) {
const key = source.id + "," + target.id;
if (visited && visited.get(key)) {
inferenceBlocked = true;
return;
}
(visited || (visited = createMap<boolean>())).set(key, true);
@ -15667,6 +15669,7 @@ namespace ts {
const symbol = isNonConstructorObject ? target.symbol : undefined;
if (symbol) {
if (contains(symbolStack, symbol)) {
inferenceBlocked = true;
return;
}
(symbolStack || (symbolStack = [])).push(symbol);
@ -15755,6 +15758,8 @@ namespace ts {
const sources = source.flags & TypeFlags.Union ? (<UnionType>source).types : [source];
const matched = new Array<boolean>(sources.length);
let typeVariableCount = 0;
const saveInferenceBlocked = inferenceBlocked;
inferenceBlocked = false;
// First infer to types that are not naked type variables. For each source type we
// track whether inferences were made from that particular type to some target.
for (const t of target.types) {
@ -15771,14 +15776,15 @@ namespace ts {
}
// If there are naked type variables in the target, create a union of the source types
// from which no inferences have been made so far and infer from that union to each naked
// type variable. If there is more than one naked type variable, give lower priority to
// the inferences as they are less specific.
// type variable. If there is more than one naked type variable, or if inference was blocked
// (meaning we didn't explore the types fully), give lower priority to the inferences as
// they are less specific.
if (typeVariableCount > 0) {
const unmatched = flatMap(sources, (s, i) => matched[i] ? undefined : s);
if (unmatched.length) {
const s = getUnionType(unmatched);
const savePriority = priority;
if (typeVariableCount > 1) {
if (typeVariableCount > 1 || inferenceBlocked) {
priority |= InferencePriority.NakedTypeVariable;
}
for (const t of target.types) {
@ -15789,6 +15795,7 @@ namespace ts {
priority = savePriority;
}
}
inferenceBlocked = saveInferenceBlocked;
}
function inferToMappedType(source: Type, target: MappedType, constraintType: Type): boolean {