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No recursive intersection property checks #37854

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Merged
merged 2 commits into from
Apr 10, 2020
Merged

No recursive intersection property checks #37854

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No recursive intersection property checks
ahejlsberg Apr 9, 2020
4ba3faa
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ahejlsberg Apr 9, 2020
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11 changes: 9 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -196,6 +196,7 @@ namespace ts {
Source = 1 << 0,
Target = 1 << 1,
PropertyCheck = 1 << 2,
InPropertyCheck = 1 << 3,
}

const enum MappedTypeModifiers {
Expand Down Expand Up @@ -15231,6 +15232,7 @@ namespace ts {
let overrideNextErrorInfo = 0; // How many `reportRelationError` calls should be skipped in the elaboration pyramid
let lastSkippedInfo: [Type, Type] | undefined;
let incompatibleStack: [DiagnosticMessage, (string | number)?, (string | number)?, (string | number)?, (string | number)?][] = [];
let inPropertyCheck = false;

Debug.assert(relation !== identityRelation || !errorNode, "no error reporting in identity checking");

Expand Down Expand Up @@ -15666,10 +15668,15 @@ namespace ts {
// function foo<T extends object>(x: { a?: string }, y: T & { a: boolean }) {
// x = y; // Mismatched property in source intersection
// }
if (result && (
//
// We suppress recursive intersection property checks because they can generate lots of work when relating
// recursive intersections that are structurally similar but not exactly identical. See #37854.
if (result && !inPropertyCheck && (
target.flags & TypeFlags.Intersection && (isPerformingExcessPropertyChecks || isPerformingCommonPropertyChecks) ||
isNonGenericObjectType(target) && source.flags & TypeFlags.Intersection && getApparentType(source).flags & TypeFlags.StructuredType && !some((<IntersectionType>source).types, t => !!(getObjectFlags(t) & ObjectFlags.NonInferrableType)))) {
inPropertyCheck = true;
result &= recursiveTypeRelatedTo(source, target, reportErrors, IntersectionState.PropertyCheck);
inPropertyCheck = false;
}

if (!result && reportErrors) {
Expand Down Expand Up @@ -15966,7 +15973,7 @@ namespace ts {
if (overflow) {
return Ternary.False;
}
const id = getRelationKey(source, target, intersectionState, relation);
const id = getRelationKey(source, target, intersectionState | (inPropertyCheck ? IntersectionState.InPropertyCheck : 0), relation);
const entry = relation.get(id);
if (entry !== undefined) {
if (reportErrors && entry & RelationComparisonResult.Failed && !(entry & RelationComparisonResult.Reported)) {
Expand Down