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Detect comparisons between large unions or intersections
If their multiplied size is greater than 1E7 (chosen based on the repro in #41517), then we'll expend a large amount of time and memory comparing them, so alert the user instead. Fixes #41517
1 parent 79ffd03 commit 935e27a

12 files changed

Lines changed: 30681 additions & 3 deletions

‎src/compiler/checker.ts‎

Lines changed: 25 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -16812,10 +16812,9 @@ namespace ts {
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if (source === target) return Ternary.True;
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if (relation === identityRelation) {
16815-
return isIdenticalTo(source, target);
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return isIdenticalTo(source, target, reportErrors);
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}
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16818-
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// We fastpath comparing a type parameter to exactly its constraint, as this is _super_ common,
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// and otherwise, for type parameters in large unions, causes us to need to compare the union to itself,
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// as we break down the _target_ union first, _then_ get the source constraint - so for every
@@ -16876,6 +16875,10 @@ namespace ts {
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return Ternary.False;
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}
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16878+
if (areUnionsOrIntersectionsTooLarge(source, target, reportErrors)) {
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return Ternary.False;
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}
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let result = Ternary.False;
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const saveErrorInfo = captureErrorCalculationState();
1688116884

@@ -17011,11 +17014,30 @@ namespace ts {
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}
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}
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17014-
function isIdenticalTo(source: Type, target: Type): Ternary {
17017+
function areUnionsOrIntersectionsTooLarge(source: Type, target: Type, reportErrors: boolean) {
17018+
if ((source.flags & TypeFlags.UnionOrIntersection) && (target.flags & TypeFlags.UnionOrIntersection)) {
17019+
const sourceSize = (source as UnionOrIntersectionType).types.length;
17020+
const targetSize = (target as UnionOrIntersectionType).types.length;
17021+
if (sourceSize * targetSize > 1E7) {
17022+
if (reportErrors) {
17023+
tracing.instant(tracing.Phase.CheckTypes, "areUnionsOrIntersectionsTooLarge_DepthLimit", { sourceId: source.id, sourceSize, targetId: target.id, targetSize });
17024+
reportError(Diagnostics.Expression_requires_comparison_of_excessively_large_unions_or_intersections);
17025+
}
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return true;
17027+
}
17028+
}
17029+
17030+
return false;
17031+
}
17032+
17033+
function isIdenticalTo(source: Type, target: Type, reportErrors: boolean): Ternary {
1701517034
const flags = source.flags & target.flags;
1701617035
if (!(flags & TypeFlags.Substructure)) {
1701717036
return Ternary.False;
1701817037
}
17038+
if (areUnionsOrIntersectionsTooLarge(source, target, reportErrors)) {
17039+
return Ternary.False;
17040+
}
1701917041
if (flags & TypeFlags.UnionOrIntersection) {
1702017042
let result = eachTypeRelatedToSomeType(<UnionOrIntersectionType>source, <UnionOrIntersectionType>target);
1702117043
if (result) {

‎src/compiler/diagnosticMessages.json‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3059,6 +3059,10 @@
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"category": "Error",
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"code": 2796
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},
3062+
"Expression requires comparison of excessively large unions or intersections.": {
3063+
"category": "Error",
3064+
"code": 2797
3065+
},
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"Import declaration '{0}' is using private name '{1}'.": {
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"category": "Error",

‎tests/baselines/reference/largeUnionIntersectionComparisons.errors.txt‎

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‎tests/baselines/reference/largeUnionIntersectionComparisons.js‎

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‎tests/baselines/reference/largeUnionIntersectionComparisons.symbols‎

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