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Increase type instantiation depth limit #45025

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Merged
merged 4 commits into from
Aug 17, 2021
Merged

Increase type instantiation depth limit #45025

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16fea3e
Bump instantiation depth limit to 500
ahejlsberg Jul 14, 2021
4f79295
Accept new baselines
ahejlsberg Jul 14, 2021
62efc71
Update tests
ahejlsberg Jul 14, 2021
d89a9bc
Accept new baselines
ahejlsberg Jul 14, 2021
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31 changes: 12 additions & 19 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -16227,28 +16227,21 @@ namespace ts {
let result = root.instantiations!.get(id);
if (!result) {
const newMapper = createTypeMapper(root.outerTypeParameters, typeArguments);
result = instantiateConditionalType(root, newMapper, aliasSymbol, aliasTypeArguments);
const checkType = root.checkType;
const distributionType = root.isDistributive ? getMappedType(checkType, newMapper) : undefined;
// Distributive conditional types are distributed over union types. For example, when the
// distributive conditional type T extends U ? X : Y is instantiated with A | B for T, the
// result is (A extends U ? X : Y) | (B extends U ? X : Y).
result = distributionType && checkType !== distributionType && distributionType.flags & (TypeFlags.Union | TypeFlags.Never) ?
mapTypeWithAlias(distributionType, t => getConditionalType(root, prependTypeMapping(checkType, t, newMapper)), aliasSymbol, aliasTypeArguments) :
getConditionalType(root, newMapper, aliasSymbol, aliasTypeArguments);
root.instantiations!.set(id, result);
}
return result;
}
return type;
}

function instantiateConditionalType(root: ConditionalRoot, mapper: TypeMapper, aliasSymbol?: Symbol, aliasTypeArguments?: readonly Type[]): Type {
// Check if we have a conditional type where the check type is a naked type parameter. If so,
// the conditional type is distributive over union types and when T is instantiated to a union
// type A | B, we produce (A extends U ? X : Y) | (B extends U ? X : Y).
if (root.isDistributive) {
const checkType = root.checkType as TypeParameter;
const instantiatedType = getMappedType(checkType, mapper);
if (checkType !== instantiatedType && instantiatedType.flags & (TypeFlags.Union | TypeFlags.Never)) {
return mapTypeWithAlias(instantiatedType, t => getConditionalType(root, prependTypeMapping(checkType, t, mapper)), aliasSymbol, aliasTypeArguments);
}
}
return getConditionalType(root, mapper, aliasSymbol, aliasTypeArguments);
}

function instantiateType(type: Type, mapper: TypeMapper | undefined): Type;
function instantiateType(type: Type | undefined, mapper: TypeMapper | undefined): Type | undefined;
function instantiateType(type: Type | undefined, mapper: TypeMapper | undefined): Type | undefined {
Expand All @@ -16259,10 +16252,10 @@ namespace ts {
if (!couldContainTypeVariables(type)) {
return type;
}
if (instantiationDepth === 50 || instantiationCount >= 5000000) {
// We have reached 50 recursive type instantiations and there is a very high likelyhood we're dealing
// with a combination of infinite generic types that perpetually generate new type identities. We stop
// the recursion here by yielding the error type.
if (instantiationDepth === 500 || instantiationCount >= 5000000) {
// We have reached 500 recursive type instantiations, or 5M type instantiations caused by the same statement
// or expression. There is a very high likelyhood we're dealing with a combination of infinite generic types
// that perpetually generate new type identities, so we stop the recursion here by yielding the error type.
tracing?.instant(tracing.Phase.CheckTypes, "instantiateType_DepthLimit", { typeId: type.id, instantiationDepth, instantiationCount });
error(currentNode, Diagnostics.Type_instantiation_is_excessively_deep_and_possibly_infinite);
return errorType;
Expand Down
5 changes: 1 addition & 4 deletions tests/baselines/reference/recursiveConditionalTypes.errors.txt
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Expand Up @@ -6,7 +6,6 @@ tests/cases/compiler/recursiveConditionalTypes.ts(21,5): error TS2322: Type 'T'
tests/cases/compiler/recursiveConditionalTypes.ts(22,5): error TS2322: Type 'Awaited<T>' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'Awaited<T>'.
tests/cases/compiler/recursiveConditionalTypes.ts(35,11): error TS2589: Type instantiation is excessively deep and possibly infinite.
tests/cases/compiler/recursiveConditionalTypes.ts(46,12): error TS2589: Type instantiation is excessively deep and possibly infinite.
tests/cases/compiler/recursiveConditionalTypes.ts(49,5): error TS2322: Type 'TupleOf<number, M>' is not assignable to type 'TupleOf<number, N>'.
Type 'number extends M ? number[] : _TupleOf<number, M, []>' is not assignable to type 'TupleOf<number, N>'.
Type 'number[] | _TupleOf<number, M, []>' is not assignable to type 'TupleOf<number, N>'.
Expand All @@ -25,7 +24,7 @@ tests/cases/compiler/recursiveConditionalTypes.ts(116,9): error TS2345: Argument
Type 'string' is not assignable to type 'number'.


==== tests/cases/compiler/recursiveConditionalTypes.ts (9 errors) ====
==== tests/cases/compiler/recursiveConditionalTypes.ts (8 errors) ====
// Awaiting promises

type Awaited<T> =
Expand Down Expand Up @@ -85,8 +84,6 @@ tests/cases/compiler/recursiveConditionalTypes.ts(116,9): error TS2345: Argument
type TT2 = TupleOf<number, number>;
type TT3 = TupleOf<number, any>;
type TT4 = TupleOf<number, 100>; // Depth error
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The comment in tests/cases/compiler/recursiveConditionalTypes.ts will need to be amended.

~~~~~~~~~~~~~~~~~~~~
!!! error TS2589: Type instantiation is excessively deep and possibly infinite.

function f22<N extends number, M extends N>(tn: TupleOf<number, N>, tm: TupleOf<number, M>) {
tn = tm;
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/recursiveConditionalTypes.types
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Expand Up @@ -105,7 +105,7 @@ type TT3 = TupleOf<number, any>;
>TT3 : number[]

type TT4 = TupleOf<number, 100>; // Depth error
>TT4 : any
>TT4 : [number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number, number]

function f22<N extends number, M extends N>(tn: TupleOf<number, N>, tm: TupleOf<number, M>) {
>f22 : <N extends number, M extends N>(tn: TupleOf<number, N>, tm: TupleOf<number, M>) => void
Expand Down