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Add type instantiation count limiter #32079

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Jul 3, 2019
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Add type instantiation count limiter #32079

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49e3f17
Add instantiation count limiter
ahejlsberg Jun 25, 2019
5c6c1a3
Add regression test
ahejlsberg Jun 28, 2019
a1c6d9e
Accept new baselines
ahejlsberg Jun 28, 2019
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7 changes: 6 additions & 1 deletion src/compiler/checker.ts
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Expand Up @@ -65,6 +65,7 @@ namespace ts {
let typeCount = 0;
let symbolCount = 0;
let enumCount = 0;
let instantiationCount = 0;
let instantiationDepth = 0;
let constraintDepth = 0;
let currentNode: Node | undefined;
Expand Down Expand Up @@ -11408,13 +11409,14 @@ namespace ts {
if (!type || !mapper || mapper === identityMapper) {
return type;
}
if (instantiationDepth === 50) {
if (instantiationDepth === 50 || instantiationCount >= 5000000) {
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Do we still need instantiationDepth if we're also looking at a total count?

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We definitely do. The depth limiter is there to catch infinitely recursive types, we'd blow the stack way before the count limiter gets to 5M.

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Fair enough. Although we could always modify instantiation to use a trampoline instead of direct recursion so we don't have to worry about stack depth, and then the total count of instantiations would really be the absolute measure of complexity, without need for a specific depth-measuring mechanism. (And would enable people to nest those if/else style conditionals more than 50 levels deep, like we've occasionally seen reports of - those may be deep, but they're often trivial)

// 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.
error(currentNode, Diagnostics.Type_instantiation_is_excessively_deep_and_possibly_infinite);
return errorType;
}
instantiationCount++;
instantiationDepth++;
const result = instantiateTypeWorker(type, mapper);
instantiationDepth--;
Expand Down Expand Up @@ -24494,6 +24496,7 @@ namespace ts {
function checkExpression(node: Expression | QualifiedName, checkMode?: CheckMode, forceTuple?: boolean): Type {
const saveCurrentNode = currentNode;
currentNode = node;
instantiationCount = 0;
const uninstantiatedType = checkExpressionWorker(node, checkMode, forceTuple);
const type = instantiateTypeWithSingleGenericCallSignature(node, uninstantiatedType, checkMode);
if (isConstEnumObjectType(type)) {
Expand Down Expand Up @@ -29204,6 +29207,7 @@ namespace ts {
if (node) {
const saveCurrentNode = currentNode;
currentNode = node;
instantiationCount = 0;
checkSourceElementWorker(node);
currentNode = saveCurrentNode;
}
Expand Down Expand Up @@ -29475,6 +29479,7 @@ namespace ts {
function checkDeferredNode(node: Node) {
const saveCurrentNode = currentNode;
currentNode = node;
instantiationCount = 0;
switch (node.kind) {
case SyntaxKind.FunctionExpression:
case SyntaxKind.ArrowFunction:
Expand Down
17 changes: 16 additions & 1 deletion tests/baselines/reference/infiniteConstraints.errors.txt
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Expand Up @@ -2,9 +2,10 @@ tests/cases/compiler/infiniteConstraints.ts(4,37): error TS2536: Type '"val"' ca
tests/cases/compiler/infiniteConstraints.ts(31,43): error TS2322: Type 'Record<"val", "dup">' is not assignable to type 'never'.
tests/cases/compiler/infiniteConstraints.ts(31,63): error TS2322: Type 'Record<"val", "dup">' is not assignable to type 'never'.
tests/cases/compiler/infiniteConstraints.ts(36,71): error TS2536: Type '"foo"' cannot be used to index type 'T[keyof T]'.
tests/cases/compiler/infiniteConstraints.ts(48,16): error TS2589: Type instantiation is excessively deep and possibly infinite.


==== tests/cases/compiler/infiniteConstraints.ts (4 errors) ====
==== tests/cases/compiler/infiniteConstraints.ts (5 errors) ====
// Both of the following types trigger the recursion limiter in getImmediateBaseConstraint

type T1<B extends { [K in keyof B]: Extract<B[Exclude<keyof B, K>], { val: string }>["val"] }> = B;
Expand Down Expand Up @@ -51,4 +52,18 @@ tests/cases/compiler/infiniteConstraints.ts(36,71): error TS2536: Type '"foo"' c
declare function function1<T extends {[K in keyof T]: Cond<T[K]>}>(): T[keyof T]["foo"];
~~~~~~~~~~~~~~~~~
!!! error TS2536: Type '"foo"' cannot be used to index type 'T[keyof T]'.

// Repro from #31823

export type Prepend<Elm, T extends unknown[]> =
T extends unknown ?
((arg: Elm, ...rest: T) => void) extends ((...args: infer T2) => void) ? T2 :
never :
never;
export type ExactExtract<T, U> = T extends U ? U extends T ? T : never : never;

type Conv<T, U = T> =
{ 0: [T]; 1: Prepend<T, Conv<ExactExtract<U, T>>>;}[U extends T ? 0 : 1];
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2589: Type instantiation is excessively deep and possibly infinite.

13 changes: 13 additions & 0 deletions tests/baselines/reference/infiniteConstraints.js
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Expand Up @@ -35,11 +35,24 @@ const shouldBeError = ensureNoDuplicates({main: value("dup"), alternate: value("

type Cond<T> = T extends number ? number : never;
declare function function1<T extends {[K in keyof T]: Cond<T[K]>}>(): T[keyof T]["foo"];

// Repro from #31823

export type Prepend<Elm, T extends unknown[]> =
T extends unknown ?
((arg: Elm, ...rest: T) => void) extends ((...args: infer T2) => void) ? T2 :
never :
never;
export type ExactExtract<T, U> = T extends U ? U extends T ? T : never : never;

type Conv<T, U = T> =
{ 0: [T]; 1: Prepend<T, Conv<ExactExtract<U, T>>>;}[U extends T ? 0 : 1];


//// [infiniteConstraints.js]
"use strict";
// Both of the following types trigger the recursion limiter in getImmediateBaseConstraint
exports.__esModule = true;
var out = myBug({ obj1: { a: "test" } });
var noError = ensureNoDuplicates({ main: value("test"), alternate: value("test2") });
var shouldBeNoError = ensureNoDuplicates({ main: value("test") });
Expand Down
50 changes: 50 additions & 0 deletions tests/baselines/reference/infiniteConstraints.symbols
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Expand Up @@ -138,3 +138,53 @@ declare function function1<T extends {[K in keyof T]: Cond<T[K]>}>(): T[keyof T]
>T : Symbol(T, Decl(infiniteConstraints.ts, 35, 27))
>T : Symbol(T, Decl(infiniteConstraints.ts, 35, 27))

// Repro from #31823

export type Prepend<Elm, T extends unknown[]> =
>Prepend : Symbol(Prepend, Decl(infiniteConstraints.ts, 35, 88))
>Elm : Symbol(Elm, Decl(infiniteConstraints.ts, 39, 20))
>T : Symbol(T, Decl(infiniteConstraints.ts, 39, 24))

T extends unknown ?
>T : Symbol(T, Decl(infiniteConstraints.ts, 39, 24))

((arg: Elm, ...rest: T) => void) extends ((...args: infer T2) => void) ? T2 :
>arg : Symbol(arg, Decl(infiniteConstraints.ts, 41, 4))
>Elm : Symbol(Elm, Decl(infiniteConstraints.ts, 39, 20))
>rest : Symbol(rest, Decl(infiniteConstraints.ts, 41, 13))
>T : Symbol(T, Decl(infiniteConstraints.ts, 39, 24))
>args : Symbol(args, Decl(infiniteConstraints.ts, 41, 45))
>T2 : Symbol(T2, Decl(infiniteConstraints.ts, 41, 59))
>T2 : Symbol(T2, Decl(infiniteConstraints.ts, 41, 59))

never :
never;
export type ExactExtract<T, U> = T extends U ? U extends T ? T : never : never;
>ExactExtract : Symbol(ExactExtract, Decl(infiniteConstraints.ts, 43, 8))
>T : Symbol(T, Decl(infiniteConstraints.ts, 44, 25))
>U : Symbol(U, Decl(infiniteConstraints.ts, 44, 27))
>T : Symbol(T, Decl(infiniteConstraints.ts, 44, 25))
>U : Symbol(U, Decl(infiniteConstraints.ts, 44, 27))
>U : Symbol(U, Decl(infiniteConstraints.ts, 44, 27))
>T : Symbol(T, Decl(infiniteConstraints.ts, 44, 25))
>T : Symbol(T, Decl(infiniteConstraints.ts, 44, 25))

type Conv<T, U = T> =
>Conv : Symbol(Conv, Decl(infiniteConstraints.ts, 44, 79))
>T : Symbol(T, Decl(infiniteConstraints.ts, 46, 10))
>U : Symbol(U, Decl(infiniteConstraints.ts, 46, 12))
>T : Symbol(T, Decl(infiniteConstraints.ts, 46, 10))

{ 0: [T]; 1: Prepend<T, Conv<ExactExtract<U, T>>>;}[U extends T ? 0 : 1];
>0 : Symbol(0, Decl(infiniteConstraints.ts, 47, 3))
>T : Symbol(T, Decl(infiniteConstraints.ts, 46, 10))
>1 : Symbol(1, Decl(infiniteConstraints.ts, 47, 11))
>Prepend : Symbol(Prepend, Decl(infiniteConstraints.ts, 35, 88))
>T : Symbol(T, Decl(infiniteConstraints.ts, 46, 10))
>Conv : Symbol(Conv, Decl(infiniteConstraints.ts, 44, 79))
>ExactExtract : Symbol(ExactExtract, Decl(infiniteConstraints.ts, 43, 8))
>U : Symbol(U, Decl(infiniteConstraints.ts, 46, 12))
>T : Symbol(T, Decl(infiniteConstraints.ts, 46, 10))
>U : Symbol(U, Decl(infiniteConstraints.ts, 46, 12))
>T : Symbol(T, Decl(infiniteConstraints.ts, 46, 10))

23 changes: 23 additions & 0 deletions tests/baselines/reference/infiniteConstraints.types
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12 changes: 12 additions & 0 deletions tests/cases/compiler/infiniteConstraints.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -36,3 +36,15 @@ const shouldBeError = ensureNoDuplicates({main: value("dup"), alternate: value("

type Cond<T> = T extends number ? number : never;
declare function function1<T extends {[K in keyof T]: Cond<T[K]>}>(): T[keyof T]["foo"];

// Repro from #31823

export type Prepend<Elm, T extends unknown[]> =
T extends unknown ?
((arg: Elm, ...rest: T) => void) extends ((...args: infer T2) => void) ? T2 :
never :
never;
export type ExactExtract<T, U> = T extends U ? U extends T ? T : never : never;

type Conv<T, U = T> =
{ 0: [T]; 1: Prepend<T, Conv<ExactExtract<U, T>>>;}[U extends T ? 0 : 1];