Crash: RangeError: Maximum call stack size exceeded in isRelatedTo with recursive tuple types and spread elements

[na7ure-a]

🔎 Search Terms

RangeError: Maximum call stack size exceeded

Recursion limit

Variadic tuple types

Recursive conditional types

isRelatedTo / checkTypeRelatedTo crash

🕗 Version & Regression Information

Versions tested: 5.7.3, 5.8.3, 5.9.3, Nightly, TS7.

⏯ Playground Link

https://www.typescriptlang.org/zh/play/?target=2&ts=6.0.0-dev.20260319&ssl=9&ssc=44&pln=8&pc=1#code/PTAEAEBcEMCcHMCmkBcpEGcBMAGAjAKwBQIEGksAlgMaqgUCuiJYASogA6wD2oAZjwC2oAMQBmABx4AnBKKQAnh0Sh21BrAA8AFQB8oALygAFEVDnQ29AA9IiAHYATDOeMN7Aa3vcA7vYDaALoAlKAA-KAA3gC+oGiRoP4A0qCU9qAeiArcfJaBYWhqGjrJgbrRRKEAPokAdPVFWnr+9gyCAEaIsIFBgQDcRIN87rSU3OkAVtxpOrrGADaFiOpNukHBSyuzUWYWsMga6f4A5IJwmbDHADSg9bXz-UQVw-aj46DQswubxc0haAA3aaOHYWUDUcbkUDWH6rUA1dyORB8NKIEFGKZpBbBAYVIA

💻 Code

// @target: es2015
// @strict: true
// Repro from #38198
type Recur<T> = (
    T extends  (unknown[]) ? {} : { [K in keyof T]?: Recur<T[K]>}
) | [...Recur<T>[number][]];


function join<T>(l: Recur<T>[]): Recur<T> {
    return ['marker', ...l];
}
function a<T>(l: Recur<T>[]): void {
    const x: Recur<T> | undefined = join(l);
}

🙁 Actual behavior

node built/local/tsc.js -noEmit  recursiveReverseMappedType_filled_0_unvalidated_mutated_batch0.ts
D:\github\TypeScript\built\local\_tsc.js:123721
      throw e;
      ^

RangeError: Maximum call stack size exceeded
    at isRelatedTo (D:\github\TypeScript\built\local\_tsc.js:65175:25)
    at checkTypeRelatedTo (D:\github\TypeScript\built\local\_tsc.js:64889:20)
    at isTypeRelatedTo (D:\github\TypeScript\built\local\_tsc.js:64822:14)
    at isTypeIdenticalTo (D:\github\TypeScript\built\local\_tsc.js:63930:12)
    at isTypeOrBaseIdenticalTo (D:\github\TypeScript\built\local\_tsc.js:69275:42)
    at inferFromMatchingTypes (D:\github\TypeScript\built\local\_tsc.js:68894:15)
    at inferFromTypes (D:\github\TypeScript\built\local\_tsc.js:68704:44)
    at inferFromTypes (D:\github\TypeScript\built\local\_tsc.js:68776:11)
    at inferToMultipleTypes (D:\github\TypeScript\built\local\_tsc.js:68964:15)
    at inferFromTypes (D:\github\TypeScript\built\local\_tsc.js:68820:9)

Node.js v22.19.0

🙂 Expected behavior

The compiler should not crash.

Additional information about the issue

No response

[BillionClaw]

Looking into this — the isRelatedTo function is hitting a stack overflow with recursive conditional types. Happy to submit a fix.