Microsoft/TypeScript

Crash: RangeError: Maximum call stack size exceeded in isReachableFlowNodeWorker with complex for loop headers

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#63092 opened on Feb 4, 2026

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 (2 comments) (0 reactions) (0 assignees)TypeScript (48,455 stars) (6,726 forks)batch import
BugDomain: check: Control FlowHelp Wanted

Description

🔎 Search Terms

"Maximum call stack size exceeded"

"isReachableFlowNodeWorker stack overflow"

"Control flow analysis crash"

"for loop reachability crash"

🕗 Version & Regression Information

Crashes in 5.7.3, 5.8.3, 5.9.3, Nightly,TS7.

⏯ Playground Link

https://www.typescriptlang.org/zh/play/?target=7&ts=6.0.0-dev.20260203#code/PTAEAEEMBtoewO4FUB2AnAppAxgC0gEbQYDCcAJhgFygBmMAzhgFAAuaAnqAN7Oj904aUAAo+AiSNoBXFNlYBLOClEBKHqFa40iUACIAjHoDcoAL6qRq0+In8ps+UpQAqNRq06E+gEwnzlta2dg5yispuVh7aunoAzP4WVsHq3ObMZszYkKx4ohip6aCQDPzGQA

💻 Code

try {
    for (
        (function () { throw "1"; })(); 
        (function* () { throw "2"; })();
        (function* () { throw "3"; })()
    ) { }
}
catch (e) { }
 as  ;

🙁 Actual behavior

 .\ts-versions\nightly\node_modules\.bin\tsc.cmd  .\reachabilityChecks8_mutated_batch0.ts
D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:123214
      throw e;
      ^
RangeError: Maximum call stack size exceeded
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70125:37)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       
    at isReachableFlowNodeWorker (D:\do\typeFuzz\ts-versions\nightly\node_modules\typescript\lib\_tsc.js:70135:77)                                                                                       

Node.js v22.19.0

🙂 Expected behavior

The compiler should not crash.

Additional information about the issue

No response

Contributor guide

Tech stack
typescript
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TypeScript compiler internalscontrol flow graph understanding
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
10
Research direction
Investigate the `isReachableFlowNodeWorker` function in the TypeScript compiler's checker.ts to understand why it causes a stack overflow with complex for loop headers. The issue reproduces with nested generator functions and throw statements in the for loop header (initializer, condition, incrementer). Look at how flow nodes are created for such constructs and trace the recursion pattern. The stack trace shows repeated calls to the same function, suggesting a cycle or deep recursion that should be handled. Examine existing tests for control flow analysis with abnormal completions (throw, yield) in loop headers. The playground link provides a code example that triggers the crash.