[ASDAlexander77]

Summary

A try inside another try's catch clause (or finally) whose typed catch did not match handed its exception to the parent's own landing pad, which is the handler already running:

try {
    try { throw 1; } catch (o) {
        try { throw "x"; } catch (e: number) {}
    }
} catch (e2) { /* never reached */ }

shape	Windows on main	Linux on main
mismatch in a parent's catch clause	left the function uncaught (0xE06D7363)	std::terminate
same, with an inner finally	hung: caught again forever	printed nothing
a try with using in a parent's finally	compiler crash in WinEHPrepare	terminate called without an active exception

• Enclosing handler. It was worked out one level up only. It now walks the whole chain of tries around this one and takes the first that receives the exception: the landing pad of a try whose body holds it, or the finally of one whose catch clause holds it. Every edge that hands an exception on now uses it instead of the parent's own pad: the mismatch rethrow, a finally's cleanup return, a cleanup-only try's rethrow, and the Linux finally rethrow and its catch-all clause.
• Linux rethrow after a using. The pad is a catch-all, but __cxa_begin_catch was emitted only for linuxTypedCatchChains, so the rethrow ran with nothing caught. It is now emitted for every Linux rethrow.

This started as a review finding about the Linux cleanup case. The actual bug is wider and on both platforms.

Not fixed here, and broken on main already: a using inside a catch clause on Windows. Its cleanup pad is not nested in the catch funclet, which fails LLVM's verifier ahead of time ("Unwind edges out of a catch must have the same unwind dest as the parent catchswitch"). Without a try around it, the JIT crashes in Win32ExceptionPass. The using variant of the test is therefore Linux-only.

Verification

• 00try_mismatch_in_catch_clause.ts (compile, jit, and the rc/none corpus): untyped and typed parent catch, inner finally, a try in the parent's finally, and two levels up through a finally. On main it fails.
• 00try_mismatch_in_catch_clause_using.ts, Linux only (compile, jit): a using, with and without a finally.
• Windows Release: 2865/2865 passed.
• Linux (WSL): 2861/2861 passed.

🤖 Generated with Claude Code