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Conditional rest parameter type cause args to be undefined #484
Description
What happened
See min repro
What you expected
it should work like normal rest parameter
Minimal reproduction
// Minimal reproduction for Perry compiler bug:
// Conditional rest parameter type `T extends void ? [] | [void] : [T]`
// causes runtime TypeError: Cannot read properties of undefined (reading 'length')
class Builder {
with<T>(id: number, ...args: T extends void ? [] | [void] : [T]): this {
console.log("args.length:", args.length);
return this;
}
}
const b = new Builder();
b.with(1);
console.log("Done");Command you ran:
perry test.ts && ./testEnvironment
- Perry version: 0.5.581
- Host OS: ArchLinux
- Target: native
- Rust toolchain (if building from source): rustc 1.95.0 (59807616e 2026-04-14)
- Installed via: from source
Diagnostic output
Perry Doctor
Environment Checks
──────────────────
✓ perry version: 0.5.581
✓ update status: up to date
✓ clang (LLVM codegen): clang version 22.1.3
✓ system linker (cc): cc (GCC) 16.1.1 20260430
✓ runtime library: /home/codehz/Projects/perry/target/release/libperry_runtime.a
⚠ project config (perry.toml): not found - run: perry init
All critical checks passed with some warnings.
Anything else
If change the rest parameter to any[] it will works
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