Prevent symbol table exhaustion during codegen by Copilot · Pull Request #6670 · RustPython/RustPython

Copilot · 2026-01-07T00:18:31Z

The compiler panicked on push_symbol_table when compiling xonsh/pytest hooks, crashing the run.

Error handling: push_symbol_table now returns a codegen error if no subtable is available, rather than panicking.
Propagation: All callers (function/class/type-param/type-alias/comprehension setup) were adjusted to bubble the failure instead of assuming infallibility.
Robustness: Symbol tables now keep a cursor instead of removing subtables, so repeated compilation paths (e.g., try/finally double passes) reuse the same entries and avoid exhaustion.

Example (simplified):

// Before: panic!("push_symbol_table: no sub_tables…")
let table = self.push_symbol_table()?; // now returns a CompileResult
self.enter_scope(name, table.typ, key, lineno)?;

Original prompt

This section details on the original issue you should resolve

<issue_title>thread 'main' panicked at crates/codegen/src/compile.rs:648:13:</issue_title>
<issue_description>```xsh
rustpython -V

Python 3.13.0alpha (heads/master:8bfe927de

```xsh
cd xonsh/
RUST_BACKTRACE=full rust-pytest

thread 'main' (16880887) panicked at crates/codegen/src/compile.rs:648:13:
push_symbol_table: no sub_tables available in pytest_runtest_protocol (type: Function)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

RUST_BACKTRACE=full rust-pytest

thread 'main' (16878492) panicked at crates/codegen/src/compile.rs:648:13:
push_symbol_table: no sub_tables available in pytest_runtest_protocol (type: Function)
stack backtrace:
   0:        0x102dc7ba0 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h2808c764b780ef77
   1:        0x10230cfb4 - core::fmt::write::h164e2e78980a3344
   2:        0x102da5654 - std::io::Write::write_fmt::hc5b2a4d160c11c86
   3:        0x102dabf88 - std::sys::backtrace::BacktraceLock::print::h765d16e49e83c7b3
   4:        0x102dae4b0 - std::panicking::default_hook::{{closure}}::hf5d7ef6cefa10586
   5:        0x102dae110 - std::panicking::default_hook::h8781bd6c5c54e4cc
   6:        0x102dae9a0 - std::panicking::panic_with_hook::h93c775fc227522dd
   7:        0x102dae68c - std::panicking::panic_handler::{{closure}}::h8561e58c9391724a
   8:        0x102dac094 - std::sys::backtrace::__rust_end_short_backtrace::h55629ed76aaa9d26
   9:        0x102d9d948 - __rustc[d9b87f19e823c0ef]::rust_begin_unwind
  10:        0x102f63924 - core::panicking::panic_fmt::hfe9cfd57c06d80d9
  11:        0x1025b79c4 - rustpython_codegen::compile::Compiler::push_symbol_table::hfeafda8d0290b5ca
  12:        0x1025ae1d0 - rustpython_codegen::compile::Compiler::push_output::ha6ee3ae42a4636e3
  13:        0x1025bddf4 - rustpython_codegen::compile::Compiler::compile_comprehension::hb484e6cf43f9f5cf
  14:        0x1025ba7ec - rustpython_codegen::compile::Compiler::compile_expression::he6bbf8bb018e050e
  15:        0x1025b9854 - rustpython_codegen::compile::Compiler::compile_expression::he6bbf8bb018e050e
  16:        0x1025b476c - rustpython_codegen::compile::Compiler::compile_statement::hc5fc9a32b46a1d02
  17:        0x1025c064c - rustpython_codegen::compile::Compiler::compile_try_statement::hc999aeecc9056ff6
  18:        0x1025b5430 - rustpython_codegen::compile::Compiler::compile_statement::hc5fc9a32b46a1d02
  19:        0x1025be78c - rustpython_codegen::compile::Compiler::compile_function_body::h9dee484648b86dae
  20:        0x1025b6500 - rustpython_codegen::compile::Compiler::compile_statement::hc5fc9a32b46a1d02
  21:        0x1025b8dd0 - rustpython_codegen::compile::Compiler::compile_class_body::h3590690ed451b898
  22:        0x1025b68f0 - rustpython_codegen::compile::Compiler::compile_statement::hc5fc9a32b46a1d02
  23:        0x1025aad50 - rustpython_codegen::compile::compile_program::ha3ec8bdff9e2b9e1
  24:        0x1025aaa18 - rustpython_codegen::compile::compile_top::haa9565b0967bdaa9
  25:        0x10262019c - rustpython_compiler::compile::hecf8b963be2e901f
  26:        0x102b492e0 - rustpython_vm::vm::compile::<impl rustpython_vm::vm::VirtualMachine>::compile_with_opts::h6b00ff523f94fe36
  27:        0x102c43ec8 - rustpython_vm::function::builtin::<impl rustpython_vm::function::builtin::sealed::PyNativeFnInternal<(rustpython_vm::function::builtin::OwnedParam<T1>,),R,rustpython_vm::vm::VirtualMachine> for F>::call_::h593b1ec8c5dcbe5b
  28:        0x102bd684c - rustpython_vm::types::slot::Callable::slot_call::h5005acbfd54ce314
  29:        0x102c11458 - rustpython_vm::protocol::callable::PyCallable::invoke::hc7b3c913f7e70e38
  30:        0x10284a180 - rustpython_vm::protocol::callable::<impl rustpython_vm::object::core::PyObject>::call_with_args::hc88ea6065efebfed
  31:        0x10297e928 - rustpython_vm::frame::ExecutingFrame::execute_call::h8fca0c22a2e74162
  32:        0x102983240 - rustpython_vm::frame::ExecutingFrame::run::h4716dfe6b63c4134
  33:        0x10281b614 - rustpython_vm::frame::<impl rustpython_vm::object::core::Py<rustpython_vm::frame::Frame>>::run::hebd968f3912dd00a
  34:        0x102b344f0 - rustpython_vm::vm::VirtualMachine::with_frame::ha2d5eded57c7e9ac
  35:        0x10283e61c - rustpython_vm::builtins::function::<impl rustpython_vm::object::core::Py<rustpython_vm::builtins::function::PyFunction>>::invoke_with_locals::hd27346d63756e6f4
  36:        0x1029943ac - rustpython_vm::types::slot::Callable::slot_call::hac99f1a27112728a
  37:        0x102c11458 - rustpython_vm::protocol::callable::PyCallable::invoke::hc7b3c913f7e70e38
  38:        0x10284a180 - rustpython_vm::protocol::callable::<impl rustpython_vm::object::core::PyObject>::call_with_args::hc88ea6065efebfed
  39:        0x1029804d8 - rustpython_vm::frame::ExecutingFrame::execute_method_call::h50295f4f91eb6167
  40:        0x1029844...

</details>



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- Fixes RustPython/RustPython#6641

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coderabbitai · 2026-01-07T00:18:36Z

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Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

youknowone · 2026-01-07T01:11:37Z

@copilot That's a meaningful enhancement, but doesn't fix the fundamental problem. Could you investigate more what caused that error and fix the fundamental problem?

Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

Copilot · 2026-01-07T01:19:04Z

@copilot That's a meaningful enhancement, but doesn't fix the fundamental problem. Could you investigate more what caused that error and fix the fundamental problem?

Root cause was that we consumed and removed sub-tables, so double-compilation paths (e.g., try/finally) could exhaust the cursor and leave no tables for later scopes. I switched to tracking a per-table cursor and resetting it when recompiling paths, so we reuse the same symbol tables instead of removing them (commit 5121b75).

github-actions · 2026-01-07T01:30:12Z

Code has been automatically formatted

The code in this PR has been formatted using cargo fmt --all.
Please pull the latest changes before pushing again:

git pull origin copilot/fix-panic-in-compile-rs

* Handle missing symbol table without panic * Update symbol table error message * Track symbol table cursors to avoid exhaustion --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com> Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Initial plan

f5c7e39

Copilot AI assigned Copilot and youknowone Jan 7, 2026

Copilot started work on behalf of youknowone January 7, 2026 00:23 View session

Copilot AI and others added 2 commits January 7, 2026 00:57

Handle missing symbol table without panic

e7879ba

Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

Update symbol table error message

109f15d

Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix panic in compile.rs at push_symbol_table~~ Stop panicking when symbol tables are exhausted during codegen Jan 7, 2026

Copilot AI requested a review from youknowone January 7, 2026 01:04

Copilot finished work on behalf of youknowone January 7, 2026 01:04

Copilot started work on behalf of youknowone January 7, 2026 01:12 View session

Track symbol table cursors to avoid exhaustion

5121b75

Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

Copilot AI changed the title ~~Stop panicking when symbol tables are exhausted during codegen~~ Prevent symbol table exhaustion during codegen Jan 7, 2026

Copilot finished work on behalf of youknowone January 7, 2026 01:19

Auto-format: cargo fmt --all

a2d4061

youknowone marked this pull request as ready for review January 8, 2026 09:15

youknowone approved these changes Jan 8, 2026

View reviewed changes

youknowone merged commit a3425b4 into main Jan 8, 2026
43 of 46 checks passed

youknowone deleted the copilot/fix-panic-in-compile-rs branch January 8, 2026 21:32

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Prevent symbol table exhaustion during codegen#6670

Prevent symbol table exhaustion during codegen#6670
youknowone merged 5 commits intomainfrom
copilot/fix-panic-in-compile-rs

Copilot AI commented Jan 7, 2026 •

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Copilot AI commented Jan 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Python 3.13.0alpha (heads/master:8bfe927de

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Copilot AI commented Jan 7, 2026 •

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