Fix stack overflow with self-referential variable definitions #8953
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@rtfeldman I wonder if this and similar checks should occur in Can instead of at runtime...? |
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@lukewilliamboswell Yeah for sure that's where they should happen - I'm surprised they don't already...I thought that had already been implemented, but I guess not? Anyway, what we definitely want to happen is:
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Add cycle detection to evalLookupLocal for top-level definitions to prevent infinite recursion when a variable references itself (e.g., a = a). The fix adds tracking of definitions currently being evaluated using the existing def_stack mechanism. When a lookup encounters a definition that is already in progress, it either creates a placeholder for recursive functions or triggers a crash with a clear error message for non-function circular references. Also adds a regression test for issue #8942. Co-Authored-By: Claude <noreply@anthropic.com>
Based on PR feedback, circular definitions like `a = a` are now detected during type checking rather than at runtime in the interpreter. Changes: - Add `circular_def` problem type to Check with clear error message - Detect circular non-function definitions in the `.processing` case when checking local lookups - Allow recursive functions (lambdas and closures) to reference themselves - Keep runtime check as safety net for edge cases The compile-time check provides better error messages and catches the issue earlier in the compilation pipeline. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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Detect circular definitions like `a = a` at compile time in canonicalization rather than at runtime. When a non-lambda expression references its own defining pattern, the reference is replaced with a runtime error node. This prevents stack overflows and provides a clear error message: "INVALID ASSIGNMENT TO ITSELF" Fixes #8942 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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@rtfeldman moved the logic into Can instead 👍 |
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Fixes #8942
This PR fixes a stack overflow that occurred when the compiler processed self-referential variable definitions like
a = a. The compiler would enter infinite recursion when trying to evaluate such definitions.evalLookupLocalfor top-level definitions using the existingdef_stackmechanismCo-authored by Claude Opus 4.5