feat: detect recursive closures properly

[dquixote-jr]

Code change made with AI, test case was human.
I'm very skeptical about this but somehow the test is passing.

relates: #977

[gemini-code-assist]

Summary of Changes

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This pull request refines the code analysis engine to accurately handle recursive function definitions, specifically within local or assignment statements. The change ensures that the scope resolver correctly identifies and tracks these recursive calls, preventing erroneous "undefined global" diagnostics for self-referencing functions. This improves the robustness and accuracy of the static analysis for Lua code.

Highlights

• Recursive Closure Detection: The scope analysis mechanism has been enhanced to correctly identify and process recursive closures, preventing issues where they might be misinterpreted.
• Undefined Global Diagnostic: A new test case was introduced to validate that recursive local functions are properly recognized and do not trigger false positive "undefined global" diagnostics.

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Changelog

• crates/emmylua_code_analysis/src/db_index/declaration/decl_tree.rs
  • Modified the walk_up method within LuaDeclarationTree to introduce a conditional check based on the level parameter for LocalOrAssignStat scope kinds.
  • Delegated deeper scope walks for LocalOrAssignStat to base_walk_up when level is not 0, ensuring proper handling of recursive contexts.
• crates/emmylua_code_analysis/src/diagnostic/test/undefined_global_test.rs
  • Added a new test function test_globals to verify the correct behavior of the UndefinedGlobal diagnostic.
  • Included a test case featuring a recursive fact function defined as a local closure, asserting that no UndefinedGlobal diagnostic is reported for its self-reference.

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[gemini-code-assist]

Code Review

The pull request aims to correctly detect recursive closures, which is important for accurate code analysis, particularly for undefined global diagnostics. While no security vulnerabilities were identified during the audit, a critical issue exists in the walk_up function within decl_tree.rs where the level parameter is not incremented during a recursive call, potentially leading to an infinite loop.