Add type checking for CloseServerStatement server argument

[logbie]

Implemented missing type checking for the server expression in CloseServerStatement.
The server handle is expected to be a string (Text type).
Added a regression test to the typechecker module.

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PR created automatically by Jules for task 612748860883063916 started by @logbie

Summary by CodeRabbit

• Bug Fixes

  • Enhanced runtime validation for server handle arguments; now emits clear errors (e.g., "Expected string for server handle") when non-string values are used.

• Tests

  • Added a unit test to verify incorrect (numeric) server arguments produce the expected type error.

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[claude]

Claude finished @logbie's task —— View job

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Code Review Complete ✅

I've reviewed this pull request thoroughly and provide the following feedback:

Todo List:

• Read repository guidelines (CLAUDE.md)
• Analyze the modified typechecker code
• Review code quality and implementation approach
• Check for potential bugs or issues
• Evaluate test coverage
• Provide comprehensive review feedback

✅ Overall Assessment: LGTM - Well Implemented Fix

This PR successfully addresses a missing type checking gap for CloseServerStatement and follows WFL project standards.

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📋 Code Quality & Implementation

Strengths:

• Consistent Type Checking Pattern: Follows the same pattern as other statement type checks in the typechecker (compare with RegisterSignalHandlerStatement)
• Proper Error Handling: Uses the existing self.type_error() method with appropriate error message format
• Smart Type Allowances: Correctly allows Type::Unknown and Type::Error types to avoid cascading error reports
• Clear Implementation: The logic is straightforward and readable

Implementation Details:

• Uses self.infer_expression_type(server) to determine the server expression type
• Enforces Type::Text requirement matching runtime expectations (src/interpreter/mod.rs:4558-4559)
• Error message "Expected string for server handle" is clear and actionable

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🧪 Test Coverage

Excellent Test Coverage:

• Test Case: test_close_server_type_check() tests the specific fix with an integer literal
• Proper Assertions: Verifies both error condition and error message content
• Test Quality: Clear test structure and descriptive failure messages
• Completeness: Covers the main error case (non-string server argument)

Test Results: ✅ All tests pass

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🔍 Potential Issues & Considerations

Minor Observations:

1. Consistency Gap: StopAcceptingConnectionsStatement still has a TODO for similar type checking (line 1507). Consider addressing this in a future PR for consistency.

2. Type Coverage: The current test only covers Integer type. Consider adding edge case tests for other non-string types (though current test is sufficient for the fix).

No Security, Performance, or Bug Concerns Identified

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🔧 Code Standards Compliance

• ✅ Formatting: Code auto-formatted with cargo fmt
• ✅ Linting: Passes cargo clippy with no warnings
• ✅ Naming: Follows snake_case convention per CLAUDE.md
• ✅ Testing: Follows TDD approach with proper test structure
• ✅ Commit Message: Uses conventional commit format

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💡 Recommendations

1. Future Enhancement: Consider implementing similar type checking for StopAcceptingConnectionsStatement to maintain consistency across server-related statements

2. Documentation: This fix resolves a type safety gap - no documentation updates needed as behavior aligns with existing WFL language expectations

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🎯 Summary

This is a solid, well-tested fix that:

• Addresses a legitimate type safety gap
• Follows established project patterns
• Includes comprehensive test coverage
• Maintains backward compatibility
• Improves overall type system consistency

Recommended Action: ✅ Approve and Merge

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds runtime type checking for the CloseServerStatement's server expression: pattern matching now binds server, line, and column, infers the server expression type, and emits a TypeError when the type is not Text/Unknown/Error. A unit test verifies a numeric argument triggers the error.

Changes

Cohort / File(s)	Summary
Type checker & tests src/typechecker/mod.rs	Refactors pattern to named fields (server, line, column), implements runtime type validation for CloseServerStatement.server (expects Text/Unknown/Error, otherwise emit TypeError with message "Expected string for server handle"), and adds test_close_server_type_check unit test asserting a numeric server argument raises the error.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related issues

• Issue #170: Related — both target CloseServerStatement validation. Note: this PR enforces a string handle (Text) while the issue expected a Server-type validation, so objectives overlap but differ in required type.

Poem

🐰 I hopped through code to mend a line,
I checked the server — must be text, not nine.
A gentle error when types go astray,
Rabbity tests hop in to save the day! 🥕

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Add type checking for CloseServerStatement server argument' accurately and specifically describes the main change: implementing type validation for the server parameter in CloseServerStatement, which is the primary focus of the changeset.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix-closeserver-typecheck-612748860883063916

Warning

Tools execution failed with the following error:

Failed to run tools: 13 INTERNAL: Received RST_STREAM with code 2 (Internal server error)

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[Copilot]

Pull request overview

This PR implements type checking for the CloseServerStatement server argument, ensuring it receives a string (Text type) rather than accepting any type unchecked.

Changes:

• Added type inference and validation for the server expression in CloseServerStatement
• Implemented error reporting when non-string types are provided for the server handle
• Added a regression test verifying that numeric server arguments are correctly rejected

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[Copilot]

The comment states 'currently passes' but this is misleading since the PR implements the fix. The comment should be updated to reflect that this test verifies the type checking behavior after the fix.

Suggested change

	// Test case: Close server with a number (should fail type checking but currently passes)
	// Test case: closing server with a numeric handle should fail type checking (regression test for the fix)

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/typechecker/mod.rs`:
- Around line 3473-3495: The test function test_close_server_type_check contains
formatting issues flagged by cargo fmt; run `cargo fmt --all` and reformat the
file so the test matches rustfmt rules (ensure indentation and spacing around
the Program/Statement::CloseServerStatement/Expression::Literal block are
corrected). Leave the test logic intact—it should still construct Program with
CloseServerStatement and call TypeChecker::new().check_types(&program) and
assert the error—only change whitespace/formatting to satisfy rustfmt as
configured by .rustfmt.toml.

[claude]

Claude finished @logbie's task —— View job

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Code Review Complete ✅

I've thoroughly reviewed this pull request implementing type checking for CloseServerStatement server arguments. Here's my comprehensive feedback:

Todo List:

• Read repository guidelines (CLAUDE.md)
• Analyze the modified typechecker code
• Review code quality and implementation approach
• Check for potential bugs or issues
• Evaluate test coverage
• Provide comprehensive review feedback

Overall Assessment: ✅ APPROVED

This is a well-implemented type safety improvement with solid test coverage.

📋 Review Summary

✅ Code Quality & Implementation

• Excellent type validation logic: The implementation correctly checks for Type::Text, Type::Unknown, and Type::Error types at src/typechecker/mod.rs:1516-1519
• Proper error handling: Clear error message "Expected string for server handle" with appropriate line/column information
• Consistent with codebase patterns: Follows existing type checking patterns used elsewhere in the typechecker
• Runtime alignment: Implementation aligns perfectly with interpreter expectations at src/interpreter/mod.rs:4594-4600 where non-text values cause runtime errors

✅ Test Coverage

• Comprehensive regression test: test_close_server_type_check() validates that numeric server arguments are properly rejected
• Appropriate test assertions: Verifies both error occurrence and specific error message content
• Test passes successfully: Confirmed via cargo test test_close_server_type_check

✅ Security & Type Safety

• Prevents runtime type errors: Catches invalid server handle types at compile time rather than runtime
• Maintains backward compatibility: Existing valid WFL programs using string server handles continue to work
• Consistent with WFL usage patterns: Analysis of TestPrograms shows servers are used as variable names (strings) in practice

✅ Performance & Standards

• No performance impact: Type checking is performed once during compilation
• Follows coding standards: Code passes cargo fmt and cargo clippy without warnings
• Follows TDD principles: Test was written to validate the type checking behavior

🔍 Detailed Analysis

Type Checking Logic

let server_type = self.infer_expression_type(server);
if server_type != Type::Text
    && server_type != Type::Unknown
    && server_type != Type::Error
{
    self.type_error(
        "Expected string for server handle".to_string(),
        Some(Type::Text),
        Some(server_type),
        *line,
        *column,
    );
}

This implementation is excellent because:

• Correctly allows Type::Unknown for unresolvable expressions
• Correctly allows Type::Error to avoid cascading errors
• Uses the standard type_error method for consistent error reporting

Real-World Usage Validation

I verified this against actual WFL programs in TestPrograms/:

close server test_server        // ✅ Valid (variable name)
close server "my_server"        // ✅ Valid (string literal)  
close server 123                // ❌ Invalid (now caught by type checker)

💡 Minor Suggestions

1. Comment Enhancement (Optional): Consider updating the test comment from "should fail type checking but currently passes" to reflect that this test validates the implemented fix.

2. Future Enhancement (Not for this PR): Consider adding additional test cases for edge cases like empty strings or very long server names, though the current test coverage is sufficient.

✅ Verification Results

• ✅ All tests pass: cargo test test_close_server_type_check
• ✅ No formatting issues: cargo fmt --all -- --check
• ✅ No lint warnings: cargo clippy --all-targets --all-features
• ✅ Follows repository guidelines (CLAUDE.md)
• ✅ Maintains backward compatibility with existing WFL programs

🎯 Recommendation

APPROVE AND MERGE - This PR successfully implements the missing type checking for CloseServerStatement server arguments with:

• Robust implementation following WFL type system patterns
• Comprehensive test coverage with regression test
• Proper error reporting with clear messaging
• No breaking changes to existing functionality
• Clean code that passes all quality checks

Great work on addressing the type safety gap! This improvement will help WFL developers catch invalid server handle usage at compile time rather than runtime.