Implement Set<T> collection type

[clank-hayen]

Summary

• Implement Set collection backed by std::unordered_set for O(1) lookup
• Add set literal syntax: {1, 2, 3} for concise set creation
• Include full set algebra: union, intersection, difference, symmetric_difference

Changes

• Lexer/Parser: Add SET token and parse Set() constructor and {expr, ...} literals
• Type Checker: Add type inference for sets and validate set method calls
• Code Generator: Generate std::unordered_set code with lambda-based set operations
• Tests: Comprehensive test suite covering all features

Set Features

Category	Methods
Query	length(), is_empty(), contains(elem)
Modification	add(elem), remove(elem), clear()
Operations	union(other), intersection(other), difference(other), symmetric_difference(other)
Predicates	is_subset(other), is_superset(other)
Iteration	for item in set { ... }

Test plan

• Build compiler with new Set implementation
• Run bishop test tests/test_sets.b
• Verify set literals work: {1, 2, 3}
• Verify set operations return new sets
• Verify iteration works correctly

Closes #37

🤖 Generated with Claude Code

[clank-hayen]

Code Review: Set Collection Type

REVIEW:

• summary: Clean, well-structured implementation of Set with comprehensive test coverage.

✅ What looks good:

1. Architecture: Properly separated files follow project conventions (sets.cpp/hpp, check_set.cpp, emit_set.cpp)
2. Type Safety: Proper type inference, element type extraction, and Set parameter validation
3. Set Operations: Union, intersection, difference, symmetric_difference all correctly implemented using lambda-based C++ generation
4. Documentation: Excellent docstrings in C++ code and comprehensive README section with examples
5. Test Coverage: 36 test cases covering creation, literals, methods, operations, predicates, and iteration
6. Error Handling: Empty set literal properly rejected with helpful error message

Security Review (OWASP Top 10):

• ✅ No injection risks - type-checked method calls only
• ✅ No data exposure concerns
• ✅ No authentication/authorization applicable
• ✅ No deserialization issues - set literals are compile-time checked

Suggestions (non-blocking):

1. Minor doc update: The Keywords section in README.md doesn't include Set. Consider adding it:

   `fn`, `return`, `struct`, `if`, `else`, `while`, `for`, `in`, `true`, `false`, `none`, `is`, `import`, `using`, `select`, `case`, `Channel`, `List`, `Pair`, `Tuple`, `Set`, `extern`, `go`, `sleep`, `err`, `fail`, `or`, `match`, `default`, `with`, `as`, `const`, `continue`, `break`
   

   Location: README.md, Keywords section near the end

2. Consider for future: The emit_set_literal function stores first_elem but doesn't use it - could be removed if not needed for type deduction.

Decision: APPROVE ✅

The implementation is correct, well-tested, follows project conventions, and introduces no security concerns. The missing keyword in the documentation is minor and non-blocking.

🤖 Reviewed by Claude Code

[clank-hayen]

Code Review: Implement Set Collection Type

Summary

Well-implemented Set collection type with comprehensive functionality. The code follows existing patterns in the codebase, has thorough test coverage, and documentation is complete.

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✅ What's Good

Parser Changes:

• Clean AST nodes (SetCreate, SetLiteral) following existing patterns
• Set literal syntax {1, 2, 3} is intuitive and matches common languages
• Proper line number tracking on all AST nodes
• Supports nested generics like Set<List<int>>

Type Checker:

• Type checking for Set methods properly validates argument types
• Correct substitution of T placeholder with actual element type
• Mixed-type detection in set literals provides clear error messages
• Integration with is_valid_type() for Set types
• For-each loop support for Set iteration is handled correctly

Code Generation:

• Uses std::unordered_set as backing - appropriate for O(1) lookup
• Set operations (union, intersection, difference, symmetric_difference) correctly implemented using IILEs
• Uses std::remove_cvref_t<decltype({})> for proper type deduction in set operations

Test Coverage (389 lines):

• Empty set creation (both inferred and typed)
• Set literals with various types (int, str, bool)
• Duplicate handling in literals
• All query methods: length(), is_empty(), contains()
• All modification methods: add(), remove(), clear()
• All set operations: union(), intersection(), difference(), symmetric_difference()
• All predicates: is_subset(), is_superset()
• Set iteration via for-each
• Typed variable declarations

Documentation:

• README.md Set section (lines 680-761) is thorough and includes:
  • Creation syntax
  • Set literals
  • All method examples
  • Set operations with clear examples
  • Iteration with caveat about unordered iteration

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Minor Observations (Non-blocking)

1. Empty set literal error message - The error "empty set literal not allowed, use Set() instead" is clear and helpful.

2. Set iteration order - Documentation correctly notes that iteration order is not guaranteed - good user expectation setting.

3. Duplicate handling - Test test_set_literal_duplicates verifies that {1, 2, 2, 3, 3, 3} correctly produces a set of length 3.

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Security Review (OWASP Top 10)

• ✅ No injection vulnerabilities
• ✅ No hardcoded secrets or credentials
• ✅ No security misconfigurations
• ✅ Type safety enforced through typechecker
• ✅ No authentication/authorization concerns (language feature, not auth)

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Decision: APPROVE ✅

The implementation is correct, secure, well-tested, and follows existing codebase patterns. Ready to merge.

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@chrishayen - Please review and merge when ready.

🤖 Reviewed by Claude Code