add Claude Code instruction

Author: neuecc

.claude/settings.local.json

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+{
+  "enableAllProjectMcpServers": false
+}

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+ZLinq is a zero-allocation LINQ library for .NET that provides high-performance alternatives to System.Linq through struct-based value types. The library offers LINQ to Span, LINQ to SIMD, and LINQ to Tree functionality across all .NET platforms including Unity and Godot.
+
+## Key Architecture
+
+### Core Design
+- **ValueEnumerable<TEnumerator, T>**: Main struct that wraps enumerators to enable method chaining without allocations
+- **IValueEnumerator<T>**: Interface defining `TryGetNext(out T current)` pattern instead of MoveNext/Current
+- **ref struct support**: In .NET 9+, ValueEnumerable is a ref struct enabling Span<T> integration
+- **Optimization methods**: `TryGetNonEnumeratedCount`, `TryGetSpan`, `TryCopyTo` for performance optimizations
+
+### Project Structure
+- `src/ZLinq/`: Core library with all LINQ operators in `Linq/` folder and SIMD implementations in `Simd/`
+- `src/ZLinq.DropInGenerator/`: Source generator for automatic ZLinq method replacement
+- `src/ZLinq.FileSystem/`, `ZLinq.Json/`, `ZLinq.Godot/`: Tree traversal extensions
+- `src/ZLinq.Unity/`: Unity package with GameObject/Transform traversal
+- `src/FileGen/`: Code generation tools for creating operators
+- `sandbox/`: Test applications and benchmarks
+- `tests/`: Comprehensive test suite including System.Linq compatibility tests
+
+## Development Commands
+
+### Building
+```bash
+dotnet build
+```
+
+### Testing
+```bash
+# Run ZLinq-specific tests
+dotnet test tests/ZLinq.Tests/
+
+# Run System.Linq compatibility tests (extensive)
+dotnet test tests/System.Linq.Tests/
+
+# Run all tests
+dotnet test
+```
+
+### Benchmarking
+```bash
+cd sandbox/Benchmark
+dotnet run -c Release
+```
+
+## Testing Guidelines
+
+- Use xUnit v3 with Shouldly for assertions
+- Global usings include `Xunit`, `Shouldly`, `ZLinq`
+- Class field naming: do NOT use `_` prefix
+- Tests target multiple frameworks: net6.0, net8.0, net9.0, net48 (Windows), net10.0 (VS Preview)
+- System.Linq.Tests project validates 99% compatibility with System.Linq using original Microsoft tests
+
+## Code Patterns
+
+### Custom Operators
+- Implement `IValueEnumerator<T>` as struct (ref struct in .NET 9+)
+- Use `TryGetNext(out T current)` instead of MoveNext/Current pattern
+- Always dispose source enumerators in Dispose()
+- Optimization methods can return false if complex to implement
+
+### SIMD Support
+- Available in .NET 8+ when `TryGetSpan` returns true
+- Covers Sum, Average, Min, Max, Contains, SequenceEqual for numeric types
+- Use `ZLinq.Simd` namespace for explicit SIMD operations
+
+### Drop-in Replacement
+- Use `ZLinqDropInAttribute` assembly attribute to auto-replace LINQ methods
+- Configure with `DropInGenerateTypes` flags for target types
+- Support custom types with `ZLinqDropInExtensionAttribute`
+
+## Important Constraints
+
+- ValueEnumerable cannot be converted to IEnumerable<T> in .NET 9+ (ref struct limitation)
+- No yield return support in custom operators - everything must be manually implemented
+- Reference types in enumerator constructors share state across copies - initialize in TryGetNext instead
+- Method chains create different types - cannot reassign to same variable
+
+## Unity Integration
+
+- Install via NuGetForUnity + git URL for Unity package
+- Provides GameObject/Transform tree traversal with Ancestors/Children/Descendants
+- Supports NativeArray, NativeSlice through AsValueEnumerable()
+- Minimum Unity version: 2022.3.12f1 for DropInGenerator support
+
+## Performance Focus
+
+ZLinq prioritizes zero-allocation performance with comprehensive SIMD support and optimization hooks. The library proves compatibility by passing 9000+ System.Linq tests while delivering superior performance in most scenarios.