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stationeers_lang/.github/copilot-instructions.md

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# Slang Language Compiler - AI Agent Instructions
## Project Overview
**Slang** is a high-level programming language that compiles to IC10 assembly for the game Stationeers. The compiler is a multi-stage Rust system with a C# BepInEx mod integration layer.
**Key Goal:** Reduce manual IC10 assembly writing by providing C-like syntax with automatic register allocation and device abstraction.
## Architecture Overview
### Compilation Pipeline
The compiler follows a strict 4-stage pipeline (in [rust_compiler/libs/compiler/src/v1.rs](rust_compiler/libs/compiler/src/v1.rs)):
1. **Tokenizer** (libs/tokenizer/src/lib.rs) - Lexical analysis using `logos` crate
- Converts source text into tokens
- Tracks line/span information for error reporting
- Supports temperature literals (c/f/k suffixes)
2. **Parser** (libs/parser/src/lib.rs) - AST construction
- Recursive descent parser producing `Expression` tree
- Validates syntax, handles device declarations, function definitions
- Output: `Expression` enum containing tree nodes
3. **Compiler (v1)** (libs/compiler/src/v1.rs) - Semantic analysis & code generation
- Variable scope management and register allocation via `VariableManager`
- Emits IL instructions to `il::Instructions`
- Error types use `lsp_types::Diagnostic` for editor integration
4. **Optimizer** (libs/optimizer/src/lib.rs) - Post-generation optimization
- Currently optimizes leaf functions
- Optional pass before final output
### Cross-Language Integration
- **Rust Library** (`slang.dll`/`.so`): Core compiler logic via `safer-ffi` C FFI bindings
- **C# Mod** (`StationeersSlang.dll`): BepInEx plugin integrating with game UI
- **Generated Headers** (via `generate-headers` binary): Auto-generated C# bindings from Rust
### Key Types & Data Flow
- `Expression` tree (parser) → `v1::Compiler` processes → `il::Instructions` output
- `InstructionNode` wraps IC10 assembly with optional source span for debugging
- `VariableManager` tracks scopes, tracks const/device/let distinctions
- `Operand` enum represents register/literal/device-property values
## Critical Workflows
### Building
```bash
cd rust_compiler
# Build for both Linux and Windows targets
cargo build --release --target=x86_64-unknown-linux-gnu
cargo build --release --target=x86_64-pc-windows-gnu
# Generate C# FFI headers (requires "headers" feature)
cargo run --features headers --bin generate-headers
# Full build (run from root)
./build.sh
```
### Testing
```bash
cd rust_compiler
# Run all tests
cargo test --package compiler --lib
# Run specific test file
cargo test --package compiler --lib tuple_literals
# Run single test
cargo test --package compiler --lib -- test::tuple_literals::test::test_tuple_literal_size_mismatch --exact --nocapture
```
### Quick Compilation
```bash
cd rust_compiler
# Compile Slang code to IC10 using current compiler changes
echo 'let x = 5;' | cargo run --bin slang -
# Or from file
cargo run --bin slang -- input.slang -o output.ic10
# Optimize the output with -z flag
cargo run --bin slang -- input.slang -o output.ic10 -z
```
## Codebase Patterns
### Test Structure
Tests follow a macro pattern in [libs/compiler/src/test/mod.rs](rust_compiler/libs/compiler/src/test/mod.rs):
```rust
#[test]
fn test_name() -> Result<()> {
let output = compile!("slang code here");
assert_eq!(expected_ic10, output);
Ok(())
}
```
- `compile!()` macro: full pipeline from source to IC10
- `compile!(result ...)` for error checking
- `compile!(debug ...)` for intermediate IR inspection
- Test files organize by feature: `binary_expression.rs`, `syscall.rs`, `tuple_literals.rs`, etc.
### Error Handling
All stages return custom Error types implementing `From<lsp_types::Diagnostic>`:
- `tokenizer::Error` - Lexical errors
- `parser::Error<'a>` - Syntax errors
- `compiler::Error<'a>` - Semantic errors (unknown identifier, type mismatch)
- Device assignment prevention: `DeviceAssignment` error if reassigning device const
### Variable Scope Management
[variable_manager.rs](rust_compiler/libs/compiler/src/variable_manager.rs) handles:
- Tracking const vs mutable (let) distinction
- Device declarations as special scope items
- Function-local scopes with parameter handling
- Register allocation via `VariableLocation`
### LSP Integration
Error types implement conversion to `lsp_types::Diagnostic` for IDE feedback:
```rust
impl<'a> From<Error<'a>> for lsp_types::Diagnostic { ... }
```
This enables real-time error reporting in the Stationeers IC10 Editor mod.
## Project-Specific Conventions
### Tuple Destructuring
The compiler supports tuple returns and multi-assignment:
```rust
let (x, y) = func(); // TupleDeclarationExpression
(x, y) = another_func(); // TupleAssignmentExpression
```
Compiler validates size matching with `TupleSizeMismatch` error.
### Device Property Access
Devices are first-class with property access:
```rust
device ac = "d0";
ac.On = true;
ac.Temperature > 20c;
```
Parsed as `MemberAccessExpression`, compiled to device I/O syscalls.
### Temperature Literals
Unique language feature - automatic unit conversion at compile time:
```rust
20c 293.15k // Celsius to Kelvin
68f 293.15k // Fahrenheit to Kelvin
```
Tokenizer produces `Literal::Number(Number(decimal, Some(Unit::Celsius)))`.
### Constants are Immutable
Once declared with `const`, reassignment is a compile error. Device assignment prevention is critical (prevents game logic bugs).
## Integration Points
### C# FFI (`csharp_mod/FfiGlue.cs`)
- Calls Rust compiler via marshaled FFI
- Passes source code, receives IC10 output
- Marshals errors as `Diagnostic` objects
### BepInEx Plugin Lifecycle
[csharp_mod/Plugin.cs](csharp_mod/Plugin.cs):
- Harmony patches for IC10 Editor integration
- Cleanup code for live-reload support (mod destruction)
- Logger integration for debug output
### CI/Build Target Matrix
- Linux: `x86_64-unknown-linux-gnu`
- Windows: `x86_64-pc-windows-gnu` (cross-compile from Linux)
- Both produce dynamic libraries + CLI binary
## Debugging Tips
1. **Print source spans:** `Span` type tracks line/column for error reporting
2. **IL inspection:** Use `compile!(debug source)` to view intermediate instructions
3. **Register allocation:** `VariableManager` logs scope changes; check for conflicts
4. **Syscall validation:** [parser/src/sys_call.rs](rust_compiler/libs/parser/src/sys_call.rs) lists all valid syscalls
5. **Tokenizer issues:** Check [tokenizer/src/token.rs](rust_compiler/libs/tokenizer/src/token.rs) for supported keywords/symbols
## Key Files for Common Tasks
| Task | File |
| -------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| Add language feature | [libs/parser/src/lib.rs](rust_compiler/libs/parser/src/lib.rs) + test in [libs/compiler/src/test/](rust_compiler/libs/compiler/src/test/) |
| Fix codegen bug | [libs/compiler/src/v1.rs](rust_compiler/libs/compiler/src/v1.rs) (~3500 lines) |
| Add syscall | [libs/parser/src/sys_call.rs](rust_compiler/libs/parser/src/sys_call.rs) |
| Optimize output | [libs/optimizer/src/lib.rs](rust_compiler/libs/optimizer/src/lib.rs) |
| Mod integration | [csharp_mod/](csharp_mod/) |
| Language docs | [docs/language-reference.md](docs/language-reference.md) |
## Dependencies to Know
- `logos` - Tokenizer with derive macros
- `rust_decimal` - Precise decimal arithmetic for temperature conversion
- `safer-ffi` - Safe C FFI between Rust and C#
- `lsp-types` - Standard for editor diagnostics
- `thiserror` - Error type derivation
- `clap` - CLI argument parsing
- `anyhow` - Error handling in main binary