rscript

A production-grade TypeScript compiler written in Rust, inspired by tsgo (TypeScript 7).

Goals

• 1:1 TypeScript compatibility: Faithful port of TypeScript's compiler behavior, verified against the official 70K+ test suite
• Performance: Leveraging Rust's zero-cost abstractions, arena allocation, string interning, and parallelism to exceed tsgo's 10x speedup over tsc
• Production-ready: Standalone CLI tool (rsc) that can replace tsc, plus an LSP server for editor integration

Architecture

rscript/
  crates/
    rscript_core/         Core utilities, arena allocator, string interning
    rscript_diagnostics/  Diagnostic messages (ported from diagnosticMessages.json)
    rscript_ast/          AST nodes, SyntaxKind (300+ variants), flag types
    rscript_scanner/      Lexer/tokenizer (port of scanner.ts)
    rscript_parser/       Recursive descent parser (port of parser.ts)
    rscript_binder/       Symbol table, scope chains, declaration merging
    rscript_checker/      Type checker (port of checker.ts)
    rscript_emitter/      JS/DTS output coordinator
    rscript_transformers/ AST transforms (TypeScript strip, JSX, decorators, downlevel)
    rscript_printer/      AST to text output
    rscript_nodebuilder/  Synthetic node construction for type display
    rscript_module/       Module resolution (Node10, Node16, Bundler, Classic)
    rscript_tsoptions/    tsconfig.json parsing, CompilerOptions
    rscript_tspath/       Path normalization, extension handling
    rscript_sourcemap/    Source map generation
    rscript_evaluator/    Constant expression evaluation
    rscript_compiler/     Program creation, compilation orchestration
    rscript_ls/           Language service (completions, hover, go-to-def)
    rscript_lsp/          Language Server Protocol implementation
    rscript_cli/          CLI binary (`rsc`)

Key Design Decisions

1. Arena Allocation (bumpalo): All AST nodes allocated in a bump arena. O(1) deallocation, cache-friendly linear layout.
2. String Interning (lasso): All identifiers interned for O(1) comparison via integer IDs.
3. ID-based Type References: Types stored in a TypeTable arena, referenced by TypeId. Avoids lifetime complexity in the checker.
4. Faithful 1:1 Port: Following tsgo's proven strategy of faithful porting rather than reimagining (which caused stc to fail).

Building

# Build everything
cargo build --release

# Run the compiler
./target/release/rsc --version
./target/release/rsc file.ts --noEmit

# Run tests
cargo test

Usage

# Type-check files
rsc file.ts --noEmit

# Compile with options
rsc src/**/*.ts --outDir dist --declaration --sourceMap

# Use tsconfig.json
rsc -p tsconfig.json

# Start language server
rsc --lsp

# Watch mode
rsc -w file.ts

Performance Targets

Metric	tsc (JS)	tsgo (Go)	rscript (Rust) Target
Cold compile	10s	1s	< 0.8s
Memory usage	1x	0.5x	< 0.3x
Incremental	5s	0.5s	< 0.4s
LSP startup	10s	1.2s	< 1s

License

MIT OR Apache-2.0