Intro | ECOSYSTEM Research

The fastest way to learn compiler construction in Rust is to build a small language—not a Rust compiler—then grow it from an AST interpreter into a bytecode or native-code compiler. A compiler typically moves through lexing, parsing, semantic analysis/type checking, an intermediate representation, optimization, and code generation. krypticmouse.hashnode Pick a practical first target Start with a language supporting: Implement only: - Integer literals and arithmetic: +, -, , / - Variables and let - Blocks and perhaps if - A print builtin - Source locations and useful errors For a first backend, choose one of these: | Target | Difficulty | Why use it | |---|---:|---| | Tree-walking interpreter | Lowest | Lets you validate parsing and semantics immediately | | Stack bytecode + VM | Moderate | Excellent for learning IR design, control flow, call frames | | WebAssembly | Moderate | Portable output and a defined binary/text target | | LLVM / Cranelift | Higher | Native-code generation without hand-writing machine code | | x86-64 assembly | Higher | Best for learning ABI, registers, stack discipline, relocation | For your systems background, I’d recommend: interpreter → bytecode VM → Cranelift or x86-64 backend. Compiler pipeline A clean implementation can look like this: A useful crate layout: Keep source spans on tokens and AST nodes from day one. Good errors become painful to retrofit. Build order 1. Define AST directly. Before parsing, manually construct AST values and write an evaluator. This validates language semantics independently of syntax. 2. Write a lexer. Produce Token { kind, span }; avoid regex-based “find the next token anywhere” approaches. Scan left-to-right with a cursor so invalid characters and positions are deterministic. 3. Write a hand-rolled parser. Recursive descent is ideal for declarations/statements, and Pratt parsing is compact and extensible for operator precedence. 4. Add an interpreter. Use HashMap<Symbol, Value environments initially. Once you add blocks/functions, represent nested scopes explicitly rather than trying to make the parser handle name resolution. 5. Add name resolution and type checking. Resolve names into symbols or local-slot indices before evaluation/codegen. That prevents every later phase from repeatedly doing string-based variable lookup. 6. Lower to an IR or bytecode. A stack VM can compile: into: 7. Only then add functions, closures, structs, generics, optimization, or native code. Rust-specific design advice - Use IDs internally instead of cloning names everywhere: ExprId, SymbolId, FunctionId. - Keep phases structurally separate. The parser should not type-check; code generation should not need to understand raw syntax tokens. - Prefer an owned AST first. Arena allocation, interning, and elaborate lifetimes can wait until profiling shows a need. - Represent failures as diagnostic collections, not a single early Result return, once you want multiple compiler errors per run. - Test each stage separately: - lexer input → token snapshot - token stream → AST snapshot - AST → evaluator result - invalid source → diagnostic snapshot - Use property testing/fuzzing later for parser robustness, especially after you add precedence, nesting, and recovery. Rust’s compiler guide is valuable after you understand the toy pipeline: it describes rustc as a multi-stage process from source through parsing, analysis, intermediate representations, and code generation. But rustc itself is a very large, bootstrapped compiler and is not a suitable first compiler project; it is written in Rust and relies on an existing Rust compiler during its build process. rustc-dev-guide.rust-lang High-value learning resources - Crafting Interpreters — a strong practical progression from tree-walk interpreter to bytecode VM. Translate the Java/C implementations into Rust yourself rather than seeking a finished Rust port. - Essentials of Compilation — more formal and backend-oriented; useful once you move toward x86 compilation. - Rustc Dev Guide — use it to map your miniature passes to real Rust compiler concepts, not as a first implementation tutorial. rustc-dev-guide.rust-lang - Tristan Hume’s write-up offers a useful reality check: a course compiler implementation reached roughly 6,800 lines of Rust, illustrating why narrow initial language scope matters. thume A concrete first milestone Aim for this within one small project: Your compiler/interpreter should: 1. Tokenize the input with byte spans. 2. Parse it into an AST. 3. Resolve x and y to bindings. 4. Check that arithmetic receives integers. 5. Evaluate it and print 21. 6. Report an error such as “undefined variable z” with its source location for print(z). Once that works, compiling the same AST into bytecode is a focused engineering change rather than a rewrite.