# Compiler Roadmap

A Rust-flavored, C-targeting language - built pipeline-first.

**Implementation language:** Rust  
**Code generation target:** x86-64 (AT&T / Intel syntax `.s` → assembled via GAS or NASM)

## Phase 1 - Lexer

- [x] Define token enum (int literal, bool literal, ident, keywords, operators, punctuation)
- [x] Implement character-by-character scanner loop
- [x] Handle whitespace & single-line comments (`//`)
- [x] Produce source spans (file, line, col) on every token
- [x] Unit-test: known inputs → expected token streams

## Phase 2 - Parser

- [ ] Write grammar for the base subset
  - `fn` declarations, `return`, `let`, int/bool literals
  - Arithmetic (`+`, `-`, `*`, `/`), comparison (`==`, `!=`, `<`, `>`)
  - Function call expressions
- [ ] Implement recursive-descent parser
- [ ] Build typed AST: `FnDecl`, `Block`, `ReturnStmt`, `LetStmt`, `BinExpr`, `CallExpr`, `Literal`, `Ident`
- [ ] Attach source spans to every AST node
- [ ] Emit structured parse errors with span info
- [ ] Unit-test: parse valid snippets, expect correct AST shapes

## Phase 3 - Semantic Analysis

- [ ] Implement scope-aware symbol table
- [ ] Name resolution pass - resolve all `Ident` nodes to their declarations
- [ ] Type inference / checking for `int` and `bool`
- [ ] Validate function return types match declared signature
- [ ] Error on use-before-declaration and undeclared symbols
- [ ] Unit-test: ill-typed programs produce correct diagnostics

## Phase 4 - x86-64 Code Generation

- [ ] Design a simple intermediate representation (linear IR, or use AST directly)
- [ ] Implement stack-frame layout for local variables
- [ ] Emit System V AMD64 ABI-compliant function prologues / epilogues
- [ ] Codegen for arithmetic & comparison expressions
- [ ] Codegen for function calls (argument passing via registers)
- [ ] Codegen for `return` statements
- [ ] Output `.s` file, assemble with NASM / GAS
- [ ] End-to-end test: compile a simple `fn` → run → correct exit code

## Planned Features (Backlog)

### Control flow
- [ ] `if` / `else` branching
- [ ] `while` loops

### Types & memory
- [ ] Typed pointers (`*T`)
- [ ] Opaque pointers (`*void` / `*opaque`)
- [ ] Raw pointer arithmetic & dereference
- [ ] Fixed-size arrays (`[T; N]`)
- [ ] Slices (`&[T]` / `[]T`)

### Composite types
- [ ] Structs & field access
- [ ] Enums (C-style tagged unions)
- [ ] Pattern matching (`match` / `switch`)

### Strings & interop
- [ ] String literals & `*u8` handling
- [ ] Variadic functions (for `printf` interop)
- [ ] `extern` / FFI declarations

### Tooling & backend
- [ ] Proper register allocator
- [ ] Debug info (DWARF)
- [ ] Standard library bootstrap (`print`, `malloc` wrapper)