Featherweight Cangjie

A compiler frontend for a subset of the Cangjie programming language that performs comprehensive static analysis and validation.

Overview

This project implements the frontend stages of a Cangjie compiler, transforming source code through multiple representations to validate syntax, types, and initialization semantics. Valid programs are pretty-printed for compilation; invalid programs generate detailed, actionable error messages.

Pipeline Stages

1. Scanner

Converts source text into tokens with kind, value, and position information for error reporting.

2. Parser

Builds an Abstract Syntax Tree (AST) from tokens using a grammar subset that excludes packages, type aliases, extensions, foreign declarations, annotations, and macros.

3. ASG Builder

Transforms the AST into an Abstract Syntax Graph (ASG) where variables are represented as edges rather than nodes, enabling precise variable resolution and scope tracking through environment structures.

4. Type Checker

Performs two-pass type inference and validation:

• Validates type declarations form a valid DAG (no cycles)
• Infers types for expressions, considering context and overload resolution
• Handles complex cases like function calls with multiple candidates and conditional branches
• Ensures assignments and operations use compatible types

5. Initialization Checker

Verifies proper variable and class initialization:

• Variables are initialized before use
• Immutable variables are not mutated
• Class constructors initialize all members
• Static/global variables respect declaration order
• Constructor functions follow proper calling conventions

Key Features

• Incremental grammar implementation: Developed layer-by-layer for maintainability
• ASG representation: Solves variable resolution problems inherent in ASTs
• Sophisticated type inference: Handles overloading, subtyping, and contextual type requirements
• Comprehensive initialization tracking: Scope-aware analysis with special handling for classes and closures

Last Updates

• Grammar and compiler extension with adding Interfaces
• Enforcing the typing/inheritance rules regarding Interfaces
• Testing the Type Checking algorithm and rules with added Interfaces
• Improving/Fixing the Type Checker for minor bugs

Next Steps

• Code refactoring and cleanup
• Grammar extension to cover more language features
• Enhanced error handling across all compilation stages

Run

• Short guide on how to run the program
• First clone this repo and make sure that Cangjie 1.0.0 and stdx library is installed
• Make sure to put the right target in cjpm.toml, see the cjpm.toml for more details
• Run the following command where TEST_FILE_NAME is the file containing input code

cjpm run --run-args="TEST_FILE_NAME"