vera

Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog.

Typed AST layer: frozen dataclass nodes with source spans, covering all grammar constructs (~50 node classes)
Lark→AST transformer: bottom-up Transformer with ~86 methods converting parse trees to typed AST nodes
CLI command: vera ast <file> prints indented text AST, vera ast --json <file> prints JSON
Convenience API: parse_to_ast(source, file) in vera/parser.py
AST tests: 83 new tests — round-trip tests for all 13 examples, node-specific tests for every construct, span tests, serialisation tests (193 total, up from 110)
TransformError: new error class for AST transformation failures, subclass of VeraError

README: added AST to project status table, vera ast CLI docs, updated project structure
SKILLS.md: added vera ast and vera ast --json to toolchain section

Parser tests: 40 new tests covering annotation comments, anonymous functions, generics, refinement types, tuple destructuring, quantifiers, assert/assume, qualified calls, function types, float literals, nested patterns, handler variations, and implies operator (110 total, up from 70)
Example programs: 8 new examples — closures, generics, refinement types, effect handlers, modules, quantifiers, pattern matching, mutual recursion (13 total, up from 5)
Design notes: network access as an effect (<Http>), JSON as a stdlib ADT, async promises/futures as an effect (<Async>) documented in spec Chapter 0

Grammar: annotation comments (/* ... */) now correctly ignored by the parser
Grammar: vera/__init__.py version was 0.1.0, corrected to match pyproject.toml
Spec Chapter 3: removed deliberation marker about @Fn0 approach, kept settled type alias approach
Spec Chapter 6: rewrote counterexample reporting section (removed incorrect example, added actionable fix suggestions)
Spec Chapter 7: cleaned up effect-contract interaction section (removed problematic get() in contract example, kept settled old()/new() syntax)

CI: GitHub Actions workflow running pytest on Python 3.11/3.12/3.13 with coverage on 3.12
Social preview: meerkat sentinel mascot using Negroni brand colour palette
Custom domain: veralang.dev with GitHub Pages and HTTPS

Parser: Lark LALR(1) parser that validates .vera source files
- vera check <file> — parse and report errors
- vera parse <file> — print the parse tree
LLM-oriented diagnostics: error messages are natural language instructions explaining what went wrong, why, how to fix it with a code example, and a spec reference
SKILLS.md: complete language reference for LLM agents, following the agent skills format
Example programs: absolute_value.vera, safe_divide.vera, increment.vera, factorial.vera, list_ops.vera
Test suite: 70 tests (54 parser, 16 error diagnostics)
Language specification chapters 0-7 and 10 (draft)
- Chapter 0: Introduction, philosophy, and diagnostics-as-instructions
- Chapter 1: Lexical structure
- Chapter 2: Type system with refinement types
- Chapter 3: Slot reference system (@T.n typed De Bruijn indices)
- Chapter 4: Expressions and statements
- Chapter 5: Function declarations
- Chapter 6: Contract system (preconditions, postconditions, verification tiers)
- Chapter 7: Algebraic effect system
- Chapter 10: Formal EBNF grammar (LALR(1) compatible)
Project structure with spec/, vera/, runtime/, tests/, examples/
Python project configuration (pyproject.toml)
Repository documentation (README, LICENSE, CONTRIBUTING, CODE_OF_CONDUCT, CHANGELOG)
GitHub issue and pull request templates

Grammar: operator precedence chain (pipe/implies ordering)
Grammar: old()/new() accept parameterised types (State<Int>)
Grammar: function signatures use @Type prefix to declare binding sites
Grammar: handler body simplified to avoid LALR reduce/reduce conflict
pyproject.toml: corrected build backend, package discovery, PEP 639 compliance

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