Implements the exhaustiveness algorithm to detect non-exhaustive pattern matches:
- Detects missing Bool patterns (true/false)
- Detects missing Option patterns (Some/None)
- Detects missing Result patterns (Ok/Err)
- Recognizes wildcards and variable patterns as catch-alls
- Warns about redundant patterns after catch-all patterns
- Integrates with the type checker to report errors
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Implement beautiful, informative error messages inspired by Elm:
- Rich diagnostic rendering with source code snippets
- Colored output with proper underlines showing error locations
- Categorized error titles (Type Mismatch, Unknown Name, etc.)
- Contextual hints and suggestions for common errors
- Support for type errors, runtime errors, and parse errors
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Implement behavioral properties for functions including:
- Property annotations: is pure, is total, is idempotent, is deterministic, is commutative
- Where clause constraints: where F is pure
- Result refinements: where result >= 0 (parsing only, not enforced)
Key changes:
- AST: BehavioralProperty enum, WhereClause enum, updated FunctionDecl
- Lexer: Added keywords (is, pure, total, idempotent, deterministic, commutative, where, assume)
- Parser: parse_behavioral_properties(), parse_where_clauses(), parse_single_property()
- Types: PropertySet for tracking function properties, updated Function type
- Typechecker: Verify pure functions don't have effects, validate where clause type params
Properties are informational/guarantees rather than type constraints - a pure
function can be used anywhere a function is expected. Property requirements
are meant to be enforced via where clauses (future work: call-site checking).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
