Various fixes to 0.2.0 release.

CHANGELOG.md

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+# Changelog
+
+All notable changes to the Goth programming language are documented in this file.
+
+## [0.2.0] - 2026-01-31
+
+Bug fixes, type checker improvements, and quality-of-life cleanup.
+
+### Type Checker
+- Cast validation: `as?` (try cast) now returns `Option<T>` instead of bare `T`
+- Record update: `Expr::Update` validates field names and types against base record
+- LetRec: extracts type annotations from `Pattern::Typed` and `Expr::Annot` instead of using `Type::Hole` for all bindings
+- Do blocks: full type threading through Map, Filter, Bind, Op, and Let operations
+- Fresh type variables: Forall instantiation uses unique `_t0`, `_t1`... variables instead of `Type::Hole`
+- Added `fromChars` type signature to builtins
+
+### Interpreter
+- `eval_filter` now propagates predicate errors instead of silently dropping elements
+- Added `fromChars` primitive for string round-tripping (`fromChars (chars s) = s`)
+- Closure equality now compares captured environment, not just code
+- Terminal raw mode: replaced unsafe `static mut` with `Mutex`, added `atexit` handler and `catch_unwind` for panic-safe terminal restoration
+- REPL `:quit` now restores terminal state before exiting
+
+### Pretty Printer
+- Implemented `OpDecl` pretty printing (was `todo!()` panic)
+- Operator precedence now delegates to `BinOp::precedence()` — no more drift between parser and printer
+
+### Documentation
+- Added CHANGELOG.md
+- LANGUAGE.md: documented 8 missing operators (⍀, ∘, ⊗, ⤇, ◁, ⊕, ▷, ≡)
+- LANGUAGE.md: clarified all integer types are i128 at runtime
+- Removed empty `examples/string/` and `examples/data-structures/` directories
+
+### Dependencies
+- thiserror: 1.0 → 2.0 (all crates)
+- Added `license` and `repository` to goth-check Cargo.toml
+
+## [0.1.0] - 2026-01-31
+
+Initial public release.
+
+### Language
+
+- De Bruijn indexed lambda calculus with curried multi-argument functions
+- Pattern matching with literal, tuple, array, variant, wildcard, guard, and or-patterns
+- Recursive bindings (`let rec`)
+- Do-notation for tensor pipelines (map, filter, bind, let, binary ops)
+- Tensor (array) types with shape tracking and broadcasting
+- Record types with labeled fields and update syntax
+- Variant (sum) types with constructor syntax
+- Uncertainty propagation: first-class `±` values with automatic error propagation through all math operations
+- Cast expressions: `as` (static), `as!` (force), `as?` (try, returns Option)
+- Unicode operator surface: `λ`, `→`, `↦`, `▸`, `⤇`, `∘`, `⊕`, `⊗`, `Σ`, `Π`, `⌿`, `⍀`, `▷`, `◁`, `≤`, `≥`, `≠`, `∧`, `∨`, `±`
+- ASCII aliases for all Unicode operators
+- String literals as character tensors
+- Effect annotations (parsed and stored, not yet enforced)
+- Type annotations with refinement types (parsed, partially checked)
+- Module system with `use` imports and file-based resolution
+
+### Standard Library
+
+- `prelude.goth` — core utilities (identity, const, flip, compose, arithmetic helpers)
+- `math.goth` — trigonometric, hyperbolic, logarithmic, and special functions
+- `list.goth` — list operations (map, filter, fold, zip, take, drop, reverse, sort, minimum, maximum)
+- `option.goth` — generic Option type (some, none, map, flatMap, getOrElse, etc.)
+- `result.goth` — generic Result type (ok, err, map, flatMap, recover, etc.)
+- `string.goth` — string manipulation (split, join, trim, contains, replace, etc.)
+- `tui.goth` — terminal UI helpers (ANSI escapes, cursor control, raw mode)
+- `crypto.goth` — pure-Goth SHA-256, SHA-1, MD5, HMAC, and PBKDF2
+
+### Interpreter
+
+- Tree-walking evaluator with global environment and closure capture
+- Partial application for all functions
+- 127 evaluator tests covering arithmetic, closures, patterns, tensors, uncertainty, I/O
+- Built-in primitives: math functions, string operations, file I/O, byte I/O, terminal control
+- Checked integer arithmetic (overflow returns error, not panic)
+- Checked shift/power operations with bounds validation
+- Thread-safe terminal state management with atexit and panic cleanup
+
+### Type Checker
+
+- Bidirectional type checking (inference + checking modes)
+- Type unification with occurs check
+- Shape unification for tensor dimensions
+- 76 type checker tests
+- Handles: let, let rec (with annotations), if/else, match, binary/unary ops, tuples, records, arrays, casts, do-blocks, field access, indexing, slicing, annotations
+- Fresh type variable generation for polymorphic instantiation
+- Type substitution across all type forms including Variant, Exists, App, Effectful, Interval
+
+### Parser
+
+- Full Goth syntax including Unicode and ASCII operator forms
+- Proper error reporting on unrecognized tokens (no silent drops)
+- Proper error reporting on unrecognized operators (no silent fallback)
+- Module parsing with declarations, function definitions, and type definitions
+- 111 parser tests
+
+### Tooling
+
+- CLI (`goth`): file execution, expression evaluation (`-e`), REPL, type checking (`-c`)
+- REPL with syntax-aware multi-line input, history, and colored output
+- AST-first LLM workflow: `--to-json` / `--from-json` for JSON AST round-tripping
+- Pretty printer for Goth syntax from AST
+
+### Known Limitations
+
+- Type checker is advisory — programs run regardless of type errors
+- Variant constructor validation requires ADT registry (not yet implemented)
+- Effect system is parsed but not enforced
+- No parametric polymorphism at runtime (evaluator is type-erased)
+- Closure equality compares code only, not captured environment