chore(main): release fern 0.2.0

[niklas-heer]

🤖 I have created a release beep boop

0.2.0 (2026-02-09)

⚠ BREAKING CHANGES

• runtime: Result type representation changed from packed int64 to heap-allocated struct.

Features

• add 🌿 branding and emoji file extension support (1526ce2)
• add automation scripts for Ralph Loop (cfa24a6)
• add complete Fern language design specification (763868f)
• add plain text demo (no color codes for nushell compatibility) (a04cc37)
• add Ralph Loop autonomous development system (990b2f9)
• add ralph-demo.sh to demonstrate the Ralph Loop workflow (9071be7)
• benchmarks: add Fern vs C vs Python benchmark suite (a9cefad)
• build: use embedded QBE backend instead of external binary (1109be5)
• checker: add let statement type checking with inference (0b0865e)
• checker: add match expression type checking (1da24bf)
• checker: add Ok/Err value constructors and improve error locations (df131da)
• checker: add source location to type error messages (5a08ff0)
• checker: add try operator (?) type checking (3d4ea49)
• checker: add type checking for calls, if, and blocks (8fd3991)
• checker: add type checking for STMT_FN, STMT_TYPE_DEF, EXPR_LIST_COMP, EXPR_INTERP_STRING (ccd3a83)
• checker: implement constructor pattern binding for Option and Result (c9a1813)
• checker: implement generic type instantiation with unification (3a5e872)
• checker: implement type checker for expressions (e150877)
• checker: implement type checking for bind, with, lambda, for, index, and pipe (3956cb2)
• checker: implement type checking for dot, range, and map expressions (cc414ae)
• cli: add -o/--output flag for build command (efcdcb8)
• cli: add colored error messages (f43e248)
• cli: add run, lex, parse commands and improve help (3fc00a3)
• cli: document emoji file extension support (.🌿) (a08e0e2)
• codegen: add defer statement code generation (2549b18)
• codegen: add for loop code generation (96f1b45)
• codegen: add runtime integration for Result, List, and ? operator (f4911ac)
• codegen: add with expression code generation (d96347e)
• codegen: implement pipe operator for Tui builder pattern (0406018)
• codegen: implement proper pointer type handling for functions (e1eaa5e)
• codegen: implement QBE code generation (Milestone 4) (0e9b265)
• codegen: implement string interpolation (11ce99a)
• compiler: implement fern build command with full compilation pipeline (7cff339)
• complete Milestone 0 - Project Setup (7552cb3)
• editor: add Tree-sitter grammar and Zed extension with indentation support (daf522d)
• examples: add string interpolation example and test target (dbec273)
• examples: add TUI demo showcasing Panel, Table, Style (a257320)
• file: add directory listing functions (57f90d1)
• io: make print/println polymorphic (Int, String, Bool) (726311c)
• lang: add built-in module system (String, List, File) (879f2fc)
• lang: add range iteration and System module type support (eea0c23)
• lang: add System module for CLI argument access (bb1b404)
• lang: add System.exec, getenv/setenv and Regex module (3d0a35e)
• lang: allow omitting return type for main() (65feb19)
• lexer,parser: implement derive clause on type definitions (e725520)
• lexer,parser: implement float literal lexing and parsing (0b68167)
• lexer,parser: implement inclusive range operator (..=) (d760e08)
• lexer,parser: implement lambda/anonymous function expressions (2249811)
• lexer,parser: implement loop constructs (8dad7a8)
• lexer,parser: implement postfix unless for return statements (77802d8)
• lexer,parser: implement record update syntax ({ base | field: value }) (dafe27a)
• lexer,parser: implement string interpolation (1d608bb)
• lexer,parser: implement where clauses on function definitions (57f94ff)
• lexer: add block comment support (/* */) (0277001)
• lexer: add Python-style indentation tracking (4652111)
• lexer: add Unicode and emoji identifier support (dcb3bb7)
• lexer: handle string escape sequences (22eb129)
• lexer: implement core lexer (TDD - GREEN phase) (f643454)
• lexer: implement hex, binary, and octal number literals (d860d20)
• list: add 'in' operator and List.any/List.all functions (daf30ca)
• lsp: implement Language Server Protocol with diagnostics and hover (bc8edd0)
• modules: add Tui.* nested module namespace support (3647bc1)
• parser: add dedent tracking for proper block termination (4074344)
• parser: add indentation support to control structures (f2353dc)
• parser: add tuple type support in type annotations (34590d9)
• parser: implement ? operator for Result propagation (Decision 11) (196428b)
• parser: implement <- bind operator parsing (5d1a089)
• parser: implement block expression parsing (d31a1c8)
• parser: implement condition-only match (match: without value) (589fdac)
• parser: implement constructor patterns and unified parse_pattern (83bd1c1)
• parser: implement defer statement parsing (c7911f7)
• parser: implement dot access expressions (f4381e9)
• parser: implement function definition parsing (14ca62e)
• parser: implement if expression parsing (TDD - GREEN phase) (3e725f3)
• parser: implement indentation-based function body parsing (834357a)
• parser: implement index access expression parsing (7f9dbb7)
• parser: implement labeled function arguments (83665c4)
• parser: implement let-else pattern for early unwrapping (15ce681)
• parser: implement list comprehensions (d3fd32a)
• parser: implement list literal parsing (b6a8014)
• parser: implement map literal parsing (%{ key: value }) (562e331)
• parser: implement match arm guards (pattern if condition -> body) (8f92b98)
• parser: implement match expression parsing (46c4723)
• parser: implement module and import declaration parsing (307f2be)
• parser: implement module declaration parsing (d268896)
• parser: implement modulo (%) and power (**) operator parsing (2c0a014)
• parser: implement multi-clause function definitions (33c86e2)
• parser: implement newtype declaration parsing (28e85f0)
• parser: implement optional type annotations for let statements (b9928f6)
• parser: implement postfix if/unless on expression statements (f7d389a)
• parser: implement postfix return guards (return x if condition) (cd1daa1)
• parser: implement range expression parsing (478e07c)
• parser: implement recursive descent parser (TDD - GREEN phase) (2dbf451)
• parser: implement rest patterns in destructuring (91edeac)
• parser: implement spawn, send, and receive expression parsing (80180d7)
• parser: implement trait and impl block parsing (96d0528)
• parser: implement tuple field access (.0, .1) (e302fd4)
• parser: implement tuple literal parsing (2adad9f)
• parser: implement tuple/constructor destructuring in let bindings (a52f270)
• parser: implement type annotation parsing (12208d8)
• parser: implement type definition parsing (658fb3b)
• parser: implement where clause on trait definitions (480f39f)
• parser: implement with expression parsing (b744b75)
• repl: add interactive REPL with line editing and history (c9cc878)
• roadmap: add FernSim deterministic actor simulation testing (2013225)
• runtime: add comprehensive List functions (590ae03)
• runtime: add comprehensive String functions (061a934)
• runtime: add Fern runtime library (ef6ccfa)
• runtime: add fern_str_lines() function (d95ea51)
• runtime: add GC header for Boehm GC integration (3ad35f8)
• runtime: add List.contains functions for membership testing (fa2bdc7)
• runtime: add Result and Option type functions (85f4abf)
• scripts: add Fern style checker scripts (11cc15c)
• scripts: enhance check_style.fn with build/test verification (b644462)
• stdlib: add built-in string and list functions (8eddaa6)
• stdlib: add file I/O functions to runtime (20dcd5c)
• stdlib: add runtime library with print/println functions (2294a4d)
• stdlib: register additional built-in functions (293d73c)
• string: add index_of, char_at, and join to String module (ec5db9e)
• string: add string_append_cstr for concatenating with C strings (2293c65)
• style: add doc comment and tagged union validation (2eda7c2)
• style: add FERN_STYLE checker and Makefile targets (4bde372)
• style: add git hygiene and improve style checker (99c723f)
• style: add uv support and rich TUI to style checker (eae5038)
• system: add cwd, chdir, hostname, user, home functions (0a2f5d9)
• test: run @doc examples via fern test --doc (0db0e53)
• tui: add Panel and Table modules for terminal UI (c8abb2c)
• tui: add Progress and Spinner modules (Phase 2) (29b6324)
• tui: add Prompt module for user input (Phase 3) (c5b01b4)
• tui: add Status badges, Live module, and color palette (665f61b)
• tui: add Term and Style modules for terminal UI (cfe0d20)
• tui: rename Prompt module to Tui.Prompt (4fecc75)
• type: implement type representation and type environment (31176bf)
• types: make print/println return Unit and support () expressions (6a49bb0)

Bug Fixes

• arena: prevent memory corruption in large allocations (edca02a)
• ast: add missing stdint.h include for Linux CI (1aec627)
• ast: remove extra semicolons from VEC_TYPE macros and simplify expr_call (e9e7b5e)
• checker: use unify for let statement type checking (537053f)
• ci: add missing stdint.h include to test_arena.c (98489fd)
• ci: add POSIX defines to runtime and libgc to lint job (0a61141)
• ci: install Boehm GC dependency for build (2732076)
• codegen: handle early return inside nested if blocks (64a117c)
• codegen: handle pointer return types from built-in functions (ef18785)
• codegen: improve type handling for tuples and string interpolation (a886a41)
• codegen: track pointer types for correct QBE type widths (6876dbc)
• codegen: use correct QBE type for list element push (e4c940b)
• codegen: use pointer types for list elements and Result unwrap (c1a4346)
• correct budget understanding - Max Plan provides UNLIMITED usage (dcb2ecb)
• errors: add POSIX_C_SOURCE for fileno() in strict C11 (27db62b)
• lexer: handle literal braces in strings correctly (1384b7e)
• lexer: ignore indentation inside brackets/parens/braces (20bc3b7)
• lexer: save/restore all state in lexer_peek (20e400b)
• linenoise: add POSIX_C_SOURCE for strdup/fileno/fchmod (d234fbb)
• linenoise: add strings.h and BSD defines for strcasecmp (3d3be14)
• make ralph-iteration.sh portable (remove head -n -1) (2174c31)
• make ralph-test.sh portable (use sed instead of head -n -1) (ec3d328)
• parser: add TOKEN_WITH to can_start_block_expr (35dc65d)
• parser: allow match expressions inside for loops (00c0c9c)
• parser: parse None as constructor pattern for Option matching (6a11459)
• parser: prevent postfix if from consuming if keywords after dedent (9ac13e0)
• parser: support inline if expressions in let bindings (6298638)
• parser: support multi-line match arms without commas (51c71d2)
• parser: track newlines to prevent tuple-as-call-args bug (86542f3)
• qbe: add POSIX_C_SOURCE for fmemopen() in strict C99 (a31d56d)
• runtime: align Option representation between codegen and runtime (fecc68b)
• runtime: use heap-allocated Option to support 64-bit pointers (87abf8a)
• runtime: use heap-allocated Result to support 64-bit values (c9e2e72)
• style: add FERN_STYLE exceptions and fix void return detection (99071ca)
• style: handle multi-rule FERN_STYLE allow comments (899166e)
• style: handle static void and variadic params in checker (7105d5f)
• tui: Panel ignores empty string titles (82735cd)
• tui: Panel renders multi-line content correctly (f020b20)

---

This PR was generated with Release Please. See documentation.

Summary by CodeRabbit

Release Notes

• New Features

  • Version 0.2.0 released with improvements across runtime, codegen, type system, parser, CLI, and tooling.

• Breaking Changes

  • Result type representation changed from packed int64 to heap-allocated struct.

• Bug Fixes

  • Multiple bug fixes across the codebase.

• Documentation

  • Added comprehensive changelog documenting release contents.

[coderabbitai]

Note

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📝 Walkthrough

Walkthrough

Bumps project version from 0.1.0 to 0.2.0: updates release manifest and public version header, and adds a new CHANGELOG.md documenting the 0.2.0 release (breaking change, features, bug fixes).

Changes

Cohort / File(s)	Summary
Version Metadata /.github/.release-please-manifest.json, include/version.h	Updated root version mapping and FERN_VERSION_STRING macro from 0.1.0 to 0.2.0.
Release Notes CHANGELOG.md	Added comprehensive changelog for 0.2.0 including a BREAKING CHANGES entry (runtime Result representation), Features, and Bug Fixes sections.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I hopped a bump from one to two,
Manifests and headers changed their hue,
A changelog blooms with tales to tell,
I nibble bytes and wag my tail—farewell!

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'chore(main): release fern 0.2.0' accurately describes the primary change—a version release from 0.1.0 to 0.2.0, including changelog documentation and version updates across manifest and header files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch release-please--branches--main--components--fern

---

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@CHANGELOG.md`:
- Line 65: The markdown entry contains unescaped asterisks in the C-style block
comment `/* */` which triggers MD037; update the CHANGELOG.md entry for the
lexer line (the commit referenced by 0277001) to wrap the block comment in an
inline code span (i.e., replace `/* */` with backtick-wrapped `/* */`) so the
asterisks are not treated as emphasis, or alternatively fix the original commit
subject that produced this release-please entry.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Markdown lint: unescaped * in /* */ triggers MD037 (spaces inside emphasis markers).

The C-style block comment syntax /* */ contains bare asterisks that some Markdown renderers may misinterpret as emphasis markers. Wrapping it in an inline code span would fix the lint warning and ensure correct rendering.

Proposed fix

-* **lexer:** add block comment support (/* */) ([0277001](https://github.com/niklas-heer/fern/commit/0277001b2524bb2e732479b02434d70093e5b4e2))
+* **lexer:** add block comment support (`/* */`) ([0277001](https://github.com/niklas-heer/fern/commit/0277001b2524bb2e732479b02434d70093e5b4e2))

Note: Since this file is auto-generated by release-please from the commit message, you may prefer to fix the original commit's subject instead, or accept this as a known cosmetic limitation of the generator.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	* **lexer:** add block comment support (/* */) ([0277001](https://github.com/niklas-heer/fern/commit/0277001b2524bb2e732479b02434d70093e5b4e2))
	* **lexer:** add block comment support (`/* */`) ([0277001](https://github.com/niklas-heer/fern/commit/0277001b2524bb2e732479b02434d70093e5b4e2))

🧰 Tools

🪛 markdownlint-cli2 (0.20.0)

[warning] 65-65: Spaces inside emphasis markers

(MD037, no-space-in-emphasis)

---

[warning] 65-65: Spaces inside emphasis markers

(MD037, no-space-in-emphasis)

🤖 Prompt for AI Agents

In `@CHANGELOG.md` at line 65, The markdown entry contains unescaped asterisks in
the C-style block comment `/* */` which triggers MD037; update the CHANGELOG.md
entry for the lexer line (the commit referenced by 0277001) to wrap the block
comment in an inline code span (i.e., replace `/* */` with backtick-wrapped `/*
*/`) so the asterisks are not treated as emphasis, or alternatively fix the
original commit subject that produced this release-please entry.

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@CHANGELOG.md`:
- Line 137: Replace the incorrect GitHub user link for the `@doc` annotation in
the changelog entry that currently reads "* **test:** run
[`@doc`](https://github.com/doc) examples via fern test --doc ([0db0e53](...))" by
removing the hyperlink around `@doc` (or changing it to plain `@doc` or to a
proper documentation link) so the annotation is not converted into a GitHub
profile link; update the changelog line accordingly and, if desired, correct the
original commit message that produced this auto-generated entry to prevent
recurrence.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Incorrect auto-generated link for @doc annotation.

The Release Please generator converted @doc into a GitHub user link pointing to https://github.com/doc, which is likely incorrect. The @doc appears to be a documentation annotation rather than a GitHub mention.

Proposed fix

-* **test:** run [`@doc`](https://github.com/doc) examples via fern test --doc ([0db0e53](https://github.com/niklas-heer/fern/commit/0db0e53bd0216af8d7893273267fd1836fd94cc8))
+* **test:** run `@doc` examples via fern test --doc ([0db0e53](https://github.com/niklas-heer/fern/commit/0db0e53bd0216af8d7893273267fd1836fd94cc8))

Note: Since this file is auto-generated from commit messages, you may prefer to fix the source commit message to prevent recurrence in future releases, or accept this as a known cosmetic limitation.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	* **test:** run [@doc](https://github.com/doc) examples via fern test --doc ([0db0e53](https://github.com/niklas-heer/fern/commit/0db0e53bd0216af8d7893273267fd1836fd94cc8))
	* **test:** run `@doc` examples via fern test --doc ([0db0e53](https://github.com/niklas-heer/fern/commit/0db0e53bd0216af8d7893273267fd1836fd94cc8))

🤖 Prompt for AI Agents

In `@CHANGELOG.md` at line 137, Replace the incorrect GitHub user link for the
`@doc` annotation in the changelog entry that currently reads "* **test:** run
[`@doc`](https://github.com/doc) examples via fern test --doc ([0db0e53](...))" by
removing the hyperlink around `@doc` (or changing it to plain `@doc` or to a
proper documentation link) so the annotation is not converted into a GitHub
profile link; update the changelog line accordingly and, if desired, correct the
original commit message that produced this auto-generated entry to prevent
recurrence.