[#336] Replace closure and function type syntax with fn() unified syntax#339
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milkyskies merged 2 commits intomainfrom Mar 17, 2026
Merged
[#336] Replace closure and function type syntax with fn() unified syntax#339milkyskies merged 2 commits intomainfrom
milkyskies merged 2 commits intomainfrom
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Unified closure and function type syntax under the fn keyword: - Closures: |x| expr -> fn(x) expr, || expr -> fn() expr - Async closures: async |x| expr -> async fn(x) expr - Function types: (T) -> R -> fn(T) -> R, () -> () -> fn() -> () Parser: fn( in expression context is a lambda, fn name( is a declaration. Removed is_function_type/scan_for_rparen_followed_by heuristics since fn keyword now unambiguously starts function types. Updated all .fl files, test fixtures, example apps, inline test strings, formatter, and lowering to use new syntax. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- design.md: all syntax tables, examples, token table, banned tokens - llms.txt: closure syntax, function types, compilation examples - site docs: 13 pages updated (guide, reference, tooling) - tree-sitter: grammar.js pipe_lambda and function_type rules - TextMate: lambda patterns updated for fn() syntax - VSCode: added closure snippet - Neovim: highlights synced with tree-sitter - Lexer: VerticalBar doc comment no longer mentions lambda delimiters Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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closes #336
Summary
|x| expr→fn(x) expr,|| expr→fn() exprasync || expr→async fn() expr(T) -> R→fn(T) -> R,() -> ()→fn() -> ()fn) for declarations, types, and closures — zero ambiguity||is now only boolean OR,|is now only union typesChanges
Compiler (parser, lowering, formatter):
fn((lambda) vsfn name((declaration) in expression contextis_function_type/scan_for_rparen_followed_byheuristics —fnkeyword is unambiguousfn(...)syntax)instead of|All .fl files: fixtures, todo-app, store example — 25 files updated
Docs: design.md, llms.txt, 13 site pages
Syntax highlighting: tree-sitter grammar, TextMate, Neovim queries, VSCode snippet
Test plan
cargo fmtcleancargo clippy -- -D warningscleanRUSTFLAGS="-D warnings" cargo testclean🤖 Generated with Claude Code