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Support doc comment before variant (#7535)
* WIP * Format doc comment before bar * Adjust loc * Update test files * Lookahead if we are in variant * Cleanup * Remove loc adjustment hack * Update test files * Update CHANGELOG * Resolve review feedback * Update tests
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‎.mcp.json

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{
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"mcpServers": {
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"ocamllsp": {
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"type": "stdio",
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"command": "mcp-language-server",
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"args": [
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"--workspace",
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"/Users/shulhi/Dev/rescript/rescript-compiler",
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"--lsp",
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"ocamllsp"
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],
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"env": {}
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}
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}
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}

‎CHANGELOG.md

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- Don't produce duplicate type definitions for recursive types on hover. https://github.com/rescript-lang/rescript/pull/7524
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- Prop punning when types don't match results in I/O error: _none_: No such file or directory. https://github.com/rescript-lang/rescript/pull/7533
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- Fix partial application with user-defined function types. https://github.com/rescript-lang/rescript/pull/7548
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- Fix doc comment before variant throwing syntax error. https://github.com/rescript-lang/rescript/pull/7535
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#### :nail_care: Polish
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‎CLAUDE.md

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# CLAUDE.md
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This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
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## Project Overview
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This is the ReScript compiler repository - a robustly typed language that compiles to efficient and human-readable JavaScript. ReScript is built using OCaml and includes a complete toolchain with compiler, build system, syntax parser, and standard library.
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## Build Commands
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### Basic Development
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```bash
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# Build compiler and copy executables
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make
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# Build in watch mode
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make watch
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# Build everything including standard library
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make lib
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# Build artifacts and update artifact list
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make artifacts
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```
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### Testing
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```bash
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# Run all tests
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make test
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# Run specific test types
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make test-syntax # Syntax parser tests
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make test-syntax-roundtrip # Roundtrip syntax tests
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make test-gentype # GenType tests
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make test-analysis # Analysis tests
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make test-tools # Tools tests
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make test-rewatch # Rewatch tests
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# Run single file test
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./cli/bsc.js myTestFile.res
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# View parse/typed trees for debugging
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./cli/bsc.js -dparsetree myTestFile.res
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./cli/bsc.js -dtypedtree myTestFile.res
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```
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### Code Quality
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```bash
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# Format code
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make format
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# Check formatting
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make checkformat
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# Lint with Biome
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npm run check
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npm run check:all
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# TypeScript type checking
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npm run typecheck
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```
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### Clean Operations
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```bash
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make clean # Clean OCaml build artifacts
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make clean-all # Clean everything including Rust/gentype
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```
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## Compiler Architecture
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The ReScript compiler follows this high-level pipeline:
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```
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ReScript Source (.res)
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↓ (ReScript Parser - compiler/syntax/)
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Surface Syntax Tree
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↓ (Frontend transformations - compiler/frontend/)
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Surface Syntax Tree
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↓ (OCaml Type Checker - compiler/ml/)
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Typedtree
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↓ (Lambda compilation - compiler/core/lam_*)
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Lambda IR
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↓ (JS compilation - compiler/core/js_*)
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JS IR
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↓ (JS output - compiler/core/js_dump*)
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JavaScript Code
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```
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### Key Directories
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- **`compiler/syntax/`** - ReScript syntax parser (MIT licensed, separate from main LGPL)
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- **`compiler/frontend/`** - AST transformations, external FFI processing, built-in attributes
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- **`compiler/ml/`** - OCaml compiler infrastructure (type checker, typedtree, etc.)
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- **`compiler/core/`** - Core compilation:
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- `lam_*` files: Lambda IR compilation and optimization passes
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- `js_*` files: JavaScript IR and code generation
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- **`compiler/ext/`** - Extended utilities and data structures
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- **`compiler/bsb/`** - Build system implementation
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- **`compiler/gentype/`** - TypeScript generation
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- **`runtime/`** - ReScript standard library (written in ReScript)
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- **`lib/`** - Compiled JavaScript output of standard library
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- **`analysis/`** - Language server and tooling support
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### Build System Components
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- **`compiler/bsb_exe/`** - Main ReScript build tool entry point
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- **`compiler/bsc/`** - Compiler binary entry point
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- **`rewatch/`** - File watcher (written in Rust)
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- **`ninja/`** - Vendored Ninja build system
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## Development Setup Notes
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- Uses OCaml 5.3.0+ with opam for compiler development
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- Uses dune as build system with specific profiles (dev, release, browser)
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- Node.js 20+ required for JavaScript tooling
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- Rust toolchain needed for rewatch file watcher
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- Python ≤3.11 required for building ninja
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## Coding Conventions
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- **OCaml code**: snake_case (e.g., `to_string`)
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- **ReScript code**: camelCase (e.g., `toString`)
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- Use DCO sign-off for all commits: `Signed-Off-By: Your Name <email>`
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## Testing Strategy
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- **Mocha tests** (`tests/tests/`) - Runtime library unit tests
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- **Build system tests** (`tests/build_tests/`) - Integration tests
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- **OUnit tests** (`tests/ounit_tests/`) - Compiler unit tests
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- **Expectation tests** - Plain `.res` files that check compilation output
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- Always include appropriate tests with new features/changes
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## Performance Notes
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The compiler is designed for fast feedback loops and scales to large codebases. When making changes:
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- Avoid introducing meaningless symbols
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- Maintain readable JavaScript output
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- Consider compilation speed impact
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- Use appropriate optimization passes in the Lambda and JS IRs

‎Example.res

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type x =
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/** first group */
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| A
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| B
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| C
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/** second group */
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| D
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| E
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| F

‎compiler/syntax/src/res_core.ml

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@@ -4886,12 +4886,35 @@ and parse_constr_decl_args p =
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* | constr-name const-args
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* | attrs constr-name const-args *)
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and parse_type_constructor_declaration_with_bar p =
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match p.Parser.token with
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| Bar ->
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let is_constructor_with_bar p =
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Parser.lookahead p (fun state ->
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match state.Parser.token with
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| DocComment _ -> (
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Parser.next state;
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match state.token with
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| Bar -> true
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| _ -> false)
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| Bar -> true
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| _ -> false)
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in
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if is_constructor_with_bar p then (
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let doc_comment_attrs =
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match p.Parser.token with
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| DocComment (loc, s) ->
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Parser.next p;
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[doc_comment_to_attribute loc s]
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| _ -> []
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in
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let start_pos = p.Parser.start_pos in
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Parser.next p;
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Some (parse_type_constructor_declaration ~start_pos p)
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| _ -> None
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let constr = parse_type_constructor_declaration ~start_pos p in
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Some
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{
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constr with
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Parsetree.pcd_attributes =
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doc_comment_attrs @ constr.Parsetree.pcd_attributes;
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})
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else None
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and parse_type_constructor_declaration ~start_pos p =
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Parser.leave_breadcrumb p Grammar.ConstructorDeclaration;
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let first_constr_decl =
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match first with
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| None ->
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let doc_comment_attrs =
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match p.Parser.token with
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| DocComment (loc, s) ->
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Parser.next p;
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[doc_comment_to_attribute loc s]
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| _ -> []
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in
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let start_pos = p.Parser.start_pos in
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ignore (Parser.optional p Token.Bar);
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parse_type_constructor_declaration ~start_pos p
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let constr = parse_type_constructor_declaration ~start_pos p in
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{constr with pcd_attributes = doc_comment_attrs @ constr.pcd_attributes}
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| Some first_constr_decl -> first_constr_decl
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in
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first_constr_decl
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in
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let kind =
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match p.Parser.token with
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| Bar | Uident _ ->
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| Bar | Uident _ | DocComment _ ->
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Parsetree.Ptype_variant (parse_type_constructor_declarations p)
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| Lbrace ->
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Parsetree.Ptype_record
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parse_record_or_object_decl ?current_type_name_path ?inline_types_context
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p
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| Private -> parse_private_eq_or_repr p
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| Bar | DotDot ->
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| Bar | DotDot | DocComment _ ->
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let priv, kind = parse_type_representation p in
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(None, priv, kind)
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| _ -> (

‎compiler/syntax/src/res_printer.ml

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in
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Doc.breakable_group ~force_break docs
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let print_listi ~get_loc ~nodes ~print ?(force_break = false) t =
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let print_listi ~get_loc ~nodes ~print ?(ignore_empty_lines = false)
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?(force_break = false) t =
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let rec loop i (prev_loc : Location.t) acc nodes =
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match nodes with
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| [] -> (prev_loc, Doc.concat (List.rev acc))
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| Some comment -> (Comment.loc comment).loc_start
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in
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let sep =
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if start_pos.pos_lnum - prev_loc.loc_end.pos_lnum > 1 then
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Doc.concat [Doc.hard_line; Doc.hard_line]
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if
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start_pos.pos_lnum - prev_loc.loc_end.pos_lnum > 1
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&& not ignore_empty_lines
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then Doc.concat [Doc.hard_line; Doc.hard_line]
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else Doc.line
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in
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let doc = print_comments (print node t i) t loc in
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~print:(fun cd cmt_tbl i ->
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let doc = print_constructor_declaration2 ~state i cd cmt_tbl in
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print_comments doc cmt_tbl cd.Parsetree.pcd_loc)
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~force_break cmt_tbl
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~force_break cmt_tbl ~ignore_empty_lines:true
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in
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Doc.breakable_group ~force_break
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(Doc.indent (Doc.concat [Doc.line; private_flag; rows]))
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let comment_doc =
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match comment_attrs with
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| [] -> Doc.nil
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| comment_attrs -> print_doc_comments ~state cmt_tbl comment_attrs
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| comment_attrs ->
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print_doc_comments ~sep:Doc.hard_line ~state cmt_tbl comment_attrs
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in
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let attrs = print_attributes ~state attrs cmt_tbl in
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let is_dot_dot_dot = cd.pcd_name.txt = "..." in
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in
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Doc.concat
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[
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bar;
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comment_doc;
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bar;
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Doc.group
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(Doc.concat
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[

‎tests/syntax_benchmarks/data/Napkinscript.res

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| PatternList
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| PatternOcamlList
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| PatternRecord
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| TypeDef
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| TypeConstrName
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| TypeParams
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| @live TypeParam
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| PackageConstraint
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| TypeRepresentation
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| RecordDecl
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| ConstructorDeclaration
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| ParameterList

‎tests/tests/src/arith_syntax.res

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type rec expression =
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| /** non-negative integer constant */
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Numeral(float)
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| /** Addition [e1 + e2] */
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Plus(expression, expression)
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| /** Difference [e1 - e2] */
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Minus(expression, expression)
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| /** Product [e1 * e2] */
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Times(expression, expression)
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| /** Quotient [e1 / e2] */
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Divide(expression, expression)
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| /** Opposite value [-e] */
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Negate(expression)
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/** non-negative integer constant */
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| Numeral(float)
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/** Addition [e1 + e2] */
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| Plus(expression, expression)
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/** Difference [e1 - e2] */
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| Minus(expression, expression)
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/** Product [e1 * e2] */
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| Times(expression, expression)
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/** Quotient [e1 / e2] */
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| Divide(expression, expression)
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/** Opposite value [-e] */
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| Negate(expression)
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| Variable(string)
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let rec str = e =>

‎tests/tests/src/condition_compilation_test.mjs

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};
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}
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36-
eq("File \"condition_compilation_test.res\", line 63, characters 5-12", 3, 3);
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eq("File \"condition_compilation_test.res\", line 60, characters 5-12", 3, 3);
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38-
eq("File \"condition_compilation_test.res\", line 64, characters 5-12", v.contents, 2);
38+
eq("File \"condition_compilation_test.res\", line 61, characters 5-12", v.contents, 2);
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Mt.from_pair_suites("Condition_compilation_test", suites.contents);
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‎tests/tests/src/condition_compilation_test.res

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| O_DSYNC
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| O_SYNC
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| O_RSYNC
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| O_SHARE_DELETE
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| O_CLOEXEC
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| O_KEEPEXEC
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let vv = 3

‎tests/tests/src/gpr_1822_test.mjs

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area = myShape.TAG === "Circle" ? 100 * 3.14 : 10 * myShape._1 | 0;
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eq("File \"gpr_1822_test.res\", line 23, characters 3-10", area, 314);
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eq("File \"gpr_1822_test.res\", line 22, characters 3-10", area, 314);
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Mt.from_pair_suites("Gpr_1822_test", suites.contents);
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‎tests/tests/src/gpr_1822_test.res

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type shape =
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| Circle(int)
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| Rectangle(int, int)
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1716
let myShape = Circle(10)

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