Hew Language Support for VS Code

Syntax highlighting and language support for the Hew programming language.

Features

• Full syntax highlighting for Hew language constructs
• Language Server Protocol — completion, hover, definition, document symbols, semantic tokens, diagnostics (language server included in the published extension)
• Document formatting — format on save via hew fmt (requires hew CLI)
• Actor declarations — actor, receive fn, receive, init
• Supervisor trees — supervisor, child, strategy, intensity, within
• Structured concurrency — scope, fork, await, select
• Generators — gen fn, yield
• Wire types — #[wire] attribute on type/enum declarations, field tags with @
• Traits and generics — trait, impl ... for, type parameters <T: Send>, generic closures |<T: Eq> left: T, right: T| -> bool { left == right }
• Pattern matching — match, =>, guards, destructuring
• Post-cutover paths — dotted paths (std.time), import selections (std.time.{Instant}), and contextual variants (.Ready)
• All built-in types — i8–i64, u8–u64, f32, f64, bool, char, string
• String variants — regular "...", raw r"...", byte b"...", interpolated f"...{expr}...", char 'x'
• Duration literals — 100ms, 5s, 1h
• Comments — //, /* */, /// (doc comments)
• Auto-closing pairs for brackets, braces, parentheses, strings
• Code folding and bracket matching

Example

actor Counter {
    var count: i32 = 0;

    receive fn increment() {
        self.count = self.count + 1;
    }

    receive fn get() -> i32 {
        self.count
    }
}

supervisor CounterSupervisor {
    strategy: one_for_one;
    intensity: 5 within 30s;
    child counter: Counter;
}

fn fibonacci(n: i32) -> i32 {
    if n <= 1 {
        n
    } else {
        fibonacci(n - 1) + fibonacci(n - 2)
    }
}

fn main() -> i32 {
    let result = fibonacci(10);
    println(result);
    0
}

Path syntax

Hew paths use dots: import std.time and clock.now(). Select several names from a module with import std.time.{Instant, Duration}, and use .Variant for a contextual enum variant in a match. The retired :: separator reports E_PATH_LEGACY_SEPARATOR, glob imports report E_IMPORT_GLOB_REMOVED, and turbofish syntax reports E_LEGACY_TURBOFISH.

Installation

From the Marketplace

Install Hew Language in VS Code, then open a .hew file. Platform packages include a matched Hew SDK for language features, formatting and debug builds. The extension starts its language server with hew lsp and uses the same SDK for its other tools. You can select an installed SDK with hew.lsp.serverPath; point it at bin/hew (or bin/hew.exe on Windows).

From VSIX (local install)

1. In the extension directory, stage the SDK for your platform and package it:

   scripts/stage-hew-sdk.sh linux-x64   # or linux-arm64, darwin-arm64, win32-x64
   npx vsce package --target linux-x64
   

2. In VS Code, open the command palette (Ctrl+Shift+P) and run: Extensions: Install from VSIX...
3. Select the generated .vsix file

From source (development)

1. Clone this repository
2. Run npm install && npm run build:dev
3. Open this folder in VS Code and press F5 to launch the Extension Development Host

Validate the controlled Hew fixtures with a compiler explicitly selected for the check:

HEW_COMPILER=/path/to/hew npm run test:fixtures

Releasing

Push a vX.Y.Z tag matching package.json; .github/workflows/release.yml packages every platform with the Hew SDK pinned in hew-release.sha256 and publishes after approval. See docs/publishing.md.

Configuration

Workspace-built hew binaries are only auto-selected in trusted workspaces by default. In Restricted Mode, trust the workspace or set hew.allowUntrustedWorkspaceBinaries in user settings to opt in.

Debugging

Before launching a Hew debug session:

• If program points to a .hew source file, make sure hew.debugger.hewPath is set or hew is on PATH so the extension can run hew build --debug.
• Make sure the selected backend executable is on PATH:
  • debuggerBackend: "auto" picks lldb-mi on macOS and gdb elsewhere.
  • debuggerBackend: "lldb" requires lldb-mi.
  • debuggerBackend: "gdb" requires gdb.

Example .vscode/launch.json:

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "hew",
      "request": "launch",
      "name": "Debug Hew Program",
      "program": "${workspaceFolder}/main.hew",
      "debuggerBackend": "auto"
    }
  ]
}

If preflight reports that a backend is unavailable, either install the required tool or switch debuggerBackend to a backend that is already installed on your system.

Supported Token Scopes

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

Updating syntax highlighting

Edit structural TextMate rules in syntaxes/hew.tmLanguage.json. Keyword and built-in type lists come from the compiler's docs/syntax-data.json; regenerate them with the shared compiler tool from this repository's root:

HEW_VSCODE_HEW="$PWD" node ../hew/tools/downstream/generate-tmgrammar.mjs
cp ../hew/dist/hew.tmLanguage.json syntaxes/hew.tmLanguage.json
npm test

Consuming receivers use consume self. Generators use gen fn, and stream iteration uses plain for. The retired async gen fn, for await and infix | after forms are highlighted as errors.