Hew Language Support for VS Code

Syntax highlighting and language support for the Hew programming language — a high-performance, network-native, actor-based language.

Features

• Full syntax highlighting for Hew v0.6 constructs
• Language Server Protocol — completion, hover, definition, document symbols, semantic tokens, diagnostics (requires hew-lsp)
• Document formatting — format on save via hew fmt (requires hew CLI)
• Actor declarations — actor, receive fn, receive, init
• Supervisor trees — supervisor, child, restart, budget, strategy
• Structured concurrency — scope, launch, cancel, spawn, await
• Generators — gen fn, async gen fn, yield, cooperate
• Wire types — wire type, wire enum, field tags with @
• Traits and generics — trait, impl ... for, type parameters [T: Send]
• Pattern matching — match, =>, guards, destructuring
• All built-in types — i8–i64, u8–u64, f32, f64, bool, char, string
• String variants — regular "...", raw r"...", interpolated f"...{expr}..."
• 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 {
    child counter: Counter
        restart(permanent)
        budget(5, 30s)
        strategy(one_for_one);
}

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
}

Installation

From VSIX (local install)

1. In the extension directory, run:

   npm run package

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

Configuration

Setting	Default	Description
hew.lsp.serverPath	""	Path to hew-lsp binary. If empty, searches trusted workspace target/, PATH, and bundled binaries.
hew.formatterPath	""	Path to hew binary for formatting. If empty, searches trusted workspace target/, PATH, and bundled binaries.
hew.debugger.hewPath	""	Path to the hew compiler used for debug builds. If empty, uses the same trusted search as hew.formatterPath.
hew.allowUntrustedWorkspaceBinaries	false	Allows auto-detecting workspace target/release and target/debug binaries even in Restricted Mode. Set this in user settings only when you explicitly trust those workspace binaries.

Workspace-built hew and hew-lsp 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

Hew Construct	TextMate Scope
fn, let, var, struct, enum, trait, impl, gen	keyword.declaration
if, else, match, loop, for, while, return, await, scope, launch, cancel	keyword.control
actor, receive, spawn, init, async, mailbox, overflow	keyword.actor
supervisor, child, restart, budget, strategy	keyword.supervisor
wire, reserved, optional, deprecated, default, list	keyword.wire
and, or	keyword.operator.logical
one_for_one, permanent, true, false, None	constant.language
i32, u64, f64, bool, string	storage.type
Result, Option, Send, Frozen, Actor, ActorRef	storage.type
PascalCase identifiers	entity.name.type
Function names in definitions	entity.name.function
Function calls	entity.name.function.call
self	variable.language.self
"string", r"raw", f"interpolated {x}"	string.quoted
42, 0xFF, 0b1010, 3.14, 100ms	constant.numeric
//, /* */, ///	comment

License

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