Flaris Language Support for Visual Studio Code

Syntax highlighting, code snippets, analyzer diagnostics and a full debugger for Flaris (.fls) files - breakpoints, stepping, variable inspection and fiber-aware call stacks, with no separate debug adapter to install.

Features

Syntax Highlighting

Complete syntax highlighting for all Flaris language features:

• Keywords: fn, class, async, await, yield, if, for, foreach, iter, while, guard, enum, etc.
• Built-in Modules: Console, Debug, Math, File, Array, Fiber, VM, and more
• Type annotations: every type the compiler knows - int, string, fn (any callable), instance, fiber, stream, block and the sized-int aliases - including array element types ([int]), unions (object|nil) and a class name in return position
• Comments: Line (//) and block (/* */) comments
• Strings & Characters: Double-quoted and triple-quoted ("""…""") strings, full escape sequence support including \uXXXX
• Numbers: Decimal, hexadecimal (0xFF), binary (0b101), octal (0o755), floats (including 1e5), and underscore separators (1_000_000)
• Operators: All arithmetic, logical, bitwise, assignment operators, the ^^ power operator, and the ≈ approximate equality operator

Code Snippets

Quick snippets for common patterns (type prefix and press Tab):

Language Features

• Auto-closing: Brackets, parentheses, quotes
• Comment toggling: Quick line/block comment with Ctrl+/ (or Cmd+/)
• Bracket matching: Highlight matching brackets
• Code folding: Fold functions, classes, and blocks
• Smart indentation: Auto-indent based on context
• Problem matcher: Inline error and warning squiggles from the analyzer
• Auto tasks.json: When a workspace containing .fls files is opened for the first time, the extension automatically creates .vscode/tasks.json with run tasks (Ctrl+Shift+B to run the current file)

Code Intelligence

Hover a function, method, class, field, enum or constant to see its declaration, the comment written above it, and its parameter and return types:

// Persist the cache to disk as JSON. Returns false when the write fails.
fn Save(path: string): bool { ... }

Hovering Save shows that signature, that sentence, path: string, and Returns bool. Optional parameters (ttl?) are marked as optional, and hovering an imported name resolves through to the declaration it binds to rather than stopping at the import line. Any contiguous run of // comments directly above a declaration is used as its documentation - no special marker is needed.

Go to Definition (F12 / Ctrl+Click) jumps to the declaration of functions, methods, classes, enums, fields, constants and variables anywhere in the workspace. It is served from an index built once at startup and kept current as you type, so it also resolves declarations you have not saved yet.

Analyzer diagnostics run automatically: flarisvm --check analyses a file when it is opened and each time it is saved, and its warnings and syntax errors appear as squiggles with the analyzer's warning code attached. Problems reported inside an imported library are shown against that library's file. Run Flaris: Analyse Current File from the command palette to check on demand.

Debugging

Press F5 on a .fls file to debug it - no launch.json needed. Set breakpoints in the gutter, step with F10/F11, and inspect locals, object fields and array elements in the Variables pane.

Breakpoints can be added and removed while the program runs, the pause button interrupts a running program at the next source line, and Open Disassembly View shows the bytecode around the selected frame.

The VM speaks the Debug Adapter Protocol itself (flarisvm --dap=<port>), over a loopback socket. Each fiber appears as a thread, so the thread picker lets you look at any fiber's stack while the program is paused.

A launch.json is only needed to change the defaults:

{
  "type": "flaris",
  "request": "launch",
  "name": "Debug current Flaris file",
  "program": "${file}",
  "cwd": "${workspaceFolder}",
  "vmArgs": ["--libs=./libs"]
}

Notes:

• Debugging disables the JIT. A JIT-compiled function runs natively and never reports its source lines, so breakpoints inside one could not be reached; the VM says so on the Debug Console when it starts.
• A file compiled with --strip carries no line information and cannot be stopped in.
• Requires a flarisvm new enough to support --dap; older builds will report an unknown argument on the Debug Console.

Installation

Open Extensions (Ctrl+Shift+X / Cmd+Shift+X), search for Flaris, and click Install - or from a terminal:

code --install-extension flaris-lang.flaris

You also need the Flaris VM itself, which the extension runs and debugs:

curl -fsSL https://www.flaris-lang.org/install.sh | sh

See flaris-lang.org for Windows and manual installs.

Examples

Basic Example

// Fibonacci with recursion
fn fib(n) {
    if (n <= 1) {
        return n;
    }
    return fib(n - 1) + fib(n - 2);
}

fn Main() {
    Console.WriteLine(fib(10));
}

Classes and Inheritance

class Animal {
    fn Constructor(name) {
        this.name = name;
    }

    fn speak() {
        Console.WriteLine(this.name, "makes a sound.");
    }
}

class Dog : Animal {
    fn Constructor(name) {
        super.Constructor(name);
    }

    fn speak() {
        Console.WriteLine(this.name, "barks.");
    }
}

fn Main() {
    let d = new Dog("Rex");
    d.speak();
}

Async / Await

import { Http } from library("Http", "1.0");

fn async fetchData(url) {
    let response = await Http.GetAsync(url);
    return Json.Parse(response);
}

Fibers and Concurrency

fn Main() {
    let worker = Fiber.New(fn() {
        for (let i = 0; i < 5; i++) {
            Console.WriteLine("Work", i);
            yield i;
        }
    });

    Fiber.Resume(worker);
}

Error Handling

try {
    let data = Json.Parse(rawInput);
} catch (e) {
    Console.WriteLine("Parse failed:", e.Error, "code:", e.Code);
} finally {
    Console.WriteLine("Done.");
}

Approximate Equality

let x = 1.0 / 3.0;
if (x ≈ 0.333333) {
    Console.WriteLine("Close enough!");
}

JIT-compiled Functions

Eligible functions are JIT-compiled automatically - no keyword needed. Use typed parameters and return types; only arithmetic, comparisons, loops, array access, and Math.*/Char.* builtins are supported inside JIT-compiled functions - general calls are not. Run flarisvm --check <file> to see which functions can be JIT-compiled and why others cannot.

// Iterative inner loop compiled to native ARM64
fn sum(arr: [int], n: int) : int {
    let s: int = 0;
    iter (i from 0 to n - 1) {
        s = s + arr[i];
    }
    return s;
}

Keyboard Shortcuts

• Ctrl+/ (Mac: Cmd+/) - Toggle line comment
• Shift+Alt+A (Mac: Shift+Opt+A) - Toggle block comment
• Ctrl+Space - Trigger IntelliSense/snippets
• Tab - Expand snippet
• F12 / Ctrl+Click - Go to Definition

Language Reference

Keywords

Control Flow:   if, else, while, do, for, foreach, iter, from, to, in, is
                switch, case, default, break, continue, return, guard
Functions:      fn, async, yield, await, inline, static
Variables:      let, var, const, global
OOP:            class, new, this, super, enum
Modules:        import, export, as, library
Error Handling: try, catch, finally, throw
Constants:      nil, true, false
Word Operators: and, or
Debug:          breakpoint

Built-in Modules

Array       Buffer      Char        Class       Collections Console
Convert     Crypto      Debug       Directory   Event       Ffi
Fiber       File        FileWatch   Hash        Json        Math
Memory      Net         Object      Os          Path        Random
Regex       Scheduler   Stream      String      Time        Timers
Type        Util        VM

Operators

Arithmetic:   +  -  *  /  %  ^^  ++  --
Assignment:   =  +=  -=  *=  /=  %=  ^^=  <<=  >>=  &=  |=  ^=  ??=
Comparison:   ==  !=  <  >  <=  >=  ≈
Logical:      &&  ||  !  and  or
Bitwise:      &  |  ^  ~  <<  >>
Other:        ??  =>

Issues & Feedback

Bug reports and feature requests are welcome on the Flaris Discord, or via the contact address at flaris-lang.org.

For a bug, please include the Flaris version (flarisvm --version), your OS, and a minimal .fls script that reproduces it.

More Information

• Flaris Language Documentation
• VSCode Extension Guidelines
• TextMate Grammar Reference

License

MIT