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Zeus

Language Server

Zeus includes a built-in Language Server Protocol (LSP) implementation that provides IDE features for any compatible editor.

Features

Real-time Diagnostics

See errors and warnings as you type, before compilation.

Syntax Highlighting

Full syntax highlighting for Zeus code.

Code Completion

Intelligent suggestions for keywords, types, and symbols.

Unused Warnings

Warnings for unused variables, functions, and classes.

Formatting

Format Document and format-on-save, powered by the built-in formatter.

Available Now

Diagnostics

The language server reports errors in real-time:

  • Lexer errors — Invalid characters, unterminated strings
  • Parser errors — Syntax mistakes, unexpected tokens
  • Type errors — Type mismatches, invalid operations
  • Semantic errors — Undefined symbols, wrong argument counts

Example error:

function main(): i32 {
  let x: i32 = "hello";  // ❌ Error: type 'string' is not assignable to 'i32'
  return x;
}

Code Completion

Press Ctrl+Space (or Cmd+Space on Mac) to see suggestions:

Keywords:

  • Control flow: if, else, while, return
  • Declarations: let, const, function, class
  • Modifiers: public, private, export, import

Types:

  • Integers: i8, i16, i32, i64, u8, u16, u32, u64
  • Floats: f32, f64
  • Others: boolean, void

Symbols:

  • Variables in scope
  • Functions with parameter signatures
  • Available classes

Unused Warnings

The server warns about declarations that are never used:

function main(): i32 {
  let unused: i32 = 5;  // ⚠️ Warning: 'unused' is declared but never used
  let used: i32 = 10;
  return used;
}

Formatting

The server implements textDocument/formatting using the built-in formatter, so Format Document (Shift+Alt+F) and format-on-save work in any LSP client. The VS Code extension enables format-on-save for .zs files by default; disable it per-workspace with:

"[zeus]": { "editor.formatOnSave": false }

The server never returns an edit for code that doesn’t parse, so a file with errors is left untouched.

Running the Server

Via VS Code

  1. Install the Zeus VS Code extension (see IDE Setup)
  2. Open any .zs file
  3. The server starts automatically

Standalone Mode

For other editors, run the server directly:

Terminal window
zeus lsp --stdio

The server communicates via standard input/output using the LSP protocol.

Editor Configuration

VS Code

See the full IDE Setup guide.

Neovim

Using nvim-lspconfig:

local lspconfig = require('lspconfig')
local configs = require('lspconfig.configs')


configs.zeus = {
  default_config = {
    cmd = { 'zeus', 'lsp', '--stdio' },
    filetypes = { 'zeus' },
    root_dir = lspconfig.util.find_git_ancestor,
  },
}


lspconfig.zeus.setup{}

Emacs

Using lsp-mode:

(lsp-register-client
  (make-lsp-client
    :new-connection (lsp-stdio-connection '("zeus" "lsp" "--stdio"))
    :major-modes '(zeus-mode)
    :server-id 'zeus-ls))

Sublime Text

Using LSP package:

{
  "clients": {
    "zeus": {
      "command": ["zeus", "lsp", "--stdio"],
      "selector": "source.zeus"
    }
  }
}

Coming Soon

Hover Information

Hover over symbols to see:

  • Type information
  • Documentation
  • Function signatures

Go to Definition

Jump to where a symbol is defined:

  • Cmd+Click on a symbol
  • Works across files for imports

Find References

Find all usages of a symbol throughout the project.

Rename Symbol

Safely rename variables, functions, or classes across the entire codebase.

Document Symbols

Outline view showing:

  • Functions
  • Classes
  • Top-level variables

Signature Help

Parameter hints while typing function calls:

add(|)  // Shows: add(a: i32, b: i32): i32

(Available now) Document Formatting

Now implemented — see Formatting above.

Troubleshooting

Server Not Starting

  1. Ensure Zeus is installed and in your PATH:

    Terminal window
    which zeus
    zeus --version

  2. Check the path in your editor configuration

  3. Look for errors in the editor’s output panel

No Diagnostics

  1. Verify the file has a .zs extension
  2. Check that the language server process is running:
    Terminal window
    ps aux | grep "zeus lsp"
  3. Try reloading the editor window

Slow Response

The language server recompiles on each change. For very large files, there may be a delay. This will be optimized in future releases.

Architecture

The Zeus LSP implementation:

  1. Receives file changes from the editor
  2. Lexes and parses the modified files
  3. Generates IR and runs type checking
  4. Collects errors and warnings
  5. Sends diagnostics back to the editor

All of this happens on every keystroke, providing instant feedback.

See Also