Milo

Appearance

IDE Setup ​

Milo includes an LSP server with diagnostics, hover, go-to-definition, and formatting. It is a subcommand of the compiler — milo lsp — so there is no separate daemon to install.

VS Code ​

Install Milo Language from the Marketplace (or from Open VSX in Cursor, VSCodium, Windsurf).

The extension launches milo lsp, so install the compiler first. It looks for milo in ~/.local/bin, ~/.milo/bin, Homebrew, /usr/local/bin, then PATH. If yours lives somewhere else:

jsonc
// settings.json
"milo.path": "/path/to/milo"

What you get ​

  • Diagnostics — type errors, move violations, and syntax errors as you type
  • Hover — type information on any expression
  • Go-to-definition — jump to function/struct/enum definitions, including into the standard library
  • Format on save — runs the same formatter as milo fmt, so the editor and the CLI can't disagree
  • Syntax highlighting — via the bundled TextMate grammar

Other editors ​

Point any LSP client at:

bash
milo lsp

Working on the compiler ​

From a checkout, build and load the extension locally:

bash
cd editors/vscode && bun install && bun run build
bun run package && code --install-extension milo-lang-*.vsix

With no milo on your PATH the extension falls back to running the checkout's compiler through bun, which is what makes F5 (Extension Development Host) pick up uncommitted compiler changes. To point it at a specific checkout, set milo.compilerRoot to the directory containing src/main.ts.