Installing the Brass LSP server

Brass provides an LSP server implementation.

Run the following command to install czls:

./x cargo install --path crates/brass_language_server

For projects managed with czpm, configure your editor to launch czpm lsp rather than czls directly: it resolves the dependencies declared in package.toml before starting the server, and in a directory without a package.toml it starts the plain server, so the same configuration works everywhere.

When diagnostics update

Type diagnostics are published when the file is saved, and when it is first opened. While you type, the server only re-parses, so syntax errors still appear immediately: a half-typed line is a syntax error long before it is a type error.

Type inference re-checks the whole module graph, which is too much work to redo on every keystroke. Editing clears the previous check’s type diagnostics rather than leaving them behind: their positions no longer describe the text on screen.

Hover, completion and go-to-definition are unaffected: each request analyzes the current text, saved or not.