rust-analyzer/docs/user/features.md

This document is an index of features that the rust-analyzer language server provides. Shortcuts are for the default VS Code layout. If there's no shortcut, you can use Ctrl+Shift+P to search for the corresponding action.

Workspace Symbol ctrl+t

Uses fuzzy-search to find types, modules and functions by name across your project and dependencies. This is the most useful feature, which improves code navigation tremendously. It mostly works on top of the built-in LSP functionality, however # and * symbols can be used to narrow down the search. Specifically,

• Foo searches for Foo type in the current workspace
• foo# searches for foo function in the current workspace
• Foo* searches for Foo type among dependencies, including stdlib
• foo#* searches for foo function among dependencies

That is, # switches from "types" to all symbols, * switches from the current workspace to dependencies.

Document Symbol ctrl+shift+o

Provides a tree of the symbols defined in the file. Can be used to

• fuzzy search symbol in a file (super useful)
• draw breadcrumbs to describe the context around the cursor
• draw outline of the file

On Typing Assists

Some features trigger on typing certain characters:

• typing let = tries to smartly add ; if = is followed by an existing expression
• Enter inside comments automatically inserts ///
• typing . in a chain method call auto-indents

Extend Selection

Extends the current selection to the encompassing syntactic construct (expression, statement, item, module, etc). It works with multiple cursors. This is a relatively new feature of LSP: https://github.com/Microsoft/language-server-protocol/issues/613, check your editor's LSP library to see if this feature is supported.

Go to Definition

Navigates to the definition of an identifier.

Go to Implementation

Navigates to the impl block of structs, enums or traits. Also implemented as a code lens.

Go to Type Defintion

Navigates to the type of an identifier.

Commands ctrl+shift+p

Run

Shows a popup suggesting to run a test/benchmark/binary at the current cursor location. Super useful for repeatedly running just a single test. Do bind this to a shortcut!

Parent Module

Navigates to the parent module of the current module.

Matching Brace

If the cursor is on any brace (<>(){}[]) which is a part of a brace-pair, moves cursor to the matching brace. It uses the actual parser to determine braces, so it won't confuse generics with comparisons.

Join Lines

Join selected lines into one, smartly fixing up whitespace and trailing commas.

Show Syntax Tree

Shows the parse tree of the current file. It exists mostly for debugging rust-analyzer itself.

Expand Macro Recursively

Shows the full macro expansion of the macro at current cursor.

Status

Shows internal statistic about memory usage of rust-analyzer.

Show RA Version

Show current rust-analyzer version.

Toggle inlay hints

Toggle inlay hints view for the current workspace. It is recommended to assign a shortcut for this command to quickly turn off inlay hints when they prevent you from reading/writing the code.

Run Garbage Collection

Manually triggers GC.

Start Cargo Watch

Start cargo watch for live error highlighting. Will prompt to install if it's not already installed.

Stop Cargo Watch

Stop cargo watch.

Structural Seach and Replace

Search and replace with named wildcards that will match any expression. The syntax for a structural search replace command is <search_pattern> ==>> <replace_pattern>. A $<name>:expr placeholder in the search pattern will match any expression and $<name> will reference it in the replacement. Available via the command rust-analyzer.ssr.

// Using structural search replace command [foo($a:expr, $b:expr) ==>> ($a).foo($b)]

// BEFORE
String::from(foo(y + 5, z))

// AFTER
String::from((y + 5).foo(z))

Assists (Code Actions)

Assists, or code actions, are small local refactorings, available in a particular context. They are usually triggered by a shortcut or by clicking a light bulb icon in the editor.

See assists.md for the list of available assists.

Magic Completions

In addition to usual reference completion, rust-analyzer provides some ✨magic✨ completions as well:

Keywords like if, else while, loop are completed with braces, and cursor is placed at the appropriate position. Even though if is easy to type, you still want to complete it, to get { } for free! return is inserted with a space or ; depending on the return type of the function.

When completing a function call, () are automatically inserted. If a function takes arguments, the cursor is positioned inside the parenthesis.

There are postfix completions, which can be triggered by typing something like foo().if. The word after . determines postfix completion. Possible variants are:

• expr.if -> if expr {} or if let ... {} for Option or Result
• expr.match -> match expr {}
• expr.while -> while expr {} or while let ... {} for Option or Result
• expr.ref -> &expr
• expr.refm -> &mut expr
• expr.not -> !expr
• expr.dbg -> dbg!(expr)

There also snippet completions:

Inside Expressions

• pd -> println!("{:?}")
• ppd -> println!("{:#?}")

Inside Modules

• tfn -> #[test] fn f(){}
• tmod ->

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_fn() {}
}

Code Highlighting

Experimental feature to let rust-analyzer highlight Rust code instead of using the default highlighter.

Rainbow Highlighting

Experimental feature that, given code highlighting using rust-analyzer is active, will pick unique colors for identifiers.

Code hints

Rust-analyzer has two types of hints to show the information about the code:

• hover hints, appearing on hover on any element.

These contain extended information on the hovered language item.

• inlay hints, shown near the element hinted directly in the editor.

Two types of inlay hints are displayed currently:

• type hints, displaying the minimal information on the type of the expression (if the information is available)
• method chaining hints, type information for multi-line method chains
• parameter name hints, displaying the names of the parameters in the corresponding methods

VS Code

In VS Code, the following settings can be used to configure the inlay hints:

• rust-analyzer.inlayHints.typeHints - enable hints for inferred types.
• rust-analyzer.inlayHints.chainingHints - enable hints for inferred types on method chains.
• rust-analyzer.inlayHints.parameterHints - enable hints for function parameters.
• rust-analyzer.inlayHints.maxLength — shortens the hints if their length exceeds the value specified. If no value is specified (null), no shortening is applied.

Note: VS Code does not have native support for inlay hints yet and the hints are implemented using decorations. This approach has limitations, the caret movement and bracket highlighting near the edges of the hint may be weird: 1, 2.