rust/docs/user/features.md

This documents is an index of features that 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 function 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 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.

Status

Shows internal statistic about memory usage of rust-analyzer

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

Assists (Code Actions)

These are triggered in a particular context via light bulb. We use custom code on the VS Code side to be able to position cursor. <|> signifies cursor

See assists.md

• Add #[derive]

// before:
struct Foo {
    <|>x: i32
}
// after:
#[derive(<|>)]
struct Foo {
    x: i32
}

• Add impl

// before:
struct Foo<'a, T: Debug> {
    <|>t: T
}
// after:
struct Foo<'a, T: Debug> {
    t: T
}

impl<'a, T: Debug> Foo<'a, T> {
    <|>
}

• Add missing impl members

// before:
trait Foo {
    fn foo(&self);
    fn bar(&self);
    fn baz(&self);
}

struct S;

impl Foo for S {
    fn bar(&self) {}
    <|>
}

// after:
trait Foo {
    fn foo(&self);
    fn bar(&self);
    fn baz(&self);
}

struct S;

impl Foo for S {
    fn bar(&self) {}
    fn foo(&self) { unimplemented!() }
    fn baz(&self) { unimplemented!() }<|>
}

• Apply De Morgan's law

// before:
fn example(x: bool) -> bool {
    !x || !x
}

// after:
fn example(x: bool) -> bool {
    !(x && x)
}

• Import path

// before:
impl std::fmt::Debug<|> for Foo {
}

// after:
use std::fmt::Debug;

impl Debug<|> for Foo {
}

• Change Visibility

// before:
<|>fn foo() {}

// after:
<|>pub(crate) fn foo() {}

// after:
<|>pub fn foo() {}

• Fill match arms

// before:
enum A {
    As,
    Bs,
    Cs(String),
    Ds(String, String),
    Es{x: usize, y: usize}
}

fn main() {
    let a = A::As;
    match a<|> {}
}

// after:
enum A {
    As,
    Bs,
    Cs(String),
    Ds(String, String),
    Es{x: usize, y: usize}
}

fn main() {
    let a = A::As;
    match <|>a {
        A::As => (),
        A::Bs => (),
        A::Cs(_) => (),
        A::Ds(_, _) => (),
        A::Es{x, y} => (),
    }
}

• Fill struct fields

// before:
struct S<'a, D> {
    a: u32,
    b: String,
    c: (i32, i32),
    d: D,
    r: &'a str,
}

fn main() {
    let s = S<|> {}
}

// after:
struct S<'a, D> {
    a: u32,
    b: String,
    c: (i32, i32),
    d: D,
    r: &'a str,
}

fn main() {
    let s = <|>S {
        a: (),
        b: (),
        c: (),
        d: (),
        r: (),
    }
}

• Flip ,

// before:
fn foo(x: usize,<|> dim: (usize, usize)) {}
// after:
fn foo(dim: (usize, usize), x: usize) {}

• Introduce variable:

// before:
fn foo() {
    foo(<|>1 + 1<|>);
}

// after:
fn foo() {
    let var_name = 1 + 1;
    foo(var_name);
}

• Inline local variable:

// before:
fn foo() {
    let a<|> = 1 + 1;
    let b = a * 10;
}

// after:
fn foo() {
    let b = (1 + 1) * 10;
}

• Remove dbg!

// before:
fn foo(n: usize) {
    if let Some(_) = dbg!(n.<|>checked_sub(4)) {
        // ...
    }
}

// after:
fn foo(n: usize) {
    if let Some(_) = n.<|>checked_sub(4) {
        // ...
    }
}

• Replace if-let with match:

// before:
impl VariantData {
    pub fn is_struct(&self) -> bool {
        if <|>let VariantData::Struct(..) = *self {
            true
        } else {
            false
        }
    }
}

// after:
impl VariantData {
    pub fn is_struct(&self) -> bool {
        <|>match *self {
            VariantData::Struct(..) => true,
            _ => false,
        }
    }
}

• Split import

// before:
use crate:<|>:db::{RootDatabase, FileSymbol};
// after:
use crate::{<|>db::{RootDatabase, FileSymbol}};

• Flip binary expression

// before:
fn foo() {
    if 1 <<|> 2 {
        println!("Who would have thought?");
    }
}
// after:
fn foo() {
    if 2 ><|> 1 {
        println!("Who would have thought?");
    }
}

• Add explicit type

// before:
fn foo() {
    let t<|> = (&2, Some(1));
}
// after:
fn foo() {
    let t<|>: (&i32, Option<i32>) = (&2, Some(1));
}

• Move guard expression to match arm body

// before:
fn f() {
    match x {
        <|>y @ 4 | y @ 5    if y > 5 => true,
        _ => false
    }
}
// after:
fn f() {
    match x {
        y @ 4 | y @ 5 => if y > 5 { <|>true },
        _ => false
    }
}

• Move if condition to match arm guard

// before:
fn f() {
    let mut t = 'a';
    let chars = "abcd";
    match t {
        '\r' => if chars.clone().next().is_some() {
            t = 'e';<|>
            false
        },
        _ => true
    }
}

// after:
fn f() {
    let mut t = 'a';
    let chars = "abcd";
    match t {
        '\r' <|>if chars.clone().next().is_some() => {
            t = 'e';
            false
        },
        _ => true
    }
}

• Move type bounds to where clause

// before:
fn foo<T: u32, F: FnOnce(T) -> T>() {}

// after:
fn foo<T, F>() where T: u32, F: FnOnce(T) -> T {}

• Make raw string unescaped

// before:
fn f() {
    let s = <|>"ab\ncd";
}

// after:
fn f() {
    let s = <|>r#"ab
cd"#;
}

• Make usual string

// before:
fn f() {
    let s = <|>r#"abcd"#;
}

// after:
fn f() {
    let s = <|>"abcd";
}

• Add hash

// before:
fn f() {
    let s = <|>r"abcd";
}

// after:
fn f() {
    let s = <|>r#"abcd"#;
}

• Remove hash

// before:
fn f() {
    let s = <|>r#"abcd"#;
}

// after:
fn f() {
    let s = <|>r"abcd";
}

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 function takes arguments, cursor is positioned inside the parenthesis.

There are postifx completions, which can be triggerd by typing something like foo().if. The word after . determines postifx completion, possible variants are:

• expr.if -> if expr {}
• expr.match -> match expr {}
• expr.while -> while expr {}
• 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(){}

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.