void-box: Skill for Claude Code

rust-analyzer Structural Search and Replace (SSR)

Use rust-analyzer's SSR for semantic code transformations in Rust projects. SSR matches code by AST structure and semantic meaning, not text.

When to Use

• Refactoring patterns across a codebase (rename, restructure, migrate APIs)
• Converting between equivalent forms (UFCS to method calls, struct literals to constructors)
• Finding all usages of a specific code pattern
• Semantic-aware search that understands type resolution

Basic Syntax

<search_pattern> ==>> <replacement_pattern>

Placeholders capture matched code:

• $name — matches any expression/type/pattern in that position
• ${name:constraint} — matches with constraints

Common Patterns

Swap function arguments

foo($a, $b) ==>> foo($b, $a)

Convert struct literal to constructor

Foo { a: $a, b: $b } ==>> Foo::new($a, $b)

UFCS to method call

Foo::method($receiver, $arg) ==>> $receiver.method($arg)

Method to UFCS

$receiver.method($arg) ==>> Foo::method($receiver, $arg)

Wrap in Result

Option<$t> ==>> Result<$t, Error>

Unwrap to expect

$e.unwrap() ==>> $e.expect("TODO")

Match only literals

Some(${a:kind(literal)}) ==>> ...

Match non-literals

Some(${a:not(kind(literal))}) ==>> ...

Constraints

Constraint	Matches
kind(literal)	Literal values: 42, "foo", true
not(...)	Negates inner constraint

How to Invoke

Via Comment Assist (Interactive)

Write a comment containing an SSR rule, then trigger code actions:

// foo($a, $b) ==>> bar($b, $a)

Actions appear: "Apply SSR in file" or "Apply SSR in workspace"

Via LSP Command

{
  "command": "rust-analyzer.ssr",
  "arguments": [{
    "query": "foo($a) ==>> bar($a)",
    "parseOnly": false
  }]
}

Via CLI

rust-analyzer ssr 'foo($a, $b) ==>> bar($b, $a)'

Key Behaviors

Path Resolution: Paths match semantically. foo::Bar matches Bar if imported from foo.