Rust - Differens

Rust extractor

The Rust extractor maps tree-sitter Rust CST nodes to canonical concepts. It detects structural changes at the item level: functions, structs, enums, traits, and their members.

Detected concepts

tree-sitter node type	Canonical concept
`function_item`	Function
`struct_item`	Struct
`enum_item`	Enum
`trait_item`	Trait
`impl_item`	Implementation
method inside `impl`	Method
`use_declaration`	Import
`mod_item`	Module declaration
`macro_definition`	Macro
`let_declaration` (top-level)	Variable
`const_item`	Constant
`type_item`	Type alias

Example

Two versions of a Rust module. One renames a function and adds a struct field:

// old.rs
pub fn parse_config(path: &str) -> Config {
    let contents = std::fs::read_to_string(path)?;
    toml::from_str(&contents).unwrap()
}

pub struct Config {
    pub workers: u32,
}

// new.rs
pub fn load_config(path: &str) -> Result<Config, Error> {
    let contents = std::fs::read_to_string(path)?;
    toml::from_str(&contents).map_err(Error::from)
}

pub struct Config {
    pub workers: u32,
    pub timeout_ms: u64,
}

Running differens old.rs new.rs:

  ~ renamed function `parse_config` to `load_config`
  ~ changed value of return type from `Config` to `Result<Config, Error>`
  + added field `timeout_ms` in struct `Config`
3 modifications

Known limitations

Macro expansion is not followed. The extractor works on the surface AST, so code generated by macros (derive, proc macros) is invisible to the diff.
impl blocks are matched to their type, but orphan impls (impl blocks in separate files) require cross-file correlation to be active.
Attribute changes (#[derive(...)], #[cfg(...)]) are reported at the item level, not as separate edit actions.