> ## Documentation Index
> Fetch the complete documentation index at: https://differens.ossl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Kotlin

> Semantic diffing for Kotlin

## Kotlin extractor

The Kotlin extractor maps tree-sitter Kotlin CST nodes to canonical concepts. The Kotlin grammar declares no field names at all, so every name is recovered from the first identifier-like child: class names from `type_identifier`, function and variable names from `simple_identifier`.

### Detected concepts

| tree-sitter node type | Canonical concept |
| - | - |
| `class_declaration` | Class |
| `function_declaration` | Function |
| `property_declaration` | Variable |
| `variable_declaration` | Variable |
| `type_alias` | TypeDef |
| `import_header` | Import |
| `package_header` | Namespace |
| `call_expression` | CallExpression |
| `assignment` | Assignment |
| `jump_expression` | Return |
| `if_expression` | IfBlock |
| `when_expression` | SwitchBlock |
| `string_literal` | string\_literal |

### Example

Renaming a function:

```kotlin theme={null}
// old.kt
class Counter { fun total(n: Int): Int { return n + 1 } }
```

```kotlin theme={null}
// new.kt
class Counter { fun sum(n: Int): Int { return n + 1 } }
```

Running `differens old.kt new.kt`:

```
~ renamed function `total` to `sum` in class `Counter`
```

### Known limitations

* The grammar's missing field names mean label recovery is positional: a declaration with two identifier children can mislabel in exotic syntax.
* Extension functions report as functions; the receiver type is part of the structure, not the name.