Go - Differens

The Go extractor maps tree-sitter Go CST nodes to canonical concepts. It detects structural changes at the package level: functions, methods, types, and interfaces.

Detected concepts

tree-sitter node type	Canonical concept
`function_declaration`	Function
`method_declaration`	Method
`type_declaration`	TypeDecl
`struct_type`	Struct
`interface_type`	Interface
`import_declaration`	Import
`var_declaration` (top-level)	Variable
`const_declaration`	Constant
`type_alias`	type_alias (unmapped)

Example

Two versions of a Go package. The second version moves the method body into a new helper function:

old.go

package users

import (
    "errors"
    "strings"
)

type Store struct{}

func (s *Store) ValidateEmail(email string) error {
    if !strings.Contains(email, "@") {
        return errors.New("invalid email")
    }
    if len(email) > 254 {
        return errors.New("email too long")
    }
    return nil
}

new.go

package users

import (
    "errors"
    "strings"
)

type Store struct{}

func (s *Store) ValidateEmail(email string) error {
    return validateEmail(email)
}

func validateEmail(email string) error {
    if !strings.Contains(email, "@") {
        return errors.New("invalid email")
    }
    if len(email) > 254 {
        return errors.New("email too long")
    }
    return nil
}

Running differens old.go new.go:

  + added function `validateEmail`
  ~ modified method `Store.ValidateEmail` (`len` → `validateEmail`, 1 removal, 1 addition)

Methods include their receiver type in human and LLM output, such as Store.ValidateEmail. Matching uses receiver identity to keep same-named methods on different types apart, including when a helper takes over an existing body. This example reports the new helper and the method edit; it does not classify an extraction as a separate action.

Known limitations

Implicit interfaces (structural typing) are not tracked. An interface implemented by coincidence is not flagged as a relationship.
Package and import changes are syntax edits. The correlator detects supported declaration moves across files; it does not resolve package relationships.
Cgo blocks are treated as opaque; the extractor does not descend into C preambles.
Generic type parameters (Go 1.18+) are parsed structurally but type parameter renames may not be detected as renames (reported as structural changes).

Semantic Extractors

Tier Adapters

Go

Detected concepts

Example

Known limitations