join-renames-sibling-references.yaml

# SPDX-FileCopyrightText: Copyright (c) 2025 Objectionary.com
# SPDX-License-Identifier: MIT
---
input: |
  ⟦ a ↦ ⟦ x ↦ "first" ⟧, b ↦ ⟦ x ↦ "second", y ↦ ξ.x ⟧ ⟧
output: |-
  ⟦ c ↦ ⟦ x ↦ "first", a🌵0 ↦ "second", y ↦ ξ.a🌵0 ⟧ ⟧
rules:
  custom:
    - name: join keeps a sibling reference with its binding
      pattern: |
        ⟦ a ↦ ⟦ !B1 ⟧, b ↦ ⟦ !B2 ⟧ ⟧
      result: |
        ⟦ c ↦ ⟦ !B3 ⟧ ⟧
      where:
        - meta: '!B3'
          function: join
          args:
            - '!B1'
            - '!B2'