fails-on-a-copy-whose-argument-reads-to-a-bare-symbol-when-not-deferring.yaml

# SPDX-FileCopyrightText: Copyright (c) 2025 Objectionary.com
# SPDX-License-Identifier: MIT
---
# yamllint disable rule:line-length
# The fork the deferral of #1892 gets through, under an 'unfold' line that
# does not say 'defer: true' (#1921). The line morphs the φ of the copy
# 'step( tup ↦ Φ.items.tail )', which asks the bare symbol '𝜎1' for 'next',
# and the firing gets stuck on that symbol, as it did since '--deep' was gone.
symbolic: |
  - λ: L_fork
    morph:
      𝑛1: $.a
      𝑛2: $.b
    unfold:
      𝑛3: 𝑛2
    join:
      𝑛4: [𝑛1, 𝑛3]
    𝑛: ⟦ φ ↦ 𝑛4 ⟧
location: 'Q.y'
input: '⟦ step(tup) ↦ ⟦ φ ↦ tup.next ⟧, items ↦ ⟦ tail ↦ ⟦ λ ⤍ 𝜎1 ⟧ ⟧, y ↦ ⟦ a ↦ ⟦ λ ⤍ 𝜎2 ⟧, b ↦ Φ.step( tup ↦ Φ.items.tail ), λ ⤍ L_fork ⟧.φ ⟧'
fails: "No entry of --symbolic answers the λ function '𝜎1'"
protocol: |
  𝕄(Φ.y):
    𝔼(L_fork):
      𝑛1·1 := 𝜎2:λ  # 𝕄(ξ.a)
      𝕄(Φ.a🌵1):
        𝑛·1·1 := Φ.step( tup ↦ Φ.items.tail )
      𝑛2·1 := 𝑛·1·1  # 𝕄(ξ.b)
      𝕄(Φ.a🌵2):
        unanswered(𝜎1)  # 𝕄(𝜎1:λ)
      stuck(𝜎1)