case idx.idx => simpa [encodeSource] using λ hhd htl ↦ ⟨encodeSource_inj hhd, encodeSource_inj htl⟩
s₀ s₁ hd✝¹ tl✝¹ : Source
h₀ : s₀ = Source.idx hd✝¹ tl✝¹
hd✝ tl✝ : Source
h₁ : s₁ = Source.idx hd✝ tl✝
⊢ encodeSource (Source.idx hd✝¹ tl✝¹) = encodeSource (Source.idx hd✝ tl✝) → Source.idx hd✝¹ tl✝¹ = Source.idx hd✝ tl✝
no goals