From 4b2c810df590501995948259682e5e8feee95f9c Mon Sep 17 00:00:00 2001
From: Frames White <me@oxinabox.net>
Date: Wed, 28 Feb 2024 08:54:06 +0800
Subject: [PATCH] Bools have no tangent

---
 src/tangent_types/abstract_zero.jl  | 3 +++
 test/tangent_types/abstract_zero.jl | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/src/tangent_types/abstract_zero.jl b/src/tangent_types/abstract_zero.jl
index 30bdba54f..a78e949dc 100644
--- a/src/tangent_types/abstract_zero.jl
+++ b/src/tangent_types/abstract_zero.jl
@@ -111,6 +111,7 @@ In general, it is more likely to produce a structural tangent.
 function zero_tangent end
 
 zero_tangent(x::Number) = zero(x)
+zero_tangent(x::Bool) = NoTangent()
 
 function zero_tangent(x::MutableTangent{P}) where {P}
     zb = backing(zero_tangent(backing(x)))
@@ -178,6 +179,8 @@ end
 
 # Sad heauristic methods we need because of unassigned values
 guess_zero_tangent_type(::Type{T}) where {T<:Number} = T
+guess_zero_tangent_type(::Type{Bool}) = NoTangent()
+
 guess_zero_tangent_type(::Type{T}) where {T<:Integer} = typeof(float(zero(T)))
 function guess_zero_tangent_type(::Type{<:Array{T,N}}) where {T,N}
     return Array{guess_zero_tangent_type(T),N}
diff --git a/test/tangent_types/abstract_zero.jl b/test/tangent_types/abstract_zero.jl
index b7d2eba5c..7da7cfadc 100644
--- a/test/tangent_types/abstract_zero.jl
+++ b/test/tangent_types/abstract_zero.jl
@@ -165,6 +165,8 @@ end
     @testset "basics" begin
         @test zero_tangent(1) === 0
         @test zero_tangent(1.0) === 0.0
+        @test zero_tangent(true) === NoTangent()
+
         mutable struct MutDemo
             x::Float64
         end