From d53d1426a5432b2f2cb46e2773752315f59f0c60 Mon Sep 17 00:00:00 2001
From: KristofferC <kristoffer.carlsson@juliacomputing.com>
Date: Mon, 13 May 2024 13:34:55 +0200
Subject: [PATCH] Revert "Support broadcasting over structured block matrices
 (#53909)"

This reverts commit 243ebc389eec78f060a47c53375b3fd48c462d76.
---
 .../LinearAlgebra/src/structuredbroadcast.jl  |  6 +-
 stdlib/LinearAlgebra/test/special.jl          |  1 -
 .../LinearAlgebra/test/structuredbroadcast.jl | 58 -------------------
 3 files changed, 2 insertions(+), 63 deletions(-)

diff --git a/stdlib/LinearAlgebra/src/structuredbroadcast.jl b/stdlib/LinearAlgebra/src/structuredbroadcast.jl
index 248ec3105de30..8f5221f4e6e41 100644
--- a/stdlib/LinearAlgebra/src/structuredbroadcast.jl
+++ b/stdlib/LinearAlgebra/src/structuredbroadcast.jl
@@ -8,8 +8,8 @@ struct StructuredMatrixStyle{T} <: Broadcast.AbstractArrayStyle{2} end
 StructuredMatrixStyle{T}(::Val{2}) where {T} = StructuredMatrixStyle{T}()
 StructuredMatrixStyle{T}(::Val{N}) where {T,N} = Broadcast.DefaultArrayStyle{N}()
 
-const StructuredMatrix{T} = Union{Diagonal{T},Bidiagonal{T},SymTridiagonal{T},Tridiagonal{T},LowerTriangular{T},UnitLowerTriangular{T},UpperTriangular{T},UnitUpperTriangular{T}}
-for ST in (Diagonal,Bidiagonal,SymTridiagonal,Tridiagonal,LowerTriangular,UnitLowerTriangular,UpperTriangular,UnitUpperTriangular)
+const StructuredMatrix = Union{Diagonal,Bidiagonal,SymTridiagonal,Tridiagonal,LowerTriangular,UnitLowerTriangular,UpperTriangular,UnitUpperTriangular}
+for ST in Base.uniontypes(StructuredMatrix)
     @eval Broadcast.BroadcastStyle(::Type{<:$ST}) = $(StructuredMatrixStyle{ST}())
 end
 
@@ -133,7 +133,6 @@ fails as `zero(::Tuple{Int})` is not defined. However,
 iszerodefined(::Type) = false
 iszerodefined(::Type{<:Number}) = true
 iszerodefined(::Type{<:AbstractArray{T}}) where T = iszerodefined(T)
-iszerodefined(::Type{<:UniformScaling{T}}) where T = iszerodefined(T)
 
 count_structedmatrix(T, bc::Broadcasted) = sum(Base.Fix2(isa, T), Broadcast.cat_nested(bc); init = 0)
 
@@ -147,7 +146,6 @@ fzero(::Type{T}) where T = T
 fzero(r::Ref) = r[]
 fzero(t::Tuple{Any}) = t[1]
 fzero(S::StructuredMatrix) = zero(eltype(S))
-fzero(::StructuredMatrix{<:AbstractMatrix{T}}) where {T<:Number} = haszero(T) ? zero(T)*I : missing
 fzero(x) = missing
 function fzero(bc::Broadcast.Broadcasted)
     args = map(fzero, bc.args)
diff --git a/stdlib/LinearAlgebra/test/special.jl b/stdlib/LinearAlgebra/test/special.jl
index 43e114e5b97c1..c6fb187add3fb 100644
--- a/stdlib/LinearAlgebra/test/special.jl
+++ b/stdlib/LinearAlgebra/test/special.jl
@@ -111,7 +111,6 @@ Random.seed!(1)
         struct TypeWithZero end
         Base.promote_rule(::Type{TypeWithoutZero}, ::Type{TypeWithZero}) = TypeWithZero
         Base.convert(::Type{TypeWithZero}, ::TypeWithoutZero) = TypeWithZero()
-        Base.zero(x::Union{TypeWithoutZero, TypeWithZero}) = zero(typeof(x))
         Base.zero(::Type{<:Union{TypeWithoutZero, TypeWithZero}}) = TypeWithZero()
         LinearAlgebra.symmetric(::TypeWithoutZero, ::Symbol) = TypeWithoutZero()
         Base.transpose(::TypeWithoutZero) = TypeWithoutZero()
diff --git a/stdlib/LinearAlgebra/test/structuredbroadcast.jl b/stdlib/LinearAlgebra/test/structuredbroadcast.jl
index e4e78ad94102c..26c6faf81f23c 100644
--- a/stdlib/LinearAlgebra/test/structuredbroadcast.jl
+++ b/stdlib/LinearAlgebra/test/structuredbroadcast.jl
@@ -298,62 +298,4 @@ end
 # structured broadcast with function returning non-number type
 @test tuple.(Diagonal([1, 2])) == [(1,) (0,); (0,) (2,)]
 
-@testset "broadcast over structured matrices with matrix elements" begin
-    function standardbroadcastingtests(D, T)
-        M = [x for x in D]
-        Dsum = D .+ D
-        @test Dsum isa T
-        @test Dsum == M .+ M
-        Dcopy = copy.(D)
-        @test Dcopy isa T
-        @test Dcopy == D
-        Df = float.(D)
-        @test Df isa T
-        @test Df == D
-        @test eltype(eltype(Df)) <: AbstractFloat
-        @test (x -> (x,)).(D) == (x -> (x,)).(M)
-        @test (x -> 1).(D) == ones(Int,size(D))
-        @test all(==(2), ndims.(D))
-        @test_throws MethodError size.(D)
-    end
-    @testset "Diagonal" begin
-        @testset "square" begin
-            A = [1 3; 2 4]
-            D = Diagonal([A, A])
-            standardbroadcastingtests(D, Diagonal)
-            @test sincos.(D) == sincos.(Matrix{eltype(D)}(D))
-            M = [x for x in D]
-            @test cos.(D) == cos.(M)
-        end
-
-        @testset "different-sized square blocks" begin
-            D = Diagonal([ones(3,3), fill(3.0,2,2)])
-            standardbroadcastingtests(D, Diagonal)
-        end
-
-        @testset "rectangular blocks" begin
-            D = Diagonal([ones(Bool,3,4), ones(Bool,2,3)])
-            standardbroadcastingtests(D, Diagonal)
-        end
-
-        @testset "incompatible sizes" begin
-            A = reshape(1:12, 4, 3)
-            B = reshape(1:12, 3, 4)
-            D1 = Diagonal(fill(A, 2))
-            D2 = Diagonal(fill(B, 2))
-            @test_throws DimensionMismatch D1 .+ D2
-        end
-    end
-    @testset "Bidiagonal" begin
-        A = [1 3; 2 4]
-        B = Bidiagonal(fill(A,3), fill(A,2), :U)
-        standardbroadcastingtests(B, Bidiagonal)
-    end
-    @testset "UpperTriangular" begin
-        A = [1 3; 2 4]
-        U = UpperTriangular([(i+j)*A for i in 1:3, j in 1:3])
-        standardbroadcastingtests(U, UpperTriangular)
-    end
-end
-
 end