From 4498570abcd2e2e52745df79736e5df5c4cc7e6d Mon Sep 17 00:00:00 2001
From: Sheehan Olver <solver@mac.com>
Date: Tue, 28 Mar 2023 21:11:03 +0100
Subject: [PATCH] Fix #97 by adding promote_rules (#234)

---
 src/FillArrays.jl | 13 ++++++++++++-
 test/runtests.jl  | 17 +++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/FillArrays.jl b/src/FillArrays.jl
index b6f43624..7abc8236 100644
--- a/src/FillArrays.jl
+++ b/src/FillArrays.jl
@@ -6,7 +6,7 @@ import Base: size, getindex, setindex!, IndexStyle, checkbounds, convert,
     +, -, *, /, \, diff, sum, cumsum, maximum, minimum, sort, sort!,
     any, all, axes, isone, iterate, unique, allunique, permutedims, inv,
     copy, vec, setindex!, count, ==, reshape, _throw_dmrs, map, zero,
-    show, view, in, mapreduce, one, reverse, promote_op
+    show, view, in, mapreduce, one, reverse, promote_op, promote_rule
 
 import LinearAlgebra: rank, svdvals!, tril, triu, tril!, triu!, diag, transpose, adjoint, fill!,
     dot, norm2, norm1, normInf, normMinusInf, normp, lmul!, rmul!, diagzero, AdjointAbsVec, TransposeAbsVec,
@@ -34,6 +34,7 @@ const AbstractFillVecOrMat{T} = Union{AbstractFillVector{T},AbstractFillMatrix{T
 
 ==(a::AbstractFill, b::AbstractFill) = axes(a) == axes(b) && getindex_value(a) == getindex_value(b)
 
+
 @inline function _fill_getindex(F::AbstractFill, kj::Integer...)
     @boundscheck checkbounds(F, kj...)
     getindex_value(F)
@@ -273,6 +274,14 @@ for (Typ, funcs, func) in ((:Zeros, :zeros, :zero), (:Ones, :ones, :one))
         copy(F::$Typ) = F
 
         getindex(F::$Typ{T,0}) where T = getindex_value(F)
+
+        promote_rule(::Type{$Typ{T, N, Axes}}, ::Type{$Typ{V, N, Axes}}) where {T,V,N,Axes} = $Typ{promote_type(T,V),N,Axes}
+        function convert(::Type{$Typ{T,N,Axes}}, A::$Typ{V,N,Axes}) where {T,V,N,Axes}
+            convert(T, getindex_value(A)) # checks that the types are convertible
+            $Typ{T,N,Axes}(axes(A))
+        end
+        convert(::Type{$Typ{T,N}}, A::$Typ{V,N,Axes}) where {T,V,N,Axes} = convert($Typ{T,N,Axes}, A)
+        convert(::Type{$Typ{T}}, A::$Typ{V,N,Axes}) where {T,V,N,Axes} = convert($Typ{T,N,Axes}, A)
     end
 end
 
@@ -284,6 +293,8 @@ for TYPE in (:Fill, :AbstractFill, :Ones, :Zeros), STYPE in (:AbstractArray, :Ab
     end
 end
 
+promote_rule(::Type{<:AbstractFill{T, N, Axes}}, ::Type{<:AbstractFill{V, N, Axes}}) where {T,V,N,Axes} = Fill{promote_type(T,V),N,Axes}
+
 """
     fillsimilar(a::AbstractFill, axes)
 
diff --git a/test/runtests.jl b/test/runtests.jl
index d8449543..e74ca316 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -194,6 +194,23 @@ include("infinitearrays.jl")
         A = FillArrays.RectDiagonal(Int[], (1:0, 1:4))
         @test !(0 in A)
     end
+
+    @testset "promotion" begin
+        Z = Zeros{Int}(5)
+        Zf = Zeros(5)
+        O = Ones{Int}(5)
+        Of = Ones{Float64}(5)
+        @test [Z,O] isa Vector{Fill{Int,1,Tuple{Base.OneTo{Int}}}}
+        @test [Z,Of] isa Vector{Fill{Float64,1,Tuple{Base.OneTo{Int}}}}
+        @test [O,O] isa Vector{Ones{Int,1,Tuple{Base.OneTo{Int}}}}
+        @test [O,Of] isa Vector{Ones{Float64,1,Tuple{Base.OneTo{Int}}}}
+        @test [Z,Zf] isa Vector{Zeros{Float64,1,Tuple{Base.OneTo{Int}}}}
+
+        @test convert(Ones{Int}, Of) ≡ convert(Ones{Int,1}, Of) ≡ convert(typeof(O), Of) ≡ O
+        @test convert(Zeros{Int}, Zf) ≡ convert(Zeros{Int,1}, Zf) ≡ convert(typeof(Z), Zf) ≡ Z
+
+        @test_throws MethodError convert(Zeros{SVector{2,Int}}, Zf)
+    end
 end
 
 @testset "indexing" begin