Fix reduction over empty array (#1115)

* Fix reduction over empty array

* bump version

Author: mateuszbaran

Project.toml

@@ -1,6 +1,6 @@
 name = "StaticArrays"
 uuid = "90137ffa-7385-5640-81b9-e52037218182"
-version = "1.5.11"
+version = "1.5.12"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/mapreduce.jl

@@ -197,18 +197,21 @@ end
     exprs = Array{Expr}(undef, Snew)
     itr = [1:n for n ∈ Snew]
     for i ∈ Base.product(itr...)
-        expr = :(f(a[$(i...)]))
-        if init === _InitialValue
-            expr = :(Base.reduce_first(op, $expr))
+        if S[D] == 0
+            expr = :(Base.mapreduce_empty(f, op, eltype(a)))
         else
-            expr = :(op(init, $expr))
-        end
-        for k = 2:S[D]
-            ik = collect(i)
-            ik[D] = k
-            expr = :(op($expr, f(a[$(ik...)])))
+            expr = :(f(a[$(i...)]))
+            if init === _InitialValue
+                expr = :(Base.reduce_first(op, $expr))
+            else
+                expr = :(op(init, $expr))
+            end
+            for k = 2:S[D]
+                ik = collect(i)
+                ik[D] = k
+                expr = :(op($expr, f(a[$(ik...)])))
+            end
         end
-
         exprs[i...] = expr
     end
 

test/mapreduce.jl

@@ -251,4 +251,11 @@ using Statistics: mean
         @test @inferred(map(f -> f, enumerate_static(v0))) === SVector{0,Tuple{Int,Float64}}()
         @test @inferred(map(f -> f, enumerate_static(m0))) === SMatrix{0,0,Tuple{Int,Float64}}()
     end
+    @testset "reduce over empty array" begin
+        # issue #1114
+        @test (@inferred reduce(|,zeros(SMatrix{0,3,Bool}); dims=Val(1), init=false)) ==
+            reduce(|,zeros(Bool,0,3); dims=1, init=false)
+        @test reduce(|,zeros(SMatrix{0,3,Bool}); dims=1, init=false) ==
+            reduce(|,zeros(Bool,0,3); dims=1, init=false)
+    end
 end