support Ref in has_fast_linear_indexing (JuliaLang#41072)

Author: stevengj

base/reducedim.jl

@@ -193,7 +193,7 @@ end
 
 has_fast_linear_indexing(a::AbstractArrayOrBroadcasted) = false
 has_fast_linear_indexing(a::Array) = true
-has_fast_linear_indexing(::Number) = true  # for Broadcasted
+has_fast_linear_indexing(::Union{Number,Ref,AbstractChar}) = true  # 0d objects, for Broadcasted
 has_fast_linear_indexing(bc::Broadcast.Broadcasted) =
     all(has_fast_linear_indexing, bc.args)
 

test/broadcast.jl

@@ -914,6 +914,12 @@ end
     # hit the `foldl` branch:
     @test IndexStyle(bcraw) == IndexCartesian()
     @test reduce(paren, bcraw) == foldl(paren, xs)
+
+    # issue #41055
+    bc = Broadcast.instantiate(Broadcast.broadcasted(Base.literal_pow, Ref(^), [1,2], Ref(Val(2))))
+    @test sum(bc, dims=1, init=0) == [5]
+    bc = Broadcast.instantiate(Broadcast.broadcasted(*, ['a','b'], 'c'))
+    @test prod(bc, dims=1, init="") == ["acbc"]
 end
 
 # treat Pair as scalar: