[WIP] operate! with add_dot

src/implementations/BigInt.jl

@@ -95,7 +95,7 @@ function operate_to!(
     return operate!(op, output, c...)
 end
 
-function operate!(op::Function, x::BigInt, args::Vararg{Any,N}) where {N}
+function operate_fallback!(op::Function, x::BigInt, args::Vararg{Any,N}) where {N}
     return operate_to!(x, op, x, args...)
 end
 

src/interface.jl

@@ -686,7 +686,7 @@ function promote_operation_fallback(
     ::Type{<:AbstractArray{A}},
     ::Type{<:AbstractArray{B}},
 ) where {A,B}
-    C = promote_operation(*, A, B)
+    C = promote_operation(LinearAlgebra.dot, A, B)
     return promote_operation(+, C, C)
 end
 

src/reduce.jl

@@ -38,16 +38,21 @@ end
 
 _concrete_eltype(x) = isempty(x) ? eltype(x) : typeof(first(x))
 
-function fused_map_reduce(op::F, args::Vararg{Any,N}) where {F<:Function,N}
-    _check_same_length(args...)
+
+function operate!(op::typeof(add_dot), output, args::Vararg{Any,N}) where {N}
     T = promote_map_reduce(op, _concrete_eltype.(args)...)
-    accumulator = neutral_element(reduce_op(op), T)
     buffer = buffer_for(op, T, eltype.(args)...)
     for I in zip(eachindex.(args)...)
-        accumulator =
-            buffered_operate!!(buffer, op, accumulator, getindex.(args, I)...)
+        output = buffered_operate!!(buffer, op, output, getindex.(args, I)...)
     end
-    return accumulator
+    return output
+end
+
+function fused_map_reduce(op::F, args::Vararg{Any,N}) where {F<:Function,N}
+    _check_same_length(args...)
+    T = promote_map_reduce(op, _concrete_eltype.(args)...)
+    accumulator = neutral_element(reduce_op(op), T)
+    return operate!(op, accumulator, args...)
 end
 
 function operate(::typeof(sum), a::AbstractArray)