Allow non-Function callable as combine argument of merge[!]

Author: tkf

base/abstractdict.jl

@@ -213,7 +213,7 @@ Dict{Int64,Int64} with 3 entries:
   1 => 0
 ```
 """
-function merge!(combine::Function, d::AbstractDict, others::AbstractDict...)
+function merge!(combine, d::AbstractDict, others::AbstractDict...)
     for other in others
         for (k,v) in other
             d[k] = haskey(d, k) ? combine(d[k], v) : v
@@ -313,7 +313,7 @@ Dict{String,Float64} with 3 entries:
   "foo" => 0.0
 ```
 """
-merge(combine::Function, d::AbstractDict, others::AbstractDict...) =
+merge(combine, d::AbstractDict, others::AbstractDict...) =
     merge!(combine, _typeddict(d, others...), others...)
 
 promoteK(K) = K

test/dict.jl

@@ -917,6 +917,9 @@ let
     end
 end
 
+struct NonFunctionCallable end
+(::NonFunctionCallable)(args...) = +(args...)
+
 @testset "Dict merge" begin
     d1 = Dict("A" => 1, "B" => 2)
     d2 = Dict("B" => 3.0, "C" => 4.0)
@@ -925,6 +928,7 @@ end
     @test @inferred merge(+, d1, d2) == Dict("A" => 1, "B" => 5, "C" => 4)
     @test @inferred merge(*, d1, d2) == Dict("A" => 1, "B" => 6, "C" => 4)
     @test @inferred merge(-, d1, d2) == Dict("A" => 1, "B" => -1, "C" => 4)
+    @test @inferred merge(NonFunctionCallable(), d1, d2) == Dict("A" => 1, "B" => 5, "C" => 4)
 end
 
 @testset "Dict merge!" begin
@@ -939,6 +943,8 @@ end
     @test d1 == Dict("A" => 1, "B" => 18, "C" => 32)
     @inferred merge!(-, d1, d2)
     @test d1 == Dict("A" => 1, "B" => 15, "C" => 28)
+    @inferred merge!(NonFunctionCallable(), d1, d2)
+    @test d1 == Dict("A" => 1, "B" => 21, "C" => 36)
 end
 
 @testset "Dict reduce merge" begin