allow standalone dotted operators

base/broadcast.jl

@@ -11,7 +11,7 @@ using .Base.Cartesian
 using .Base: Indices, OneTo, tail, to_shape, isoperator, promote_typejoin,
              _msk_end, unsafe_bitgetindex, bitcache_chunks, bitcache_size, dumpbitcache, unalias
 import .Base: copy, copyto!, axes
-export broadcast, broadcast!, BroadcastStyle, broadcast_axes, broadcastable, dotview, @__dot__, broadcast_preserving_zero_d
+export broadcast, broadcast!, BroadcastStyle, broadcast_axes, broadcastable, dotview, @__dot__, broadcast_preserving_zero_d, BroadcastOp
 
 ## Computing the result's axes: deprecated name
 const broadcast_axes = axes
@@ -1261,4 +1261,10 @@ end
 end
 @inline broadcasted(::S, f, args...) where S<:BroadcastStyle = Broadcasted{S}(f, args)
 
+struct BroadcastOp{F} <: Function
+    f::F
+end
+
+@inline (op::BroadcastOp)(x...) = op.f.(x...)
+
 end # module

src/julia-syntax.scm

@@ -1884,13 +1884,15 @@
       `(= ,lhs ,rhs)))
 
 (define (expand-forms e)
-  (if (or (atom? e) (memq (car e) '(quote inert top core globalref outerref module toplevel ssavalue null true false meta using import export thismodule toplevel-only)))
-      e
-      (let ((ex (get expand-table (car e) #f)))
+  (cond
+    ((atom? e) (if (dotop-named? e) `(call (top BroadcastOp) ,(undotop e)) e))
+    ((memq (car e) '(quote inert top core globalref outerref module toplevel ssavalue null true false meta using import export thismodule toplevel-only))
+      e)
+    (else (let ((ex (get expand-table (car e) #f)))
         (if ex
             (ex e)
             (cons (car e)
-                  (map expand-forms (cdr e)))))))
+                  (map expand-forms (cdr e))))))))
 
 ;; table mapping expression head to a function expanding that form
 (define expand-table

test/broadcast.jl

@@ -923,3 +923,7 @@ k4 = similar(u)
 f(a,b,c,d,e) = @. a = a + 1*(b+c+d+e)
 @allocated f(u,k1,k2,k3,k4)
 @test (@allocated f(u,k1,k2,k3,k4)) == 0
+
+@test identity(.+) == Broadcast.BroadcastOp(+)
+@test identity.(.*) == Broadcast.BroadcastOp(*)
+@test map(.+, [[1,2], [3,4]], [5, 6]) == [[6,7], [9,10]]