[RFC] monkey patch setindex

src/Setfield.jl

@@ -3,6 +3,7 @@ module Setfield
 using MacroTools
 using MacroTools: isstructdef, splitstructdef, postwalk
 
+include("setindex.jl")
 include("lens.jl")
 include("sugar.jl")
 include("functionlenses.jl")

src/lens.jl

@@ -7,7 +7,7 @@ export constructorof
 
 
 import Base: get
-using Base: setindex, getproperty
+using Base: getproperty
 
 """
     Lens

src/setindex.jl

@@ -0,0 +1,13 @@
+Base.@propagate_inbounds function setindex(args...)
+    Base.setindex(args...)
+end
+
+for T in [:Array, :Dict]
+    @eval begin
+        Base.@propagate_inbounds function setindex(o::$T, args...)
+            new = copy(o)
+            setindex!(new, args...)
+            new
+        end
+    end
+end

test/perf.jl

@@ -42,7 +42,7 @@ function lens_set_i((obj, val, i))
 end
 
 function hand_set_i((obj, val, i))
-    @inbounds setindex(obj, val, i)
+    @inbounds Base.setindex(obj, val, i)
 end
 
 function benchmark_lens_vs_hand(b_lens::Benchmark, b_hand::Benchmark)

test/runtests.jl

@@ -1,5 +1,6 @@
 module TestSetfield
 
+include("test_setindex.jl")
 include("test_examples.jl")
 include("test_setmacro.jl")
 include("test_core.jl")

test/test_setindex.jl

@@ -0,0 +1,21 @@
+module TestSetindex
+using Setfield
+using Test
+
+@testset "setindex" begin
+    arr = [1,2,3]
+    @test_throws MethodError Base.setindex(arr, 10, 1)
+    @test Setfield.setindex(arr, 10, 1) == [10, 2, 3]
+    @test arr == [1,2,3]
+    @test @set(arr[1] = 10) == [10, 2, 3]
+    @test arr == [1,2,3]
+
+    d = Dict(:a => 1, :b => 2)
+    @test_throws MethodError Base.setindex(d, 10, :a)
+    @test Setfield.setindex(d, 10, :a) == Dict(:a=>10, :b=>2)
+    @test d == Dict(:a => 1, :b => 2)
+    @test @set(d[:a] = 10) == Dict(:a=>10, :b=>2)
+    @test d == Dict(:a => 1, :b => 2)
+end
+
+end