From b346588d5e9a8e5b3c98a615da2e9c49647f35ce Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Sat, 21 Sep 2019 18:44:00 -0700
Subject: [PATCH 01/11] Support indexing based involving end

---
 Project.toml    |  1 +
 src/Setfield.jl |  3 ++-
 src/lens.jl     |  9 +++++++++
 src/sugar.jl    | 19 +++++++++++++++++++
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 39391ef..70889e9 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,6 +3,7 @@ uuid = "efcf1570-3423-57d1-acb7-fd33fddbac46"
 version = "0.4.1"
 
 [deps]
+GroundEffects = "d00d4687-65cd-4fba-8fd9-ecb45a036ebe"
 MacroTools = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
 
 [compat]
diff --git a/src/Setfield.jl b/src/Setfield.jl
index 62e5f1e..f9be3b2 100644
--- a/src/Setfield.jl
+++ b/src/Setfield.jl
@@ -1,7 +1,8 @@
 __precompile__(true)
 module Setfield
+using GroundEffects
 using MacroTools
-using MacroTools: isstructdef, splitstructdef
+using MacroTools: isstructdef, splitstructdef, postwalk
 
 include("lens.jl")
 include("sugar.jl")
diff --git a/src/lens.jl b/src/lens.jl
index 17d5968..760169b 100644
--- a/src/lens.jl
+++ b/src/lens.jl
@@ -278,6 +278,15 @@ Base.@propagate_inbounds set(obj, ::ConstIndexLens{I}, val) where I =
     end
 end
 
+struct DynamicIndexLens{F} <: Lens
+    f::F
+end
+
+Base.@propagate_inbounds get(obj, I::DynamicIndexLens) = obj[I.f(obj)...]
+
+Base.@propagate_inbounds set(obj, I::DynamicIndexLens, val) =
+    setindex(obj, val, I.f(obj)...)
+
 """
     FunctionLens(f)
     @lens f(_)
diff --git a/src/sugar.jl b/src/sugar.jl
index dee7bb6..8e907a7 100644
--- a/src/sugar.jl
+++ b/src/sugar.jl
@@ -52,6 +52,17 @@ end
 
 is_interpolation(x) = x isa Expr && x.head == :$
 
+foldtree(op, init, x) = op(init, x)
+foldtree(op, init, ex::Expr) =
+    op(foldl((acc, x) -> foldtree(op, acc, x), ex.args; init=init), ex)
+
+need_dynamic_lens(ex) =
+    foldtree(false, ex) do yes, x
+        yes || x === :end || x === :_
+    end
+
+replace_underscore(ex, to) = postwalk(x -> x === :_ ? to : x, ex)
+
 function parse_obj_lenses(ex)
     if @capture(ex, front_[indices__])
         obj, frontlens = parse_obj_lenses(front)
@@ -63,6 +74,14 @@ function parse_obj_lenses(ex)
             end
             index = esc(Expr(:tuple, [x.args[1] for x in indices]...))
             lens = :(ConstIndexLens{$index}())
+        elseif obj == esc(:_) && any(need_dynamic_lens, indices)
+            @gensym collection
+            indices = replace_underscore.(indices, collection)
+            lex = GroundEffects.lower(:($collection[$(indices...)]))
+            @assert lex.args[1] == getindex
+            @assert lex.args[2] == collection
+            lindices = esc.(lex.args[3:end])
+            lens = :(DynamicIndexLens($(esc(collection)) -> ($(lindices...),)))
         else
             index = esc(Expr(:tuple, indices...))
             lens = :(IndexLens($index))

From 2b8c79b7a7fb19f8a2efbd5ee1f7bd4646d6adee Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 18:16:39 -0700
Subject: [PATCH 02/11] Move lowering code needed here from GroundEffects

---
 Project.toml    |  1 -
 src/Setfield.jl |  2 +-
 src/lowering.jl | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/sugar.jl    |  2 +-
 4 files changed, 90 insertions(+), 3 deletions(-)
 create mode 100644 src/lowering.jl

diff --git a/Project.toml b/Project.toml
index 70889e9..39391ef 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,7 +3,6 @@ uuid = "efcf1570-3423-57d1-acb7-fd33fddbac46"
 version = "0.4.1"
 
 [deps]
-GroundEffects = "d00d4687-65cd-4fba-8fd9-ecb45a036ebe"
 MacroTools = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
 
 [compat]
diff --git a/src/Setfield.jl b/src/Setfield.jl
index f9be3b2..19436b9 100644
--- a/src/Setfield.jl
+++ b/src/Setfield.jl
@@ -1,9 +1,9 @@
 __precompile__(true)
 module Setfield
-using GroundEffects
 using MacroTools
 using MacroTools: isstructdef, splitstructdef, postwalk
 
+include("lowering.jl")
 include("lens.jl")
 include("sugar.jl")
 include("functionlenses.jl")
diff --git a/src/lowering.jl b/src/lowering.jl
new file mode 100644
index 0000000..ba5f5ae
--- /dev/null
+++ b/src/lowering.jl
@@ -0,0 +1,88 @@
+module Lowering
+
+using Base.Meta: isexpr
+
+"""
+    lower(ex)
+
+A modified version of `GroundEffects.lower` that only handles indexing.
+"""
+lower(ex) = something(handle_ref(lower, ex), ex)
+
+function handle_ref(lower, ex)
+    isexpr(ex, :ref) || return nothing
+    statements, collection, indices = _handle_ref(lower, ex)
+    push!(statements, Expr(:call, Base.getindex, collection, indices...))
+    if length(statements) == 1
+        return statements[1]
+    else
+        return Expr(:block, statements...)
+    end
+end
+
+function _handle_ref(lower, ex)
+    statements = []
+    if length(ex.args) == 1
+        collection = ex.args[1]
+        indices = []
+    else
+        if ex.args[1] isa Symbol
+            collection = ex.args[1]
+        else
+            @gensym collection
+            push!(statements, :($collection = $(ex.args[1])))
+        end
+        indices = lower_indices(lower, collection, ex.args[2:end])
+    end
+    return statements, collection, indices
+end
+
+lower_indices(lower, collection, indices) =
+    map(index -> lower_index(lower, collection, index), indices)
+
+function lower_index(lower, collection, index)
+    ex = handle_dotcall(index) do ex
+        lower_index(lower, collection, ex)
+    end
+    ex === nothing || return something(ex)
+
+    if isexpr(index, :call)
+        return Expr(:call, lower_indices(lower, collection, index.args)...)
+    elseif index === :end
+        return :($(Base.lastindex)($collection))
+    end
+    return lower(index)
+end
+
+function isdotopcall(ex)
+    ex isa Expr && !isempty(ex.args) || return false
+    op = ex.args[1]
+    return op isa Symbol && Base.isoperator(op) && startswith(string(op), ".")
+end
+
+isdotcall(ex) =
+    isexpr(ex, :.) && length(ex.args) == 2 && isexpr(ex.args[2], :tuple)
+
+function handle_dotcall(lower, ex)
+    isdotcall(ex) || isdotopcall(ex) || return nothing
+    return Expr(:call, Base.materialize, handle_lazy_dotcall(lower, ex))
+end
+
+function handle_lazy_dotcall(lower, ex)
+    if isdotcall(ex)
+        args = [
+            lower(ex.args[1])
+            map(x -> handle_lazy_dotcall(lower, x), ex.args[2].args)
+        ]
+    elseif isdotopcall(ex)
+        args = [
+            Symbol(String(ex.args[1])[2:end])
+            map(x -> handle_lazy_dotcall(lower, x), ex.args[2:end])
+        ]
+    else
+        return lower(ex)
+    end
+    return Expr(:call, Base.broadcasted, args...)
+end
+
+end  # module
diff --git a/src/sugar.jl b/src/sugar.jl
index 8e907a7..09d5dfe 100644
--- a/src/sugar.jl
+++ b/src/sugar.jl
@@ -77,7 +77,7 @@ function parse_obj_lenses(ex)
         elseif obj == esc(:_) && any(need_dynamic_lens, indices)
             @gensym collection
             indices = replace_underscore.(indices, collection)
-            lex = GroundEffects.lower(:($collection[$(indices...)]))
+            lex = Lowering.lower(:($collection[$(indices...)]))
             @assert lex.args[1] == getindex
             @assert lex.args[2] == collection
             lindices = esc.(lex.args[3:end])

From 6f7c35e230d180b3681cfd4302b93451e9eb9f3a Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 18:25:57 -0700
Subject: [PATCH 03/11] Add tests

---
 test/test_core.jl | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/test/test_core.jl b/test/test_core.jl
index 7f54dfc..4084ebd 100644
--- a/test/test_core.jl
+++ b/test/test_core.jl
@@ -104,6 +104,10 @@ end
     i = 1
     si = @set t.a[i] = 10
     @test s1 === si
+    se = @set t.a[end] = 20
+    @test se === T((1,20),(3,4))
+    se1 = @set t.a[end-1] = 10
+    @test s1 === se1
 
     s1 = @set t.a[$1] = 10
     @test s1 === T((10,2),(3,4))
@@ -257,6 +261,18 @@ end
     @test get([4,5,6,7], l) == [4,5,6]
 end
 
+@testset "DynamicIndexLens" begin
+    l = @lens _[end]
+    obj = (1,2,3)
+    @test get(obj, l) == 3
+    @test set(obj, l, true) == (1,2,true)
+
+    l = @lens _[end÷2]
+    obj = (1,2,3)
+    @test get(obj, l) == 1
+    @test set(obj, l, true) == (true,2,3)
+end
+
 @testset "ConstIndexLens" begin
     obj = (1, 2.0, '3')
     l = @lens _[$1]

From 8a3101bcb8b0dca2f1010f83aed58cc8758ecf22 Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 18:31:10 -0700
Subject: [PATCH 04/11] Make it work with set

---
 src/sugar.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sugar.jl b/src/sugar.jl
index 09d5dfe..19b2bfe 100644
--- a/src/sugar.jl
+++ b/src/sugar.jl
@@ -74,7 +74,7 @@ function parse_obj_lenses(ex)
             end
             index = esc(Expr(:tuple, [x.args[1] for x in indices]...))
             lens = :(ConstIndexLens{$index}())
-        elseif obj == esc(:_) && any(need_dynamic_lens, indices)
+        elseif any(need_dynamic_lens, indices)
             @gensym collection
             indices = replace_underscore.(indices, collection)
             lex = Lowering.lower(:($collection[$(indices...)]))

From 8da84a0db22a7b915a3b8c9ed5303fa39e1417a3 Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 18:36:59 -0700
Subject: [PATCH 05/11] Unsupport dot calls in index

---
 src/lowering.jl | 39 +++------------------------------------
 1 file changed, 3 insertions(+), 36 deletions(-)

diff --git a/src/lowering.jl b/src/lowering.jl
index ba5f5ae..95151a7 100644
--- a/src/lowering.jl
+++ b/src/lowering.jl
@@ -41,11 +41,9 @@ lower_indices(lower, collection, indices) =
     map(index -> lower_index(lower, collection, index), indices)
 
 function lower_index(lower, collection, index)
-    ex = handle_dotcall(index) do ex
-        lower_index(lower, collection, ex)
-    end
-    ex === nothing || return something(ex)
-
+    # GroundEffects handles dot calls here but we don't need to do
+    # this because `setindex(::Tuple, ::Tuple, ::Tuple)` is not
+    # supported.
     if isexpr(index, :call)
         return Expr(:call, lower_indices(lower, collection, index.args)...)
     elseif index === :end
@@ -54,35 +52,4 @@ function lower_index(lower, collection, index)
     return lower(index)
 end
 
-function isdotopcall(ex)
-    ex isa Expr && !isempty(ex.args) || return false
-    op = ex.args[1]
-    return op isa Symbol && Base.isoperator(op) && startswith(string(op), ".")
-end
-
-isdotcall(ex) =
-    isexpr(ex, :.) && length(ex.args) == 2 && isexpr(ex.args[2], :tuple)
-
-function handle_dotcall(lower, ex)
-    isdotcall(ex) || isdotopcall(ex) || return nothing
-    return Expr(:call, Base.materialize, handle_lazy_dotcall(lower, ex))
-end
-
-function handle_lazy_dotcall(lower, ex)
-    if isdotcall(ex)
-        args = [
-            lower(ex.args[1])
-            map(x -> handle_lazy_dotcall(lower, x), ex.args[2].args)
-        ]
-    elseif isdotopcall(ex)
-        args = [
-            Symbol(String(ex.args[1])[2:end])
-            map(x -> handle_lazy_dotcall(lower, x), ex.args[2:end])
-        ]
-    else
-        return lower(ex)
-    end
-    return Expr(:call, Base.broadcasted, args...)
-end
-
 end  # module

From 7d7ba154ba79f81fc1ecb1dd8b96f3100b7efd4a Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 18:44:18 -0700
Subject: [PATCH 06/11] Simplify src/lowering.jl using the assumption of
 Setfield usage

---
 src/lowering.jl | 27 +++------------------------
 1 file changed, 3 insertions(+), 24 deletions(-)

diff --git a/src/lowering.jl b/src/lowering.jl
index 95151a7..80193a2 100644
--- a/src/lowering.jl
+++ b/src/lowering.jl
@@ -11,30 +11,9 @@ lower(ex) = something(handle_ref(lower, ex), ex)
 
 function handle_ref(lower, ex)
     isexpr(ex, :ref) || return nothing
-    statements, collection, indices = _handle_ref(lower, ex)
-    push!(statements, Expr(:call, Base.getindex, collection, indices...))
-    if length(statements) == 1
-        return statements[1]
-    else
-        return Expr(:block, statements...)
-    end
-end
-
-function _handle_ref(lower, ex)
-    statements = []
-    if length(ex.args) == 1
-        collection = ex.args[1]
-        indices = []
-    else
-        if ex.args[1] isa Symbol
-            collection = ex.args[1]
-        else
-            @gensym collection
-            push!(statements, :($collection = $(ex.args[1])))
-        end
-        indices = lower_indices(lower, collection, ex.args[2:end])
-    end
-    return statements, collection, indices
+    collection = ex.args[1] :: Symbol
+    indices = lower_indices(lower, collection, ex.args[2:end])
+    return Expr(:call, Base.getindex, collection, indices...)
 end
 
 lower_indices(lower, collection, indices) =

From 683df6e9949d044f29025288712daf0b4be28a6a Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 18:52:54 -0700
Subject: [PATCH 07/11] Avoid failure in documentation build

---
 src/lowering.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lowering.jl b/src/lowering.jl
index 80193a2..f71c9c5 100644
--- a/src/lowering.jl
+++ b/src/lowering.jl
@@ -2,11 +2,11 @@ module Lowering
 
 using Base.Meta: isexpr
 
-"""
+#=
     lower(ex)
 
 A modified version of `GroundEffects.lower` that only handles indexing.
-"""
+=#
 lower(ex) = something(handle_ref(lower, ex), ex)
 
 function handle_ref(lower, ex)

From 4264829cf54f1261793b24f2cea1ac832f1ba1ce Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 19:02:50 -0700
Subject: [PATCH 08/11] Stop using GroundEffects.jl-compatible internal
 interface

---
 src/Setfield.jl |  1 -
 src/lowering.jl | 34 ----------------------------------
 src/sugar.jl    | 14 ++++++++++----
 3 files changed, 10 insertions(+), 39 deletions(-)
 delete mode 100644 src/lowering.jl

diff --git a/src/Setfield.jl b/src/Setfield.jl
index 19436b9..576f9cf 100644
--- a/src/Setfield.jl
+++ b/src/Setfield.jl
@@ -3,7 +3,6 @@ module Setfield
 using MacroTools
 using MacroTools: isstructdef, splitstructdef, postwalk
 
-include("lowering.jl")
 include("lens.jl")
 include("sugar.jl")
 include("functionlenses.jl")
diff --git a/src/lowering.jl b/src/lowering.jl
deleted file mode 100644
index f71c9c5..0000000
--- a/src/lowering.jl
+++ /dev/null
@@ -1,34 +0,0 @@
-module Lowering
-
-using Base.Meta: isexpr
-
-#=
-    lower(ex)
-
-A modified version of `GroundEffects.lower` that only handles indexing.
-=#
-lower(ex) = something(handle_ref(lower, ex), ex)
-
-function handle_ref(lower, ex)
-    isexpr(ex, :ref) || return nothing
-    collection = ex.args[1] :: Symbol
-    indices = lower_indices(lower, collection, ex.args[2:end])
-    return Expr(:call, Base.getindex, collection, indices...)
-end
-
-lower_indices(lower, collection, indices) =
-    map(index -> lower_index(lower, collection, index), indices)
-
-function lower_index(lower, collection, index)
-    # GroundEffects handles dot calls here but we don't need to do
-    # this because `setindex(::Tuple, ::Tuple, ::Tuple)` is not
-    # supported.
-    if isexpr(index, :call)
-        return Expr(:call, lower_indices(lower, collection, index.args)...)
-    elseif index === :end
-        return :($(Base.lastindex)($collection))
-    end
-    return lower(index)
-end
-
-end  # module
diff --git a/src/sugar.jl b/src/sugar.jl
index 19b2bfe..fff0166 100644
--- a/src/sugar.jl
+++ b/src/sugar.jl
@@ -63,6 +63,15 @@ need_dynamic_lens(ex) =
 
 replace_underscore(ex, to) = postwalk(x -> x === :_ ? to : x, ex)
 
+function lower_index(collection::Symbol, index)
+    if isexpr(index, :call)
+        return Expr(:call, lower_index.(collection, index.args)...)
+    elseif index === :end
+        return :($(Base.lastindex)($collection))
+    end
+    return index
+end
+
 function parse_obj_lenses(ex)
     if @capture(ex, front_[indices__])
         obj, frontlens = parse_obj_lenses(front)
@@ -77,10 +86,7 @@ function parse_obj_lenses(ex)
         elseif any(need_dynamic_lens, indices)
             @gensym collection
             indices = replace_underscore.(indices, collection)
-            lex = Lowering.lower(:($collection[$(indices...)]))
-            @assert lex.args[1] == getindex
-            @assert lex.args[2] == collection
-            lindices = esc.(lex.args[3:end])
+            lindices = esc.(lower_index.(collection, indices))
             lens = :(DynamicIndexLens($(esc(collection)) -> ($(lindices...),)))
         else
             index = esc(Expr(:tuple, indices...))

From c70d7a9c782227c61ade7e5bfbfe576729f7e931 Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 22:37:48 -0700
Subject: [PATCH 09/11] Add more tests

---
 test/test_core.jl | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/test/test_core.jl b/test/test_core.jl
index 4084ebd..e4b43dc 100644
--- a/test/test_core.jl
+++ b/test/test_core.jl
@@ -195,6 +195,8 @@ end
             @lens _.b.a.b[i]
             @lens _.b.a.b[$2]
             @lens _.b.a.b[$i]
+            @lens _.b.a.b[end]
+            @lens _.b.a.b[identity(end) - 1]
             @lens _
         ]
         val1, val2 = randn(2)
@@ -230,6 +232,8 @@ end
           ((@lens _.b.a.b[$(i+1)]),  4  ),
           ((@lens _.b.a.b[$2]   ),   4.0),
           ((@lens _.b.a.b[$(i+1)]),  4.0),
+          ((@lens _.b.a.b[end]),     4.0),
+          ((@lens _.b.a.b[end÷2+1]), 4.0),
           ((@lens _             ),   obj),
           ((@lens _             ),   :xy),
           (MultiPropertyLens((a=(@lens _), b=(@lens _))), (a=1, b=2)),
@@ -271,6 +275,13 @@ end
     obj = (1,2,3)
     @test get(obj, l) == 1
     @test set(obj, l, true) == (true,2,3)
+
+    two = 2
+    plusone(x) = x + 1
+    l = @lens _.a[plusone(end) - two].b
+    obj = (a=(1, (a=10, b=20), 3), b=4)
+    @test get(obj, l) == 20
+    @test set(obj, l, true) == (a=(1, (a=10, b=true), 3), b=4)
 end
 
 @testset "ConstIndexLens" begin

From de98e801e6a97b2d757ff31b60880360cdf7308a Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 1 Oct 2019 23:01:59 -0700
Subject: [PATCH 10/11] Support multi-dimensional DynamicIndexLens

---
 src/sugar.jl              | 13 +++++++++----
 test/test_staticarrays.jl | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/src/sugar.jl b/src/sugar.jl
index fff0166..d735047 100644
--- a/src/sugar.jl
+++ b/src/sugar.jl
@@ -63,11 +63,15 @@ need_dynamic_lens(ex) =
 
 replace_underscore(ex, to) = postwalk(x -> x === :_ ? to : x, ex)
 
-function lower_index(collection::Symbol, index)
+function lower_index(collection::Symbol, index, dim)
     if isexpr(index, :call)
-        return Expr(:call, lower_index.(collection, index.args)...)
+        return Expr(:call, lower_index.(collection, index.args, dim)...)
     elseif index === :end
-        return :($(Base.lastindex)($collection))
+        if dim === nothing
+            return :($(Base.lastindex)($collection))
+        else
+            return :($(Base.lastindex)($collection, $dim))
+        end
     end
     return index
 end
@@ -86,7 +90,8 @@ function parse_obj_lenses(ex)
         elseif any(need_dynamic_lens, indices)
             @gensym collection
             indices = replace_underscore.(indices, collection)
-            lindices = esc.(lower_index.(collection, indices))
+            dims = length(indices) == 1 ? nothing : 1:length(indices)
+            lindices = esc.(lower_index.(collection, indices, dims))
             lens = :(DynamicIndexLens($(esc(collection)) -> ($(lindices...),)))
         else
             index = esc(Expr(:tuple, indices...))
diff --git a/test/test_staticarrays.jl b/test/test_staticarrays.jl
index 4ec707c..ea9d3e7 100644
--- a/test/test_staticarrays.jl
+++ b/test/test_staticarrays.jl
@@ -17,5 +17,25 @@ using StaticArrays
     v = @SVector [1,2,3]
     @test (@set v[1] = 10) === @SVector [10,2,3]
     @test_broken (@set v[1] = π) === @SVector [π,2,3]
+
+    @testset "Multi-dynamic indexing" begin
+        two = 2
+        plusone(x) = x + 1
+        l1 = @lens _.a[2, 1].b
+        l2 = @lens _.a[plusone(end) - two, end÷2].b
+        m_orig = @SMatrix [
+            (a=1, b=10) (a=2, b=20)
+            (a=3, b=30) (a=4, b=40)
+            (a=5, b=50) (a=6, b=60)
+        ]
+        m_mod = @SMatrix [
+            (a=1, b=10) (a=2, b=20)
+            (a=3, b=3000) (a=4, b=40)
+            (a=5, b=50) (a=6, b=60)
+        ]
+        obj = (a=m_orig, b=4)
+        @test get(obj, l1) === get(obj, l2) === 30
+        @test set(obj, l1, 3000) === set(obj, l2, 3000) === (a=m_mod, b=4)
+    end
 end
 end

From 6c7b02aecaf36ece3ce3862d36c0105a7ae878de Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Thu, 3 Oct 2019 13:17:52 -0700
Subject: [PATCH 11/11] Check index lens types in the tests

---
 test/test_core.jl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/test/test_core.jl b/test/test_core.jl
index e4b43dc..6c2c532 100644
--- a/test/test_core.jl
+++ b/test/test_core.jl
@@ -246,32 +246,39 @@ end
 
 @testset "IndexLens" begin
     l = @lens _[]
+    @test l isa Setfield.IndexLens
     x = randn()
     obj = Ref(x)
     @test get(obj, l) == x
 
     l = @lens _[][]
+    @test l.outer isa Setfield.IndexLens
+    @test l.inner isa Setfield.IndexLens
     inner = Ref(x)
     obj = Base.RefValue{typeof(inner)}(inner)
     @test get(obj, l) == x
 
     obj = (1,2,3)
     l = @lens _[1]
+    @test l isa Setfield.IndexLens
     @test get(obj, l) == 1
     @test set(obj, l, 6) == (6,2,3)
 
 
     l = @lens _[1:3]
+    @test l isa Setfield.IndexLens
     @test get([4,5,6,7], l) == [4,5,6]
 end
 
 @testset "DynamicIndexLens" begin
     l = @lens _[end]
+    @test l isa Setfield.DynamicIndexLens
     obj = (1,2,3)
     @test get(obj, l) == 3
     @test set(obj, l, true) == (1,2,true)
 
     l = @lens _[end÷2]
+    @test l isa Setfield.DynamicIndexLens
     obj = (1,2,3)
     @test get(obj, l) == 1
     @test set(obj, l, true) == (true,2,3)