diff --git a/.travis.yml b/.travis.yml
index d40604c..162d36c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,7 +4,8 @@ os:
   - linux
   - osx
 julia:
-  - 0.6
+  - 0.7
+  - 1.0
   - nightly
 notifications:
   email: false
@@ -25,13 +26,10 @@ git:
 #before_script: # homebrew for mac
 #  - if [ $TRAVIS_OS_NAME = osx ]; then brew install gcc; fi
 
-# uncomment the following lines to override the default test script
-script:
-  - julia -e 'Pkg.clone(pwd()); Pkg.build("Setfield"); VERSION < v"0.7-" && Pkg.add("StaticArrays"); Pkg.test("Setfield"; coverage=true)'
 after_success:
   # push coverage results to Coveralls
-  - julia -e 'cd(Pkg.dir("Setfield")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())'
+  - julia -e 'using Pkg; cd(Pkg.dir("Setfield")); Pkg.add("Coverage"); using Coverage; Coveralls.submit(Coveralls.process_folder())'
   # push coverage results to Codecov
-  - julia -e 'cd(Pkg.dir("Setfield")); Pkg.add("Coverage"); using Coverage; Codecov.submit(Codecov.process_folder())'
-  - julia -e 'Pkg.add("Documenter")'
-  - julia -e 'cd(Pkg.dir("Setfield")); include(joinpath("docs", "make.jl"))'
+  - julia -e 'using Pkg; cd(Pkg.dir("Setfield")); Pkg.add("Coverage"); using Coverage; Codecov.submit(Codecov.process_folder())'
+  - julia -e 'using Pkg; Pkg.add("Documenter")'
+  - julia -e 'using Pkg; cd(Pkg.dir("Setfield")); include(joinpath("docs", "make.jl"))'
diff --git a/REQUIRE b/REQUIRE
index a612f60..157645b 100644
--- a/REQUIRE
+++ b/REQUIRE
@@ -1,2 +1,2 @@
-julia 0.6
-MacroTools
+julia 0.7-
+MacroTools 0.4.4
diff --git a/src/Setfield.jl b/src/Setfield.jl
index 62bc9bb..cbab666 100644
--- a/src/Setfield.jl
+++ b/src/Setfield.jl
@@ -1,22 +1,9 @@
 __precompile__(true)
 module Setfield
-
-if isdefined(Base, :getproperty)
-    using Base: getproperty
-else
-    const getproperty = getfield
-    # the following breaks type stability:
-    # @inline getproperty(obj, name) = getfield(obj, name)
-end
-if isdefined(Base, :setproperty!)
-    using Base: setproperty!
-else
-    const setproperty! = setfield!
-    # @inline setproperty!(obj, name, val) = setfield!(obj, name, val)
-end
+using MacroTools
+using MacroTools: isstructdef, splitstructdef
 
 include("lens.jl")
 include("sugar.jl")
-include("macrotools.jl")
 include("settable.jl")
 end
diff --git a/src/lens.jl b/src/lens.jl
index e48b2ff..eb15367 100644
--- a/src/lens.jl
+++ b/src/lens.jl
@@ -2,11 +2,8 @@ export Lens, set, get, modify
 export @lens
 export set, get, modify
 
-import Base: get, setindex
-
-abstract type MutationPolicy end
-struct EncourageMutation <: MutationPolicy end
-struct ForbidMutation <: MutationPolicy end
+import Base: get
+using Base: setindex, getproperty
 
 """
     Lens
@@ -74,17 +71,15 @@ Replace a deeply nested part of `obj` by `val`. See also [`Lens`](@ref).
 """
 function set end
 
-set(l::Lens, obj, val) = set(l,obj,val,ForbidMutation())
-modify(f,l::Lens, obj) = modify(f, l,obj,ForbidMutation())
-@inline function modify(f, l::Lens, obj, m::MutationPolicy)
+@inline function modify(f, l::Lens, obj)
     old_val = get(l, obj)
     new_val = f(old_val)
-    set(l, obj, new_val, m)
+    set(l, obj, new_val)
 end
 
 struct IdentityLens <: Lens end
 get(::IdentityLens, obj) = obj
-set(::IdentityLens, obj, val,::MutationPolicy) = val
+set(::IdentityLens, obj, val) = val
 
 struct PropertyLens{fieldname} <: Lens end
 
@@ -99,14 +94,8 @@ function assert_hasfield(T, field)
     end
 end
 
-@generated function set(l::PropertyLens{field}, obj, val, m::MutationPolicy) where {field}
-    T = obj
-    M = m
-    if T.mutable && (M == EncourageMutation)
-        :(setproperty!(obj, field, val); obj)
-    else
-        :(setproperty(obj, Val{field}(), val))
-    end
+@generated function set(l::PropertyLens{field}, obj, val) where {field}
+    :(setproperty(obj, Val{field}(), val))
 end
 
 @generated constructor_of(::Type{T}) where T =
@@ -146,10 +135,10 @@ function get(l::ComposedLens, obj)
     get(l.lens1, inner_obj)
 end
 
-function set(l::ComposedLens, obj, val, m::MutationPolicy)
+function set(l::ComposedLens, obj, val)
     inner_obj = get(l.lens2, obj)
-    inner_val = set(l.lens1, inner_obj, val, m)
-    set(l.lens2, obj, inner_val, m)
+    inner_val = set(l.lens1, inner_obj, val)
+    set(l.lens2, obj, inner_val)
 end
 
 struct IndexLens{I <: Tuple} <: Lens
@@ -157,11 +146,4 @@ struct IndexLens{I <: Tuple} <: Lens
 end
 
 get(l::IndexLens, obj) = getindex(obj, l.indices...)
-set(l::IndexLens, obj, val, ::ForbidMutation) = Base.setindex(obj, val, l.indices...)
-function set(l::IndexLens, obj, val, ::EncourageMutation)
-    if applicable(setindex!, obj, val, l.indices)
-        setindex!(obj, val, l.indices...)
-    else
-        set(l, obj, val, ForbidMutation())
-    end
-end
+set(l::IndexLens, obj, val) = setindex(obj, val, l.indices...)
diff --git a/src/macrotools.jl b/src/macrotools.jl
deleted file mode 100644
index b2e4df0..0000000
--- a/src/macrotools.jl
+++ /dev/null
@@ -1,69 +0,0 @@
-using MacroTools
-
-const STRUCTSYMBOL = VERSION < v"0.7-" ? :type : :struct
-isstructdef(ex) = Meta.isexpr(ex, STRUCTSYMBOL)
-
-function splittypedef(ex)
-    ex = MacroTools.striplines(ex)
-    ex = MacroTools.flatten(ex)
-    d = Dict{Symbol, Any}()
-    if @capture(ex, struct header_ body__ end)
-        d[:mutable] = false
-    elseif @capture(ex, mutable struct header_ body__ end)
-        d[:mutable] = true
-    else
-        parse_error(ex)
-    end
-    
-    if @capture header nameparam_ <: super_
-        nothing
-    elseif @capture header nameparam_
-        super = :Any
-    else
-        parse_error(ex)
-    end
-    d[:supertype] = super
-    if @capture nameparam name_{param__}
-        nothing
-    elseif @capture nameparam name_
-        param = []
-    else
-        parse_error(ex)
-    end
-    d[:name] = name
-    d[:params] = param
-    d[:fields] = []
-    d[:constructors] = []
-    for item in body
-        if @capture item field_::T_
-            push!(d[:fields], (field, T))
-        elseif item isa Symbol
-            push!(d[:fields], (item, Any))
-        else
-            push!(d[:constructors], item)
-        end
-    end
-    d
-end
-
-function combinetypedef(d)::Expr
-    name = d[:name]
-    parameters = d[:params]
-    nameparam = isempty(parameters) ? name : :($name{$(parameters...)})
-    header = :($nameparam <: $(d[:supertype]))
-    fields = map(d[:fields]) do field
-        fieldname, typ = field
-        :($fieldname::$typ)
-    end
-    body = quote
-        $(fields...)
-        $(d[:constructors]...)
-    end
-
-    Expr(STRUCTSYMBOL, d[:mutable], header, body)
-end
-
-function combinefield(x)
-    fieldname, T = x
-    :($fieldname::$T)
-end
diff --git a/src/settable.jl b/src/settable.jl
index 1368d53..32ddd0a 100644
--- a/src/settable.jl
+++ b/src/settable.jl
@@ -1,10 +1,9 @@
 export @settable
-using MacroTools: prewalk, splitdef, combinedef
+using MacroTools: prewalk
+using MacroTools: splitdef, combinedef
+using MacroTools: splitstructdef, isstructdef, combinestructdef
 
 macro settable(ex)
-    if VERSION < v"0.7-"
-        __module__ = current_module()
-    end
     esc(settable(__module__, ex))
 end
 
@@ -87,7 +86,7 @@ function posonly_constructor(dtype::Dict)::Expr
 end
 
 function add_posonly_constructor(ex::Expr)::Expr
-    dtype = splittypedef(ex)
+    dtype = splitstructdef(ex)
     if isempty(dtype[:constructors])
         ex
     elseif has_posonly_constructor(dtype)
@@ -95,7 +94,7 @@ function add_posonly_constructor(ex::Expr)::Expr
     else
         push!(dtype[:constructors], posonly_constructor(dtype))
         @assert has_posonly_constructor(dtype)
-        combinetypedef(dtype)
+        combinestructdef(dtype)
     end
 end
 
diff --git a/src/sugar.jl b/src/sugar.jl
index 716cccc..b4ea674 100644
--- a/src/sugar.jl
+++ b/src/sugar.jl
@@ -1,4 +1,4 @@
-export @set, @set!, @lens
+export @set, @lens
 using MacroTools
 
 """
@@ -27,48 +27,11 @@ T(T(2, 2), 2)
 julia> @set t.a.b = 3
 T(T(2, 3), 2)
 ```
-See also [`@set!`](@ref).
 """
 macro set(ex)
     atset_impl(ex)
 end
 
-"""
-    @set! assignment
-
-Update deeply nested parts of an object. In contrast to `@set`, `@set!`
-overwrites the variable binding and mutates the original object
-if possible. 
-```jldoctest
-julia> using Setfield
-
-julia> struct T;a;b end
-
-julia> t = T(1,2)
-T(1, 2)
-
-julia> @set! t.a = 5
-T(5, 2)
-
-julia> t
-T(5, 2)
-
-julia> @set t.a = 10
-T(10, 2)
-
-julia> t
-T(5, 2)
-```
-### Warning
-Since `@set!` rebinds the variable, it will cause type instabilites
-for updates that change the type.
-
-See also [`@set`](@ref).
-"""
-macro set!(ex)
-    atset_impl(ex, :(EncourageMutation()), true)
-end
-
 function parse_obj_lenses(ex)
     if @capture(ex, front_[indices__])
         obj, frontlens = parse_obj_lenses(front)
@@ -103,7 +66,7 @@ struct _UpdateOp{OP,V}
 end
 (u::_UpdateOp)(x) = u.op(x, u.val)
 
-function atset_impl(ex::Expr, mut=:(ForbidMutation()), rebind=false)
+function atset_impl(ex::Expr)
     @assert ex.head isa Symbol
     @assert length(ex.args) == 2
     ref, val = ex.args
@@ -112,18 +75,15 @@ function atset_impl(ex::Expr, mut=:(ForbidMutation()), rebind=false)
     ret = if ex.head == :(=)
         quote
             lens = $lens
-            set(lens, $obj, $val, $mut)
+            set(lens, $obj, $val)
         end
     else
         op = UPDATE_OPERATOR_TABLE[ex.head]
         f = :(_UpdateOp($op,$val))
         quote
-            modify($f, $lens, $obj, $mut)
+            modify($f, $lens, $obj)
         end
     end
-    if rebind
-        ret = :($obj = $ret)
-    end
     ret
 end
 
diff --git a/test/runtests.jl b/test/runtests.jl
index ba6813a..9711fee 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -20,9 +20,6 @@ using Setfield
     include("test_core.jl")
 end
 
-@testset "macrotools" begin
-    include("test_macrotools.jl")
-end
 @testset "settable" begin
     include("test_settable.jl")
 end
@@ -35,10 +32,8 @@ end
     include("test_kwonly.jl")
 end
 
-@static if VERSION < v"0.7-"
 @testset "QuickTypes.jl" begin
     include("test_quicktypes.jl")
 end
-end
 
 end  # module
diff --git a/test/test_core.jl b/test/test_core.jl
index e4a40c2..beea620 100644
--- a/test/test_core.jl
+++ b/test/test_core.jl
@@ -178,68 +178,6 @@ end
     @test compose(la, id) === la
 end
 
-@testset "Mutability" begin
-
-    @testset "array" begin
-        v_init = [1,2,3]
-        v = v_init
-        @set! v[1] = 2
-        @test v_init[1] == 2
-        @test v === v_init
-
-        # Julia 0.7 with --depwarn=error:
-        is_deperror07 = VERSION >= v"0.7-" && Base.JLOptions().depwarn == 2
-
-        v = randn(3)
-        # @set! v[:] .= 0  # dot-call not supported
-        @test_broken v == [0,0,0.]
-        if is_deperror07
-            v[:] .= 1
-        else
-            v = @test_deprecated07 (@set! v[:] = 1; v)
-        end
-        @test v == [1,1,1.]
-        if is_deperror07
-            v[2:3] .= 4
-        else
-            v = @test_deprecated07 (@set! v[2:3] = 4; v)
-        end
-        @test v == [1,4,4]
-        # @set! v[1:2] .= 5  # dot-call not supported
-        @test_broken v == [5,5,4]
-    end
-
-    @testset "@set vs @set!" begin
-        m1 = M(1,2)
-        m2 = @set m1.a = 10
-        @test !(m2 === m1)
-        @test m1.a === 1
-        @test m2.a === 10
-        m3 = @set! m1.a = 100
-        @test m3 === m1
-        @test m1.a === 100
-    end
-
-    @testset "composition only mutates the innermost" begin
-        m_init = M(1,2)
-        m = m_init
-        @set! m.a = 10
-        @test m_init.a == 10
-        @test m === m_init
-        m_inner_init = M(1,2)
-        m_init = M(m_inner_init, 2)
-        m = m_init
-        @set! m.a.a = 2
-        @test m.a.a == 2
-        @test m === m_init
-        @test m.a === m_inner_init
-    end
-
-    obj = (1,)
-    @set! obj[1] = 2
-    @test obj === (2,)
-end
-
 struct A{X, Y}
     x::X
     y::Y
diff --git a/test/test_macrotools.jl b/test/test_macrotools.jl
deleted file mode 100644
index 2915191..0000000
--- a/test/test_macrotools.jl
+++ /dev/null
@@ -1,46 +0,0 @@
-using MacroTools
-using Setfield: splittypedef, combinetypedef
-
-@testset "combinetypedef, splittypedef" begin
-    ex = :(struct S end)
-    @test ex |> splittypedef |> combinetypedef |> Base.remove_linenums! == 
-        :(struct S <: Any end)
-    
-    @test splittypedef(ex) == Dict(
-        :constructors => Any[],
-        :mutable => false,
-        :params => Any[],
-        :name => :S,
-        :fields => Any[],
-        :supertype => :Any)
-
-    ex = :(mutable struct T end)
-    @test splittypedef(ex)[:mutable] === true
-    @test ex |> splittypedef |> combinetypedef |> Base.remove_linenums! == 
-        :(mutable struct T <: Any end)
-
-    ex = :(struct S{A,B} <: AbstractS{B}
-                               a::A
-                           end)
-    @test splittypedef(ex) == Dict(
-        :constructors => Any[],
-        :mutable => false,
-        :params => Any[:A, :B],
-        :name => :S,
-        :fields => Any[(:a, :A)],
-        :supertype => :(AbstractS{B}),)
-
-    @test ex |> splittypedef |> combinetypedef |> Base.remove_linenums! == 
-        ex |> Base.remove_linenums!
-
-    ex = :(struct S{A} <: Foo; S(a::A) where {A} = new{A}() end)
-    @test ex |> splittypedef |> combinetypedef |>
-        Base.remove_linenums! |> MacroTools.flatten ==
-        ex |> Base.remove_linenums! |> MacroTools.flatten
-
-    constructors = splittypedef(ex)[:constructors]
-    @test length(constructors) == 1
-    @test first(constructors) ==
-        :((S(a::A) where A) = new{A}()) |> MacroTools.flatten
-
-end
diff --git a/test/test_quicktypes.jl b/test/test_quicktypes.jl
index cdae5a8..099e8a9 100644
--- a/test/test_quicktypes.jl
+++ b/test/test_quicktypes.jl
@@ -1,10 +1,5 @@
 module TestQuicktypes
-
-@static if VERSION < v"0.7-"
-    using Base.Test
-else
-    using Test
-end
+using Test
 
 import Base: ==
 import MacroTools
@@ -64,13 +59,13 @@ end
 end
 
 
-@qstruct Pack{T}(animals::Vector{T})
+@qstruct Pack{T, N}(animals::NTuple{N, T})
 
 @testset "Pack" begin
-    x = Pack([Cat(:Tama, 1), Cat(:Pochi, 2)])
+    x = Pack((Cat(:Tama, 1), Cat(:Pochi, 2)))
 
-    @set! x.animals[2].nlegs = 5
-    @test x.animals == [Cat(:Tama, 1), Cat(:Pochi, 2, 5)]
+    x = @set x.animals[2].nlegs = 5
+    @test x.animals == (Cat(:Tama, 1), Cat(:Pochi, 2, 5))
 end
 
 
@@ -116,10 +111,9 @@ end
 @qstruct Group{x}(members::x; _concise_show=true)
 
 @testset "Group" begin
-    x = Group([0, 1])
-
-    x = @set! x.members[2] = 111
-    @test x.members == [0, 111]
+    x = Group((0, 1))
+    x = @set x.members[2] = 111
+    @test x.members == (0, 111)
 end
 
 @settable @qstruct_fp Plane1(nwheels, weight::Number; brand=:zoomba)