diff --git a/.gitignore b/.gitignore
index b9f53d7..f463bd2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 *.jl.cov
 *.jl.*.cov
 *.jl.mem
+/Manifest.toml
 
 .DS_Store
 
diff --git a/Manifest.toml b/Manifest.toml
deleted file mode 100644
index dffc979..0000000
--- a/Manifest.toml
+++ /dev/null
@@ -1,15 +0,0 @@
-# This file is machine-generated - editing it directly is not advised
-
-[[Base64]]
-uuid = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
-
-[[Markdown]]
-deps = ["Base64"]
-uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"
-
-[[Random]]
-deps = ["Serialization"]
-uuid = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
-
-[[Serialization]]
-uuid = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
diff --git a/Project.toml b/Project.toml
index b8db1c3..0db26ed 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,10 +3,12 @@ uuid = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
 version = "0.5.5"
 
 [deps]
+ExprTools = "e2ba6199-217a-4e67-a87a-7c52f15ade04"
 Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 
 [compat]
+ExprTools = "0.1"
 julia = "1"
 
 [extras]
diff --git a/src/MacroTools.jl b/src/MacroTools.jl
index 4bd41dd..5a214fa 100644
--- a/src/MacroTools.jl
+++ b/src/MacroTools.jl
@@ -1,6 +1,8 @@
 module MacroTools
 
 using Markdown, Random
+using ExprTools: splitdef, combinedef
+
 export @match, @capture
 
 include("match/match.jl")
diff --git a/src/utils.jl b/src/utils.jl
index 7cb4a88..dc44a79 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -259,127 +259,6 @@ function gatherwheres(ex)
   end
 end
 
-"""    splitdef(fdef)
-
-Match any function definition
-
-```julia
-function name{params}(args; kwargs)::rtype where {whereparams}
-   body
-end
-```
-
-and return `Dict(:name=>..., :args=>..., etc.)`. The definition can be rebuilt by
-calling `MacroTools.combinedef(dict)`, or explicitly with
-
-```
-rtype = get(dict, :rtype, :Any)
-all_params = [get(dict, :params, [])..., get(dict, :whereparams, [])...]
-:(function \$(dict[:name]){\$(all_params...)}(\$(dict[:args]...);
-                                            \$(dict[:kwargs]...))::\$rtype
-      \$(dict[:body])
-  end)
-```
-"""
-function splitdef(fdef)
-  error_msg = "Not a function definition: $(repr(fdef))"
-  @assert(@capture(longdef1(fdef),
-                   function (fcall_ | fcall_) body_ end),
-          "Not a function definition: $fdef")
-  fcall_nowhere, whereparams = gatherwheres(fcall)
-  func = args = kwargs = rtype = nothing
-  if @capture(fcall_nowhere, ((func_(args__; kwargs__)) |
-                              (func_(args__; kwargs__)::rtype_) |
-                              (func_(args__)) |
-                              (func_(args__)::rtype_)))
-  elseif isexpr(fcall_nowhere, :tuple)
-    if length(fcall_nowhere.args) > 1 && isexpr(fcall_nowhere.args[1], :parameters)
-      args = fcall_nowhere.args[2:end]
-      kwargs = fcall_nowhere.args[1].args
-    else
-      args = fcall_nowhere.args
-    end
-  elseif isexpr(fcall_nowhere, :(::))
-    args = Any[fcall_nowhere]
-  else
-    throw(ArgumentError(error_msg))
-  end
-  if func !== nothing
-    @assert(@capture(func, (fname_{params__} | fname_)), error_msg)
-    di = Dict(:name=>fname, :args=>args,
-              :kwargs=>(kwargs===nothing ? [] : kwargs), :body=>body)
-  else
-    params = nothing
-    di = Dict(:args=>args, :kwargs=>(kwargs===nothing ? [] : kwargs), :body=>body)
-  end
-  if rtype !== nothing; di[:rtype] = rtype end
-  if whereparams !== nothing; di[:whereparams] = whereparams end
-  if params !== nothing; di[:params] = params end
-  di
-end
-
-"""
-    combinedef(dict::Dict)
-
-`combinedef` is the inverse of `splitdef`. It takes a splitdef-like Dict
-and returns a function definition. """
-function combinedef(dict::Dict)
-  rtype = get(dict, :rtype, nothing)
-  params = get(dict, :params, [])
-  wparams = get(dict, :whereparams, [])
-  body = block(dict[:body])
-  if haskey(dict, :name)
-    name = dict[:name]
-    name_param = isempty(params) ? name : :($name{$(params...)})
-    # We need the `if` to handle parametric inner/outer constructors like
-    # SomeType{X}(x::X) where X = SomeType{X}(x, x+2)
-    if isempty(wparams)
-      if rtype==nothing
-        @q(function $name_param($(dict[:args]...);
-                                $(dict[:kwargs]...))
-          $(body.args...)
-          end)
-      else
-        @q(function $name_param($(dict[:args]...);
-                                $(dict[:kwargs]...))::$rtype
-          $(body.args...)
-          end)
-      end
-    else
-      if rtype==nothing
-        @q(function $name_param($(dict[:args]...);
-                                $(dict[:kwargs]...)) where {$(wparams...)}
-          $(body.args...)
-          end)
-      else
-        @q(function $name_param($(dict[:args]...);
-                                $(dict[:kwargs]...))::$rtype where {$(wparams...)}
-          $(body.args...)
-          end)
-      end
-    end
-  else
-    if isempty(dict[:kwargs])
-      arg = :($(dict[:args]...),)
-    else
-      arg = Expr(:tuple, Expr(:parameters, dict[:kwargs]...), dict[:args]...)
-    end
-    if isempty(wparams)
-      if rtype==nothing
-        @q($arg -> $body)
-      else
-        @q(($arg::$rtype) -> $body)
-      end
-    else
-      if rtype==nothing
-        @q(($arg where {$(wparams...)}) -> $body)
-      else
-        @q(($arg::$rtype where {$(wparams...)}) -> $body)
-      end
-    end
-  end
-end
-
 """
     combinearg(arg_name, arg_type, is_splat, default)
 
diff --git a/test/split.jl b/test/split.jl
index 940a68c..2496919 100644
--- a/test/split.jl
+++ b/test/split.jl
@@ -1,75 +1,8 @@
 using MacroTools: splitstructdef, combinestructdef
 
-macro nothing_macro()
-end
+macro nothing_macro() end
 @test @expand(@nothing_macro) === nothing
 
-macro splitcombine(fundef) # should be a no-op
-    dict = splitdef(fundef)
-    esc(MacroTools.combinedef(dict))
-end
-
-# Macros for testing that splitcombine doesn't break
-# macrocalls in bodies
-macro zeroarg()
-   :(1)
-end
-macro onearg(x)
-   :(1+$(esc(x)))
-end
-
-let
-    # Ideally we'd compare the result against :(function f(x)::Int 10 end),
-    # but it fails because of :line and :block differences
-    @test longdef(:(f(x)::Int = 10)).head == :function
-    @test longdef(:(f(x::T) where U where T = 2)).head == :function
-    @test shortdef(:(function f(x)::Int 10 end)).head != :function
-    @test map(splitarg, (:(f(a=2, x::Int=nothing, y, args...))).args[2:end]) ==
-        [(:a, :Any, false, 2), (:x, :Int, false, :nothing),
-         (:y, :Any, false, nothing), (:args, :Any, true, nothing)]
-    @test splitarg(:(::Int)) == (nothing, :Int, false, nothing)
-
-    @splitcombine foo(x) = x+2
-    @test foo(10) == 12
-    @splitcombine add(a, b=2; c=3, d=4)::Float64 = a+b+c+d
-    @test add(1; d=10) === 16.0
-    @splitcombine fparam(a::T) where {T} = T
-    @test fparam([]) == Vector{Any}
-    struct Orange end
-    @splitcombine (::Orange)(x) = x+2
-    @test Orange()(10) == 12
-    @splitcombine fwhere(a::T) where T = T
-    @test fwhere(10) == Int
-    @splitcombine manywhere(x::T, y::Vector{U}) where T <: U where U = (T, U)
-    @test manywhere(1, Number[2.0]) == (Int, Number)
-    @splitcombine fmacro0() = @zeroarg
-    @test fmacro0() == 1
-    @splitcombine fmacro1() = @onearg 1
-    @test fmacro1() == 2
-
-    struct Foo{A, B}
-        a::A
-        b::B
-    end
-    # Parametric outer constructor
-    @splitcombine Foo{A}(a::A) where A = Foo{A, A}(a,a)
-    @test Foo{Int}(2) == Foo{Int, Int}(2, 2)
-
-    @test (@splitcombine x -> x + 2)(10) === 12
-    @test (@splitcombine (a, b=2; c=3, d=4) -> a+b+c+d)(1; d=10) === 16
-    @test (@splitcombine ((a, b)::Tuple{Int,Int} -> a + b))((1, 2)) == 3
-    @test (@splitcombine ((a::T) where {T}) -> T)([]) === Vector{Any}
-    @test (@splitcombine ((x::T, y::Vector{U}) where T <: U where U) -> (T, U))(1, Number[2.0]) ==
-          (Int, Number)
-    @test (@splitcombine () -> @zeroarg)() == 1
-    @test (@splitcombine () -> @onearg 1)() == 2
-    @test (@splitcombine function (x) x + 2 end)(10) === 12
-    @test (@splitcombine function (a::T) where {T} T end)([]) === Vector{Any}
-    @test (@splitcombine function (x::T, y::Vector{U}) where T <: U where U
-               (T, U)
-           end)(1, Number[2.0]) == (Int, Number)
-end
-
 @testset "combinestructdef, splitstructdef" begin
     ex = :(struct S end)
     @test ex |> splitstructdef |> combinestructdef |> Base.remove_linenums! ==