Deprecate def/4 and friends in favor of def/2 with unquote and friends

Author: José Valim

CHANGELOG.md

@@ -42,6 +42,7 @@
   * [IO] `IO.stream(device)` and `IO.binstream(device)` are deprecated in favor of `IO.stream(device, :line)` and `IO.binstream(device, :line)`
   * [Kernel] `list_to_binary/1`, `binary_to_list/1` and `binary_to_list/3` are deprecated in favor of `String.from_char_list!/1` and `String.to_char_list!/1` for characters and `:binary.list_to_bin/1`, `:binary.bin_to_list/1` and `:binary.bin_to_list/3` for bytes
   * [Kernel] `to_binary/1` is deprecated in favor of `to_string/1`
+  * [Kernel] Deprecate `def/4` and friends in favor of `def/2` with unquote and friends
   * [Macro] `Macro.unescape_binary/1` and `Macro.unescape_binary/2` are deprecated in favor of `Macro.unescape_string/1` and `Macro.unescape_string/2`
   * [Mix] `:umbrella` option for umbrella paths has been deprecated in favor of `:in_umbrella`
 

lib/elixir/lib/kernel.ex

@@ -1317,38 +1317,7 @@ defmodule Kernel do
   """
   defmacro def(name, do: contents)
 
-  @doc """
-  This macro allows a function to be defined more explicitly
-  by accepting the name, args and guards as different entries.
-
-  Unlike `def/2`, the macro arguments are evaluated
-  and therefore require quoting.
-
-  The `name` must be an atom, the `arguments` a list where each
-  element represents another argument and `guards` a list of
-  clauses, where each clause is disjunct.
-
-  ## Examples
-
-  The most common mistake when using this macro is to pass the
-  arguments without quoting:
-
-      def :some_function, [first_arg, second_arg], is_list(first_arg) do
-        # ...
-      end
-
-  However, the example above will fail because it will attempt to
-  evaluate `[first_arg, second_arg]` and fail because the variable
-  `first_arg` is not defined. Therefore, we need to use quote:
-
-      name   = :some_function
-      args   = quote(do: [first_arg, second_arg])
-      guards = quote(do: is_list(first_arg))
-      exprs  = quote(do: ...)
-
-      def name, args, guards, do: exprs
-
-  """
+  @doc false
   defmacro def(name, args, guards, do: contents)
 
   @doc """
@@ -1372,9 +1341,7 @@ defmodule Kernel do
   """
   defmacro defp(name, do: contents)
 
-  @doc """
-  The same as `def/4` but generates a private function.
-  """
+  @doc false
   defmacro defp(name, args, guards, do: contents)
 
   @doc """
@@ -1398,9 +1365,7 @@ defmodule Kernel do
   """
   defmacro defmacro(name, do: contents)
 
-  @doc """
-  The same as `def/4` but generates a macro.
-  """
+  @doc false
   defmacro defmacro(name, args, guards, do: contents)
 
   @doc """
@@ -1411,9 +1376,7 @@ defmodule Kernel do
   """
   defmacro defmacrop(name, do: contents)
 
-  @doc """
-  The same as `def/4` but generates a private macro.
-  """
+  @doc false
   defmacro defmacrop(name, args, guards, do: contents)
 
   @doc %B"""
@@ -3381,10 +3344,8 @@ defmodule Kernel do
 
   """
   defmacro defdelegate(funs, opts) do
-    quote do
-      funs = unquote(Macro.escape(funs, unquote: true))
-      opts = unquote(opts)
-
+    funs = Macro.escape(funs, unquote: true)
+    quote bind_quoted: [funs: funs, opts: opts] do
       target = Keyword.get(opts, :to) ||
         raise(ArgumentError, message: "Expected to: to be given as argument")
 
@@ -3402,10 +3363,11 @@ defmodule Kernel do
             false -> args
           end
 
-        fun  = Keyword.get(opts, :as, name)
-        body = quote do: unquote(target).unquote(fun)(unquote_splicing(actual_args))
+        fun = Keyword.get(opts, :as, name)
 
-        def name, args, [], do: body
+        def unquote(name)(unquote_splicing(args)) do
+          unquote(target).unquote(fun)(unquote_splicing(actual_args))
+        end
       end
     end
   end

lib/elixir/lib/protocol.ex

@@ -406,7 +406,7 @@ defmodule Protocol.DSL do
     type_args = lc _ inlist :lists.seq(2, arity), do: quote(do: term)
     type_args = [quote(do: t) | type_args]
 
-    quote do
+    meta = quote do
       name  = unquote(name)
       arity = unquote(arity)
 
@@ -416,13 +416,17 @@ defmodule Protocol.DSL do
       # signature that will be used by docs
       Kernel.def unquote(name)(unquote_splicing(args))
 
-      { args, body } = Protocol.DSL.args_and_body(__MODULE__, name, arity)
-      Kernel.def unquote(name), args, [], do: body
-
       # Convert the spec to callback if possible,
       # otherwise generate a dummy callback
       Protocol.DSL.callback_from_spec(__MODULE__, name, arity) ||
         @callback unquote(name)(unquote_splicing(type_args)) :: term
     end
+
+    impl = quote bind_quoted: [name: name, arity: arity] do
+      { args, body } = Protocol.DSL.args_and_body(__MODULE__, name, arity)
+      Kernel.def unquote(name)(unquote_splicing(args)), do: unquote(body)
+    end
+
+    [meta, impl]
   end
 end

lib/elixir/src/elixir_macros.erl

@@ -190,6 +190,7 @@ translate({Kind, Meta, [Call, Expr]}, S) when ?defs(Kind) ->
   { elixir_def:wrap_definition(Kind, Meta, TCall, TExpr, CheckClauses, SE), SE };
 
 translate({Kind, Meta, [Name, Args, Guards, Expr]}, S) when ?defs(Kind) ->
+  elixir_errors:deprecation(Meta, S#elixir_scope.file, "~ts/4 is deprecated, please use ~ts/2 instead", [Kind, Kind]),
   assert_module_scope(Meta, Kind, S),
   assert_no_function_scope(Meta, Kind, S),
   { TName, SN }   = translate_each(Name, S),

lib/elixir/test/elixir/module_test.exs

@@ -23,16 +23,13 @@ defmodule ModuleTest.ToBeUsed do
   defmacro callback(env) do
     value = Module.get_attribute(env.module, :has_callback)
     quote do
-      name  = :original_value
-      args  = [1]
-      guard = []
-      def name, args, guard, do: unquote(value)
+      def original_value(1), do: unquote(value)
     end
   end
 end
 
 defmodule ModuleTest.ToUse do
-  35 = __ENV__.line # Moving the next line around can make tests fail
+  32 = __ENV__.line # Moving the next line around can make tests fail
   def original_value(2), do: true
   use ModuleTest.ToBeUsed
 end
@@ -62,7 +59,7 @@ defmodule ModuleTest do
   end
 
   test :line_from_macro do
-    assert ModuleTest.ToUse.line == 37
+    assert ModuleTest.ToUse.line == 34
   end
 
   ## Callbacks

lib/ex_unit/lib/ex_unit/callbacks.ex

@@ -107,9 +107,9 @@ defmodule ExUnit.Callbacks do
   Called before the start of each test.
   """
   defmacro setup(var // quote(do: _), block) do
-    quote do
+    quote bind_quoted: [var: escape(var), block: escape(block)] do
       name = :"__ex_unit_setup_#{length(@ex_unit_setup)}"
-      defp name, [unquote(escape var)], [], unquote(escape block)
+      defp unquote(name)(unquote(var)), unquote(block)
       @ex_unit_setup [name|@ex_unit_setup]
     end
   end
@@ -119,9 +119,9 @@ defmodule ExUnit.Callbacks do
   message, `teardown` will not be run.
   """
   defmacro teardown(var // quote(do: _), block) do
-    quote do
+    quote bind_quoted: [var: escape(var), block: escape(block)] do
       name = :"__ex_unit_teardown_#{length(@ex_unit_teardown)}"
-      defp name, [unquote(escape var)], [], unquote(escape block)
+      defp unquote(name)(unquote(var)), unquote(block)
       @ex_unit_teardown [name|@ex_unit_teardown]
     end
   end
@@ -131,9 +131,9 @@ defmodule ExUnit.Callbacks do
   the current module and before any `setup` callbacks.
   """
   defmacro setup_all(var // quote(do: _), block) do
-    quote do
+    quote bind_quoted: [var: escape(var), block: escape(block)] do
       name = :"__ex_unit_setup_all_#{length(@ex_unit_setup_all)}"
-      defp name, [unquote(escape var)], [], unquote(escape block)
+      defp unquote(name)(unquote(var)), unquote(block)
       @ex_unit_setup_all [name|@ex_unit_setup_all]
     end
   end
@@ -142,9 +142,9 @@ defmodule ExUnit.Callbacks do
   Called once after the last test finishes without emitting an :exit message.
   """
   defmacro teardown_all(var // quote(do: _), block) do
-    quote do
+    quote bind_quoted: [var: escape(var), block: escape(block)] do
       name = :"__ex_unit_teardown_all_#{length(@ex_unit_teardown_all)}"
-      defp name, [unquote(escape var)], [], unquote(escape block)
+      defp unquote(name)(unquote(var)), unquote(block)
       @ex_unit_teardown_all [name|@ex_unit_teardown_all]
     end
   end

lib/ex_unit/lib/ex_unit/case.ex

@@ -96,8 +96,7 @@ defmodule ExUnit.Case do
         :"test_#{message}"
       end
 
-      def unquote(message)(unquote(var)), do:
-        unquote(contents)
+      def unquote(message)(unquote(var)), do: unquote(contents)
     end
   end
 end

lib/ex_unit/lib/ex_unit/doc_test.ex

@@ -130,9 +130,9 @@ defmodule ExUnit.DocTest do
   This macro is auto-imported with every `ExUnit.Case`.
   """
   defmacro doctest(mod, opts // []) do
-    quote do
-      lc { name, test } inlist unquote(__MODULE__).__doctests__(unquote(mod), unquote(opts)) do
-        def name, quote(do: [_]), [], do: test
+    quote bind_quoted: binding do
+      lc { name, test } inlist ExUnit.DocTest.__doctests__(mod, opts) do
+        def unquote(name)(_), do: unquote(test)
       end
     end
   end

lib/mix/lib/mix/generator.ex

@@ -75,8 +75,8 @@ defmodule Mix.Generator do
   `_text` that expects no argument.
   """
   defmacro embed_text(name, contents) do
-    quote do
-      defp :"#{unquote(name)}_text", [], [], do: unquote(contents)
+    quote bind_quoted: [name: name, contents: Macro.escape(contents)] do
+      defp unquote(:"#{name}_text")(), do: unquote(contents)
     end
   end
 end