Move some runtime deprecations to compile time

Author: José Valim

lib/elixir/lib/option_parser.ex

@@ -559,7 +559,7 @@ defmodule OptionParser do
 
         true ->
           # TODO: Remove this in Elixir v2.0
-          IO.warn("Not passing the :switches or :strict option to OptionParser is deprecated")
+          IO.warn("not passing the :switches or :strict option to OptionParser is deprecated")
           {[], false}
       end
 

lib/elixir/test/elixir/option_parser_test.exs

@@ -376,7 +376,7 @@ end
 defmodule OptionsParserDeprecationsTest do
   use ExUnit.Case, async: false
 
-  @warning ~r[Not passing the :switches or :strict option to OptionParser is deprecated]
+  @warning ~r[not passing the :switches or :strict option to OptionParser is deprecated]
 
   def assert_deprecated(fun) do
     assert ExUnit.CaptureIO.capture_io(:stderr, fun) =~ @warning

lib/iex/lib/iex/helpers.ex

@@ -1095,8 +1095,8 @@ defmodule IEx.Helpers do
   end
 
   @doc false
+  @deprecated "Use import_file_if_available/1 instead"
   defmacro import_file(path, opts) when is_binary(path) and is_list(opts) do
-    IO.warn("import_file/2 is deprecated, please use import_file_if_available/1 instead")
     import_file_if_available(path, Keyword.get(opts, :optional, false))
   end
 

lib/mix/lib/mix/utils.ex

@@ -350,14 +350,14 @@ defmodule Mix.Utils do
   defp quoted(data), do: [?", to_string(data), ?"]
 
   @doc false
+  @deprecated "Use Macro.underscore/1 instead"
   def underscore(value) do
-    IO.warn("Mix.Utils.underscore/1 is deprecated, use Macro.underscore/1 instead")
     Macro.underscore(value)
   end
 
   @doc false
+  @deprecated "Use Macro.camelize/1 instead"
   def camelize(value) do
-    IO.warn("Mix.Utils.camelize/1 is deprecated, use Macro.camelize/1 instead")
     Macro.camelize(value)
   end