Deprecate to_binary in favor of to_string

We also rename Binary.Chars to String.Chars.

As Binary.Chars was the protocol used for interpolation,
it is semantically correct to have a protocol that works
on strings, instead of raw binaries.

Author: José Valim

lib/eex/lib/eex/engine.ex

@@ -43,7 +43,7 @@ defmodule EEx.Engine do
   def handle_expr(buffer, "=", expr) do
     quote do
       tmp = unquote(buffer)
-      tmp <> to_binary(unquote(expr))
+      tmp <> to_string(unquote(expr))
     end
   end
 

lib/elixir/lib/binary/chars.ex

@@ -118,8 +118,7 @@ defmodule Code do
   end
 
   defp do_eval_string(string, binding, opts) when is_list(binding) do
-    { value, binding, _scope } =
-      :elixir.eval String.to_char_list!(string), binding, opts
+    { value, binding, _scope } = :elixir.eval to_char_list(string), binding, opts
     { value, binding }
   end
 
@@ -216,10 +215,10 @@ defmodule Code do
   `Macro.to_string/1`, which converts a quoted form to a string/binary
   representation.
   """
-  def string_to_quoted(string, opts // []) do
+  def string_to_quoted(string, opts // []) when is_list(opts) do
     file = Keyword.get opts, :file, "nofile"
     line = Keyword.get opts, :line, 1
-    res  = :elixir_translator.forms(String.to_char_list!(string), line, file, opts)
+    res  = :elixir_translator.forms(to_char_list(string), line, file, opts)
 
     case res do
       { :ok, forms } -> { :ok, unpack_quote(line, forms) }
@@ -235,10 +234,10 @@ defmodule Code do
 
   Check `string_to_quoted/2` for options information.
   """
-  def string_to_quoted!(string, opts // []) do
+  def string_to_quoted!(string, opts // []) when is_list(opts) do
     file = Keyword.get opts, :file, "nofile"
     line = Keyword.get opts, :line, 1
-    res  = :elixir_translator.forms!(String.to_char_list!(string), line, file, opts)
+    res  = :elixir_translator.forms!(to_char_list(string), line, file, opts)
     unpack_quote(line, res)
   end
 

lib/elixir/lib/code.ex

@@ -593,8 +593,8 @@ defmodule Enum do
 
   def join(collection, joiner) when is_binary(joiner) do
     Enumerable.reduce(collection, "", fn
-      entry, ""  -> to_binary(entry)
-      entry, acc -> acc <> joiner <> to_binary(entry)
+      entry, ""  -> to_string(entry)
+      entry, acc -> acc <> joiner <> to_string(entry)
     end)
   end
 
@@ -653,18 +653,11 @@ defmodule Enum do
 
   def map_join(collection, joiner, mapper) when is_binary(joiner) do
     Enumerable.reduce(collection, "", fn
-      entry, ""  -> to_binary(mapper, entry)
-      entry, acc -> acc <> joiner <> to_binary(mapper, entry)
+      entry, ""  -> to_string(mapper, entry)
+      entry, acc -> acc <> joiner <> to_string(mapper, entry)
     end)
   end
 
-  defp to_binary(mapper, entry) do
-    case mapper.(entry) do
-      x when is_binary(x) -> x
-      o -> Binary.Chars.to_binary(o)
-    end
-  end
-
   @doc """
   Invokes the given `fun` for each item in the `collection`
   while also keeping an accumulator. Returns a tuple where
@@ -1312,7 +1305,7 @@ defmodule Enum do
 
   ## Helpers
 
-  @compile { :inline, chunks_n: 5, chunks_step: 4 }
+  @compile { :inline, chunks_n: 5, chunks_step: 4, to_string: 2 }
 
   defp chunks_n(acc, buffer, i, n, step) when i == n do
     acc = [:lists.reverse(buffer)|acc]
@@ -1346,6 +1339,13 @@ defmodule Enum do
     map_reduce(collection, 0, reducer)
   end
 
+  defp to_string(mapper, entry) do
+    case mapper.(entry) do
+      x when is_binary(x) -> x
+      o -> String.Chars.to_string(o)
+    end
+  end
+
   ## Implementations
 
   ## all?

lib/elixir/lib/enum.ex

@@ -304,7 +304,7 @@ defmodule Exception do
   """
   def format_file_line(file, line, cwd // nil) do
     if file do
-      file = to_binary(file)
+      file = to_string(file)
       file = if cwd, do: Path.relative_to(file, cwd), else: Path.relative_to_cwd(file)
 
       if line && line != 0 do