Only escape contents outside of interpolation, closes #9812

Author: josevalim

lib/elixir/lib/macro.ex

@@ -1022,11 +1022,13 @@ defmodule Macro do
 
         binary when is_binary(binary) ->
           binary = inspect_no_limit(binary)
-          binary_part(binary, 1, byte_size(binary) - 2)
+
+          binary
+          |> binary_part(1, byte_size(binary) - 2)
+          |> escape_sigil(left)
       end)
 
-    escaped = escape_sigil(parts, left)
-    <<left::binary, escaped::binary, right::binary>>
+    <<left::binary, parts::binary, right::binary>>
   end
 
   defp escape_sigil(parts, "("), do: String.replace(parts, ")", ~S"\)")

lib/elixir/test/elixir/macro_test.exs

@@ -344,6 +344,7 @@ defmodule MacroTest do
       assert Macro.to_string(quote(do: ~R"\n123")) == ~S/~R"\n123"/
 
       assert Macro.to_string(quote(do: ~S["'(123)'"])) == ~S/~S["'(123)'"]/
+      assert Macro.to_string(quote(do: ~s"#{"foo"}")) == ~S/~s"#{"foo"}"/
 
       assert Macro.to_string(
                quote do
@@ -704,6 +705,12 @@ defmodule MacroTest do
       assert Macro.to_string(quote(do: 'abc')) == "'abc'"
     end
 
+    test "string" do
+      assert Macro.to_string(quote(do: "")) == ~S/""/
+      assert Macro.to_string(quote(do: "abc")) == ~S/"abc"/
+      assert Macro.to_string(quote(do: "#{"abc"}")) == ~S/"#{"abc"}"/
+    end
+
     test "last arg keyword list" do
       assert Macro.to_string(quote(do: foo([]))) == "foo([])"
       assert Macro.to_string(quote(do: foo(x: y))) == "foo(x: y)"