Fix formatter for tilde inside bitstrings, closes #7558

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: José Valim

lib/elixir/lib/code/formatter.ex

@@ -1351,8 +1351,17 @@ defmodule Code.Formatter do
   defp bitstring_segment_to_algebra({{:::, _, [segment, spec]}, i}, state, last) do
     {doc, state} = quoted_to_algebra(segment, :parens_arg, state)
     {spec, state} = bitstring_spec_to_algebra(spec, state)
-    doc = concat(concat(doc, "::"), wrap_in_parens_if_inspected_atom(spec))
-    {bitstring_wrap_parens(doc, i, last), state}
+
+    spec = wrap_in_parens_if_inspected_atom(spec)
+    spec = if i == last, do: bitstring_wrap_parens(spec, i, last), else: spec
+
+    doc =
+      doc
+      |> bitstring_wrap_parens(i, -1)
+      |> concat("::")
+      |> concat(spec)
+
+    {doc, state}
   end
 
   defp bitstring_segment_to_algebra({segment, i}, state, last) do
@@ -1370,21 +1379,19 @@ defmodule Code.Formatter do
     quoted_to_algebra_with_parens_if_operator(spec, :parens_arg, state)
   end
 
-  defp bitstring_wrap_parens(doc, i, last) do
-    if i == 0 or i == last do
-      string = format_to_string(doc)
+  defp bitstring_wrap_parens(doc, i, last) when i == 0 or i == last do
+    string = format_to_string(doc)
 
-      if (i == 0 and String.starts_with?(string, "<<")) or
-           (i == last and String.ends_with?(string, ">>")) do
-        wrap_in_parens(doc)
-      else
-        doc
-      end
+    if (i == 0 and String.starts_with?(string, ["~", "<<"])) or
+         (i == last and String.ends_with?(string, [">>"])) do
+      wrap_in_parens(doc)
     else
       doc
     end
   end
 
+  defp bitstring_wrap_parens(doc, _, _), do: doc
+
   ## Literals
 
   defp list_to_algebra(meta, args, state) do

lib/elixir/test/elixir/code_formatter/containers_test.exs

@@ -247,13 +247,19 @@ defmodule Code.Formatter.ContainersTest do
       assert_format "<<1,2,3>>", "<<1, 2, 3>>"
     end
 
-    test "add parens on first and last in case of ambiguity" do
+    test "add parens on first and last in case of binary ambiguity" do
       assert_format "<< <<>> >>", "<<(<<>>)>>"
       assert_format "<< <<>> + <<>> >>", "<<(<<>> + <<>>)>>"
       assert_format "<< 1 + <<>> >>", "<<(1 + <<>>)>>"
       assert_format "<< <<>> + 1 >>", "<<(<<>> + 1)>>"
       assert_format "<< <<>>, <<>>, <<>> >>", "<<(<<>>), <<>>, (<<>>)>>"
-      assert_format "<< <<>>::1, <<>>::2, <<>>::3 >>", "<<(<<>>::1), <<>>::2, <<>>::3>>"
+      assert_format "<< <<>>::1, <<>>::2, <<>>::3 >>", "<<(<<>>)::1, <<>>::2, <<>>::3>>"
+      assert_format "<< <<>>::<<>> >>", "<<(<<>>)::(<<>>)>>"
+    end
+
+    test "add parens on first in case of operator ambiguity" do
+      assert_format "<< ~~~1::8 >>", "<<(~~~1)::8>>"
+      assert_format "<< ~s[foo]::binary >>", "<<(~s[foo])::binary>>"
     end
 
     test "with modifiers" do

lib/elixir/test/elixir/kernel/expansion_test.exs

@@ -1945,7 +1945,7 @@ defmodule Kernel.ExpansionTest do
       message = ~r"literal <<>> in bitstring supports only type specifiers"
 
       assert_raise CompileError, message, fn ->
-        expand(quote(do: <<(<<"foo">>::32)>>))
+        expand(quote(do: <<(<<"foo">>)::32>>))
       end
     end