Fix formatter for :* in bitstring modifiers (#12923)

Author: sabiwara

lib/elixir/lib/code/formatter.ex

@@ -1419,7 +1419,9 @@ 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, state.normalize_bitstring_modifiers)
+
+    {spec, state} =
+      bitstring_spec_to_algebra(spec, state, state.normalize_bitstring_modifiers, :"::")
 
     spec = wrap_in_parens_if_inspected_atom(spec)
     spec = if i == last, do: bitstring_wrap_parens(spec, i, last), else: spec
@@ -1438,15 +1440,17 @@ defmodule Code.Formatter do
     {bitstring_wrap_parens(doc, i, last), state}
   end
 
-  defp bitstring_spec_to_algebra({op, _, [left, right]}, state, normalize_modifiers)
+  defp bitstring_spec_to_algebra({op, _, [left, right]}, state, normalize_modifiers, paren_op)
        when op in [:-, :*] do
     normalize_modifiers = normalize_modifiers && op != :*
-    {left, state} = bitstring_spec_to_algebra(left, state, normalize_modifiers)
+    {left, state} = bitstring_spec_to_algebra(left, state, normalize_modifiers, op)
     {right, state} = bitstring_spec_element_to_algebra(right, state, normalize_modifiers)
-    {concat(concat(left, Atom.to_string(op)), right), state}
+    doc = concat(concat(left, Atom.to_string(op)), right)
+    doc = if paren_op == :*, do: wrap_in_parens(doc), else: doc
+    {doc, state}
   end
 
-  defp bitstring_spec_to_algebra(spec, state, normalize_modifiers) do
+  defp bitstring_spec_to_algebra(spec, state, normalize_modifiers, _paren_op) do
     bitstring_spec_element_to_algebra(spec, state, normalize_modifiers)
   end
 

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

@@ -275,6 +275,8 @@ defmodule Code.Formatter.ContainersTest do
       assert_format "<< 1 :: 2 - unit(3) >>", "<<1::2-unit(3)>>"
       assert_format "<< 1 :: 2 * 3 - unit(4) >>", "<<1::2*3-unit(4)>>"
       assert_format "<< 1 :: 2 - unit(3) - 4 / 5 >>", "<<1::2-unit(3)-(4 / 5)>>"
+      assert_format "<<0 :: ( x - 1 ) * 5>>", "<<0::(x-1)*5>>"
+      assert_format "<<0 :: 2 * 3 * 4>>", "<<0::(2*3)*4>>"
     end
 
     test "in comprehensions" do