1 files changed, 48 insertions, 0 deletions
diff --git a/lib/prism/translation/parser/builder.rb b/lib/prism/translation/parser/builder.rb
index ee3da1ee67..d3b51f4275 100644
--- a/lib/prism/translation/parser/builder.rb
+++ b/lib/prism/translation/parser/builder.rb
@@ -6,7 +6,55 @@ module Prism
       # A builder that knows how to convert more modern Ruby syntax
       # into whitequark/parser gem's syntax tree.
       class Builder < ::Parser::Builders::Default
+        # It represents the `it` block argument, which is not yet implemented in the Parser gem.
+        def itarg
+          n(:itarg, [:it], nil)
+        end
 
+        # The following three lines have been added to support the `it` block parameter syntax in the source code below.
+        #
+        #   if args.type == :itarg
+        #     block_type = :itblock
+        #     args = :it
+        #
+        # https://github.com/whitequark/parser/blob/v3.3.7.1/lib/parser/builders/default.rb#L1122-L1155
+        def block(method_call, begin_t, args, body, end_t)
+          _receiver, _selector, *call_args = *method_call
+
+          if method_call.type == :yield
+            diagnostic :error, :block_given_to_yield, nil, method_call.loc.keyword, [loc(begin_t)]
+          end
+
+          last_arg = call_args.last
+          if last_arg && (last_arg.type == :block_pass || last_arg.type == :forwarded_args)
+            diagnostic :error, :block_and_blockarg, nil, last_arg.loc.expression, [loc(begin_t)]
+          end
+
+          if args.type == :itarg
+            block_type = :itblock
+            args = :it
+          elsif args.type == :numargs
+            block_type = :numblock
+            args = args.children[0]
+          else
+            block_type = :block
+          end
+
+          if [:send, :csend, :index, :super, :zsuper, :lambda].include?(method_call.type)
+            n(block_type, [ method_call, args, body ],
+              block_map(method_call.loc.expression, begin_t, end_t))
+          else
+            # Code like "return foo 1 do end" is reduced in a weird sequence.
+            # Here, method_call is actually (return).
+            actual_send, = *method_call
+            block =
+              n(block_type, [ actual_send, args, body ],
+                block_map(actual_send.loc.expression, begin_t, end_t))
+
+            n(method_call.type, [ block ],
+              method_call.loc.with_expression(join_exprs(method_call, block)))
+          end
+        end
       end
     end
   end