Implementing unwrap_splice from https://github.com/elixir-lang/elixir/blob/de39bbaca277002797e52ffbde617ace06233a2b/lib/elixir/src/elixir_parser.yrl#L704-L714 in Erlang (original) vs Java using JInterface

elixir_parser.yrl

%% Every time the parser sees a (unquote_splicing())
%% it assumes that a block is being spliced, wrapping
%% the splicing in a __block__. But in the stab clause,
%% we can have (unquote_splicing(1,2,3)) -> :ok, in such
%% case, we don't actually want the block, since it is
%% an arg style call. unwrap_splice unwraps the splice
%% from such blocks.
unwrap_splice([{'__block__', [], [{unquote_splicing, _, _}] = Splice}]) ->
  Splice;

unwrap_splice(Other) -> Other.

ElixirPsiImpUtil.java

package org.elixir_lang.psi.impl;

import com.ericsson.otp.erlang.*;
import org.elixir_lang.Macro;

public class ElixirPsiImplUtil {
   private static final OtpErlangAtom UNQUOTE_SPLICING = new OtpErlangAtom("unquote_splicing");
   
   /**
     * Unwraps <code>quote_splicing</code> in stabOperation.
     *
     * @param quotedArguments base quoted arguments from the noParenthesesArguments or parenthesesArguments
     * @return quoted arguments with quote_splicing inside block extracted to just the splice
     * @see <a href="https://github.com/elixir-lang/elixir/blob/de39bbaca277002797e52ffbde617ace06233a2b/lib/elixir/src/elixir_parser.yrl#L704-L714"><code>unwrap_splice</code></a>
     * @see <a href="https://github.com/elixir-lang/elixir/blob/de39bbaca277002797e52ffbde617ace06233a2b/lib/elixir/src/elixir_parser.yrl#L276-L281"><code>unwrap_splice</code> in <code>stab_expr</code></a>
     */
    private static OtpErlangObject[] unwrapSplice(OtpErlangObject[] quotedArguments) {
        OtpErlangObject[] unwrapped = quotedArguments;
        
        // [_]
        if (quotedArguments.length == 1) {
            OtpErlangObject quotedArgument = quotedArguments[0];

            // [{:__block__, _, _}]
            if (Macro.isBlock(quotedArgument)) {
                OtpErlangTuple expression = (OtpErlangTuple) quotedArgument;

                OtpErlangObject blockArgument = expression.elementAt(2);

                // [{:__block__, _, blockArgument} when is_list(blockArgument)
                if (blockArgument instanceof OtpErlangList) {
                    OtpErlangList blockArgumentList = (OtpErlangList) blockArgument;

                    // [{:__block__, _, [_]}]
                    if (blockArgumentList.arity() == 1) {
                        OtpErlangObject blockArgumentListElement = blockArgumentList.elementAt(0);

                        // [{:__block__, _, [{_, _, _}]}]
                        if (Macro.isExpression(blockArgumentListElement)) {
                            OtpErlangTuple blockArgumentExpression = (OtpErlangTuple) blockArgumentListElement;

                            OtpErlangObject blockArgumentReceiver = blockArgumentExpression.elementAt(0);

                            // [{:__block__, _, [{:unquote_splicing, _, _}]
                            if (blockArgumentReceiver.equals(UNQUOTE_SPLICING)) {
                                unwrapped = blockArgumentList.elements();
                            }
                        }
                    }
                }
            }
        }
        
        return unwrapped;
    }
}