xai-org/x-algorithm · error · ParseFailure

col %d: Type %s received %d parameters, %d expected

Error message

col %d: Type %s received %d parameters, %d expected

What it means

After resolving a composite head, getCompositeType checks the number of type parameters (child count) against the expected arity from getCompositeClassInfoFromName. A mismatch throws ParseFailure with received vs expected counts.

Source

Thrown at botmaker/src/java/com/twitter/botmaker/compiler/types/TypeCompiler.java:78

      builder.append('.').append(tree.getChild(index).getText());
    }
    return builder.toString();
  }

  private static Type getCompositeType(
      Tree tree,
      TypeContext context
  ) throws ParseFailure, SemanticCheckFailure {
    String tname = tree.getChild(0).getText();
    Optional<Pair<Class<?>, Integer>> infoOpt = Type.getCompositeClassInfoFromName(tname);
    if (!infoOpt.isPresent()) {
      throw new ParseFailure(String.format(
          "col %d: Unrecognized type: %s",
          tree.getCharPositionInLine() + 1, tname));
    }
    Pair<Class<?>, Integer> info = infoOpt.get();
    if (info.getSecond() != tree.getChildCount() - 1 && info.getSecond() != Type.ANY_NUM_PARAMS) {
      throw new ParseFailure(String.format(
          "col %d: Type %s received %d parameters, %d expected",
          tree.getCharPositionInLine() + 1, tname, tree.getChildCount() - 1, info.getSecond()));
    }
    ImmutableList.Builder<Type> paramTypesBuilder = ImmutableList.builder();
    for (int i = 1; i < tree.getChildCount(); i++) {
      paramTypesBuilder.add(getType(tree.getChild(i), context));
    }
    return Type.of(info.getFirst(), paramTypesBuilder.build());
  }

  public static Optional<Type> getPrimitiveType(String name) {
    return Type.getPrimitiveTypeFromName(name);
  }

  public static Type getTypeFromClassName(String className) throws SemanticCheckFailure {

    Class<?> clazz;
    try {

View on GitHub (pinned to 24c60942c5)

Solutions

1. Supply exactly the expected parameter count: List/Set take 1, Map/Pair take 2
2. Check the message's 'received N, expected M' and fix the type expression
3. Use nested composites (Map[INT, List[STRING]]) instead of flattening

Example fix

// before
m: Map[INT]
// after
m: Map[INT, STRING]

int expected = Type.getCompositeClassInfoFromName(head).get().getSecond();
if (expected != Type.ANY_NUM_PARAMS && given != expected) rejectRule();

catch ParseFailure; report received/expected counts to the author

When it happens

Trigger: Writing e.g. Map[INT] (1 param, expects 2), List[INT, STRING] (2 params, expects 1), or Pair with 3 parameters in a rule's type expression.

Common situations: Copy-pasting generic signatures from Java/Scala without adjusting arity; assuming Map takes one key-value param; editor auto-complete inserting extra brackets.

Related errors

• col %d: Unrecognized type: %s
• Derived Feature %s has %d parameters, received %d
• Mock function expects either 1 or 3 arguments but %d receive
• MockPass function expects either 1 arguments but %d received
• MockPassAll function expects 1 arguments but %d received

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/4930a630d485c57f. Report an issue: GitHub.