xai-org/x-algorithm · error · SemanticCheckFailure

StructTuple expects pairs of name and values, but a %s recei

Error message

StructTuple expects pairs of name and values, but a %s received

What it means

Every child of ToStructTuple() must be a ToPair node representing a fieldName: value pair. Any non-ToPair child fails semantic checking with the child's string representation. Like Copy-on-struct, this is a syntactic requirement, not just a type check.

Source

Thrown at botmaker/src/java/com/twitter/botmaker/function/collection/ToStructTuple.java:51

  @Override
  protected Object apply(Context<Runtime> context, List<Object> args) throws Exception {
    return StructTuple.of(fieldNames, args);
  }

  public static ToStructTuple of(
      String funcName, ImmutableList<ASTNode> children) throws SemanticCheckFailure {

    if (children.size() == 0) {
      throw new SemanticCheckFailure("StructTuple should have at least one field");
    }

    ImmutableList.Builder<String> fieldNamesBuilder = ImmutableList.builder();
    ImmutableList.Builder<Type> fieldTypesBuilder = ImmutableList.builder();
    ImmutableList.Builder<ASTNode> childrenBuilder = ImmutableList.builder();
    for (ASTNode child : children) {
      if (!(child instanceof ToPair)) {
        throw new SemanticCheckFailure(
            String.format(
                "StructTuple expects pairs of name and values, but a %s received", child));
      }

      fieldNamesBuilder.add(((Constant) child.getChildren().get(0)).getValue().toString());
      fieldTypesBuilder.add(((ASTNode) child.getChildren().get(1)).getReturnType());
      childrenBuilder.add((ASTNode) child.getChildren().get(1));
    }

    ImmutableList<String> fieldNames = fieldNamesBuilder.build();
    ImmutableList<Type> fieldTypes = fieldTypesBuilder.build();
    Signature signature = new Signature(
        fieldTypes,
        Type.structTupleOf(fieldNames, fieldTypes)
    );

    return new ToStructTuple(funcName, fieldNames, childrenBuilder.build()) {

View on GitHub (pinned to 24c60942c5)

Solutions

Write every field as name: value: ToStructTuple(id: 1, name: "x")
When building the AST, wrap each name/value in ToPair before calling ToStructTuple.of

Example fix

// before
ToStructTuple("id", 1)
// after
ToStructTuple(id: 1)

Defensive patterns

Strategy: validation

Validate before calling

// host code: all children must be ToPair
for (ASTNode c : children) {
  if (!(c instanceof ToPair)) throw new IllegalArgumentException("expected pair, got " + c);
}

Prevention

Write struct fields as name: value only
Never pass bare positional values to ToStructTuple

When it happens

Trigger: ToStructTuple("a", "b", 1) — bare positional values instead of name: value pairs; or programmatically passing non-ToPair AST nodes.

Common situations: Copying positional function-call style into struct construction; generating children from unvalidated config.

Related errors

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/9dfa4d3d3339a24a. Report an issue: GitHub.