usememos/memos · error

arithmetic requires two arguments

Error message

arithmetic requires two arguments

What it means

evaluateNumeric constant-folds arithmetic (_+_, _-_, _*_, _/_, _%_) on timestamps, durations, and integers, and requires the binary operator to have exactly two operands. A hand-constructed AST with wrong arity is rejected here; text-parsed filters normally cannot produce this because the CEL grammar fixes binary arity.

Source

Thrown at internal/filter/parser.go:548

		if ident.GetName() == "now" {
			return now.Unix(), true, nil
		}
		return 0, false, nil
	}

	call := expr.GetCallExpr()
	if call == nil {
		return 0, false, nil
	}

	switch call.Function {
	case "timestamp":
		return evaluateTimestamp(call)
	case "duration":
		return evaluateDuration(call)
	case "_+_", "_-_", "_*_", "_/_", "_%_":
		if len(call.Args) != 2 {
			return 0, false, errors.New("arithmetic requires two arguments")
		}
		left, ok, err := evaluateNumeric(call.Args[0], now)
		if err != nil {
			return 0, false, err
		}
		if !ok {
			return 0, false, nil
		}
		right, ok, err := evaluateNumeric(call.Args[1], now)
		if err != nil {
			return 0, false, err
		}
		if !ok {
			return 0, false, nil
		}
		switch call.Function {
		case "_+_":
			return left + right, true, nil

View on GitHub (pinned to 14d757ce1f)

Solutions

1. Ensure binary arithmetic calls always carry exactly two args when constructing or rewriting ASTs
2. Re-serialize the AST to a filter string and re-parse to validate
3. Add unit tests asserting arity invariants after each rewrite pass

Example fix

// before (rewrite dropped an operand)
call.Args = call.Args[:1]

// after
call.Args = []*exprv1.Expr{left, right}

// Go (AST builder/rewriter): enforce binary arity
switch fn {
case "_+_", "_-_", "_*_", "_/_%_":
    if len(args) != 2 { return errors.New("binary op needs two operands") }
}

When it happens

Trigger: Directly building an exprv1.Expr_Call for arithmetic with len(Args) != 2, e.g. an AST optimizer collapsing '_-_' to one operand after removing a foldable term.

Common situations: AST manipulation code (partial evaluators, filter rewriters) that mutates Args arrays; integrating third-party CEL tooling that emits non-canonical call nodes.

Related errors

• NOT expects exactly one argument
• division by zero
• modulo by zero
• filter expression is empty
• filter must evaluate to a boolean value

AI-assisted analysis of usememos/memos@14d757ce1f (2026-08-15). Data as JSON: /api/errors/6235dd3ac5c15522. Report an issue: GitHub.