go-delve/delve · error

wrong number of arguments to real: %d

Error message

wrong number of arguments to real: %d

What it means

The `real()` builtin in Delve's evaluator extracts the real part of a numeric value and requires exactly one argument. Any other argument count returns this arity error immediately.

Source

Thrown at pkg/proc/eval.go:2037

	}

	arg := args[0]
	arg.loadValue(loadSingleValue)

	if arg.Unreadable != nil {
		return nil, arg.Unreadable
	}

	if arg.Kind != reflect.Complex64 && arg.Kind != reflect.Complex128 {
		return nil, fmt.Errorf("invalid argument %s (type %s) to imag", astutil.ExprToString(nodeargs[0]), arg.TypeString())
	}

	return newConstant(constant.Imag(arg.Value), arg.bi, arg.mem), nil
}

func realBuiltin(args []*Variable, nodeargs []ast.Expr) (*Variable, error) {
	if len(args) != 1 {
		return nil, fmt.Errorf("wrong number of arguments to real: %d", len(args))
	}

	arg := args[0]
	arg.loadValue(loadSingleValue)

	if arg.Unreadable != nil {
		return nil, arg.Unreadable
	}

	if arg.Value == nil || ((arg.Value.Kind() != constant.Int) && (arg.Value.Kind() != constant.Float) && (arg.Value.Kind() != constant.Complex)) {
		return nil, fmt.Errorf("invalid argument %s (type %s) to real", astutil.ExprToString(nodeargs[0]), arg.TypeString())
	}

	return newConstant(constant.Real(arg.Value), arg.bi, arg.mem), nil
}

func minBuiltin(args []*Variable, nodeargs []ast.Expr) (*Variable, error) {
	return minmaxBuiltin("min", token.LSS, args, nodeargs)

View on GitHub (pinned to a23773e6c3)

Solutions

1. Pass exactly one argument: `real(<expr>)`.
2. To combine values use `complex(re, im)` instead.
3. Validate the args slice length before invoking the evaluator programmatically.

Example fix

// before
real(re, im)
// after
complex(re, im)
real(c)

args, err := parseCallArgs(expr)
if err != nil || len(args) != 1 {
    return fmt.Errorf("real takes exactly 1 argument, got %d", len(args))
}

val, err := eval(expr)
if err != nil && strings.Contains(err.Error(), "wrong number of arguments to real") {
    // fix the call arity and retry
}

When it happens

Trigger: Evaluating `real()` with zero arguments or `real(a, b)` with two or more (eval.go:2037, realBuiltin).

Common situations: Typos like `real(re, im)` (confusing real with complex), or programmatic expression construction with miscounted args.

Related errors

• wrong number of arguments to len: %d
• wrong number of arguments to complex: %d
• wrong number of arguments to imag: %d
• shift count must not be negative
• invalid argument %s (type %s) for cap

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/dd7bbc5026697e1f. Report an issue: GitHub.