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Invalid number of parameters

Velox reports Invalid number of parameters when the actual argument list does not contain exactly the arguments required by the selected script-visible declaration. It applies to routines and to property accessors whose indexes are compiled as parameters.

Example​

procedure SetPair(var Target: String; const LeftValue, RightValue: String);
begin
  Target := LeftValue + RightValue;
end;

procedure ScriptEvent(var Value: Variant);
var
  TextValue: String;
begin
  SetPair(TextValue, 'A'); // Error: Invalid number of parameters
  Value := TextValue;
end;

Supply the missing argument in declaration order:

SetPair(TextValue, 'A', 'B');

An additional argument produces the same diagnostic.

How Velox detects it​

The compiler first parses the actual arguments, then ValidateParameters walks the selected declaration and the parsed values in order. It emits this error in either of two cases:

  • a declared parameter has no remaining actual value; or
  • a non-empty actual value remains after every declared parameter has been matched.

After the counts match, the same validation assigns the expected type and parameter mode to each actual argument. A wrong type normally reports Type mismatch; passing a literal or calculation to a var/out-style parameter normally reports Variable Expected. Those are not parameter-count failures.

Correction procedure​

  1. Read the exact declaration shown for the Code Library entry or property.
  2. Count actual arguments at the same parenthesis level; ignore commas inside nested calls.
  3. Supply one argument for each exposed parameter, in order, and remove extras.
  4. Confirm that the selected overload is actually exposed by Velox. A Delphi overload that is not registered is unavailable to the script.
  5. After the count is correct, resolve any separate type or variable-mode diagnostic.

Edge cases and quirks​

  • An unclosed nested call can make the outer argument count appear wrong. Correct bracket and parenthesis errors first.
  • Indexed and default properties use the same parameter validator for their index values, so the message can refer to Object[Index] rather than a visibly named routine.
  • The message does not state the expected or actual count. Use the registered declaration as the contract.
  • Parameter names do not affect calls; count, order, type and mode do.
  • Comma (',') expected - missing separation between peer arguments.
  • Variable Expected - a var-style parameter received a non-variable expression.
  • Type mismatch - the count matches but an argument type does not.

External references​