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No result

Velox reports No result when a callable with no return type is used where the compiler must produce an expression value. A procedure can change state or var parameters, but it cannot be assigned, compared or passed as the value of another argument.

Example​

procedure IncrementValue(var Number: Integer);
begin
  Number := Number + 1;
end;

procedure ScriptEvent(var Value: Variant);
var
  Counter: Integer;
begin
  Counter := 1;
  Value := IncrementValue(Counter); // Error: No result
end;

Call the procedure as a statement, then use the state it changed:

IncrementValue(Counter);
Value := Counter;

How Velox detects it​

The compiler resolves a call to its registered or script-declared result type. During bytecode generation, _ProcessFunction receives a destination register when the surrounding expression needs a value. If the call's ResultType is nil while that destination exists, it emits ecNoResult and stops compiling the expression.

A function used as a statement is the opposite case: the call has a result but no surrounding destination requires it. The current compiler permits the call and discards the returned value.

Common causes​

  • Assigning a procedure call to a variable.
  • Comparing a procedure call with a value.
  • Passing a procedure call as another routine's argument.
  • Confusing a var output parameter with a function result.
  • Selecting a similarly named procedure instead of the function overload expected from Delphi.

Correction procedure​

  1. Check the exact Code Library declaration and determine whether it is a procedure or function.
  2. For a procedure, call it as a standalone statement.
  3. Read its documented var parameter, property or other state only after the call.
  4. If a value-returning overload is required, confirm that Velox actually registers that overload.

Edge cases and quirks​

  • Adding parentheses does not create a result; it only changes call syntax.
  • A procedure may still have material side effects. Removing the call just to clear the diagnostic can change behaviour.
  • The error is emitted before normal event execution, so the procedure has not partly run.
  • A separate Variable Expected error can occur first when a procedure's var parameter receives a literal or calculation.
  • Invalid number of parameters - the selected callable has a different argument count.
  • Variable Expected - an output argument is not assignable storage.
  • Functions - interpreting registered procedure and function declarations.

External references​