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is not needed

is not needed is a compiler warning, not an error. Velox has found a Boolean literal that does not change the result of an and or or expression and identifies the redundant text in the formatted message.

Example​

procedure ScriptEvent(var Value: Variant);
var
  IsValid: Boolean;
begin
  IsValid := Value <> '';
  if True and IsValid then // Warning: "True and" is not needed
    Value := 'valid';
end;

Remove the identity operand:

if IsValid then
  Value := 'valid';

Exact warning forms​

The current compiler emits only these four forms:

Expression shapeMessage parameterEquivalent expression
True and X"True and"X
X and True"and True"X
False or X"False or"X
X or False"or False"X

False and X and True or X instead produce the Calculation always evaluates to warning because the literal fixes the complete result.

How Velox detects it​

During expression type resolution and constant folding, the compiler checks Boolean and and or expressions when at least one operand is a compile-time value. It emits ewIsNotNeeded at the position of the redundant literal and continues compilation.

Velox enables short-circuit Boolean evaluation. Removing any of the four identity literals preserves both the logical result and evaluation of the meaningful operand: X is still the operand that must be evaluated to determine the expression.

Edge cases and quirks​

  • The warning applies to Boolean operands. Integer bitwise and/or expressions are not this rule.
  • xor has no identity warning in this implementation even though X xor False is logically X.
  • A constant or alias that the compiler has already reduced to True or False can trigger the warning even when the source does not contain an obvious literal at first glance.
  • The warning location belongs to the redundant constant operand, which may differ from the start of the complete expression.
  • Calculation always evaluates to - a Boolean literal fixes the complete result.
  • Boolean - operator precedence and short-circuit behaviour.

External references​