Optimizer does not account for INF and NAN

[Muqsit]

Description

Operator Strength Reduction optimizer directly substitutes a sub-expression x - x with 0, not accounting for INF or NAN values being supplied to x (inf - inf and nan - nan must produce nan). Other affected cases include 0 * inf returning 0 instead of NAN, and sqrt(-1) / sqrt(-1) getting substituted for 1 despite sqrt(-1) === NAN (NAN / NAN === NAN).

As variable resolution occurs during evaluation, x - x cannot be resolved during parsing although 1 - 1 and inf - inf can. One way to address this would be to resolve operations between numeric literal operands during parsing and implement a mechanism to toggle optimizations that disregard INF and NAN (like GCC's FloatingPointMath flags).

Workarounds

1. Filter out operator strength reduction optimization from ExpressionOptimizerRegistry

   $parser = Parser::createDefault();
   
   $optimizations = new ExpressionOptimizerRegistry();
   foreach($parser->getExpressionOptimizerRegistry()->getRegistered() as $identifier => $value){
   	if(!($value instanceof OperatorStrengthReductionExpressionOptimizer)){
   		$optimizations->register($identifier, $value);
   	}
   }
   
   $parser = new Parser(
   	$parser->getBinaryOperatorRegistry(),
   	$parser->getUnaryOperatorRegistry(),
   	$parser->getConstantRegistry(),
   	$parser->getFunctionRegistry(),
   	$optimizations,
   	$parser->getScanner()
   );

2. Disable optimizations altogether — $parser = Parser::createUnoptimized();