Follow the float step of PHP 8.3 in character ranges

PHP 8.3 keeps a step with a fractional part, or one beyond the integer
range such as -1e20, as a float and then compares numbers, in which a
digit keeps its value and any other character is 0: range('a', '9', -0.5)
throws, range('a', 'z', -1e20) returns [0.0].

is_numeric() on PHP 7.4 rejects a numeric string with trailing
whitespace, which PHP 8 treats as a number, so the helper strips it.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: zonuexe

src/Type/Php/RangeFunctionArgumentsHelper.php

@@ -14,6 +14,7 @@
 use function is_string;
 use function ord;
 use function range;
+use function rtrim;
 use function strlen;
 use const PHP_INT_MIN;
 use const PHP_VERSION_ID;
@@ -29,6 +30,9 @@ final class RangeFunctionArgumentsHelper
 	/** 2 ** 53, above which a float no longer holds every integer */
 	private const PRECISE_INTEGER_LIMIT = 9007199254740992;
 
+	/** 2 ** 63, from which PHP 8.3 keeps an integral float step as a float */
+	private const INTEGER_STEP_LIMIT = 9.2233720368547758E18;
+
 	/**
 	 * Calls range() on the PHP version PHPStan itself runs on.
 	 *
@@ -137,12 +141,10 @@ public static function isNegativeStepOnIncreasingRange(int|float|string $start,
 			return false;
 		}
 
-		if (self::isCharacter($start) && self::isCharacter($end)) {
-			// a step with a fractional part turns both characters into 0
-			if (is_float($step) && floor($step) !== $step) {
-				return false;
-			}
-
+		// PHP 8.3 keeps a step with a fractional part or beyond the integer range as a float,
+		// and then compares numbers, in which only a digit keeps its value
+		$isFloatStep = is_float($step) && (floor($step) !== $step || abs($step) >= self::INTEGER_STEP_LIMIT);
+		if (!$isFloatStep && self::isCharacter($start) && self::isCharacter($end)) {
 			return ord($start[0]) < ord($end[0]);
 		}
 
@@ -158,7 +160,15 @@ public static function isNegativeStepOnIncreasingRange(int|float|string $start,
 	 */
 	private static function isCharacter(int|float|string $value): bool
 	{
-		return is_string($value) && $value !== '' && (strlen($value) === 1 || !is_numeric($value));
+		return is_string($value) && $value !== '' && (strlen($value) === 1 || !self::isNumeric($value));
+	}
+
+	/**
+	 * PHP 8 accepts whitespace after a numeric string, which is_numeric() on PHP 7.4 does not.
+	 */
+	private static function isNumeric(int|float|string $value): bool
+	{
+		return is_numeric($value) || (is_string($value) && is_numeric(rtrim($value, " \t\n\r\v\f")));
 	}
 
 	private static function isImprecise(int|float|string $value): bool
@@ -168,7 +178,7 @@ private static function isImprecise(int|float|string $value): bool
 
 	private static function toNumber(int|float|string $value): float
 	{
-		return is_numeric($value) ? (float) $value : 0.0;
+		return self::isNumeric($value) ? (float) $value : 0.0;
 	}
 
 }

tests/PHPStan/Type/Php/RangeFunctionArgumentsHelperTest.php

@@ -27,8 +27,18 @@ public static function dataIsNegativeStepOnIncreasingRange(): iterable
 		yield ['ab', 'z', -1, true];
 		yield ['a', 'z', -1.0, true];
 
-		// a step with a fractional part turns both characters into 0
+		// PHP 8.3 keeps a step with a fractional part or beyond the integer range as a float,
+		// which turns a character into 0 unless it is a digit
 		yield ['a', 'z', -0.5, false];
+		yield ['0', '9', -0.0001, true];
+		yield ['a', '9', -0.0001, true];
+		yield ['9', 'a', -0.0001, false];
+		yield ['a', 'z', -1e20, false];
+		yield ['a', '9', -1e20, true];
+
+		// a numeric string with whitespace around it is a number, also on PHP 7.4
+		yield ['5 ', 3, -1, false];
+		yield [' 5', 3, -1, false];
 
 		// an empty string or a character next to a number is 0
 		yield ['', 'a', -1, false];