Nothing is lower than null

Author: VincentLanglet

src/Type/NullType.php

@@ -110,6 +110,10 @@ public function isSmallerThan(Type $otherType, PhpVersion $phpVersion): TrinaryL
 			return $otherType->isGreaterThan($this, $phpVersion);
 		}
 
+		if ($otherType->isObject()->yes()) {
+			return TrinaryLogic::createYes();
+		}
+
 		return TrinaryLogic::createMaybe();
 	}
 
@@ -123,6 +127,10 @@ public function isSmallerThanOrEqual(Type $otherType, PhpVersion $phpVersion): T
 			return $otherType->isGreaterThanOrEqual($this, $phpVersion);
 		}
 
+		if ($otherType->isObject()->yes()) {
+			return TrinaryLogic::createYes();
+		}
+
 		return TrinaryLogic::createMaybe();
 	}
 

src/Type/Traits/UndecidedComparisonCompoundTypeTrait.php

@@ -13,11 +13,19 @@ trait UndecidedComparisonCompoundTypeTrait
 
 	public function isGreaterThan(Type $otherType, PhpVersion $phpVersion): TrinaryLogic
 	{
+		if ($otherType->isNull()->yes() && $this->isObject()->yes()) {
+			return TrinaryLogic::createYes();
+		}
+
 		return TrinaryLogic::createMaybe();
 	}
 
 	public function isGreaterThanOrEqual(Type $otherType, PhpVersion $phpVersion): TrinaryLogic
 	{
+		if ($otherType->isNull()->yes()) {
+			return TrinaryLogic::createYes();
+		}
+
 		return TrinaryLogic::createMaybe();
 	}
 

src/Type/Traits/UndecidedComparisonTypeTrait.php

@@ -5,18 +5,27 @@
 use PHPStan\Php\PhpVersion;
 use PHPStan\TrinaryLogic;
 use PHPStan\Type\MixedType;
+use PHPStan\Type\NullType;
 use PHPStan\Type\Type;
 
 trait UndecidedComparisonTypeTrait
 {
 
 	public function isSmallerThan(Type $otherType, PhpVersion $phpVersion): TrinaryLogic
 	{
+		if ($otherType->isNull()->yes()) {
+			return TrinaryLogic::createNo();
+		}
+
 		return TrinaryLogic::createMaybe();
 	}
 
 	public function isSmallerThanOrEqual(Type $otherType, PhpVersion $phpVersion): TrinaryLogic
 	{
+		if ($otherType->isNull()->yes() && $this->isObject()->yes()) {
+			return TrinaryLogic::createNo();
+		}
+
 		return TrinaryLogic::createMaybe();
 	}
 
@@ -32,11 +41,15 @@ public function getSmallerOrEqualType(PhpVersion $phpVersion): Type
 
 	public function getGreaterType(PhpVersion $phpVersion): Type
 	{
-		return new MixedType();
+		return new MixedType(subtractedType: new NullType());
 	}
 
 	public function getGreaterOrEqualType(PhpVersion $phpVersion): Type
 	{
+		if ($this->isObject()->yes()) {
+			return new MixedType(subtractedType: new NullType());
+		}
+
 		return new MixedType();
 	}
 

src/Type/TypeCombinator.php

@@ -544,6 +544,11 @@ private static function unionWithSubtractedType(
 			$subtractedType = $type->getSubtractedType() === null
 				? $subtractedType
 				: self::union($type->getSubtractedType(), $subtractedType);
+
+			$subtractedType = self::intersect(
+				$type->getTypeWithoutSubtractedType(),
+				$subtractedType,
+			);
 			if ($subtractedType instanceof NeverType) {
 				$subtractedType = null;
 			}

tests/PHPStan/Analyser/nsrt/bcmath-number.php

@@ -190,10 +190,10 @@ public function bcVsNull(Number $a): void
 		assertType('*ERROR*', $a ** $b);
 		assertType('*ERROR*', $a << $b);
 		assertType('*ERROR*', $a >> $b);
-		assertType('bool', $a < $b);
-		assertType('bool', $a <= $b);
-		assertType('bool', $a > $b);
-		assertType('bool', $a >= $b);
+		assertType('false', $a < $b);
+		assertType('false', $a <= $b);
+		assertType('true', $a > $b);
+		assertType('true', $a >= $b);
 		assertType('int<-1, 1>', $a <=> $b);
 		assertType('bool', $a == $b);
 		assertType('bool', $a != $b);