Improve loose comparison on intersection type

Author: staabm

src/TrinaryLogic.php

@@ -47,6 +47,18 @@ public static function createFromBoolean(bool $value): self
 		return self::$registry[$yesNo] ??= new self($yesNo);
 	}
 
+	public static function createFromBooleanType(BooleanType $type): self
+	{
+		if ($type->isTrue()->yes()) {
+			return self::createYes();
+		}
+		if ($type->isFalse()->yes()) {
+			return self::createNo();
+		}
+
+		return self::createMaybe();
+	}
+
 	private static function create(int $value): self
 	{
 		self::$registry[$value] ??= new self($value);

src/Type/Accessory/AccessoryNonEmptyStringType.php

@@ -11,6 +11,7 @@
 use PHPStan\Type\BooleanType;
 use PHPStan\Type\CompoundType;
 use PHPStan\Type\Constant\ConstantArrayType;
+use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\ErrorType;
@@ -322,6 +323,9 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		if ($type->isString()->yes() && $type->isNonEmptyString()->no()) {
+			return new ConstantBooleanType(false);
+		}
 		return new BooleanType();
 	}
 

src/Type/IntersectionType.php

@@ -716,7 +716,9 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
-		return new BooleanType();
+		return $this->intersectResults(
+			static fn (Type $innerType): TrinaryLogic => TrinaryLogic::createFromBooleanType($innerType->looseCompare($type, $phpVersion))
+		)->toBooleanType();
 	}
 
 	public function isOffsetAccessible(): TrinaryLogic

src/Type/UnionType.php

@@ -676,21 +676,9 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
-		$lastResult = null;
-		foreach ($this->types as $innerType) {
-			$result = $innerType->looseCompare($type, $phpVersion);
-			if ($lastResult === null) {
-				$lastResult = $result;
-				continue;
-			}
-			if ($lastResult->equals($result)) {
-				continue;
-			}
-
-			return new BooleanType();
-		}
-
-		return $lastResult ?? new BooleanType();
+		return $this->unionResults(
+			static fn (Type $innerType): TrinaryLogic => TrinaryLogic::createFromBooleanType($innerType->looseCompare($type, $phpVersion))
+		)->toBooleanType();
 	}
 
 	public function isOffsetAccessible(): TrinaryLogic

tests/PHPStan/Analyser/nsrt/loose-comparisons.php

@@ -698,4 +698,40 @@ public function sayConstUnion(
 		assertType('bool', $constMix == $looseZero);
 	}
 
+	/**
+	 * @param uppercase-string $upper
+	 * @param lowercase-string $lower
+	 */
+	public function sayIntersection(
+		string $upper,
+		string $lower,
+		string $s,
+	): void
+	{
+		assertType('bool', '' == $upper);
+		if ($upper != '') {
+			assertType('false', '' == $upper);
+		}
+		assertType('bool', '0' == $upper);
+		assertType('bool', 'a' == $upper); // should be false
+		assertType('bool', 'abc' == $upper); // should be false
+		assertType('bool', 'aBc' == $upper);
+		assertType('bool', strtoupper($s) == $upper);
+		assertType('bool', strtolower($s) == $upper); // should be false
+		assertType('bool', $upper == $lower); // should be false
+
+		assertType('bool', '' == $lower);
+		if ($lower != '') {
+			assertType('false', '' == $lower);
+		}
+		assertType('bool', '0' == $lower);
+		assertType('bool', 'A' == $lower); // should be false
+		assertType('bool', 'ABC' == $lower); // should be false
+		assertType('bool', 'AbC' == $lower);
+		assertType('bool', strtoupper($s) == $lower); // should be false
+		assertType('bool', strtolower($s) == $lower);
+		assertType('bool', $lower == $upper); // should be false
+	}
+
+
 }