Improve loose comparison on string types

src/Type/Accessory/AccessoryNonEmptyStringType.php

@@ -323,9 +323,14 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		if ($type->isNull()->yes()) {
+			return new ConstantBooleanType(false);
+		}
+
 		if ($type->isString()->yes() && $type->isNonEmptyString()->no()) {
 			return new ConstantBooleanType(false);
 		}
+
 		return new BooleanType();
 	}
 

src/Type/Accessory/AccessoryNonFalsyStringType.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\ErrorType;
 use PHPStan\Type\FloatType;
@@ -19,6 +20,7 @@
 use PHPStan\Type\IntersectionType;
 use PHPStan\Type\IsSuperTypeOfResult;
 use PHPStan\Type\ObjectWithoutClassType;
+use PHPStan\Type\StaticTypeFactory;
 use PHPStan\Type\StringType;
 use PHPStan\Type\Traits\MaybeCallableTypeTrait;
 use PHPStan\Type\Traits\NonArrayTypeTrait;
@@ -322,6 +324,11 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		$falseyTypes = StaticTypeFactory::falsey();
+		if ($falseyTypes->isSuperTypeOf($type)->yes()) {
+			return new ConstantBooleanType(false);
+		}
+
 		return new BooleanType();
 	}
 

src/Type/Accessory/AccessoryNumericStringType.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;
@@ -324,6 +325,14 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		if ($type->isNull()->yes()) {
+			return new ConstantBooleanType(false);
+		}
+
+		if ($type->isString()->yes() && $type->isNumericString()->no()) {
+			return new ConstantBooleanType(false);
+		}
+
 		return new BooleanType();
 	}
 

src/Type/StringType.php

@@ -10,6 +10,7 @@
 use PHPStan\TrinaryLogic;
 use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
 use PHPStan\Type\Constant\ConstantArrayType;
+use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\Traits\MaybeCallableTypeTrait;
@@ -267,6 +268,10 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		if ($type->isArray()->yes()) {
+			return new ConstantBooleanType(false);
+		}
+
 		return new BooleanType();
 	}
 

tests/PHPStan/Analyser/nsrt/loose-comparisons-php7.php

@@ -61,4 +61,15 @@ public function sayInt(
 		assertType('bool', $int == $phpStr);
 		assertType('bool', $int == 'a');
 	}
+
+	/**
+	 * @param "abc"|"def" $constNonFalsy
+	 */
+	public function sayConstUnion(
+		$constNonFalsy,
+	): void
+	{
+		assertType('true', $constNonFalsy == 0);
+		assertType('true', "" == 0);
+	}
 }

tests/PHPStan/Analyser/nsrt/loose-comparisons-php8.php

@@ -68,4 +68,15 @@ public function sayInt(
 		assertType('false', $intRange == 'a');
 	}
 
+	/**
+	 * @param "abc"|"def" $constNonFalsy
+	 */
+	public function sayConstUnion(
+		$constNonFalsy,
+	): void
+	{
+		assertType('false', $constNonFalsy == 0);
+		assertType('false', "" == 0);
+	}
+
 }

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

@@ -526,6 +526,7 @@ public function sayEmptyArray(
 	 * @param array{} $emptyArr
 	 * @param 'php' $phpStr
 	 * @param '' $emptyStr
+	 * @param non-falsy-string $nonFalsyString
 	 */
 	public function sayNonFalsyStr(
 		$true,
@@ -540,7 +541,8 @@ public function sayNonFalsyStr(
 		$null,
 		$emptyArr,
 		$phpStr,
-		$emptyStr
+		$emptyStr,
+		$nonFalsyString
 	): void
 	{
 		assertType('true', $phpStr == $true);
@@ -555,6 +557,100 @@ public function sayNonFalsyStr(
 		assertType('false', $phpStr == $emptyArr);
 		assertType('true', $phpStr == $phpStr);
 		assertType('false', $phpStr == $emptyStr);
+
+		assertType('bool', $nonFalsyString == $true);
+		assertType('false', $nonFalsyString == $false);
+		assertType('bool', $nonFalsyString == $one);
+		assertType('false', $nonFalsyString == $zero);
+		assertType('bool', $nonFalsyString == $minusOne);
+		assertType('bool', $nonFalsyString == $oneStr);
+		assertType('false', $nonFalsyString == $zeroStr);
+		assertType('bool', $nonFalsyString == $minusOneStr);
+		assertType('bool', $nonFalsyString == $plusOneStr);
+		assertType('false', $nonFalsyString == $null);
+		assertType('false', $nonFalsyString == $emptyArr);
+		assertType('bool', $nonFalsyString == $phpStr);
+		assertType('false', $nonFalsyString == $emptyStr);
+	}
+
+	/**
+	 * @param true $true
+	 * @param false $false
+	 * @param 1 $one
+	 * @param 0 $zero
+	 * @param -1 $minusOne
+	 * @param '1' $oneStr
+	 * @param '0' $zeroStr
+	 * @param '-1' $minusOneStr
+	 * @param '+1' $plusOneStr
+	 * @param null $null
+	 * @param array{} $emptyArr
+	 * @param 'php' $phpStr
+	 * @param '' $emptyStr
+	 * @param numeric-string $numericStr
+	 */
+	public function sayStr(
+		$true,
+		$false,
+		$one,
+		$zero,
+		$minusOne,
+		$oneStr,
+		$zeroStr,
+		$minusOneStr,
+		$plusOneStr,
+		$null,
+		$emptyArr,
+		string $string,
+		$phpStr,
+		$emptyStr,
+		$numericStr,
+		?string $stringOrNull,
+	): void
+	{
+		assertType('bool', $string == $true);
+		assertType('bool', $string == $false);
+		assertType('bool', $string == $one);
+		assertType('bool', $string == $zero);
+		assertType('bool', $string == $minusOne);
+		assertType('bool', $string == $oneStr);
+		assertType('bool', $string == $zeroStr);
+		assertType('bool', $string == $minusOneStr);
+		assertType('bool', $string == $plusOneStr);
+		assertType('bool', $string == $null);
+		assertType('bool', $string == $stringOrNull);
+		assertType('false', $string == $emptyArr);
+		assertType('bool', $string == $phpStr);
+		assertType('bool', $string == $emptyStr);
+		assertType('bool', $string == $numericStr);
+
+		assertType('bool', $numericStr == $true);
+		assertType('bool', $numericStr == $false);
+		assertType('bool', $numericStr == $one);
+		assertType('bool', $numericStr == $zero);
+		assertType('bool', $numericStr == $minusOne);
+		assertType('bool', $numericStr == $oneStr);
+		assertType('bool', $numericStr == $zeroStr);
+		assertType('bool', $numericStr == $minusOneStr);
+		assertType('bool', $numericStr == $plusOneStr);
+		assertType('false', $numericStr == $null);
+		assertType('bool', $numericStr == $stringOrNull);
+		assertType('false', $numericStr == $emptyArr);
+		assertType('bool', $numericStr == $string);
+		assertType('false', $numericStr == $phpStr);
+		assertType('false', $numericStr == $emptyStr);
+		if (is_numeric($string)) {
+			assertType('bool', $numericStr == $string);
+		}
+
+		assertType('false', "" == 1);
+		assertType('true', "" == null);
+		assertType('false', "" == true);
+		assertType('true', "" == false);
+		assertType('false', "" == "1");
+		assertType('false', "" == "0");
+		assertType('false', "" == "-1");
+		assertType('false', "" == []);
 	}
 
 	/**
@@ -657,11 +753,13 @@ public function sayInt(
 	 * @param true|1|"1" $looseOne
 	 * @param false|0|"0" $looseZero
 	 * @param false|1 $constMix
+	 * @param "abc"|"def" $constNonFalsy
 	 */
 	public function sayConstUnion(
 		$looseOne,
 		$looseZero,
-		$constMix
+		$constMix,
+		$constNonFalsy,
 	): void
 	{
 		assertType('true', $looseOne == 1);
@@ -696,6 +794,14 @@ public function sayConstUnion(
 		assertType('bool', $constMix == $looseOne);
 		assertType('bool', $looseZero == $constMix);
 		assertType('bool', $constMix == $looseZero);
+
+		assertType('false', $constNonFalsy == 1);
+		assertType('false', $constNonFalsy == null);
+		assertType('true', $constNonFalsy == true);
+		assertType('false', $constNonFalsy == false);
+		assertType('false', $constNonFalsy == "1");
+		assertType('false', $constNonFalsy == "0");
+		assertType('false', $constNonFalsy == []);
 	}
 
 	/**