Improve loose comparison on uppercase/lowercase string

Co-Authored-By: Vincent Langlet <[email protected]>

Author: staabm

src/Type/Accessory/AccessoryLowercaseStringType.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;
@@ -326,6 +327,10 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		if ($type->isString()->yes() && $type->isLowercaseString()->no()) {
+			return new ConstantBooleanType(false);
+		}
+
 		return new BooleanType();
 	}
 

src/Type/Accessory/AccessoryUppercaseStringType.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;
@@ -326,6 +327,10 @@ public function isScalar(): TrinaryLogic
 
 	public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 	{
+		if ($type->isString()->yes() && $type->isUppercaseString()->no()) {
+			return new ConstantBooleanType(false);
+		}
+
 		return new BooleanType();
 	}
 

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

@@ -717,28 +717,21 @@ public function sayIntersection(
 	): 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('false', 'a' == $upper);
+		assertType('false', 'abc' == $upper);
+		assertType('false', 'aBc' == $upper);
 		assertType('bool', strtoupper($s) == $upper);
-		assertType('bool', strtolower($s) == $upper); // should be false
-		assertType('bool', $upper == $lower); // should be false
+		assertType('bool', strtolower($s) == $upper);
+		assertType('bool', $upper == $lower);
 
-		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('false', 'A' == $lower);
+		assertType('false', 'ABC' == $lower);
+		assertType('false', 'AbC' == $lower);
+		assertType('bool', strtoupper($s) == $lower);
 		assertType('bool', strtolower($s) == $lower);
-		assertType('bool', $lower == $upper); // should be false
+		assertType('bool', $lower == $upper);
 
 		assertType('false', $arr == $i);
 		assertType('false', $nonEmptyArr == $i);
@@ -748,6 +741,14 @@ public function sayIntersection(
 		assertType('false', $nonEmptyArr == $emptyArr);
 		assertType('bool', $arr == $nonEmptyArr);
 		assertType('bool', $nonEmptyArr == $arr);
+
+		assertType('bool', '' == $lower);
+		if ($lower != '') {
+			assertType('false', '' == $lower);
+		}
+		if ($upper != '') {
+			assertType('false', '' == $upper);
+		}
 	}
 
 }