Add isObject() guard in ImplicitToStringCallHelper for constant scalar intersections

The TypeCombinator narrowing excludes constant scalar values (0, '', '0',
false, 0.0) because TemplateTypeFactory can't create proper template types
for all of them. This means types like `false&T` and `0.0&T` remain as
intersections where MixedType::hasMethod('__toString') returns Yes,
causing false positive purity errors.

Add an early return in ImplicitToStringCallHelper when isObject()->no()
to handle these remaining cases. Since __toString() can only be called on
objects, non-object types always use PHP's built-in string conversion.

Add test cases using empty() + !\is_array() which narrows to constant
scalar falsy values.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Analyser/ExprHandler/Helper/ImplicitToStringCallHelper.php

@@ -28,6 +28,15 @@ public function processImplicitToStringCall(Expr $expr, MutatingScope $scope): E
 		$impurePoints = [];
 
 		$exprType = $scope->getType($expr);
+		if ($exprType->isObject()->no()) {
+			return new ExpressionResult(
+				$scope,
+				hasYield: false,
+				isAlwaysTerminating: false,
+				throwPoints: [],
+				impurePoints: [],
+			);
+		}
 		$toStringMethod = $scope->getMethodReflection($exprType, '__toString');
 		if ($toStringMethod === null) {
 			return new ExpressionResult(

tests/PHPStan/Rules/Pure/data/bug-14511-method.php

@@ -31,4 +31,17 @@ public function testStringConcat(mixed $val): ?string
 		return null;
 	}
 
+	/**
+	 * @phpstan-pure
+	 * @template T of mixed
+	 * @param T $val
+	 */
+	public function testEmptyNonArray(mixed $val): ?string
+	{
+		if (empty($val) && !\is_array($val)) {
+			return (string) $val;
+		}
+		return null;
+	}
+
 }

tests/PHPStan/Rules/Pure/data/bug-14511.php

@@ -61,3 +61,15 @@ function testStringVal(mixed $val): ?string {
 	}
 	return null;
 }
+
+/**
+ * @phpstan-pure
+ * @template T of mixed
+ * @param T $val
+ */
+function testEmptyNonArray(mixed $val): ?string {
+	if (empty($val) && !\is_array($val)) {
+		return (string) $val;
+	}
+	return null;
+}