fix has_method('__toString') coercison

Author: staabm

src/Type/Traits/ObjectTypeTrait.php

@@ -21,6 +21,7 @@
 use PHPStan\Type\MixedType;
 use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
 
 trait ObjectTypeTrait
 {
@@ -275,6 +276,10 @@ public function toArrayKey(): Type
 
 	public function toCoercedArgumentType(bool $strictTypes): Type
 	{
+		if (!$strictTypes) {
+			return TypeCombinator::union($this, $this->toString());
+		}
+
 		return $this;
 	}
 

tests/PHPStan/Analyser/nsrt/bug-12393b.php

@@ -571,3 +571,17 @@ public function __toString(): string {
         return 'Foo';
     }
 }
+
+class ObjectWithToStringMethod {
+    private string $foo;
+
+    public function doFoo(object $foo): void {
+        if (method_exists($foo, '__toString')) {
+            $this->foo = $foo;
+            assertType('string', $this->foo);
+        }
+    }
+    public function __toString(): string {
+        return 'Foo';
+    }
+}