bug symfony#29223 [Validator] Added the missing constraints instance checks (thomasbisignani)

This PR was merged into the 2.8 branch.

Discussion
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[Validator] Added the missing constraints instance checks

| Q             | A
| ------------- | ---
| Branch?       | 2.8
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

This PR adds the constraints instance checks missing to limit the validators use.

This behavior is already implemented in all built-in validators, but it was missed in two validators.

Commits
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0ecaead [Validator] Added the missing constraints instance checks

Author: nicolas-grekas

src/Symfony/Component/Validator/Constraints/BicValidator.php

@@ -13,6 +13,7 @@
 
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
 
 /**
  * @author Michael Hirschler <michael.vhirsch@gmail.com>
@@ -26,6 +27,10 @@ class BicValidator extends ConstraintValidator
      */
     public function validate($value, Constraint $constraint)
     {
+        if (!$constraint instanceof Bic) {
+            throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\Bic');
+        }
+
         if (null === $value || '' === $value) {
             return;
         }

src/Symfony/Component/Validator/Constraints/CountValidator.php

@@ -26,6 +26,10 @@ class CountValidator extends ConstraintValidator
      */
     public function validate($value, Constraint $constraint)
     {
+        if (!$constraint instanceof Count) {
+            throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\Count');
+        }
+
         if (null === $value) {
             return;
         }

src/Symfony/Component/Validator/Constraints/UuidValidator.php

@@ -83,14 +83,14 @@ class UuidValidator extends ConstraintValidator
      */
     public function validate($value, Constraint $constraint)
     {
-        if (null === $value || '' === $value) {
-            return;
-        }
-
         if (!$constraint instanceof Uuid) {
             throw new UnexpectedTypeException($constraint, __NAMESPACE__.'\Uuid');
         }
 
+        if (null === $value || '' === $value) {
+            return;
+        }
+
         if (!is_scalar($value) && !(\is_object($value) && method_exists($value, '__toString'))) {
             throw new UnexpectedTypeException($value, 'string');
         }