diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 62eeaf6ac5..69f1d7d141 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -20,6 +20,21 @@ parameters:
 			count: 1
 			path: src/Faker/Extension/ContainerBuilder.php
 
+		-
+			message: "#^Method Faker\\\\Generator\\:\\:optional\\(\\) should return Faker\\\\Generator but returns Faker\\\\ChanceGenerator\\.$#"
+			count: 1
+			path: src/Faker/Generator.php
+
+		-
+			message: "#^Method Faker\\\\Generator\\:\\:unique\\(\\) should return Faker\\\\Generator but returns Faker\\\\UniqueGenerator\\.$#"
+			count: 1
+			path: src/Faker/Generator.php
+
+		-
+			message: "#^Method Faker\\\\Generator\\:\\:valid\\(\\) should return Faker\\\\Generator but returns Faker\\\\ValidGenerator\\.$#"
+			count: 1
+			path: src/Faker/Generator.php
+
 		-
 			message: "#^Unreachable statement \\- code above always terminates\\.$#"
 			count: 1
@@ -735,6 +750,15 @@ parameters:
 			count: 2
 			path: src/Faker/Provider/Base.php
 
+		-
+			message:
+				"""
+					#^Instantiation of deprecated class Faker\\\\DefaultGenerator\\:
+					Use ChanceGenerator instead$#
+				"""
+			count: 1
+			path: src/Faker/Provider/Base.php
+
 		-
 			message: "#^Negated boolean expression is always false\\.$#"
 			count: 1
diff --git a/psalm.baseline.xml b/psalm.baseline.xml
index 3908786358..04ca4ec424 100644
--- a/psalm.baseline.xml
+++ b/psalm.baseline.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<files psalm-version="4.7.1@cd53e047a58f71f646dd6bf45476076ab07b5d44">
+<files psalm-version="4.17.0@6f4707aa41c9174353a6434bba3fc8840f981d9c">
   <file src="src/Faker/Calculator/Luhn.php">
     <InvalidReturnStatement occurrences="1">
       <code>0</code>
@@ -9,10 +9,17 @@
     </InvalidReturnType>
   </file>
   <file src="src/Faker/Generator.php">
-    <InvalidThrow occurrences="1">
-      <code>ContainerExceptionInterface</code>
-    </InvalidThrow>
-  </file>
+    <InvalidReturnStatement occurrences="3">
+      <code>$this-&gt;uniqueGenerator</code>
+      <code>new ChanceGenerator($this, $weight, $default)</code>
+      <code>new ValidGenerator($this, $validator, $maxRetries)</code>
+    </InvalidReturnStatement>
+    <InvalidReturnType occurrences="3">
+      <code>self</code>
+      <code>self</code>
+      <code>self</code>
+    </InvalidReturnType>
+    </file>
   <file src="src/Faker/ORM/CakePHP/EntityPopulator.php">
     <UndefinedClass occurrences="1">
       <code>TableRegistry</code>
diff --git a/src/Faker/ChanceGenerator.php b/src/Faker/ChanceGenerator.php
new file mode 100644
index 0000000000..25aaa4c6e6
--- /dev/null
+++ b/src/Faker/ChanceGenerator.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Faker;
+
+use Faker\Extension\Extension;
+
+/**
+ * This generator returns a default value for all called properties
+ * and methods. It works with Faker\Generator::optional().
+ *
+ * @mixin Generator
+ */
+class ChanceGenerator
+{
+    private $generator;
+    private $weight;
+    protected $default;
+
+    /**
+     * @param Extension|Generator $generator
+     */
+    public function __construct($generator, float $weight, $default = null)
+    {
+        $this->default = $default;
+        $this->generator = $generator;
+        $this->weight = $weight;
+    }
+
+    public function ext(string $id)
+    {
+        return new self($this->generator->ext($id), $this->weight, $this->default);
+    }
+
+    /**
+     * Catch and proxy all generator calls but return only valid values
+     *
+     * @param string $attribute
+     *
+     * @deprecated Use a method instead.
+     */
+    public function __get($attribute)
+    {
+        trigger_deprecation('fakerphp/faker', '1.14', 'Accessing property "%s" is deprecated, use "%s()" instead.', $attribute, $attribute);
+
+        return $this->__call($attribute, []);
+    }
+
+    /**
+     * @param string $name
+     * @param array  $arguments
+     */
+    public function __call($name, $arguments)
+    {
+        if (mt_rand(1, 100) <= (100 * $this->weight)) {
+            return call_user_func_array([$this->generator, $name], $arguments);
+        }
+
+        return $this->default;
+    }
+}
diff --git a/src/Faker/Core/Number.php b/src/Faker/Core/Number.php
index 17903052d7..f7af0c2960 100644
--- a/src/Faker/Core/Number.php
+++ b/src/Faker/Core/Number.php
@@ -40,7 +40,7 @@ public function randomDigitNotZero(): int
         return mt_rand(1, 9);
     }
 
-    public function randomFloat(int $nbMaxDecimals = null, float $min = 0, float $max = null): float
+    public function randomFloat(?int $nbMaxDecimals = null, float $min = 0, ?float $max = null): float
     {
         if (null === $nbMaxDecimals) {
             $nbMaxDecimals = $this->randomDigit();
diff --git a/src/Faker/DefaultGenerator.php b/src/Faker/DefaultGenerator.php
index 81aa4f6452..688f4766a8 100644
--- a/src/Faker/DefaultGenerator.php
+++ b/src/Faker/DefaultGenerator.php
@@ -4,9 +4,11 @@
 
 /**
  * This generator returns a default value for all called properties
- * and methods. It works with Faker\Generator\Base->optional().
+ * and methods.
  *
  * @mixin Generator
+ *
+ * @deprecated Use ChanceGenerator instead
  */
 class DefaultGenerator
 {
@@ -14,9 +16,16 @@ class DefaultGenerator
 
     public function __construct($default = null)
     {
+        trigger_deprecation('fakerphp/faker', '1.16', 'Class "%s" is deprecated, use "%s" instead.', __CLASS__, ChanceGenerator::class);
+
         $this->default = $default;
     }
 
+    public function ext()
+    {
+        return $this;
+    }
+
     /**
      * @param string $attribute
      *
diff --git a/src/Faker/Extension/NumberExtension.php b/src/Faker/Extension/NumberExtension.php
index 7d0b45860b..ebfa8c3113 100644
--- a/src/Faker/Extension/NumberExtension.php
+++ b/src/Faker/Extension/NumberExtension.php
@@ -37,7 +37,7 @@ public function randomDigitNotZero(): int;
      *
      * @example 48.8932
      */
-    public function randomFloat(?int $nbMaxDecimals, float $min, float $max): float;
+    public function randomFloat(?int $nbMaxDecimals, float $min, ?float $max): float;
 
     /**
      * Returns a random integer with 0 to $nbDigits digits.
diff --git a/src/Faker/Generator.php b/src/Faker/Generator.php
index e01db1cdbb..3d7ce6a6c9 100644
--- a/src/Faker/Generator.php
+++ b/src/Faker/Generator.php
@@ -2,7 +2,6 @@
 
 namespace Faker;
 
-use Psr\Container\ContainerExceptionInterface;
 use Psr\Container\ContainerInterface;
 
 /**
@@ -122,18 +121,6 @@
  *
  * @method string toUpper($string = '')
  *
- * @property mixed $optional
- *
- * @method mixed optional($weight = null, $default = null)
- *
- * @property UniqueGenerator $unique
- *
- * @method UniqueGenerator unique($reset = false, $maxRetries = 10000)
- *
- * @property ValidGenerator $valid
- *
- * @method ValidGenerator valid($validator = null, $maxRetries = 10000)
- *
  * @property int $biasedNumberBetween
  *
  * @method int biasedNumberBetween($min = 0, $max = 100, $function = 'sqrt')
@@ -565,6 +552,11 @@ class Generator
 
     private $container;
 
+    /**
+     * @var UniqueGenerator
+     */
+    private $uniqueGenerator;
+
     public function __construct(ContainerInterface $container = null)
     {
         $this->container = $container ?: Extension\ContainerBuilder::getDefault();
@@ -575,7 +567,6 @@ public function __construct(ContainerInterface $container = null)
      *
      * @param class-string<T> $id
      *
-     * @throws ContainerExceptionInterface
      * @throws Extension\ExtensionNotFound
      *
      * @return T
@@ -610,6 +601,79 @@ public function getProviders()
         return $this->providers;
     }
 
+    /**
+     * With the unique generator you are guaranteed to never get the same two
+     * values.
+     *
+     * <code>
+     * // will never return twice the same value
+     * $faker->unique()->randomElement(array(1, 2, 3));
+     * </code>
+     *
+     * @param bool $reset      If set to true, resets the list of existing values
+     * @param int  $maxRetries Maximum number of retries to find a unique value,
+     *                         After which an OverflowException is thrown.
+     *
+     * @throws \OverflowException When no unique value can be found by iterating $maxRetries times
+     *
+     * @return self A proxy class returning only non-existing values
+     */
+    public function unique($reset = false, $maxRetries = 10000)
+    {
+        if ($reset || $this->uniqueGenerator === null) {
+            $this->uniqueGenerator = new UniqueGenerator($this, $maxRetries);
+        }
+
+        return $this->uniqueGenerator;
+    }
+
+    /**
+     * Get a value only some percentage of the time.
+     *
+     * @param float $weight A probability between 0 and 1, 0 means that we always get the default value.
+     *
+     * @return self
+     */
+    public function optional(float $weight = 0.5, $default = null)
+    {
+        if ($weight > 1) {
+            trigger_deprecation('fakerphp/faker', '1.16', 'First argument ($weight) to method "optional()" must be between 0 and 1. You passed %f, we assume you meant %f.', $weight, $weight / 100);
+            $weight = $weight / 100;
+        }
+
+        return new ChanceGenerator($this, $weight, $default);
+    }
+
+    /**
+     * To make sure the value meet some criteria, pass a callable that verifies the
+     * output. If the validator fails, the generator will try again.
+     *
+     * The value validity is determined by a function passed as first argument.
+     *
+     * <code>
+     * $values = array();
+     * $evenValidator = function ($digit) {
+     *   return $digit % 2 === 0;
+     * };
+     * for ($i=0; $i < 10; $i++) {
+     *   $values []= $faker->valid($evenValidator)->randomDigit;
+     * }
+     * print_r($values); // [0, 4, 8, 4, 2, 6, 0, 8, 8, 6]
+     * </code>
+     *
+     * @param ?\Closure $validator  A function returning true for valid values
+     * @param int       $maxRetries Maximum number of retries to find a valid value,
+     *                              After which an OverflowException is thrown.
+     *
+     * @throws \OverflowException When no valid value can be found by iterating $maxRetries times
+     *
+     * @return self A proxy class returning only valid values
+     */
+    public function valid(?\Closure $validator = null, int $maxRetries = 10000)
+    {
+        return new ValidGenerator($this, $validator, $maxRetries);
+    }
+
     public function seed($seed = null)
     {
         if ($seed === null) {
diff --git a/src/Faker/UniqueGenerator.php b/src/Faker/UniqueGenerator.php
index 8dddeec283..fef167b6d1 100644
--- a/src/Faker/UniqueGenerator.php
+++ b/src/Faker/UniqueGenerator.php
@@ -2,6 +2,8 @@
 
 namespace Faker;
 
+use Faker\Extension\Extension;
+
 /**
  * Proxy for other generators that returns only unique values.
  *
@@ -11,14 +13,7 @@
  */
 class UniqueGenerator
 {
-    /**
-     * @var Generator
-     */
     protected $generator;
-
-    /**
-     * @var int
-     */
     protected $maxRetries;
 
     /**
@@ -34,12 +29,20 @@ class UniqueGenerator
     protected $uniques = [];
 
     /**
-     * @param int $maxRetries
+     * @param Extension|Generator                $generator
+     * @param int                                $maxRetries
+     * @param array<string, array<string, null>> $uniques
      */
-    public function __construct(Generator $generator, $maxRetries = 10000)
+    public function __construct($generator, $maxRetries = 10000, &$uniques = [])
     {
         $this->generator = $generator;
         $this->maxRetries = $maxRetries;
+        $this->uniques = &$uniques;
+    }
+
+    public function ext(string $id)
+    {
+        return new self($this->generator->ext($id), $this->maxRetries, $this->uniques);
     }
 
     /**
diff --git a/src/Faker/ValidGenerator.php b/src/Faker/ValidGenerator.php
index 691d46dda9..bf40945697 100644
--- a/src/Faker/ValidGenerator.php
+++ b/src/Faker/ValidGenerator.php
@@ -2,6 +2,8 @@
 
 namespace Faker;
 
+use Faker\Extension\Extension;
+
 /**
  * Proxy for other generators, to return only valid values. Works with
  * Faker\Generator\Base->valid()
@@ -15,10 +17,11 @@ class ValidGenerator
     protected $maxRetries;
 
     /**
-     * @param callable|null $validator
-     * @param int           $maxRetries
+     * @param Extension|Generator $generator
+     * @param callable|null       $validator
+     * @param int                 $maxRetries
      */
-    public function __construct(Generator $generator, $validator = null, $maxRetries = 10000)
+    public function __construct($generator, $validator = null, $maxRetries = 10000)
     {
         if (null === $validator) {
             $validator = static function () {
@@ -32,6 +35,11 @@ public function __construct(Generator $generator, $validator = null, $maxRetries
         $this->maxRetries = $maxRetries;
     }
 
+    public function ext(string $id)
+    {
+        return new self($this->generator->ext($id), $this->validator, $this->maxRetries);
+    }
+
     /**
      * Catch and proxy all generator calls but return only valid values
      *
diff --git a/test/Faker/DefaultGeneratorTest.php b/test/Faker/DefaultGeneratorTest.php
index e009c5ccef..23eced28ea 100644
--- a/test/Faker/DefaultGeneratorTest.php
+++ b/test/Faker/DefaultGeneratorTest.php
@@ -25,6 +25,9 @@ public function testGeneratorReturnsDefaultValueForAnyPropertyGet()
         self::assertNotNull($generator->bar);
     }
 
+    /**
+     * @group legacy
+     */
     public function testGeneratorReturnsDefaultValueForAnyMethodCall()
     {
         $generator = new DefaultGenerator(123);
diff --git a/test/Faker/Provider/BaseTest.php b/test/Faker/Provider/BaseTest.php
index 2e874eafa5..9e1f8ef59f 100644
--- a/test/Faker/Provider/BaseTest.php
+++ b/test/Faker/Provider/BaseTest.php
@@ -401,7 +401,7 @@ public function testOptionalAllowsChainingProviderCallRandomlyReturnNull()
         $values = [];
 
         for ($i = 0; $i < 10; ++$i) {
-            $values[] = $faker->optional(50)->randomDigit;
+            $values[] = $faker->optional(0.5)->randomDigit;
         }
         self::assertContains(null, $values);
     }
@@ -532,11 +532,11 @@ public function testValidThrowsExceptionWhenNoValidValueCanBeGenerated()
         }
     }
 
-    public function testValidThrowsExceptionWhenParameterIsNotCollable()
+    public function testValidThrowsExceptionWhenParameterIsNotCallable()
     {
-        $this->expectException(\InvalidArgumentException::class);
         $faker = new \Faker\Generator();
         $faker->addProvider(new \Faker\Provider\Base($faker));
+        $this->expectException(\TypeError::class);
         $faker->valid(12)->randomElement([1, 3, 5, 7, 9]);
     }
 
diff --git a/test/Faker/UniqueGeneratorTest.php b/test/Faker/UniqueGeneratorTest.php
new file mode 100644
index 0000000000..bf7b147c8d
--- /dev/null
+++ b/test/Faker/UniqueGeneratorTest.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace Faker\Test;
+
+use Faker\Extension\NumberExtension;
+
+/**
+ * @covers \Faker\UniqueGenerator
+ */
+final class UniqueGeneratorTest extends TestCase
+{
+    public function testUniqueGeneratorKeepsUniquesAcrossExtensions(): void
+    {
+        $this->expectException(\OverflowException::class);
+
+        for ($i = 0; $i < 3; ++$i) {
+            $this->faker->unique()->ext(NumberExtension::class)->numberBetween(0, 1);
+        }
+    }
+
+    public function testUniqueGeneratorRetries(): void
+    {
+        for ($i = 0; $i < 10; ++$i) {
+            $this->faker->unique()->ext(NumberExtension::class)->numberBetween(0, 9);
+        }
+    }
+}
diff --git a/test/Faker/ValidGeneratorTest.php b/test/Faker/ValidGeneratorTest.php
new file mode 100644
index 0000000000..e9fafe967f
--- /dev/null
+++ b/test/Faker/ValidGeneratorTest.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Faker\Test;
+
+/**
+ * @covers \Faker\ValidGenerator
+ */
+final class ValidGeneratorTest extends TestCase
+{
+    public function testValidator(): void
+    {
+        $this->expectException(\OverflowException::class);
+
+        $validator = static function ($value) {
+            return $value !== 0;
+        };
+        $this->faker->valid($validator, 10)->numberBetween(0, 0);
+    }
+}