optimize syntax (#4931)

Co-authored-by: 李铭昕 <[email protected]>

Author: assert6

src/Definition/DefinitionSource.php

@@ -33,7 +33,7 @@ public function __construct(array $source)
      */
     public function getDefinition(string $name): ?DefinitionInterface
     {
-        return $this->source[$name] ?? $this->source[$name] = $this->autowire($name);
+        return $this->source[$name] ??= $this->autowire($name);
     }
 
     /**

src/Definition/ObjectDefinition.php

@@ -53,11 +53,7 @@ public function setClassName(string $className = null): void
 
     public function getClassName(): string
     {
-        if ($this->className !== null) {
-            return $this->className;
-        }
-
-        return $this->name;
+        return $this->className ?? $this->name;
     }
 
     public function isClassExists(): bool

tests/Definition/DefinitionSourceTest.php

@@ -29,7 +29,8 @@ protected function tearDown(): void
     public function testGetDefinition()
     {
         $source = new DefinitionSource([]);
-        $source->getDefinition(Bar::class);
+        $bar = $source->getDefinition(Bar::class);
         $this->assertSame(1, count($source->getDefinitions()));
+        $this->assertSame($bar, $source->getDefinition(Bar::class));
     }
 }