Refine PropertyResolver extensions null-safety

See spring-projectsgh-22687

Author: sdeleuze

spring-core/src/main/kotlin/org/springframework/core/env/PropertyResolverExtensions.kt

@@ -39,8 +39,8 @@ operator fun PropertyResolver.get(key: String) : String? = getProperty(key)
  * @author Sebastien Deleuze
  * @since 5.1
  */
-inline fun <reified T> PropertyResolver.getProperty(key: String) : T =
-		getProperty(key, T::class.java) as T
+inline fun <reified T> PropertyResolver.getProperty(key: String) : T? =
+		getProperty(key, T::class.java)
 
 /**
  * Extension for [PropertyResolver.getRequiredProperty] providing a
@@ -49,5 +49,5 @@ inline fun <reified T> PropertyResolver.getProperty(key: String) : T =
  * @author Sebastien Deleuze
  * @since 5.1
  */
-inline fun <reified T> PropertyResolver.getRequiredProperty(key: String) : T =
+inline fun <reified T: Any> PropertyResolver.getRequiredProperty(key: String) : T =
 		getRequiredProperty(key, T::class.java)

spring-core/src/test/kotlin/org/springframework/core/env/PropertyResolverExtensionsTests.kt

@@ -40,21 +40,14 @@ class PropertyResolverExtensionsTests {
 	@Test
 	fun `getProperty extension`() {
 		every { propertyResolver.getProperty("name", String::class.java) } returns "foo"
-		propertyResolver.getProperty<String>("name")
-		verify { propertyResolver.getProperty("name", String::class.java) }
-	}
-
-	@Test
-	fun `getProperty extension with nullable type`() {
-		every { propertyResolver.getProperty("name", String::class.java) } returns null
-		propertyResolver.getProperty<String?>("name")
+		val name: String? = propertyResolver.getProperty<String>("name")
 		verify { propertyResolver.getProperty("name", String::class.java) }
 	}
 
 	@Test
 	fun `getRequiredProperty extension`() {
 		every { propertyResolver.getRequiredProperty("name", String::class.java) } returns "foo"
-		propertyResolver.getRequiredProperty<String>("name")
+		val name: String = propertyResolver.getRequiredProperty<String>("name")
 		verify { propertyResolver.getRequiredProperty("name", String::class.java) }
 	}