Reapply "UPDATE_KOTLIN_VERSION: 2.0.0-dev-4562"

This reverts commit 4cb46567d944d5319373211397062b1a08ab5b77.
diff --git a/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt b/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt
index 9d9c14f..a6ea9b9 100644
--- a/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt
+++ b/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt
@@ -20,10 +20,10 @@
 import com.google.devtools.ksp.common.impl.KSNameImpl
 import com.google.devtools.ksp.common.memoized
 import com.google.devtools.ksp.symbol.*
-import org.jetbrains.kotlin.backend.common.serialization.findPackage
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
+import org.jetbrains.kotlin.descriptors.findPackage
 import org.jetbrains.kotlin.load.java.descriptors.JavaClassDescriptor
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.parents
@@ -50,7 +50,7 @@
             is ClassDescriptor -> KSClassDeclarationDescriptorImpl.getCached(containingDescriptor)
             is FunctionDescriptor -> KSFunctionDeclarationDescriptorImpl.getCached(containingDescriptor)
             else -> null
-        } as KSDeclaration?
+        }
     }
 
     override val parent: KSNode? by lazy {
diff --git a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt
index e06136a..bb6dcc6 100644
--- a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt
+++ b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt
@@ -38,6 +38,7 @@
         }.maxByOrNull { it.lastModified() }!!
         val compilerArgs = mutableListOf(
             "-no-stdlib",
+            "-language-version", "1.9",
             "-Xplugin=${kspPluginJar.absolutePath}",
             "-Xplugin=${kspApiJar.absolutePath}",
             "-P", "plugin:$kspPluginId:apclasspath=${processorJar.absolutePath}",
diff --git a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt
index ec541ea..a3442aa 100644
--- a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt
+++ b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt
@@ -223,7 +223,6 @@
             Assert.assertTrue(jarFile.getEntry("hello/HELLO.class").size > 0)
             Assert.assertTrue(jarFile.getEntry("com/example/AClassBuilder.class").size > 0)
         }
-        Assert.assertTrue(result.output.contains("w: Language version 2.0 is experimental"))
         project.restore(buildFile.path)
     }
 
@@ -263,7 +262,6 @@
             Assert.assertTrue(jarFile.getEntry("hello/HELLO.class").size > 0)
             Assert.assertTrue(jarFile.getEntry("com/example/AClassBuilder.class").size > 0)
         }
-        Assert.assertTrue(result.output.contains("w: Language version 2.0 is experimental"))
         project.restore(buildFile.path)
         project.restore(gradleProperties.path)
     }
@@ -304,12 +302,12 @@
         gradleRunner.withArguments("build").buildAndFail().let {
             Assert.assertEquals(TaskOutcome.SUCCESS, it.task(":workload:kspKotlin")?.outcome)
             Assert.assertEquals(TaskOutcome.FAILED, it.task(":workload:compileKotlin")?.outcome)
-            Assert.assertTrue("Unresolved reference: AClassBuilder" in it.output)
+            Assert.assertTrue("Unresolved reference 'AClassBuilder'" in it.output)
         }
         gradleRunner.withArguments("build").buildAndFail().let {
             Assert.assertEquals(TaskOutcome.UP_TO_DATE, it.task(":workload:kspKotlin")?.outcome)
             Assert.assertEquals(TaskOutcome.FAILED, it.task(":workload:compileKotlin")?.outcome)
-            Assert.assertTrue("Unresolved reference: AClassBuilder" in it.output)
+            Assert.assertTrue("Unresolved reference 'AClassBuilder'" in it.output)
         }
 
         project.restore("workload/build.gradle.kts")